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Sample records for cerevisiae microbial cell

  1. Thionine increases electricity generation from microbial fuel cell using Saccharomyces cerevisiae and exoelectrogenic mixed culture.

    PubMed

    Rahimnejad, Mostafa; Najafpour, Ghasem Darzi; Ghoreyshi, Ali Asghar; Talebnia, Farid; Premier, Giuliano C; Bakeri, Gholamreza; Kim, Jung Rae; Oh, Sang-Eun

    2012-08-01

    Microbial fuel cells (MFCs) have been shown to be capable of clean energy production through the oxidation of biodegradable organic waste using various bacterial species as biocatalysts. In this study we found Saccharomyces cerevisiae, previously known electrochemcially inactive or less active species, can be acclimated with an electron mediator thionine for electrogenic biofilm formation in MFC, and electricity production is improved with facilitation of electron transfer. Power generation of MFC was also significantly increased by thionine with both aerated and non-aerated cathode. With electrochemically active biofilm enriched with swine wastewater, MFC power increased more significantly by addition of thionine. The optimum mediator concentration was 500 mM of thionine with S. cerevisae in MFC with the maximum voltage and current generation in the microbial fuel cell were 420 mV and 700 mA/m(2), respectively. Cyclic voltametry shows that thionine improves oxidizing and reducing capability in both pure culture and acclimated biofilm as compared to non-mediated cell. The results obtained indicated that thionine has great potential to enhance power generation from unmediated yeast or electrochemically active biofilm in MFC.

  2. Outward electron transfer by Saccharomyces cerevisiae monitored with a bi-cathodic microbial fuel cell-type activity sensor.

    PubMed

    Ducommun, Raphaël; Favre, Marie-France; Carrard, Delphine; Fischer, Fabian

    2010-03-01

    A Janus head-like bi-cathodic microbial fuel cell was constructed to monitor the electron transfer from Saccharomyces cerevisiae to a woven carbon anode. The experiments were conducted during an ethanol cultivation of 170 g/l glucose in the presence and absence of yeast-peptone medium. First, using a basic fuel-cell type activity sensor, it was shown that yeast-peptone medium contains electroactive compounds. For this purpose, 1% solutions of soy peptone and yeast extract were subjected to oxidative conditions, using a microbial fuel cell set-up corresponding to a typical galvanic cell, consisting of culture medium in the anodic half-cell and 0.5 M K(3)Fe(CN)(6) in the cathodic half-cell. Second, using a bi-cathodic microbial fuel cell, it was shown that electrons were transferred from yeast cells to the carbon anode. The participation of electroactive compounds in the electron transport was separated as background current. This result was verified by applying medium-free conditions, where only glucose was fed, confirming that electrons are transferred from yeast cells to the woven carbon anode. Knowledge about the electron transfer through the cell membrane is of importance in amperometric online monitoring of yeast fermentations and for electricity production with microbial fuel cells.

  3. Dominance of Saccharomyces cerevisiae in alcoholic fermentation processes: role of physiological fitness and microbial interactions.

    PubMed

    Albergaria, Helena; Arneborg, Nils

    2016-03-01

    Winemaking, brewing and baking are some of the oldest biotechnological processes. In all of them, alcoholic fermentation is the main biotransformation and Saccharomyces cerevisiae the primary microorganism. Although a wide variety of microbial species may participate in alcoholic fermentation and contribute to the sensory properties of end-products, the yeast S. cerevisiae invariably dominates the final stages of fermentation. The ability of S. cerevisiae to outcompete other microbial species during alcoholic fermentation processes, such as winemaking, has traditionally been ascribed to its high fermentative power and capacity to withstand the harsh environmental conditions, i.e. high levels of ethanol and organic acids, low pH values, scarce oxygen availability and depletion of certain nutrients. However, in recent years, several studies have raised evidence that S. cerevisiae, beyond its remarkable fitness for alcoholic fermentation, also uses defensive strategies mediated by different mechanisms, such as cell-to-cell contact and secretion of antimicrobial peptides, to combat other microorganisms. In this paper, we review the main physiological features underlying the special aptitude of S. cerevisiae for alcoholic fermentation and discuss the role of microbial interactions in its dominance during alcoholic fermentation, as well as its relevance for winemaking.

  4. Microbial Cell Imaging

    SciTech Connect

    Doktycz, Mitchel John; Sullivan, Claretta; Mortensen, Ninell P; Allison, David P

    2011-01-01

    the maximum scan size (roughly 100 x 100 {mu}m) and the restricted movement of the cantilever in the Z (or height) direction. In most commercial AFMs, the Z range is restricted to roughly 10 {mu}m such that the height of cells to be imaged must be seriously considered. Nevertheless, AFM can provide structural-functional information at nanometer resolution and do so in physiologically relevant environments. Further, instrumentation for scanning probe microscopy continues to advance. Systems for high-speed imaging are becoming available, and techniques for looking inside the cells are being demonstrated. The ability to combine AFM with other imaging modalities is likely to have an even greater impact on microbiological studies. AFM studies of intact microbial cells started to appear in the literature in the 1990s. For example, AFM studies of Saccharomyces cerevisiae examined buddings cars after cell division and detailed changes related to cell growth processes. Also, the first AFM studies of bacterial biofilms appeared. In the late 1990s, AFM studies of intact fungal spores described clear changes in spore surfaces upon germination, and studies of individual bacterial cells were also described. These early bacterial imaging studies examined changes in bacterial morphology due to antimicrobial peptides exposure and bacterial adhesion properties. The majority of these early studies were carried out on dried samples and took advantage of the resolving power of AFM. The lack of cell mounting procedures presented an impediment for cell imaging studies. Subsequently, several approaches to mounting microbial cells have been developed, and these techniques are described later. Also highlighted are general considerations for microbial imaging and a description of some of the various applications of AFM to microbiology.

  5. Cell Wall Assembly in Saccharomyces cerevisiae

    PubMed Central

    Lesage, Guillaume; Bussey, Howard

    2006-01-01

    An extracellular matrix composed of a layered meshwork of β-glucans, chitin, and mannoproteins encapsulates cells of the yeast Saccharomyces cerevisiae. This organelle determines cellular morphology and plays a critical role in maintaining cell integrity during cell growth and division, under stress conditions, upon cell fusion in mating, and in the durable ascospore cell wall. Here we assess recent progress in understanding the molecular biology and biochemistry of cell wall synthesis and its remodeling in S. cerevisiae. We then review the regulatory dynamics of cell wall assembly, an area where functional genomics offers new insights into the integration of cell wall growth and morphogenesis with a polarized secretory system that is under cell cycle and cell type program controls. PMID:16760306

  6. Cell wall construction in Saccharomyces cerevisiae.

    PubMed

    Klis, Frans M; Boorsma, Andre; De Groot, Piet W J

    2006-02-01

    In this review, we discuss new insights in cell wall architecture and cell wall construction in the ascomycetous yeast Saccharomyces cerevisiae. Transcriptional profiling studies combined with biochemical work have provided ample evidence that the cell wall is a highly adaptable organelle. In particular, the protein population that is anchored to the stress-bearing polysaccharides of the cell wall, and forms the interface with the outside world, is highly diverse. This diversity is believed to play an important role in adaptation of the cell to environmental conditions, in growth mode and in survival. Cell wall construction is tightly controlled and strictly coordinated with progression of the cell cycle. This is reflected in the usage of specific cell wall proteins during consecutive phases of the cell cycle and in the recent discovery of a cell wall integrity checkpoint. When the cell is challenged with stress conditions that affect the cell wall, a specific transcriptional response is observed that includes the general stress response, the cell wall integrity pathway and the calcineurin pathway. This salvage mechanism includes increased expression of putative cell wall assemblases and some potential cross-linking cell wall proteins, and crucial changes in cell wall architecture. We discuss some more enzymes involved in cell wall construction and also potential inhibitors of these enzymes. Finally, we use both biochemical and genomic data to infer that the architectural principles used by S. cerevisiae to build its cell wall are also used by many other ascomycetous yeasts and also by some mycelial ascomycetous fungi.

  7. Metabolic Differences in Microbial Cell Populations Revealed by Nanophotonic Ionization

    SciTech Connect

    Walker, Bennett; Antonakos, Cory; Retterer, Scott T; Vertes, Akos

    2013-01-01

    ellular differences are linked to cell differentiation, the proliferation of cancer and to the development of drug resistance in microbial infections. Due to sensitivity limitations, however, large- scale metabolic analysis at the single cell level is only available for cells significantly larger in volume than Saccharomyces cerevisiae (~30 fL). Here we demonstrate that by a nanophotonic ionization platform and mass spectrometry, over one hundred up to 108 metabolites, or up to 18% of the known S. cerevisiae metabolome, can be identified in very small cell populations (n < 100). Under ideal conditions, r Relative quantitation of up to 4% of the metabolites is achieved at the single cell level.

  8. Exploration and comparison of inborn capacity of aerobic and anaerobic metabolisms of Saccharomyces cerevisiae for microbial electrical current production.

    PubMed

    Mao, Longfei; Verwoerd, Wynand S

    2013-01-01

    Saccharomyces cerevisiae possesses numerous advantageous biological features, such as being robust, easily handled, mostly non-pathogenic and having high catabolic rates, etc., which can be considered as merits for being used as a promising biocatalyst in microbial fuel cells (MFCs) for electricity generation. Previous studies have developed efficient MFC configurations to convert metabolic electron shuttles, such as cytoplasmic NADH, into usable electric current. However, no studies have elucidated the maximum potential of S. cerevisiae for current output and the underlying metabolic pathways, resulting from the interaction of thousands of reactions inside the cell during MFC operation. To address these two key issues, this study used in silico metabolic engineering techniques, flux balance analysis (FBA), and flux variability analysis with target flux minimization (FATMIN), to model the metabolic perturbation of S. cerevisiae under the MFC-energy extraction. The FBA results showed that, in the cytoplasmic NADH-dependent mediated electron transfer (MET) mode, S. cerevisiae had a potential to produce currents at up to 5.781 A/gDW for the anaerobic and 6.193 A/gDW for the aerobic environments. The FATMIN results showed that the aerobic and anaerobic metabolisms are resilient, relying on six and five contributing reactions respectively for high current production. Two reactions, catalyzed by glutamate dehydrogenase (NAD) (EC 1.4.1.3) and methylene tetrahydrofolate dehydrogenase (NAD) (EC 1.5.1.5), were shared in both current-production modes and contributed to over 80% of the identified maximum current outputs. It is also shown that the NADH regeneration was much less energy costly than biomass production rate. Taken together, our finding suggests that S. cerevisiae should receive more research effort for MFC electricity production.

  9. Exploration and comparison of inborn capacity of aerobic and anaerobic metabolisms of Saccharomyces cerevisiae for microbial electrical current production

    PubMed Central

    Mao, Longfei; Verwoerd, Wynand S

    2013-01-01

    Saccharomyces cerevisiae possesses numerous advantageous biological features, such as being robust, easily handled, mostly non-pathogenic and having high catabolic rates, etc., which can be considered as merits for being used as a promising biocatalyst in microbial fuel cells (MFCs) for electricity generation. Previous studies have developed efficient MFC configurations to convert metabolic electron shuttles, such as cytoplasmic NADH, into usable electric current. However, no studies have elucidated the maximum potential of S. cerevisiae for current output and the underlying metabolic pathways, resulting from the interaction of thousands of reactions inside the cell during MFC operation. To address these two key issues, this study used in silico metabolic engineering techniques, flux balance analysis (FBA), and flux variability analysis with target flux minimization (FATMIN), to model the metabolic perturbation of S. cerevisiae under the MFC-energy extraction. The FBA results showed that, in the cytoplasmic NADH-dependent mediated electron transfer (MET) mode, S. cerevisiae had a potential to produce currents at up to 5.781 A/gDW for the anaerobic and 6.193 A/gDW for the aerobic environments. The FATMIN results showed that the aerobic and anaerobic metabolisms are resilient, relying on six and five contributing reactions respectively for high current production. Two reactions, catalyzed by glutamate dehydrogenase (NAD) (EC 1.4.1.3) and methylene tetrahydrofolate dehydrogenase (NAD) (EC 1.5.1.5), were shared in both current-production modes and contributed to over 80% of the identified maximum current outputs. It is also shown that the NADH regeneration was much less energy costly than biomass production rate. Taken together, our finding suggests that S. cerevisiae should receive more research effort for MFC electricity production. PMID:23969939

  10. Applications of Microbial Cell Sensors

    NASA Astrophysics Data System (ADS)

    Shimomura-Shimizu, Mifumi; Karube, Isao

    Since the first microbial cell sensor was studied by Karube et al. in 1977, many types of microbial cell sensors have been developed as analytical tools. The microbial cell sensor utilizes microbes as a sensing element and a transducer. The characteristics of microbial cell sensors as sensing devices are a complete contrast to those of enzyme sensors or immunosensors, which are highly specific for the substrates of interest, although the specificity of the microbial cell sensor has been improved by genetic modification of the microbe used as the sensing element. Microbial cell sensors have the advantages of tolerance to measuring conditions, a long lifetime, and good cost performance, and have the disadvantage of a long response time. In this review, applications of microbial cell sensors are summarized.

  11. Glucose-based microbial production of the hormone melatonin in yeast Saccharomyces cerevisiae.

    PubMed

    Germann, Susanne M; Baallal Jacobsen, Simo A; Schneider, Konstantin; Harrison, Scott J; Jensen, Niels B; Chen, Xiao; Stahlhut, Steen G; Borodina, Irina; Luo, Hao; Zhu, Jiangfeng; Maury, Jérôme; Forster, Jochen

    2016-05-01

    Melatonin is a natural mammalian hormone that plays an important role in regulating the circadian cycle in humans. It is a clinically effective drug exhibiting positive effects as a sleep aid and a powerful antioxidant used as a dietary supplement. Commercial melatonin production is predominantly performed by complex chemical synthesis. In this study, we demonstrate microbial production of melatonin and related compounds, such as serotonin and N-acetylserotonin. We generated Saccharomyces cerevisiae strains that comprise heterologous genes encoding one or more variants of an L-tryptophan hydroxylase, a 5-hydroxy-L-tryptophan decarboxylase, a serotonin acetyltransferase, an acetylserotonin O-methyltransferase, and means for providing the cofactor tetrahydrobiopterin via heterologous biosynthesis and recycling pathways. We thereby achieved de novo melatonin biosynthesis from glucose. We furthermore accomplished increased product titers by altering expression levels of selected pathway enzymes and boosting co-factor supply. The final yeast strain produced melatonin at a titer of 14.50 ± 0.57 mg L(-1) in a 76h fermentation using simulated fed-batch medium with glucose as sole carbon source. Our study lays the basis for further developing a yeast cell factory for biological production of melatonin.

  12. Yeast surface display of dehydrogenases in microbial fuel-cells.

    PubMed

    Gal, Idan; Schlesinger, Orr; Amir, Liron; Alfonta, Lital

    2016-12-01

    Two dehydrogenases, cellobiose dehydrogenase from Corynascus thermophilus and pyranose dehydrogenase from Agaricus meleagris, were displayed for the first time on the surface of Saccharomyces cerevisiae using the yeast surface display system. Surface displayed dehydrogenases were used in a microbial fuel cell and generated high power outputs. Surface displayed cellobiose dehydrogenase has demonstrated a midpoint potential of -28mV (vs. Ag/AgCl) at pH=6.5 and was used in a mediator-less anode compartment of a microbial fuel cell producing a power output of 3.3μWcm(-2) using lactose as fuel. Surface-displayed pyranose dehydrogenase was used in a microbial fuel cell and generated high power outputs using different substrates, the highest power output that was achieved was 3.9μWcm(-2) using d-xylose. These results demonstrate that surface displayed cellobiose dehydrogenase and pyranose dehydrogenase may successfully be used in microbial bioelectrochemical systems.

  13. Identification of Two Saccharomyces cerevisiae Cell Wall Mannan Chemotypes

    PubMed Central

    Cawley, T. N.; Ballou, Clinton E.

    1972-01-01

    We have obtained evidence for two structurally and antigenically different Saccharomyces cerevisiae cell wall mannans. One, which occurs widely and is found in S. cerevisiae strain 238C, is already known to be a neutral mannan which yields mannose, mannobiose, mannotriose, and mannotetraose on acetolysis of the (1 → 6)-linked backbone. The other, which was found in S. cerevisiae brewer's strains, is a phosphomannan with a structure very similar to that of Kloeckera brevis mannan. S. cerevisiae (brewer's yeast strain) was agglutinated by antiserum prepared against Kloeckera brevis cells. The mannan, isolated from a proteolytic digest of the cell wall of the former, did not react with S. cerevisiae 238C antiserum, whereas it cross-reacted strongly with K. brevis antiserum. Controlled acetolysis cleaved the (1 → 6)-linkages in the polysaccharide backbone and released mannose, mannobiose, mannotriose, and mannotriose phosphate. Mild acid treatment of the phosphomannan hydrolyzed the phosphodiester linkage, yielding phosphomonoester mannan and mannose. The resulting phosphomonoester mannan reacted with antiserum prepared against K. brevis possessing monoester phosphate groups on the cell surface. α-d-Mannose-1-phosphate completely inhibited the precipitin reaction between brewer's yeast mannan and the homologous antiserum. Flocculent and nonflocculent strains of this yeast were shown to have similar structural and immunological properties. PMID:4559821

  14. Microbial fuel cells

    SciTech Connect

    Nealson, Kenneth H; Pirbazari, Massoud; Hsu, Lewis

    2013-04-09

    A microbial fuel cell includes an anode compartment with an anode and an anode biocatalyst and a cathode compartment with a cathode and a cathode biocatalyst, with a membrane positioned between the anode compartment and the cathode compartment, and an electrical pathway between the anode and the cathode. The anode biocatalyst is capable of catalyzing oxidation of an organic substance, and the cathode biocatalyst is capable of catalyzing reduction of an inorganic substance. The reduced organic substance can form a precipitate, thereby removing the inorganic substance from solution. In some cases, the anode biocatalyst is capable of catalyzing oxidation of an inorganic substance, and the cathode biocatalyst is capable of catalyzing reduction of an organic or inorganic substance.

  15. Evaluation of microbial qPCR workflows using engineered Saccharomyces cerevisiae

    PubMed Central

    Da Silva, S.M.; Vang, L.K.; Olson, N.D.; Lund, S.P.; Downey, A.S.; Kelman, Z.; Salit, M.L.; Lin, N.J.; Morrow, J.B.

    2016-01-01

    Aims We describe the development and interlaboratory study of modified Saccharomyces cerevisiae as a candidate material to evaluate a full detection workflow including DNA extraction and quantitative polymerase chain reaction (qPCR). Methods and results S. cerevisiae NE095 was prepared by stable insertion of DNA sequence External RNA Control Consortium-00095 into S. cerevisiae BY4739 to convey selectivity. For the interlaboratory study, a binomial regression model was used to select three cell concentrations, high (4 × 107 cells ml−1), intermediate (4 × 105 cells ml−1) and low (4 × 103 cells ml−1), and the number of samples per concentration. Seven participants, including potential end users, had combined rates of positive qPCR detection (quantification cycle <37) of 100%, 40%, and 0% for high, intermediate, and low concentrations, respectively. Conclusions The NE095 strain was successfully detected by all participants, with the high concentration indicating a potential target concentration for a reference material. Significance and impact of the study The engineered yeast has potential to support measurement assurance for the analytical process of qPCR, encompassing the method, equipment, and operator, to increase confidence in results and better inform decision-making in areas of applied microbiology. This material can also support process assessment for other DNA-based detection technologies. PMID:27077050

  16. Microbial Fuel Cells and Sensors

    DTIC Science & Technology

    2007-11-02

    funding foreign research over Quality U.S. research needs to be investigated by government officials. PATENT INFORMATION: Improved fuel cell designs and...Zeikus. Analysis of microbial electrochemical activity in marine sediment. (In preparation) REPOT D CUM NTA ON AGEForm Approved REPOT D CUM NTATON

  17. The microbial cell cycle

    SciTech Connect

    Nurse, P.; Streiblova, E.

    1984-01-01

    This book concentrates on the major problems of cell cycle control in microorganisms. A wide variety of microorganisms, ranging from bacteria and yeasts to hyphal fungi, algae, and ciliates are analyzed, with emphasis on the basic similarities among the organisms. Different ways of looking at cell cycle control which emphasize aspects of the problem such as circadian rhythms, limit cycle oscillators, and cell size models, are considered. New approaches such as the study of cell cycle mutants, and cloning of cell cycle control genes are also presented.

  18. Indentation with atomic force microscope, Saccharomyces cerevisiae cell gains elasticity under ethanol stress.

    PubMed

    Niu, Yuan-Pu; Lin, Xiang-Hua; Dong, Shi-Jun; Yuan, Qi-Peng; Li, Hao

    2016-10-01

    During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane is the first target to be attacked by the accumulated ethanol. In such a prominent position, S. cerevisiae cell membrane could reversely provide protection through changing fluidity or elasticity secondary to remodeled membrane components or structure during the fermentation process. However, there is yet to be a direct observation of the real effect of the membrane compositional change. In this study, atomic force microscope-based strategy was performed to determine Young's modulus of S. cerevisiae to directly clarify ethanol stress-associated changes and roles of S. cerevisiae cell membrane fluidity and elasticity. Cell survival rate decreased while the cell swelling rate and membrane permeability increased as ethanol concentration increased from 0% to 20% v/v. Young's modulus decreased continuously from 3.76MPa to 1.53MPa while ethanol stress increased from 0% to 20% v/v, indicating that ethanol stress induced the S. cerevisiae membrane fluidity and elasticity changes. Combined with the fact that membrane composition varies under ethanol stress, to some extent, this could be considered as a forced defensive act to the ethanol stress by S. cerevisiae cells. On the other hand, the ethanol stress induced loosening of cell membrane also caused S. cerevisiae cell to proactively remodel membrane to make cell membrane more agreeable to the increase of environmental threat. Increased ethanol stress made S. cerevisiae cell membrane more fluidized and elastic, and eventually further facilitated yeast cell's survival.

  19. Microbial transformations of ferulic acid by Saccharomyces cerevisiae and Pseudomonas fluorescens.

    PubMed Central

    Huang, Z; Dostal, L; Rosazza, J P

    1993-01-01

    Saccharomyces cerevisiae (dry baker's yeast) and Pseudomonas fluorescens were used to convert trans-ferulic acid into 4-hydroxy-3-methoxystyrene in 96 and 89% yields, respectively. The metabolites were isolated by solid-phase extraction and analyzed by thin-layer chromatography and high-performance liquid chromatography. The identities of the metabolites were determined by 1H- and 13C-nuclear magnetic resonance spectroscopy and by mass spectrometry. The mechanism of the decarboxylation of ferulic acid was investigated by measuring the degree and position of deuterium incorporated into the styrene derivative from D2O by mass spectrometry and by both proton and deuterium nuclear magnetic resonance spectroscopies. Resting cells of baker's yeast reduced ferulic acid to 4-hydroxy-3-methoxyphenylpropionic acid in 54% yield when incubations were under an argon atmosphere. PMID:8395165

  20. Towards a Microbial Thermoelectric Cell

    PubMed Central

    Rodríguez-Barreiro, Raúl; Abendroth, Christian; Vilanova, Cristina; Moya, Andrés; Porcar, Manuel

    2013-01-01

    Microbial growth is an exothermic process. Biotechnological industries produce large amounts of heat, usually considered an undesirable by-product. In this work, we report the construction and characterization of the first microbial thermoelectric cell (MTC), in which the metabolic heat produced by a thermally insulated microbial culture is partially converted into electricity through a thermoelectric device optimized for low ΔT values. A temperature of 41°C and net electric voltage of around 250–600 mV was achieved with 1.7 L baker’s yeast culture. This is the first time microbial metabolic energy has been converted into electricity with an ad hoc thermoelectric device. These results might contribute towards developing a novel strategy to harvest excess heat in the biotechnology industry, in processes such as ethanol fermentation, auto thermal aerobic digestion (ATAD) or bioremediation, which could be coupled with MTCs in a single unit to produce electricity as a valuable by-product of the primary biotechnological product. Additionally, we propose that small portable MTCs could be conceived and inoculated with suitable thermophilic of hyperthermophilic starter cultures and used for powering small electric devices. PMID:23468862

  1. Proteome analysis of aerobically and anaerobically grown Saccharomyces cerevisiae cells.

    PubMed

    Bruckmann, Astrid; Hensbergen, Paul J; Balog, Crina I A; Deelder, André M; Brandt, Raymond; Snoek, I S Ishtar; Steensma, H Yde; van Heusden, G Paul H

    2009-01-30

    The yeast Saccharomyces cerevisiae is able to grow under aerobic as well as anaerobic conditions. We and others previously found that transcription levels of approximately 500 genes differed more than two-fold when cells from anaerobic and aerobic conditions were compared. Here, we addressed the effect of anaerobic growth at the post-transcriptional level by comparing the proteomes of cells isolated from steady-state glucose-limited anaerobic and aerobic cultures. Following two-dimensional gel electrophoresis and mass spectrometry we identified 110 protein spots, corresponding to 75 unique proteins, of which the levels differed more than two-fold between aerobically and anaerobically-grown cells. For 21 of the 110 spots, the intensities decreased more than two-fold whereas the corresponding mRNA levels increased or did not change significantly under anaerobic conditions. The intensities of the other 89 spots changed in the same direction as the mRNA levels of the corresponding genes, although to different extents. For some genes of glycolysis a small increase in mRNA levels, 1.5-2 fold, corresponded to a 5-10 fold increase in protein levels. Extrapolation of our results suggests that transcriptional regulation is the major but not exclusive mechanism for adaptation of S. cerevisiae to anaerobic growth conditions.

  2. Cell Wall β-(1,6)-Glucan of Saccharomyces cerevisiae

    PubMed Central

    Aimanianda, Vishukumar; Clavaud, Cécile; Simenel, Catherine; Fontaine, Thierry; Delepierre, Muriel; Latgé, Jean-Paul

    2009-01-01

    Despite its essential role in the yeast cell wall, the exact composition of the β-(1,6)-glucan component is not well characterized. While solubilizing the cell wall alkali-insoluble fraction from a wild type strain of Saccharomyces cerevisiae using a recombinant β-(1,3)-glucanase followed by chromatographic characterization of the digest on an anion exchange column, we observed a soluble polymer that eluted at the end of the solvent gradient run. Further characterization indicated this soluble polymer to have a molecular mass of ∼38 kDa and could be hydrolyzed only by β-(1,6)-glucanase. Gas chromatographymass spectrometry and NMR (1H and 13C) analyses confirmed it to be a β-(1,6)-glucan polymer with, on average, branching at every fifth residue with one or two β-(1,3)-linked glucose units in the side chain. This polymer peak was significantly reduced in the corresponding digests from mutants of the kre genes (kre9 and kre5) that are known to play a crucial role in the β-(1,6)-glucan biosynthesis. In the current study, we have developed a biochemical assay wherein incubation of UDP-[14C]glucose with permeabilized S. cerevisiae yeasts resulted in the synthesis of a polymer chemically identical to the branched β-(1,6)-glucan isolated from the cell wall. Using this assay, parameters essential for β-(1,6)-glucan synthetic activity were defined. PMID:19279004

  3. Photosynthetic Microbial Fuel Cells.

    PubMed

    Laureanti, Joseph A; Jones, Anne K

    2017-01-10

    This chapter presents the current state of research on bioelectrochemical systems that include phototrophic organisms. First, we describe what is known of how phototrophs transfer electrons from internal metabolism to external substrates. This includes efforts to understand both the source of electrons and transfer pathways within cells. Second, we consider technological progress toward producing bio-photovoltaic devices with phototrophs. Efforts to improve these devices by changing the species included, the electrode surfaces, and chemical mediators are described. Finally, we consider future directions for this research field.

  4. Production of recombinant Agaricus bisporus tyrosinase in Saccharomyces cerevisiae cells.

    PubMed

    Lezzi, Chiara; Bleve, Gianluca; Spagnolo, Stefano; Perrotta, Carla; Grieco, Francesco

    2012-12-01

    It has been demonstrated that Agaricus bisporus tyrosinase is able to oxidize various phenolic compounds, thus being an enzyme of great importance for a number of biotechnological applications. The tyrosinase-coding PPO2 gene was isolated by reverse-transcription polymerase chain reaction (RT-PCR) using total RNA extracted from the mushroom fruit bodies as template. The gene was sequenced and cloned into pYES2 plasmid, and the resulting pY-PPO2 recombinant vector was then used to transform Saccharomyces cerevisiae cells. Native polyacrylamide gel electrophoresis followed by enzymatic activity staining with L-3,4-dihydroxyphenylalanine (L-DOPA) indicated that the recombinant tyrosinase is biologically active. The recombinant enzyme was overexpressed and biochemically characterized, showing that the catalytic constants of the recombinant tyrosinase were higher than those obtained when a commercial tyrosinase was used, for all the tested substrates. The present study describes the recombinant production of A. bisporus tyrosinase in active form. The produced enzyme has similar properties to the one produced in the native A. bisporus host, and its expression in S. cerevisiae provides good potential for protein engineering and functional studies of this important enzyme.

  5. Industrial systems biology of Saccharomyces cerevisiae enables novel succinic acid cell factory.

    PubMed

    Otero, José Manuel; Cimini, Donatella; Patil, Kiran R; Poulsen, Simon G; Olsson, Lisbeth; Nielsen, Jens

    2013-01-01

    Saccharomyces cerevisiae is the most well characterized eukaryote, the preferred microbial cell factory for the largest industrial biotechnology product (bioethanol), and a robust commerically compatible scaffold to be exploitted for diverse chemical production. Succinic acid is a highly sought after added-value chemical for which there is no native pre-disposition for production and accmulation in S. cerevisiae. The genome-scale metabolic network reconstruction of S. cerevisiae enabled in silico gene deletion predictions using an evolutionary programming method to couple biomass and succinate production. Glycine and serine, both essential amino acids required for biomass formation, are formed from both glycolytic and TCA cycle intermediates. Succinate formation results from the isocitrate lyase catalyzed conversion of isocitrate, and from the α-keto-glutarate dehydrogenase catalyzed conversion of α-keto-glutarate. Succinate is subsequently depleted by the succinate dehydrogenase complex. The metabolic engineering strategy identified included deletion of the primary succinate consuming reaction, Sdh3p, and interruption of glycolysis derived serine by deletion of 3-phosphoglycerate dehydrogenase, Ser3p/Ser33p. Pursuing these targets, a multi-gene deletion strain was constructed, and directed evolution with selection used to identify a succinate producing mutant. Physiological characterization coupled with integrated data analysis of transcriptome data in the metabolically engineered strain were used to identify 2(nd)-round metabolic engineering targets. The resulting strain represents a 30-fold improvement in succinate titer, and a 43-fold improvement in succinate yield on biomass, with only a 2.8-fold decrease in the specific growth rate compared to the reference strain. Intuitive genetic targets for either over-expression or interruption of succinate producing or consuming pathways, respectively, do not lead to increased succinate. Rather, we demonstrate how

  6. Hydrogen peroxide removal with magnetically responsive Saccharomyces cerevisiae cells.

    PubMed

    Safarik, Ivo; Sabatkova, Zdenka; Safarikova, Mirka

    2008-09-10

    Hydrogen peroxide (HP) is a promising chemical sanitizer for use in the food industry. Its residues have to be decomposed, usually using an enzyme process employing catalase. In order to offer an inexpensive biocatalyst and to simplify subsequent manipulation, we have prepared magnetically responsive alginate beads containing entrapped Saccharomyces cerevisiae cells and magnetite microparticles. Larger beads (2-3 mm in diameter) were prepared by dropping the mixture into calcium chloride solution, while microbeads (the diameter of majority of particles ranged between 50 and 100 microm) were prepared using the water in oil emulsification process. In general, microbeads enabled more efficient HP decomposition. The prepared microparticulate biocatalyst caused efficient decomposition of HP in water solutions (up to 2% concentration), leaving very low residual HP concentration after treatment (below 0.001% under appropriate conditions). The biocatalyst was stable; the same catalytic activity was observed after one month storage at 4 degrees C, and the microbeads could be used at least five times.

  7. Carbon nanotube dispersed conductive network for microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Matsumoto, S.; Yamanaka, K.; Ogikubo, H.; Akasaka, H.; Ohtake, N.

    2014-08-01

    Microbial fuel cells (MFCs) are promising devices for capturing biomass energy. Although they have recently attracted considerable attention, their power densities are too low for practical use. Increasing their electrode surface area is a key factor for improving the performance of MFC. Carbon nanotubes (CNTs), which have excellent electrical conductivity and extremely high specific surface area, are promising materials for electrodes. However, CNTs are insoluble in aqueous solution because of their strong intertube van der Waals interactions, which make practical use of CNTs difficult. In this study, we revealed that CNTs have a strong interaction with Saccharomyces cerevisiae cells. CNTs attach to the cells and are dispersed in a mixture of water and S. cerevisiae, forming a three-dimensional CNT conductive network. Compared with a conventional two-dimensional electrode, such as carbon paper, the three-dimensional conductive network has a much larger surface area. By applying this conductive network to MFCs as an anode electrode, power density is increased to 176 μW/cm2, which is approximately 25-fold higher than that in the case without CNTs addition. Maximum current density is also increased to approximately 8-fold higher. These results suggest that three-dimensional CNT conductive network contributes to improve the performance of MFC by increasing surface area.

  8. Ethanol fermentation in an immobilized cell reactor using Saccharomyces cerevisiae.

    PubMed

    Najafpour, Ghasem; Younesi, Habibollah; Syahidah Ku Ismail, Ku

    2004-05-01

    Fermentation of sugar by Saccharomyces cerevisiae, for production of ethanol in an immobilized cell reactor (ICR) was successfully carried out to improve the performance of the fermentation process. The fermentation set-up was comprised of a column packed with beads of immobilized cells. The immobilization of S. cerevisiae was simply performed by the enriched cells cultured media harvested at exponential growth phase. The fixed cell loaded ICR was carried out at initial stage of operation and the cell was entrapped by calcium alginate. The production of ethanol was steady after 24 h of operation. The concentration of ethanol was affected by the media flow rates and residence time distribution from 2 to 7 h. In addition, batch fermentation was carried out with 50 g/l glucose concentration. Subsequently, the ethanol productions and the reactor productivities of batch fermentation and immobilized cells were compared. In batch fermentation, sugar consumption and ethanol production obtained were 99.6% and 12.5% v/v after 27 h while in the ICR, 88.2% and 16.7% v/v were obtained with 6 h retention time. Nearly 5% ethanol production was achieved with high glucose concentration (150 g/l) at 6 h retention time. A yield of 38% was obtained with 150 g/l glucose. The yield was improved approximately 27% on ICR and a 24 h fermentation time was reduced to 7 h. The cell growth rate was based on the Monod rate equation. The kinetic constants (K(s) and mu(m)) of batch fermentation were 2.3 g/l and 0.35 g/lh, respectively. The maximum yield of biomass on substrate (Y(X-S)) and the maximum yield of product on substrate (Y(P-S)) in batch fermentations were 50.8% and 31.2% respectively. Productivity of the ICR were 1.3, 2.3, and 2.8 g/lh for 25, 35, 50 g/l of glucose concentration, respectively. The productivity of ethanol in batch fermentation with 50 g/l glucose was calculated as 0.29 g/lh. Maximum production of ethanol in ICR when compared to batch reactor has shown to increase

  9. Microbial electrolysis cell with a microbial biocathode.

    PubMed

    Jeremiasse, Adriaan W; Hamelers, Hubertus V M; Buisman, Cees J N

    2010-04-01

    This study demonstrates, for the first time, the proof-of-principle of an MEC in which both the anodic and cathodic reaction are catalyzed by microorganisms. No expensive chemical catalysts, such as platinum, are needed. Two of these MECs were simultaneously operated and reached a maximum of 1.4 A/m(2) at an applied cell voltage of 0.5 V. At a cathode potential of -0.7 V, the biocathode in the MECs had a higher current density (MEC 1: 1.9 A/m(2), MEC 2: 3.3 A/m(2)) than a control cathode (0.3 A/m(2), graphite felt without biofilm) in an electrochemical half cell. This indicates that hydrogen production is catalyzed at the biocathode, likely by electrochemically active microorganisms. The cathodic hydrogen recovery was 17% for MEC 1 and 21% for MEC 2. Hydrogen losses were ascribed to diffusion through membrane and tubing, and methane formation. After 1600 h of operation, the current density of the MECs had decreased to 0.6 A/m(2), probably caused by precipitation of calcium phosphate on the biocathode. The slow deteriorating effect of calcium phosphate, and the production of methane show the importance of studying the combination of bioanode and biocathode in one electrochemical cell, and of studying long term performance of such an MEC.

  10. Microbial fuel cells: novel microbial physiologies and engineering approaches.

    PubMed

    Lovley, Derek R

    2006-06-01

    The possibility of generating electricity with microbial fuel cells has been recognized for some time, but practical applications have been slow to develop. The recent development of a microbial fuel cell that can harvest electricity from the organic matter stored in marine sediments has demonstrated the feasibility of producing useful amounts of electricity in remote environments. Further study of these systems has led to the discovery of microorganisms that conserve energy to support their growth by completely oxidizing organic compounds to carbon dioxide with direct electron transfer to electrodes. This suggests that self-sustaining microbial fuel cells that can effectively convert a diverse range of waste organic matter or renewable biomass to electricity are feasible. Significant progress has recently been made to increase the power output of systems designed to convert organic wastes to electricity, but substantial additional optimization will be required for large-scale electricity production.

  11. Molecular basis of cell integrity and morphogenesis in Saccharomyces cerevisiae.

    PubMed Central

    Cid, V J; Durán, A; del Rey, F; Snyder, M P; Nombela, C; Sánchez, M

    1995-01-01

    In fungi and many other organisms, a thick outer cell wall is responsible for determining the shape of the cell and for maintaining its integrity. The budding yeast Saccharomyces cerevisiae has been a useful model organism for the study of cell wall synthesis, and over the past few decades, many aspects of the composition, structure, and enzymology of the cell wall have been elucidated. The cell wall of budding yeasts is a complex and dynamic structure; its arrangement alters as the cell grows, and its composition changes in response to different environmental conditions and at different times during the yeast life cycle. In the past few years, we have witnessed a profilic genetic and molecular characterization of some key aspects of cell wall polymer synthesis and hydrolysis in the budding yeast. Furthermore, this organism has been the target of numerous recent studies on the topic of morphogenesis, which have had an enormous impact on our understanding of the intracellular events that participate in directed cell wall synthesis. A number of components that direct polarized secretion, including those involved in assembly and organization of the actin cytoskeleton, secretory pathways, and a series of novel signal transduction systems and regulatory components have been identified. Analysis of these different components has suggested pathways by which polarized secretion is directed and controlled. Our aim is to offer an overall view of the current understanding of cell wall dynamics and of the complex network that controls polarized growth at particular stages of the budding yeast cell cycle and life cycle. PMID:7565410

  12. Interaction between lanthanide ions and Saccharomyces cerevisiae cells.

    PubMed

    Ene, Cristian D; Ruta, Lavinia L; Nicolau, Ioana; Popa, Claudia V; Iordache, Virgil; Neagoe, Aurora D; Farcasanu, Ileana C

    2015-10-01

    Lanthanides are a group of non-essential elements with important imaging and therapeutic applications. Although trivalent lanthanide ions (Ln³⁺) are used as potent blockers of Ca²⁺ channels, the systematic studies correlating Ln³⁺ accumulation and toxicity to Ca²⁺ channel blocking activity are scarce. In this study, we made use of the eukaryotic model Saccharomyces cerevisiae to investigate the correlation between Ln³⁺ accumulation, their toxicity and their capacity to block the exogenous stress-induced Ca²⁺ influx into the cytosol. It was found that the Ln³⁺ blocked the Ca²⁺ entry into the yeast cells only when present at concentration high enough to allow rapid binding to cell surface. At lower concentrations, Ln³⁺ were taken up by the cell, but Ca²⁺ blockage was no longer achieved. At 1 mM concentration, all ions from the Ln³⁺ series could block Ca²⁺ entry into cytosol with the exception of La³⁺, and to a lesser extent, Pr³⁺ and Nd³⁺. The plasma membrane Ca²⁺-channel Cch1/Mid1 contributed to La³⁺ and Gd³⁺ entry into the cells, with a significant preference for La³⁺. The results open the possibility to obtain cells loaded with controlled amounts and ratios of Ln³⁺.

  13. Effects of organic and inorganic additives on flotation recovery of washed cells of Saccharomyces cerevisiae resuspended in water.

    PubMed

    DeSousa, Sandro Rogério; Laluce, Cecilia; Jafelicci, Miguel

    2006-03-01

    Separation of microbial cells by flotation recovery is usually carried out in industrial reactors or wastewater treatment systems, which contain a complex mixture of microbial nutrients and excretion products. In the present study, the separation of yeast cells by flotation recovery was carried out using a simple flotation recovery systems containing washed yeast cells resuspended in water in order to elucidate the effects of additives (defined amounts of organic and inorganic acids, ethanol, surfactants and sodium chloride) on the cellular interactions at interfaces (cell/aqueous phase and cell/air bubble). When sodium chloride, organic acids (notably propionic, succinic and acetic acids) and organic surfactants (sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB) and Nonidet P40) were added to the flotation recovery system, significant increases in the cell recovery of yeast hydrophobic cells (Saccharomyces cerevisiae, strain FLT-01) were observed. The association of ethanol to acetic acid solution (a minor by-product of alcoholic fermentation) in the flotation recovery system, containing washed cells of strain FLT-01 resuspended in water, leading to an increased flotation recovery at pH 5.5. Thus, the association among products of the cellular metabolism (e.g., ethanol and acetic acid) can improve yeast cell recovery by flotation recovery.

  14. Cell size and budding during starvation of the yeast Saccharomyces cerevisiae.

    PubMed Central

    Johnston, G C

    1977-01-01

    When starved for nitrogen, cells of the yeast Saccharomyces cerevisiae produced abnormally small cells. Nonetheless, during starvation, only cells of a size characteristic of growing cells were capable of initiating a bud. Even when growth was severely limited, some event(s) in G1 required growth to a critical size for completion. PMID:334753

  15. Effects of low-intensity ultrasound on the growth, cell membrane permeability and ethanol tolerance of Saccharomyces cerevisiae.

    PubMed

    Dai, Chunhua; Xiong, Feng; He, Ronghai; Zhang, Weiwei; Ma, Haile

    2017-05-01

    Effects of low-intensity ultrasound (at different frequency, treatment time and power) on Saccharomyces cerevisiae in different growth phase were evaluated by the biomass in the paper. In addition, the cell membrane permeability and ethanol tolerance of sonicated Saccharomyces cerevisiae were also researched. The results revealed that the biomass of Saccharomyces cerevisiae increased by 127.03% under the optimum ultrasonic conditions such as frequency 28kHz, power 140W/L and ultrasonic time 1h when Saccharomyces cerevisiae cultured to the latent anaphase. And the membrane permeability of Saccharomyces cerevisiae in latent anaphase enhanced by ultrasound, resulting in the augment of extracellular protein, nucleic acid and fructose-1,6-diphosphate (FDP) contents. In addition, sonication could accelerate the damage of high concentration alcohol to Saccharomyces cerevisiae although the ethanol tolerance of Saccharomyces cerevisiae was not affected significantly by ultrasound.

  16. Changes of Saccharomyces cerevisiae cell membrane components and promotion to ethanol tolerance during the bioethanol fermentation.

    PubMed

    Dong, Shi-Jun; Yi, Chen-Feng; Li, Hao

    2015-12-01

    During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane might provide main protection to tolerate accumulated ethanol, and S. cerevisiae cells might also remodel their membrane compositions or structure to try to adapt to or tolerate the ethanol stress. However, the exact changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation still remains poorly understood. This study was performed to clarify changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation. Both cell diameter and membrane integrity decreased as fermentation time lasting. Moreover, compared with cells at lag phase, cells at exponential and stationary phases had higher contents of ergosterol and oleic acid (C18:1) but lower levels of hexadecanoic (C16:0) and palmitelaidic (C16:1) acids. Contents of most detected phospholipids presented an increase tendency during fermentation process. Increased contents of oleic acid and phospholipids containing unsaturated fatty acids might indicate enhanced cell membrane fluidity. Compared with cells at lag phase, cells at exponential and stationary phases had higher expressions of ACC1 and HFA1. However, OLE1 expression underwent an evident increase at exponential phase but a decrease at following stationary phase. These results indicated that during bioethanol fermentation process, yeast cells remodeled membrane and more changeable cell membrane contributed to acquiring higher ethanol tolerance of S. cerevisiae cells. These results highlighted our knowledge about relationship between the variation of cell membrane structure and compositions and ethanol tolerance, and would contribute to a better understanding of bioethanol fermentation process and construction of industrial ethanologenic strains with higher ethanol tolerance.

  17. Analysis of Cell Cycle Progression in Saccharomyces cerevisiae Using the Budding Index and Tubulin Staining.

    PubMed

    Muñoz-Barrera, Marta; Monje-Casas, Fernando

    2017-01-01

    The budding index and the morphology of the spindle and the nucleus are excellent markers for the analysis of the progression through the different stages of the cell cycle in Saccharomyces cerevisiae. Here, we describe a protocol to evaluate the budding index in this model organism using phase contrast microscopy. We also describe an indirect immunofluorescence method designed for the visualization of microtubules and the nucleus in S. cerevisiae. Finally, we explain how both methodologies can be used in order to analyze cell cycle progression in the budding yeast.

  18. Bioconversion of lactose/whey to fructose diphosphate with recombinant Saccharomyces cerevisiae cells

    SciTech Connect

    Compagno, C.; Tura, A.; Ranzi, B.M.; Martegani, E. )

    1993-07-01

    Genetically engineered Saccharomyces cerevisiae strains that express Escherichia coli [beta]-galactosidase gene are able to bioconvert lactose or whey into fructose-1,6-diphosphate (FDP). High FDP yields from whey were obtained with an appropriate ratio between cell concentration and inorganic phosphate. The biomass of transformed cells can be obtained from different carbon sources, according to the expression vector bearing the lacZ gene. The authors showed that whey can be used as the carbon source for S. cerevisiae growth and as the substrate for bioconversion to fructose diphosphate.

  19. A novel approach to regulate cell membrane permeability for ATP and NADH formation in Saccharomyces cerevisiae induced by air cold plasma

    NASA Astrophysics Data System (ADS)

    Xiaoyu, DONG; Tingting, LIU; Yuqin, XIONG

    2017-02-01

    Air cold plasma has been used as a novel method for enhancing microbial fermentation. The aim of this work was to explore the effect of plasma on membrane permeability and the formation of ATP and NADH in Saccharomyces cerevisiae, so as to provide valuable information for large-scale application of plasma in the fermentation industry. Suspensions of S. cerevisiae cells were exposed to air cold plasma for 0, 1, 2, 3, 4 and 5 min, and then subjected to various analyses prior to fermentation (0 h) and at the 9 and 21 h stages of fermentation. Compared with non-exposed cells, cells exposed to plasma for 1 min exhibited a marked increase in cytoplasmic free Ca2+ concentration as a result of the significant increase in membrane potential prior to fermentation. At the same time, the ATP level in the cell suspension decreased by about 40%, resulting in a reduction of about 60% in NADH prior to culturing. However, the levels of ATP and NADH in the culture at the 9 and 21 h fermentation stages were different from the level at 0 h. Taken together, the results indicated that exposure of S. cerevisiae to air cold plasma could increase its cytoplasmic free Ca2+ concentration by improving the cell membrane potential, consequently leading to changes in ATP and NADH levels. Supported by National Natural Science Foundation of China (Nos. 21246012, 21306015 and 21476032).

  20. Why should cell biologists study microbial pathogens?

    PubMed

    Welch, Matthew D

    2015-12-01

    One quarter of all deaths worldwide each year result from infectious diseases caused by microbial pathogens. Pathogens infect and cause disease by producing virulence factors that target host cell molecules. Studying how virulence factors target host cells has revealed fundamental principles of cell biology. These include important advances in our understanding of the cytoskeleton, organelles and membrane-trafficking intermediates, signal transduction pathways, cell cycle regulators, the organelle/protein recycling machinery, and cell-death pathways. Such studies have also revealed cellular pathways crucial for the immune response. Discoveries from basic research on the cell biology of pathogenesis are actively being translated into the development of host-targeted therapies to treat infectious diseases. Thus there are many reasons for cell biologists to incorporate the study of microbial pathogens into their research programs.

  1. Analysis of rumen microbial populations in lactating dairy cattle fed diets varying in carbohydrate profiles and Saccharomyces cerevisiae fermentation product.

    PubMed

    Mullins, C R; Mamedova, L K; Carpenter, A J; Ying, Y; Allen, M S; Yoon, I; Bradford, B J

    2013-09-01

    The rumen microbial ecosystem is a critical factor that links diets to bovine physiology and productivity; however, information about dietary effects on microbial populations has generally been limited to small numbers of samples and qualitative assessment. To assess whether consistent shifts in microbial populations occur in response to common dietary manipulations in dairy cattle, samples of rumen contents were collected from 2 studies for analysis by quantitative real-time PCR (qPCR). In one study, lactating Holstein cows (n=8) were fed diets in which a nonforage fiber source replaced an increasing proportion of forages and concentrates in a 4×4 Latin square design, and samples of ruminal digesta were collected at 9-h intervals over 3 d at the end of each period. In the second study, lactating Holstein cows (n=15) were fed diets with or without the inclusion of a Saccharomyces cerevisiae fermentation product (SCFP) in a crossover design. In this study, rumen liquid and solid samples were collected during total rumen evacuations before and after feeding in a 42-h period. In total, 146 samples of ruminal digesta were used for microbial DNA isolation and analysis by qPCR. Validated primer sets were used to quantify total bacterial and anaerobic fungal populations as well as 12 well-studied bacterial taxa. The relative abundance of the target populations was similar to those previously reported. No significant treatment effects were observed for any target population. A significant interaction of treatment and dry matter intake was observed, however, for the abundance of Eubacterium ruminantium. Increasing dry matter intake was associated with a quadratic decrease in E. ruminantium populations in control animals but with a quadratic increase in E.ruminantium populations in cows fed SCFP. Analysis of sample time effects revealed that Fibrobacter succinogenes and fungal populations were more abundant postfeeding, whereas Ruminococcus albus tended to be more abundant

  2. Cell wall dynamics modulate acetic acid-induced apoptotic cell death of Saccharomyces cerevisiae

    PubMed Central

    Rego, António; Duarte, Ana M.; Azevedo, Flávio; Sousa, Maria J.; Côrte-Real, Manuela; Chaves, Susana R.

    2014-01-01

    Acetic acid triggers apoptotic cell death in Saccharomyces cerevisiae, similar to mammalian apoptosis. To uncover novel regulators of this process, we analyzed whether impairing MAPK signaling affected acetic acid-induced apoptosis and found the mating-pheromone response and, especially, the cell wall integrity pathways were the major mediators, especially the latter, which we characterized further. Screening downstream effectors of this pathway, namely targets of the transcription factor Rlm1p, highlighted decreased cell wall remodeling as particularly important for acetic acid resistance. Modulation of cell surface dynamics therefore emerges as a powerful strategy to increase acetic acid resistance, with potential application in industrial fermentations using yeast, and in biomedicine to exploit the higher sensitivity of colorectal carcinoma cells to apoptosis induced by acetate produced by intestinal propionibacteria. PMID:28357256

  3. Expression of a Dianthus flavonoid glucosyltransferase in Saccharomyces cerevisiae for whole-cell biocatalysis.

    PubMed

    Werner, Sean R; Morgan, John A

    2009-07-15

    Glycosyltransferases are promising biocatalysts for the synthesis of small molecule glycosides. In this study, Saccharomyces cerevisiae expressing a flavonoid glucosyltransferase (GT) from Dianthus caryophyllus (carnation) was investigated as a whole-cell biocatalyst. Two yeast expression systems were compared using the flavonoid naringenin as a model substrate. Under in vitro conditions, naringenin-7-O-glucoside was formed and a higher specific glucosyl transfer activity was found using a galactose inducible expression system compared to a constitutive expression system. However, S. cerevisiae expressing the GT constitutively was significantly more productive than the galactose inducible system under in vivo conditions. Interestingly, the glycosides were recovered directly from the culture broth and did not accumulate intracellularly. A previously uncharacterized naringenin glycoside formed using the D. caryophyllus GT was identified as naringenin-4'-O-glucoside. It was found that S. cerevisiae cells hydrolyze naringenin-7-O-glucoside during whole-cell biocatalysis, resulting in a low final glycoside titer. When phloretin was added as a substrate to the yeast strain expressing the GT constitutively, the natural product phlorizin was formed. This study demonstrates S. cerevisiae is a promising whole-cell biocatalyst host for the production of valuable glycosides.

  4. Recovery of Saccharomyces cerevisiae sublethally injured cells after Pulsed Electric Fields.

    PubMed

    Somolinos, M; Mañas, P; Condón, S; Pagán, R; García, D

    2008-07-31

    The objective was to investigate the influence of the recovery liquid medium on the repair of Saccharomyces cerevisiae sublethally injured cells after Pulsed Electric Fields (PEF) in media of different pH. Sublethal injury was detected in the yeast S. cerevisiae after 50 pulses at 12.0 kV cm(-1) in both pH 4.0 and 7.0, by using a selective medium plating technique. PEF treatments cause a repairable sublethal injury in S. cerevisiae. Injured cells showed their maximum repair capacity when suspended in Sabouraud Broth compared to Peptone Water or citrate-phosphate buffer of pH 4.0. The extent to which cells repair their injuries depended on the treatment medium pH, and on the nature of the storage medium. No repair was detected when the recovery liquid medium was citrate-phosphate buffer of pH 7.0. Acid conditions favour repair and survival of PEF-treated S. cerevisiae cells. This work contributes to the description of the mechanisms of PEF injury and inactivation, which would be useful in defining adequate PEF treatments, alone or in combination with additional hurdles, to assure food stability.

  5. [Advances in microbial solar cells--A review].

    PubMed

    Guo, Xiaoyun; Yu, Changping; Zheng, Tianling

    2015-08-04

    The energy crisis has become one of the major problems hindering the development of the world. The emergence of microbial fuel cells provides a new solution to the energy crisis. Microbial solar cells, integrating photosynthetic organisms such as plants and microalgae into microbial fuel cells, can convert solar energy into electrical energy. Microbial solar cell has steady electric energy, and broad application prospects in wastewater treatment, biodiesel processing and intermediate metabolites production. Here we reviewed recent progress of microbial solar cells from the perspective of the role of photosynthetic organisms in microbial fuel cells, based on a vast amount of literature, and discussed their advantages and deficiency. At last, brief analysis of the facing problems and research needs of microbial fuel cells are undertaken. This work was expected to be beneficial for the application of the microbial solar cells technology.

  6. Autonomous, Retrievable, Deep Sea Microbial Fuel Cell

    NASA Astrophysics Data System (ADS)

    Richter, K.

    2014-12-01

    Microbial fuel cells (MFCs) work by providing bacteria in anaerobic sediments with an electron acceptor (anode) that stimulates metabolism of organic matter. The buried anode is connected via control circuitry to a cathode exposed to oxygen in the overlying water. During metabolism, bacteria release hydrogen ions into the sediment and transfer electrons extra-cellularly to the anode, which eventually reduce dissolved oxygen at the cathode, forming water. The open circuit voltage is approximately 0.8 v. The voltage between electrodes is operationally kept at 0.4 v with a potentiastat. The current is chiefly limited by the rate of microbial metabolism at the anode. The Office of Naval Research has encouraged development of microbial fuel cells in the marine environment at a number of academic and naval institutions. Earlier work in shallow sediments of San Diego Bay showed that the most important environmental parameters that control fuel cell power output in San Diego Bay were total organic carbon in the sediment and seasonal water temperature. Current MFC work at SPAWAR includes extension of microbial fuel cell tests to the deep sea environment (>1000 m) and, in parallel, testing microbial fuel cells in the laboratory under deep sea conditions. One question we are asking is whether MFC power output from deep water sediments repressurized and chilled in the laboratory comparable to those measured in situ. If yes, mapping the power potential of deep sea sediments may be made much easier, requiring sediment grabs and lab tests rather than deployment and retrieval of fuel cells. Another question we are asking is whether in situ temperature and total organic carbon in the deep sea sediment can predict MFC power. If yes, then we can make use of the large collection of publicly available, deep sea oceanographic measurements to make these predictions, foregoing expensive work at sea. These regressions will be compared to those derived from shallow water measurements.

  7. Interval scanning photomicrography of microbial cell populations.

    NASA Technical Reports Server (NTRS)

    Casida, L. E., Jr.

    1972-01-01

    A single reproducible area of the preparation in a fixed focal plane is photographically scanned at intervals during incubation. The procedure can be used for evaluating the aerobic or anaerobic growth of many microbial cells simultaneously within a population. In addition, the microscope is not restricted to the viewing of any one microculture preparation, since the slide cultures are incubated separately from the microscope.

  8. Single-cell transcriptomics for microbial eukaryotes.

    PubMed

    Kolisko, Martin; Boscaro, Vittorio; Burki, Fabien; Lynn, Denis H; Keeling, Patrick J

    2014-11-17

    One of the greatest hindrances to a comprehensive understanding of microbial genomics, cell biology, ecology, and evolution is that most microbial life is not in culture. Solutions to this problem have mainly focused on whole-community surveys like metagenomics, but these analyses inevitably loose information and present particular challenges for eukaryotes, which are relatively rare and possess large, gene-sparse genomes. Single-cell analyses present an alternative solution that allows for specific species to be targeted, while retaining information on cellular identity, morphology, and partitioning of activities within microbial communities. Single-cell transcriptomics, pioneered in medical research, offers particular potential advantages for uncultivated eukaryotes, but the efficiency and biases have not been tested. Here we describe a simple and reproducible method for single-cell transcriptomics using manually isolated cells from five model ciliate species; we examine impacts of amplification bias and contamination, and compare the efficacy of gene discovery to traditional culture-based transcriptomics. Gene discovery using single-cell transcriptomes was found to be comparable to mass-culture methods, suggesting single-cell transcriptomics is an efficient entry point into genomic data from the vast majority of eukaryotic biodiversity.

  9. Microbial fuel cells for biosensor applications.

    PubMed

    Yang, Huijia; Zhou, Minghua; Liu, Mengmeng; Yang, Weilu; Gu, Tingyue

    2015-12-01

    Microbial fuel cells (MFCs) face major hurdles for real-world applications as power generators with the exception of powering small sensor devices. Despite tremendous improvements made in the last two decades, MFCs are still too expensive to build and operate and their power output is still too small. In view of this, in recently years, intensive researches have been carried out to expand the applications into other areas such as acid and alkali production, bioremediation of aquatic sediments, desalination and biosensors. Unlike power applications, MFC sensors have the immediate prospect to be practical. This review covers the latest developments in various proposed biosensor applications using MFCs including monitoring microbial activity, testing biochemical oxygen demand, detection of toxicants and detection of microbial biofilms that cause biocorrosion.

  10. Ethanol production from nonsterilized carob pod extract by free and immobilized Saccharomyces cerevisiae cells using fed-batch culture

    SciTech Connect

    Roukas, T. . Dept. of Food Science and Technology)

    1994-02-05

    The production of ethanol from carob pod extract by free and immobilized Saccharomyces cerevisiae cells in batch and fed-batch culture was investigated. Fed-batch culture proved to be a better fermentation system for the production of ethanol than batch culture. In fed-batch culture, both free and immobilized S. cerevisiae cells gave the same maximum concentration of final ethanol at an initial sugar concentration of 300 g/L and F = 167 mL/h. The maximum ethanol productivity was obtained with both free and immobilized cells at a substrate concentration of 300 g/L and F = 334 mL/h. In repeated fed-batch culture, immobilized S. cerevisiae cells gave a higher overall ethanol concentration compared with the free cells. The immobilized S. cerevisiae cells in Ca-alginate beads retained their ability to produce ethanol for 10 days.

  11. Membrane fluidity sensoring microbial fuel cell.

    PubMed

    Choi, Youngjin; Jung, Eunkyoung; Kim, Sunghyun; Jung, Seunho

    2003-04-01

    A study has been performed to examine the effect of temperature and ethanolic stresses on the coulombic efficiency of a microbial fuel cell. The conventional-type fuel cell containing Gram-negative bacteria, Proteus vulgaris, was investigated as a model system. From current output measurements, it was found that the coulombic yields were altered by environmental stresses such as temperature shock or ethanol treatment to the bacteria. While high-temperature or ethanolic shock led to a remarkable decrement in coulombic output, the low-temperature shock induced a slight increase in microbial fuel cell efficiency. These results indicate that the membrane fluidity is affected considerably by environmental stress, which in turn affects the electron transfer process through the bacterial cell membrane to and from the electrode. This interpretation was confirmed by the cyclic voltammetric study of a mediator on an electrode surface modified with the lipids extracted from the membrane of P. vulgaris under the given stress. Markedly different electrochemical behaviors were observed depending on the environmental stress. A reciprocal relationship between coulomb output and the ratio of saturation/unsaturation of fatty acids has been observed. This is the first report, to our knowledge, that the structural adaptation of membrane fatty acids in response to the environmental shock can regulate the coulombic efficiency of a microbial fuel cell.

  12. A theoretical study of the thermodynamics of microbial growth using Saccharomyces cerevisiae and a different free energy equation.

    PubMed

    Battley, Edwin H

    2013-06-01

    Microbial growth is a biological process that has been previously treated as a chemical reaction operating in accord with the Gibbs free energy equation, Delta G = Delta H-T Delta S. The heat of yeast growth was the first to be measured, in 1856, by direct calorimetry of a large wine vat. Until then there was a tendency for biologists to continue with the old notion that the energy change accompanying the growth of microorganisms was reflected in the amount of heat that was produced during this process. The application of chemical thermodynamics to systems involving microbial growth did not occur until much later. The full application of the Gibbs equation to microbial growth did not take place until the experimental measurement of yeast cell entropy was made in 1997 Further investigations then showed that the quantity of thermal energy for solid substances represented by TS was twice that of the quantity of thermal energy represented by Qab that is experimentally necessary to raise T of a substance from 0/K to T/K. Since there can only be one value for this, the use of the equation Delta X = Delta H-Delta Qab was investigated with respect to microbial growth, and is described in this review.

  13. From microbial communities to cells

    NASA Technical Reports Server (NTRS)

    Margulis, L.

    1985-01-01

    The eukraotic cell, the unit of structure of protoctists, plants, fungi, and animals, is not at all homologous to prokaryotic cells. Instead the eukaryotic cell is homologous to communities of microorganisms such as those of the sulfuretum. This research is based on the hypothesis that at least four different interacting community members entered the original associations that, when stabilized, led to the emergence of eukaryotic cells. These are: (1) host nucleocytoplasm (thermoplasma like archaebacteria); (2) mitochrondria (paracoccus or bdellovibryo like respiring bacteria; and (3) plastids (cyanobacteria) and undulipodia. Tubulin like protein was found in the free living spirochete Spirochaeta bajacaliforniensis and in several other spirochetes. The amino acid sequence was to see if the spirochete protein is homologous to the tubulin of undulipodial and mitotic spindle microtubules.

  14. Preparation of a Saccharomyces cerevisiae cell-free extract for in vitro translation.

    PubMed

    Wu, Cheng; Sachs, Matthew S

    2014-01-01

    Eukaryotic cell-free in vitro translation systems have been in use since the 1970s. These systems can faithfully synthesize polypeptides when programmed with mRNA, enabling the production of polypeptides for analysis as well as permitting analyses of the cis- and trans-acting factors that regulate translation. Here we describe the preparation and use of cell-free translation systems from the yeast Saccharomyces cerevisiae.

  15. Wireless sensors powered by microbial fuel cells.

    PubMed

    Shantaram, Avinash; Beyenal, Haluk; Raajan, Raaja; Veluchamy, Angathevar; Lewandowski, Zbigniew

    2005-07-01

    Monitoring parameters characterizing water quality, such as temperature, pH, and concentrations of heavy metals in natural waters, is often followed by transmitting the data to remote receivers using telemetry systems. Such systems are commonly powered by batteries, which can be inconvenient at times because batteries have a limited lifetime and must be recharged or replaced periodically to ensure that sufficient energy is available to power the electronics. To avoid these inconveniences, a microbial fuel cell was designed to power electrochemical sensors and small telemetry systems to transmit the data acquired by the sensors to remote receivers. The microbial fuel cell was combined with low-power, high-efficiency electronic circuitry providing a stable power source for wireless data transmission. To generate enough power for the telemetry system, energy produced by the microbial fuel cell was stored in a capacitor and used in short bursts when needed. Since commercial electronic circuits require a minimum 3.3 V input and our cell was able to deliver a maximum of 2.1 V, a DC-DC converter was used to boost the potential. The DC-DC converter powered a transmitter, which gathered the data from the sensor and transmitted it wirelessly to a remote receiver. To demonstrate the utility of the system, temporal variations in temperature were measured, and the data were wirelessly transmitted to a remote receiver.

  16. Exoelectrogenic bacteria that power microbial fuel cells.

    PubMed

    Logan, Bruce E

    2009-05-01

    There has been an increase in recent years in the number of reports of microorganisms that can generate electrical current in microbial fuel cells. Although many new strains have been identified, few strains individually produce power densities as high as strains from mixed communities. Enriched anodic biofilms have generated power densities as high as 6.9 W per m(2) (projected anode area), and therefore are approaching theoretical limits. To understand bacterial versatility in mechanisms used for current generation, this Progress article explores the underlying reasons for exocellular electron transfer, including cellular respiration and possible cell-cell communication.

  17. Microbial fuel cell with improved anode

    DOEpatents

    Borole, Abhijeet P.

    2010-04-13

    The present invention relates to a method for preparing a microbial fuel cell, wherein the method includes: (i) inoculating an anodic liquid medium in contact with an anode of the microbial fuel cell with one or more types of microorganisms capable of functioning by an exoelectrogenic mechanism; (ii) establishing a biofilm of the microorganisms on and/or within the anode along with a substantial absence of planktonic forms of the microorganisms by substantial removal of the planktonic microorganisms during forced flow and recirculation conditions of the anodic liquid medium; and (iii) subjecting the microorganisms of the biofilm to a growth stage by incorporating one or more carbon-containing nutritive compounds in the anodic liquid medium during biofilm formation or after biofilm formation on the anode has been established.

  18. Molecular characterization of propolis-induced cell death in Saccharomyces cerevisiae.

    PubMed

    de Castro, Patrícia Alves; Savoldi, Marcela; Bonatto, Diego; Barros, Mário Henrique; Goldman, Maria Helena S; Berretta, Andresa A; Goldman, Gustavo Henrique

    2011-03-01

    Propolis, a natural product of plant resins, is used by the bees to seal holes in their honeycombs and protect the hive entrance. However, propolis has also been used in folk medicine for centuries. Here, we apply the power of Saccharomyces cerevisiae as a model organism for studies of genetics, cell biology, and genomics to determine how propolis affects fungi at the cellular level. Propolis is able to induce an apoptosis cell death response. However, increased exposure to propolis provides a corresponding increase in the necrosis response. We showed that cytochrome c but not endonuclease G (Nuc1p) is involved in propolis-mediated cell death in S. cerevisiae. We also observed that the metacaspase YCA1 gene is important for propolis-mediated cell death. To elucidate the gene functions that may be required for propolis sensitivity in eukaryotes, the full collection of about 4,800 haploid S. cerevisiae deletion strains was screened for propolis sensitivity. We were able to identify 138 deletion strains that have different degrees of propolis sensitivity compared to the corresponding wild-type strains. Systems biology revealed enrichment for genes involved in the mitochondrial electron transport chain, vacuolar acidification, negative regulation of transcription from RNA polymerase II promoter, regulation of macroautophagy associated with protein targeting to vacuoles, and cellular response to starvation. Validation studies indicated that propolis sensitivity is dependent on the mitochondrial function and that vacuolar acidification and autophagy are important for yeast cell death caused by propolis.

  19. Endomitotic effect of a cell cycle mutation of Saccharomyces cerevisiae

    SciTech Connect

    Schild, D.; Ananthaswamy, H.N.; Mortimer, R.K.

    1981-03-01

    A recessive temperature-sensitive mutation of Saccharomyces cerevisiae has been isolated and shown to cause an increase in ploidy in both haploids and diploids. Genetic analysis revealed that the strain carrying the mutation was an aa diploid, although MNNG mutagenesis had been done on an a haploid strain. When the mutant strain was crossed with an ..cap alpha cap alpha.. diploid and the resultant tetraploid sporulated, some of the meiotic progeny of this tetraploid were themselves tetraploid, as shown by both genetic analysis and DNA measurements, instead of diploid as expected of tetraploid meiosis. The ability of these tetraploids to continue to produce tetraploid meiotic progeny was followed for four generations. It was found that tetraploidization was independent of sporulation temperature, but was dependent on the temperature of germination and the growth of the spores. Increase in ploidy occurred when the spores were germinated and grown at 30/sup 0/, but did not occur at 23/sup 0/. Two cycles of sporulation and growth at 23/sup 0/ resulted in haploids, which were shown to diploidize within 24 hr when grown at 30/sup 0/.

  20. Growth performance and gastrointestinal microbial ecology responses of piglets receiving Saccharomyces cerevisiae fermentation products after an oral challenge with Escherichia coli (K88).

    PubMed

    Kiarie, E; Bhandari, S; Scott, M; Krause, D O; Nyachoti, C M

    2011-04-01

    The effects of Saccharomyces cerevisiae fermentation products (YFP) on growth performance and gastrointestinal (GIT) microbial ecology in 90 weanling pigs orally challenged with Escherichia coli K88(+) (ETEC) were investigated. The YFP were an original YFP product (XPC) and a water-suspendable yeast fermentation prototype (WSYFP) from a commercial company. Treatments consisted of a negative control (NC, no in-feed or in-water additive), carbadox (AB, 55 mg of carbadox/kg of feed), XPC (in feed, 0.2%), and WSYFP (in water, 0.5, 1, or 2 g/pig per day), and each was allotted to 5 pens (3 pigs/pen). The diets met the 1998 NRC specifications. Pigs were acclimated to treatments for a 7-d period before an ETEC challenge. On d 8, blood was collected from pigs to determine the baseline packed cell volume (PCV) measurement, and pigs were orally challenged with ETEC. At various time points postchallenge, blood samples were taken, performance measures and fecal consistency scores were recorded, and gut digesta and tissue samples were taken to evaluate GIT morphology, microbial ecology, and metabolites. Preplanned contrasts were used for comparison. Pigs receiving YFP had greater ADFI than NC pigs on d 3 (424 vs. 378 g/d; P = 0.01) and d 7 (506 vs. 458 g/d; P = 0.03) postchallenge. This effect of YFP on ADFI was similar to that of AB on d 3, but pigs receiving AB ate more (576 vs. 506 g/d; P = 0.03) at d 7 than pigs receiving YFP. Pigs exhibited reduced (P < 0.001) PCV upon ETEC challenge; however, pigs receiving additives sustained a greater (P < 0.05) PCV at 72 h compared with the NC group. Compared with the NC pigs, pigs receiving YFP showed a smaller (P < 0.05) number of ileal mucosa adherent ETEC and prevalence of the order Enterobacteriales in the ileal digesta, which corresponded to less (5.09 vs. 6.97 mg/dL; P = 0.03) colonic ammonia on d 7 postchallenge. Most of the indices for ileal digesta bacterial richness and diversity were greater (P < 0.01) for YFP pigs compared

  1. Glucose Signaling-Mediated Coordination of Cell Growth and Cell Cycle in Saccharomyces Cerevisiae

    PubMed Central

    Busti, Stefano; Coccetti, Paola; Alberghina, Lilia; Vanoni, Marco

    2010-01-01

    Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their habitat and respond quickly to frequent changes in the sugar availability in the environment: the cAMP/PKA pathways (with its two branches comprising Ras and the Gpr1/Gpa2 module), the Rgt2/Snf3-Rgt1 pathway and the main repression pathway involving the kinase Snf1. The cAMP/PKA pathway plays the prominent role in responding to changes in glucose availability and initiating the signaling processes that promote cell growth and division. Snf1 (the yeast homologous to mammalian AMP-activated protein kinase) is primarily required for the adaptation of yeast cell to glucose limitation and for growth on alternative carbon source, but it is also involved in the cellular response to various environmental stresses. The Rgt2/Snf3-Rgt1 pathway regulates the expression of genes required for glucose uptake. Many interconnections exist between the diverse glucose sensing systems, which enables yeast cells to fine tune cell growth, cell cycle and their coordination in response to nutritional changes. PMID:22219709

  2. Molecular mechanisms of pyrimidine dimer excision in Saccharomyces cerevisiae: excision of dimers in cell extracts

    SciTech Connect

    Reynolds, R.J.; Love, J.D.; Friedberg, E.C.

    1981-08-01

    Cell-free extracts prepared from rad1-19, rad2-2, rad3-1, rad4-3, rad7-1, rad10-1, rad14-1, rad16-1, and cycl-1 (rad7) mutants of Saccharomyces cerevisiae all catalyze the preferential excision of thymine-containing pyrimidine dimers from ultraviolet-irradiated DNA specifically incised with M. luteus ultraviolet deoxyribonucleic acid incising activity.

  3. Involvement of Rho-type GTPase in control of cell size in Saccharomyces cerevisiae.

    PubMed

    Kikuchi, Yo; Mizuuchi, Eri; Nogami, Satoru; Morishita, Shinichi; Ohya, Yoshikazu

    2007-06-01

    Maintaining specific cell size, which is important for many organisms, is achieved by coordinating cell growth and cell division. In the budding yeast Saccharomyces cerevisiae, the existence of two cell-size checkpoints is proposed: at the first checkpoint, cell size is monitored before budding at the G1/S transition, and at the second checkpoint, actin depolymerization occurring in the small bud is monitored before the G2/M transition. Morphological analyses have revealed that the small GTPase Rho1p participates in cell-size control at both the G1/S and the G2/M boundaries. One group of rho1 mutants (rho1A) underwent premature entry into mitosis, leading to the birth of abnormally small cells. In another group of rho1 mutants (rho1B), the mother cells failed to reach an appropriate size before budding, and expression of the G1 cyclin Cln2p began at an earlier phase of the cell cycle. Analyses of mutants defective in Rho1p effector proteins indicate that Skn7p, Fks1p and Mpk1p are involved in cell-size control. Thus, Rho1p and its downstream regulatory pathways are involved in controlling cell size in S. cerevisiae.

  4. Development of stress tolerant Saccharomyces cerevisiae strains by metabolic engineering: New aspects from cell flocculation and zinc supplementation.

    PubMed

    Cheng, Cheng; Zhang, Mingming; Xue, Chuang; Bai, Fengwu; Zhao, Xinqing

    2017-02-01

    Budding yeast Saccharomyces cerevisiae is widely studied for the production of biofuels from lignocellulosic biomass. However, economic production is currently challenged by the repression of cell growth and compromised fermentation performance of S. cerevisiae strains in the presence of various environmental stresses, including toxic level of final products, inhibitory compounds released from the pretreatment of cellulosic feedstocks, high temperature, and so on. Therefore, it is important to improve stress tolerance of S. cerevisiae to these stressful conditions to achieve efficient and economic production. In this review, the latest advances on development of stress tolerant S. cerevisiae strains are summarized, with the emphasis on the impact of cell flocculation and zinc addition. It was found that cell flocculation affected ethanol tolerance and acetic acid tolerance of S. cerevisiae, and addition of zinc to a suitable level improved stress tolerance of yeast cells to ethanol, high temperature and acetic acid. Further studies on the underlying mechanisms by which cell flocculation and zinc status affect stress tolerance will not only enrich our knowledge on stress response and tolerance mechanisms of S. cerevisiae, but also provide novel metabolic engineering strategies to develop robust yeast strains for biofuels production.

  5. Effect of Saccharomyces cerevisiae on alfalfa nutrient degradation characteristics and rumen microbial populations of steers fed diets with different concentrate-to-forage ratios

    PubMed Central

    2014-01-01

    Live yeast (Saccharomyces cerevisiae) constitutes an effective additive for animal production; its probiotic effect may be related to the concentrate-to-forage ratio (CTFR). The objective of this study was to assess the effects of S. cerevisiae (SC) on fiber degradation and rumen microbial populations in steers fed diets with different levels of dietary concentrate. Ten Simmental × Local crossbred steers (450 ± 50 kg BW) were assigned to a control group or an SC group. Both groups were fed the same basal diet but the SC group received SC supplementation (8 × 109 cfu/h/d through the ruminal fistula) following a two-period crossover design. Each period consisted of four phases, each of which lasted 17 d: 10 d for dietary adaptation, 6 d for degradation study, and 1 d for rumen sample collection. From the 1st to the 4th phase, steers were fed in a stepwise fashion with increasing CTFRs, i.e., 30:70, 50:50, 70:30, and 90:10. The kinetics of dry matter and fiber degradation of alfalfa pellets were evaluated; the rumen microbial populations were detected using real-time PCR. The results revealed no significant (P > 0.05) interactions between dietary CTFR and SC for most parameters. Dietary CTFR had a significant effect (P < 0.01) on degradation characteristics of alfalfa pellets and the copies of rumen microorganism; the increasing concentrate level resulted in linear, quadratic or cubic variation trend for these parameters. SC supplementation significantly (P < 0.05) affected dry matter (DM) and neutral detergent fiber (NDF) degradation rates (cDM, cNDF) and NDF effective degradability (EDNDF). Compared with the control group, there was an increasing trend of rumen fungi and protozoa in SC group (P < 0.1); copies of total bacteria in SC group were significantly higher (P < 0.05). Additionally, percentage of Ruminobacter amylophilus was significantly lower (P < 0.05) but percentage of Selenomonas ruminantium was significantly

  6. Recent advances in amino acid production by microbial cells.

    PubMed

    Hirasawa, Takashi; Shimizu, Hiroshi

    2016-12-01

    Amino acids have been utilized for the production of foods, animal feeds and pharmaceuticals. After the discovery of the glutamic acid-producing bacterium Corynebacterium glutamicum by Japanese researchers, the production of amino acids, which are primary metabolites, has been achieved using various microbial cells as hosts. Recently, metabolic engineering studies on the rational design of amino acid-producing microbial cells have been successfully conducted. Moreover, the technology of systems biology has been applied to metabolic engineering for the creation of amino acid-producing microbial cells. Currently, new technologies including synthetic biology, single-cell analysis, and evolutionary engineering have been utilized to create amino acid-producing microbial cells. In addition, useful compounds from amino acids have been produced by microbial cells. Here, current researches into the metabolic engineering of microbial cells toward production of amino acids and amino acid-related compounds are reviewed.

  7. Proton transfer in microbial electrolysis cells

    DOE PAGES

    Borole, Abhijeet P.; Lewis, Alex J.

    2017-02-15

    Proton transfer and electron transfer are of prime importance in the development of microbial electrochemical cells. While electron transfer is primarily controlled by biology, proton transfer is controlled by process engineering and cell design. To develop commercially feasible technologies around the concept of a bioelectrochemical cell, real feedstocks have to be explored and associated limitations have to be identified. Here in this study, the proton transfer rate was quantified for a microbial electrolysis cell (MEC) and its dependence on process parameters was investigated using a proton balance model. The reaction system consisted of a biomass-derived pyrolytic aqueous stream as amore » substrate producing hydrogen in a flow-through MEC. The proton transfer rate increased with anode flow rate and organic loading rate up to a maximum of 0.36 ± 0.01 moles per m2 per h, equivalent to a hydrogen production rate of 9.08 L per L per day. Higher rates of hydrogen production, reaching 11.7 ± 0.2 L per L per day were achieved, when additional protons were provided via the cathode buffer. Electrochemical impedance spectroscopy shows that proton transfer was the dominant resistance in the production of hydrogen. The quantification of proton transfer rates for MECs with potential for biorefinery application and the demonstration of high hydrogen production rates approaching those required for commercial consideration indicate the strong potential of this technology for renewable hydrogen production. Understanding the transport phenomenon in bioelectrochemical cells is of great significance since these systems have potential for wide-ranging applications including energy production, bioremediation, chemical and nanomaterial synthesis, electro-fermentation, energy storage, desalination, and produced water treatment. Electron transfer in anode biofilms has been investigated extensively, but proton transfer studies are also important, since many cathodic half reactions

  8. Discriminative power of fatty acid methyl ester (FAME) analysis using the microbial identification system (MIS) for Candida (Torulopsis) glabrata and Saccharomyces cerevisiae.

    PubMed

    Peltroche-Llacsahuanga, H; Schmidt, S; Lütticken, R; Haase, G

    2000-12-01

    Candida (Torulopsis) glabrata is frequently isolated in cases of fungal infection and commonly shows acquired or innate fluconazole resistance. Saccharomyces cerevisiae, an emerging opportunistic yeast pathogen, causes serious systemic infections in immunocompromised, and vaginitis and superficial infections in immunocompetent patients. For both species reliable identification in the routine laboratory is mandatory, but species identification of strains, e.g. trehalose-negative C. glabrata, may be difficult. Therefore, gas-liquid chromatography (GLC) of whole cell fatty acid methyl ester (FAME) profiles, that is independent of assimilation profiles of strains and suitable for reliable and rapid identification of clinically important yeasts, was applied. However, frequent misidentification of C. glabrata as S. cerevisiae has been reported when using the Yeast Clinical Database of MIS. Accuracy of MIS identification may be strongly influenced by the amounts of cell mass analyzed. Therefore, the present study compared the MIS results of these two yeasts achieved with different cell masses. Primarily we optimized, especially with respect to cost-effectiveness, the recommended streaking technique yielding a maximal recovery of 90-130 mg of cell mass from one plate, enabling testing of poor growing strains of C. glabrata. For all C. glabrata strains tested (n = 10) the highest identification scores (SI [Similarity Index] range 0.525-0.963, median 0.832) were achieved with 30 to 45 mg of cell mass. Only 5 of 10 S. cerevisiae strains revealed good library comparisons (SI > or = 0.5) when using 30 mg of cell mass, whereas with 45 mg all strains but two revealed this SI-level. For S. cerevisiae a higher amount of cell mass processed (up to 90 mg) was correlated with better identification scores (SI range using 90 mg: 0.464-0.870, median, 0.737). Several passages prior to FAME analysis of C. glabrata strains on recommended media revealed narrowing of SI ranges, but

  9. Quantitation of alpha-factor internalization and response during the Saccharomyces cerevisiae cell cycle.

    PubMed Central

    Zanolari, B; Riezman, H

    1991-01-01

    The alpha-factor pheromone binds to specific cell surface receptors on Saccharomyces cerevisiae a cells. The pheromone is then internalized, and cell surface receptors are down-regulated. At the same time, a signal is transmitted that causes changes in gene expression and cell cycle arrest. We show that the ability of cells to internalize alpha-factor is constant throughout the cell cycle, a cells are also able to respond to pheromone throughout the cycle even though there is cell cycle modulation of the expression of two pheromone-inducible genes, FUS1 and STE2. Both of these genes are expressed less efficiently near or just after the START point of the cell cycle in response to alpha-factor. For STE2, the basal level of expression is modulated in the same manner. Images PMID:1656226

  10. Shape recognition of microbial cells by colloidal cell imprints

    NASA Astrophysics Data System (ADS)

    Borovička, Josef; Stoyanov, Simeon D.; Paunov, Vesselin N.

    2013-08-01

    We have engineered a class of colloids which can recognize the shape and size of targeted microbial cells and selectively bind to their surfaces. These imprinted colloid particles, which we called ``colloid antibodies'', were fabricated by partial fragmentation of silica shells obtained by templating the targeted microbial cells. We successfully demonstrated the shape and size recognition between such colloidal imprints and matching microbial cells. High percentage of binding events of colloidal imprints with the size matching target particles was achieved. We demonstrated selective binding of colloidal imprints to target microbial cells in a binary mixture of cells of different shapes and sizes, which also resulted in high binding selectivity. We explored the role of the electrostatic interactions between the target cells and their colloid imprints by pre-coating both of them with polyelectrolytes. Selective binding occurred predominantly in the case of opposite surface charges of the colloid cell imprint and the targeted cells. The mechanism of the recognition is based on the amplification of the surface adhesion in the case of shape and size match due to the increased contact area between the target cell and the colloidal imprint. We also tested the selective binding for colloid imprints of particles of fixed shape and varying sizes. The concept of cell recognition by colloid imprints could be used for development of colloid antibodies for shape-selective binding of microbes. Such colloid antibodies could be additionally functionalized with surface groups to enhance their binding efficiency to cells of specific shape and deliver a drug payload directly to their surface or allow them to be manipulated using external fields. They could benefit the pharmaceutical industry in developing selective antimicrobial therapies and formulations.

  11. [Advance in producing higher alcohols by microbial cell factories].

    PubMed

    Liu, Zengran; Zhang, Guangyi

    2013-10-01

    Higher alcohols have a high energy density, low hygroscopicity and can be mixed with gasoline at any ratio. It is the trend to replace fossil fuels with biofuels produced via microbial fermentation of renewable resources. We reviewed the progress in the development of engineered Saccharomyces cerevisiae and Escherichia coli that can produce higher alcohols, as well as the related technology platforms. We mainly focused on the construction of CoA-dependent pathways and alpha-keto acid mediated non-fermentative pathways, analyzed their respective characteristics, and summarized the construction strategies. The problems to be solved and future research direction were also discussed.

  12. Genetic improvement of Saccharomyces cerevisiae wine strains for enhancing cell viability after desiccation stress.

    PubMed

    López-Martínez, Gema; Pietrafesa, Rocchina; Romano, Patrizia; Cordero-Otero, Ricardo; Capece, Angela

    2013-08-01

    In the last few decades spontaneous grape must fermentations have been replaced by inoculated fermentation with Saccharomyces cerevisiae strains as active dry yeast (ADY). Among the essential genes previously characterized to overcome the cell-drying/rehydration process, six belong to the group of very hydrophilic proteins known as hydrophilins. Among them, only SIP18 has shown early transcriptional response during dehydration stress. In fact, the overexpression in S. cerevisiae of gene SIP18 increases cell viability after the dehydration process. The purpose of this study was to characterize dehydration stress tolerance of three wild and one commercial S. cerevisiae strains of wine origin. The four strains were submitted to transformation by insertion of the gene SIP18. Selected transformants were submitted to the cell-drying-rehydration process and yeast viability was evaluated by both viable cell count and flow cytometry. The antioxidant capacity of SIP18p was illustrated by ROS accumulation reduction after H2 O2 attack. Growth data as cellular duplication times and lag times were calculated to estimate cell vitality after the cell rehydration process. The overexpressing SIP18 strains showed significantly longer time of lag phase despite less time needed to stop the leakage of intracellular compounds during the rehydration process. Subsequently, the transformants were tested in inoculated grape must fermentation at laboratory scale in comparison to untransformed strains. Chemical analyses of the resultant wines indicated that no significant change for the content of secondary compounds was detected. The obtained data showed that the transformation enhances the viability of ADY without affecting fermentation efficiency and metabolic behaviour.

  13. Invert sugar formation with Saccharomyces cerevisiae cells encapsulated in magnetically responsive alginate microparticles

    NASA Astrophysics Data System (ADS)

    Safarik, Ivo; Sabatkova, Zdenka; Safarikova, Mirka

    2009-05-01

    Invert sugar (an equimolar mixture of glucose and fructose prepared by sucrose hydrolysis) is a very important food component. We have prepared magnetically responsive alginate microbeads containing entrapped Saccharomyces cerevisiae cells and magnetite microparticles which can be easily separated in an appropriate magnetic separator. The microbeads (typical diameter between 50 and 100 μm) were prepared using the water-in-oil emulsification process. The prepared microbeads containing yeast cells with invertase activity enabled efficient sucrose conversion. The biocatalyst was quite stable; the same catalytic activity was observed after one month storage at 4 °C and the microbeads could be used at least six times.

  14. Decreased fluidity of cell membranes causes a metal ion deficiency in recombinant Saccharomyces cerevisiae producing carotenoids.

    PubMed

    Liu, Peitong; Sun, Liang; Sun, Yuxia; Shang, Fei; Yan, Guoliang

    2016-04-01

    The genome-wide transcriptional responses of S. cerevisiae to heterologous carotenoid biosynthesis were investigated using DNA microarray analysis. The results show that the genes involved in metal ion transport were specifically up-regulated in the recombinant strain, and metal ions, including Cu(2+), Fe(2+), Mn(2+), and Mg(2+), were deficient in the recombinant strain compared to the ion content of the parent strain. The decrease in metal ions was ascribed to a decrease in cell membrane (CM) fluidity caused by lower levels of unsaturated fatty acids and ergosterol. This was confirmed by the observation that metal ion levels were restored when CM fluidity was increased by supplying linoleic acid. In addition, a 24.3 % increase in the β-carotene concentration was observed. Collectively, our results suggest that heterologous production of carotenoids in S. cerevisiae can induce cellular stress by rigidifying the CM, which can lead to a deficiency in metal ions. Due to the importance of CM fluidity in cellular physiology, maintaining normal CM fluidity might be a potential approach to improving carotenoid production in genetically engineered S. cerevisiae.

  15. Dynactin is involved in a checkpoint to monitor cell wall synthesis in Saccharomyces cerevisiae.

    PubMed

    Suzuki, Masaya; Igarashi, Ryoji; Sekiya, Mizuho; Utsugi, Takahiko; Morishita, Shinichi; Yukawa, Masashi; Ohya, Yoshikazu

    2004-09-01

    Checkpoint controls ensure the completion of cell cycle events with high fidelity in the correct order. Here we show the existence of a novel checkpoint that ensures coupling of cell wall synthesis and mitosis. In response to a defect in cell wall synthesis, S. cerevisiae cells arrest the cell-cycle before spindle pole body separation. This arrest results from the regulation of the M-phase cyclin Clb2p at the transcriptional level through the transcription factor Fkh2p. Components of the dynactin complex are required to achieve the G2 arrest whilst keeping cells highly viable. Thus, the dynactin complex has a function in a checkpoint that monitors cell wall synthesis.

  16. Members of the Hsp70 family of proteins in the cell wall of Saccharomyces cerevisiae.

    PubMed Central

    López-Ribot, J L; Chaffin, W L

    1996-01-01

    Western blot (immunoblot) analysis of cell wall and cytosolic extracts obtained from parental and ssa1 and ssa2 single- and double-mutant strains of Saccharomyces cerevisiae showed that the heat shock protein 70 (Hsp70) products of these genes, previously thought to be restricted to the cell interior, are also present in the cell wall. A cell wall location was further confirmed by indirect immunofluorescence with intact cells and biotinylation of extracellular Hsp70. Hsp70s have been implicated in translocation across the membrane and as molecular chaperones, and changes in the profile of cell wall proteins suggested that these proteins may have a similar role in the cell wall. PMID:8755907

  17. Production of non-alcoholic beer using free and immobilized cells of Saccharomyces cerevisiae deficient in the tricarboxylic acid cycle.

    PubMed

    Navrátil, Marián; Dömény, Zoltán; Sturdík, Ernest; Smogrovicová, Daniela; Gemeiner, Peter

    2002-04-01

    Production of non-alcoholic beer using Saccharomyces cerevisiae has been studied. Non-recombinant mutant strains with a defect in the synthesis of tricarboxylic-acid-cycle enzymes were used and applied in both free and pectate-immobilized form, using both batch and packed-bed continuous systems. After fermentation, basic parameters of the beer produced by five mutant strains were compared with a standard strain of brewing yeast. Results showed that the beer prepared by mutant yeast cells was characterized by lower levels of total alcohols, with ethanol concentrations between 0.07 and 0.31% (w/w). The organic acids produced, especially lactic acid, in concentrations up to 1.38 g x l(-1) had a strong protective effect on the microbial stability of the final product and thus the usual addition of lactic acid could be omitted. Application of the yeast mutants appears to be a good alternative to the classical methods for the production of non-alcoholic beer.

  18. The Saccharomyces cerevisiae Fin1 protein forms cell cycle-specific filaments between spindle pole bodies.

    PubMed

    van Hemert, Martijn J; Lamers, Gerda E M; Klein, Dionne C G; Oosterkamp, Tjerk H; Steensma, H Yde; van Heusden, G Paul H

    2002-04-16

    The FIN1 gene from the yeast Saccharomyces cerevisiae encodes a basic protein with putative coiled-coil regions. Here we show that in large-budded cells a green fluorescent protein-Fin1 fusion protein is visible as a filament between the two spindle pole bodies. In resting cells the protein is undetectable, and in small-budded cells it is localized in the nucleus. During late mitosis it localizes on the spindle pole bodies. Filaments of cyano fluorescent protein-tagged Fin1 colocalize with filaments of green fluorescent protein-tagged Tub1 only in large-budded cells. By electron and atomic force microscopy we showed that purified recombinant Fin1p self-assembles into filaments with a diameter of approximately 10 nm. Our results indicate that the Fin1 protein forms a cell cycle-specific filament, additional to the microtubules, between the spindle pole bodies of dividing yeast cells.

  19. The Saccharomyces cerevisiae Fin1 protein forms cell cycle-specific filaments between spindle pole bodies

    PubMed Central

    van Hemert, Martijn J.; Lamers, Gerda E. M.; Klein, Dionne C. G.; Oosterkamp, Tjerk H.; Steensma, H. Yde; van Heusden, G. Paul H.

    2002-01-01

    The FIN1 gene from the yeast Saccharomyces cerevisiae encodes a basic protein with putative coiled-coil regions. Here we show that in large-budded cells a green fluorescent protein-Fin1 fusion protein is visible as a filament between the two spindle pole bodies. In resting cells the protein is undetectable, and in small-budded cells it is localized in the nucleus. During late mitosis it localizes on the spindle pole bodies. Filaments of cyano fluorescent protein-tagged Fin1 colocalize with filaments of green fluorescent protein-tagged Tub1 only in large-budded cells. By electron and atomic force microscopy we showed that purified recombinant Fin1p self-assembles into filaments with a diameter of ≈10 nm. Our results indicate that the Fin1 protein forms a cell cycle-specific filament, additional to the microtubules, between the spindle pole bodies of dividing yeast cells. PMID:11929974

  20. Electrochemical detection of intracellular and cell membrane redox systems in Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Rawson, Frankie J.; Downard, Alison J.; Baronian, Keith H.

    2014-06-01

    Redox mediators can interact with eukaryote cells at a number of different cell locations. While cell membrane redox centres are easily accessible, the redox centres of catabolism are situated within the cytoplasm and mitochondria and can be difficult to access. We have systematically investigated the interaction of thirteen commonly used lipophilic and hydrophilic mediators with the yeast Saccharomyces cerevisiae. A double mediator system is used in which ferricyanide is the final electron acceptor (the reporter mediator). After incubation of cells with mediators, steady state voltammetry of the ferri/ferrocyanide redox couple allows quantitation of the amount of mediator reduced by the cells. The plateau current at 425 mV vs Ag/AgCl gives the analytical signal. The results show that five of the mediators interact with at least three different trans Plasma Membrane Electron Transport systems (tPMETs), and that four mediators cross the plasma membrane to interact with cytoplasmic and mitochondrial redox molecules. Four of the mediators inhibit electron transfer from S. cerevisiae. Catabolic inhibitors were used to locate the cellular source of electrons for three of the mediators.

  1. Involvement of mitochondria and metacaspase elevation in harpin Pss-induced cell death of Saccharomyces cerevisiae.

    PubMed

    Sripriya, Paranthaman; Vedantam, Lakshmi Vasudev; Podile, Appa Rao

    2009-08-15

    Expression of a proteinaceous elicitor harpin(Pss,) encoded by hrpZ of Pseudomonas syringae pv. syringae 61, under GAL1 promoter in Saccharomyces cerevisiae Y187 resulted in galactose-inducible yeast cell death (YCD). Extracellular treatment of harpin did not affect the growth of yeast. The observed YCD was independent of the stage of cell cycle. "Petite" mutant of S. cerevisiae Y187 pYEUT-hrpZ was insensitive to cell death indicating the involvement of mitochondria in this YCD. Loss in mitochondrial potential, but no leakage of Cytochrome c from mitochondria into the cytosol, were notable features in harpin(Pss)-induced YCD. Cyclosporin A had no effect on hrpZ expressing yeast cells, further confirmed that there was no release of Cytochrome c. Elevation of caspase activity has been reported for the first time in this form of cell death induced by harpin expression. Release of reactive oxygen species and clear loss of membrane integrity were evident with the absence of nuclear fragmentation and chromosomal condensation, while annexin V and propidium iodide staining showed features typical of necrosis.

  2. Electrochemical detection of intracellular and cell membrane redox systems in Saccharomyces cerevisiae

    PubMed Central

    Rawson, Frankie J.; Downard, Alison J.; Baronian, Keith H.

    2014-01-01

    Redox mediators can interact with eukaryote cells at a number of different cell locations. While cell membrane redox centres are easily accessible, the redox centres of catabolism are situated within the cytoplasm and mitochondria and can be difficult to access. We have systematically investigated the interaction of thirteen commonly used lipophilic and hydrophilic mediators with the yeast Saccharomyces cerevisiae. A double mediator system is used in which ferricyanide is the final electron acceptor (the reporter mediator). After incubation of cells with mediators, steady state voltammetry of the ferri/ferrocyanide redox couple allows quantitation of the amount of mediator reduced by the cells. The plateau current at 425 mV vs Ag/AgCl gives the analytical signal. The results show that five of the mediators interact with at least three different trans Plasma Membrane Electron Transport systems (tPMETs), and that four mediators cross the plasma membrane to interact with cytoplasmic and mitochondrial redox molecules. Four of the mediators inhibit electron transfer from S. cerevisiae. Catabolic inhibitors were used to locate the cellular source of electrons for three of the mediators. PMID:24910017

  3. Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell

    EPA Science Inventory

    Multi-anode microbial electrochemical cells (MXCs) are considered as one of the most promising configurations for scale-up of MXCs, but fundamental understanding of anode kinetics governing current density is limited in the MXCs. In this study we first assessed microbial communi...

  4. Combining microbial cultures for efficient production of electricity from butyrate in a microbial electrochemical cell.

    PubMed

    Miceli, Joseph F; Garcia-Peña, Ines; Parameswaran, Prathap; Torres, César I; Krajmalnik-Brown, Rosa

    2014-10-01

    Butyrate is an important product of anaerobic fermentation; however, it is not directly used by characterized strains of the highly efficient anode respiring bacteria (ARB) Geobacter sulfurreducens in microbial electrochemical cells. By combining a butyrate-oxidizing community with a Geobacter rich culture, we generated a microbial community which outperformed many naturally derived communities found in the literature for current production from butyrate and rivaled the highest performing natural cultures in terms of current density (∼ 11A/m(2)) and Coulombic efficiency (∼ 70%). Microbial community analyses support the shift in the microbial community from one lacking efficient ARB in the marine hydrothermal vent community to a community consisting of ∼ 80% Geobacter in the anode biofilm. This demonstrates the successful production and adaptation of a novel microbial culture for generating electrical current from butyrate with high current density and high Coulombic efficiency, by combining two mixed microbial cultures containing complementing biochemical pathways.

  5. Energy from algae using microbial fuel cells.

    PubMed

    Velasquez-Orta, Sharon B; Curtis, Tom P; Logan, Bruce E

    2009-08-15

    Bioelectricity production from a phytoplankton, Chlorella vulgaris, and a macrophyte, Ulva lactuca was examined in single chamber microbial fuel cells (MFCs). MFCs were fed with the two algae (as powders), obtaining differences in energy recovery, degradation efficiency, and power densities. C. vulgaris produced more energy generation per substrate mass (2.5 kWh/kg), but U. lactuca was degraded more completely over a batch cycle (73 +/- 1% COD). Maximum power densities obtained using either single cycle or multiple cycle methods were 0.98 W/m(2) (277 W/m(3)) using C. vulgaris, and 0.76 W/m(2) (215 W/m(3)) using U. lactuca. Polarization curves obtained using a common method of linear sweep voltammetry (LSV) overestimated maximum power densities at a scan rate of 1 mV/s. At 0.1 mV/s, however, the LSV polarization data was in better agreement with single- and multiple-cycle polarization curves. The fingerprints of microbial communities developed in reactors had only 11% similarity to inocula and clustered according to the type of bioprocess used. These results demonstrate that algae can in principle, be used as a renewable source of electricity production in MFCs.

  6. Increasing ethanol productivity during xylose fermentation by cell recycling of recombinant Saccharomyces cerevisiae.

    PubMed

    Roca, C; Olsson, L

    2003-01-01

    The influence of cell recycling of xylose-fermenting Saccharomyces cerevisiae TMB3001 was investigated during continuous cultivation on a xylose-glucose mixture. By using cell recycling at the dilution rate ( D) of 0.05 h(-1), the cell-mass concentration could be increased from 2.2 g l(-1) to 22 g l(-1). Consequently, the volumetric ethanol productivity increased ten-fold, from 0.5 g l(-1) h(-1) to 5.35 g l(-1) h(-1). By increasing the biomass concentration, the xylose consumption rate increased from 0.75 g xylose l(-1) h(-1) without recycling to 1.9 g l(-1) h(-1) with recycling. The specific ethanol productivity was in the range of 0.23-0.26 g g(-1) h(-1) with or without cell recycling, showing that an increased cell-mass concentration did not influence the efficiency of the yeast.

  7. Microbial fuel cells and microbial electrolysis cells for the production of bioelectricity and biomaterials.

    PubMed

    Zhou, Minghua; Yang, Jie; Wang, Hongyu; Jin, Tao; Xu, Dake; Gu, Tingyue

    2013-01-01

    Today's global energy crisis requires a multifaceted solution. Bioenergy is an important part of the solution. The microbial fuel cell (MFC) technology stands out as an attractive potential technology in bioenergy. MFCs can convert energy stored in organic matter directly into bioelectricity. MFCs can also be operated in the electrolysis mode as microbial electrolysis cells to produce bioproducts such as hydrogen and ethanol. Various wastewaters containing low-grade organic carbons that are otherwise unutilized can be used as feed streams for MFCs. Despite major advances in the past decade, further improvements in MFC power output and cost reduction are needed for MFCs to be practical. This paper analysed MFC operating principles using bioenergetics and bioelectrochemistry. Several major issues were explored to improve the MFC performance. An emphasis was placed on the use of catalytic materials for MFC electrodes. Recent advances in the production of various biomaterials using MFCs were also investigated.

  8. Two stage bioethanol refining with multi litre stacked microbial fuel cell and microbial electrolysis cell.

    PubMed

    Sugnaux, Marc; Happe, Manuel; Cachelin, Christian Pierre; Gloriod, Olivier; Huguenin, Gérald; Blatter, Maxime; Fischer, Fabian

    2016-12-01

    Ethanol, electricity, hydrogen and methane were produced in a two stage bioethanol refinery setup based on a 10L microbial fuel cell (MFC) and a 33L microbial electrolysis cell (MEC). The MFC was a triple stack for ethanol and electricity co-generation. The stack configuration produced more ethanol with faster glucose consumption the higher the stack potential. Under electrolytic conditions ethanol productivity outperformed standard conditions and reached 96.3% of the theoretically best case. At lower external loads currents and working potentials oscillated in a self-synchronized manner over all three MFC units in the stack. In the second refining stage, fermentation waste was converted into methane, using the scale up MEC stack. The bioelectric methanisation reached 91% efficiency at room temperature with an applied voltage of 1.5V using nickel cathodes. The two stage bioethanol refining process employing bioelectrochemical reactors produces more energy vectors than is possible with today's ethanol distilleries.

  9. Fermentation temperature modulates phosphatidylethanolamine and phosphatidylinositol levels in the cell membrane of Saccharomyces cerevisiae.

    PubMed

    Henderson, Clark M; Zeno, Wade F; Lerno, Larry A; Longo, Marjorie L; Block, David E

    2013-09-01

    During alcoholic fermentation, Saccharomyces cerevisiae is exposed to a host of environmental and physiological stresses. Extremes of fermentation temperature have previously been demonstrated to induce fermentation arrest under growth conditions that would otherwise result in complete sugar utilization at "normal" temperatures and nutrient levels. Fermentations were carried out at 15°C, 25°C, and 35°C in a defined high-sugar medium using three Saccharomyces cerevisiae strains with diverse fermentation characteristics. The lipid composition of these strains was analyzed at two fermentation stages, when ethanol levels were low early in stationary phase and in late stationary phase at high ethanol concentrations. Several lipids exhibited dramatic differences in membrane concentration in a temperature-dependent manner. Principal component analysis (PCA) was used as a tool to elucidate correlations between specific lipid species and fermentation temperature for each yeast strain. Fermentations carried out at 35°C exhibited very high concentrations of several phosphatidylinositol species, whereas at 15°C these yeast strains exhibited higher levels of phosphatidylethanolamine and phosphatidylcholine species with medium-chain fatty acids. Furthermore, membrane concentrations of ergosterol were highest in the yeast strain that experienced stuck fermentations at all three temperatures. Fluorescence anisotropy measurements of yeast cell membrane fluidity during fermentation were carried out using the lipophilic fluorophore diphenylhexatriene. These measurements demonstrate that the changes in the lipid composition of these yeast strains across the range of fermentation temperatures used in this study did not significantly affect cell membrane fluidity. However, the results from this study indicate that fermenting S. cerevisiae modulates its membrane lipid composition in a temperature-dependent manner.

  10. Permeabilization of yeast Saccharomyces cerevisiae cell walls using nanosecond high power electrical pulses

    NASA Astrophysics Data System (ADS)

    Stirke, A.; Zimkus, A.; Balevicius, S.; Stankevic, V.; Ramanaviciene, A.; Ramanavicius, A.; Zurauskiene, N.

    2014-12-01

    The electrical field-induced changes of the yeast Saccharomyces cerevisiae cells permeabilization to tetraphenylphosphonium (TPP+) ions were studied using square-shaped, nanosecond duration high power electrical pulses. It was obtained that pulses having durations ranging from 10 ns to 60 ns, and generating electric field strengths up to 190 kV/cm significantly (up to 65 times) increase the absorption rate of TPP+ ions without any detectible influence on the yeast cell viability. The modelling of the TPP+ absorption process using a second order rate equation demonstrates that depending on the duration of the pulses, yeast cell clusters of different sizes are homogeniously permeabilized. It was concluded, that nanosecond pulse-induced permeabilization can be applied to increase the operational speed of whole cell biosensors.

  11. The immunosuppressant SR 31747 blocks cell proliferation by inhibiting a steroid isomerase in Saccharomyces cerevisiae.

    PubMed Central

    Silve, S; Leplatois, P; Josse, A; Dupuy, P H; Lanau, C; Kaghad, M; Dhers, C; Picard, C; Rahier, A; Taton, M; Le Fur, G; Caput, D; Ferrara, P; Loison, G

    1996-01-01

    SR 31747 is a novel immunosuppressant agent that arrests cell proliferation in the yeast Saccharomyces cerevisiae, SR 31747-treated cells accumulate the same aberrant sterols as those found in a mutant impaired in delta 8- delta 7-sterol isomerase. Sterol isomerase activity is also inhibited by SR 31747 in in vitro assays. Overexpression of the sterol isomerase-encoding gene, ERG2, confers enhanced SR resistance. Cells growing anaerobically on ergosterol-containing medium are not sensitive to SR. Disruption of the sterol isomerase-encoding gene is lethal in cells growing in the absence of exogenous ergosterol, except in SR-resistant mutants lacking either the SUR4 or the FEN1 gene product. The results suggest that sterol isomerase is the target of SR 31747 and that both the SUR4 and FEN1 gene products are required to mediate the proliferation arrest induced by ergosterol depletion. PMID:8649379

  12. Types of cell death and methods of their detection in yeast Saccharomyces cerevisiae.

    PubMed

    Wloch-Salamon, D M; Bem, A E

    2013-02-01

    The occurrence of programmed cell death in unicellular organisms is a subject that arouses great interest of theoreticians and experimental scientists. Already found evolutionarily conserved genes and metabolic pathways confirmed its existence in yeast, protozoa and even bacteria. In the yeast Saccharomyces cerevisiae, at least three main types of death are distinguished: apoptosis, necrosis and autophagy. Their classification suggested by the Nomenclature Committee on Cell Death initially based on the morphological characteristics has now been extended to include the measurable biochemical characteristics. Several laboratory methods previously used to detect the types of cell death of higher eucaryotes and later developed and successfully used for the analysis of yeast cells are here critically reviewed. Their advantages and limitations are described.

  13. Programming microbial population dynamics by engineered cell-cell communication.

    PubMed

    Song, Hao; Payne, Stephen; Tan, Cheemeng; You, Lingchong

    2011-07-01

    A major aim of synthetic biology is to program novel cellular behavior using engineered gene circuits. Early endeavors focused on building simple circuits that fulfill simple functions, such as logic gates, bistable toggle switches, and oscillators. These gene circuits have primarily focused on single-cell behaviors since they operate intracellularly. Thus, they are often susceptible to cell-cell variations due to stochastic gene expression. Cell-cell communication offers an efficient strategy to coordinate cellular behavior at the population level. To this end, we review recent advances in engineering cell-cell communication to achieve reliable population dynamics, spanning from communication within single species to multispecies, from one-way sender-receiver communication to two-way communication in synthetic microbial ecosystems. These engineered systems serve as well-defined model systems to better understand design principles of their naturally occurring counterparts and to facilitate novel biotechnology applications.

  14. Microbial fuel cells and microbial ecology: applications in ruminant health and production research.

    PubMed

    Bretschger, Orianna; Osterstock, Jason B; Pinchak, William E; Ishii, Shun'ichi; Nelson, Karen E

    2010-04-01

    Microbial fuel cell (MFC) systems employ the catalytic activity of microbes to produce electricity from the oxidation of organic, and in some cases inorganic, substrates. MFC systems have been primarily explored for their use in bioremediation and bioenergy applications; however, these systems also offer a unique strategy for the cultivation of synergistic microbial communities. It has been hypothesized that the mechanism(s) of microbial electron transfer that enable electricity production in MFCs may be a cooperative strategy within mixed microbial consortia that is associated with, or is an alternative to, interspecies hydrogen (H(2)) transfer. Microbial fermentation processes and methanogenesis in ruminant animals are highly dependent on the consumption and production of H(2)in the rumen. Given the crucial role that H(2) plays in ruminant digestion, it is desirable to understand the microbial relationships that control H(2) partial pressures within the rumen; MFCs may serve as unique tools for studying this complex ecological system. Further, MFC systems offer a novel approach to studying biofilms that form under different redox conditions and may be applied to achieve a greater understanding of how microbial biofilms impact animal health. Here, we present a brief summary of the efforts made towards understanding rumen microbial ecology, microbial biofilms related to animal health, and how MFCs may be further applied in ruminant research.

  15. Microbial Fuel Cells and Microbial Ecology: Applications in Ruminant Health and Production Research

    PubMed Central

    Osterstock, Jason B.; Pinchak, William E.; Ishii, Shun’ichi; Nelson, Karen E.

    2009-01-01

    Microbial fuel cell (MFC) systems employ the catalytic activity of microbes to produce electricity from the oxidation of organic, and in some cases inorganic, substrates. MFC systems have been primarily explored for their use in bioremediation and bioenergy applications; however, these systems also offer a unique strategy for the cultivation of synergistic microbial communities. It has been hypothesized that the mechanism(s) of microbial electron transfer that enable electricity production in MFCs may be a cooperative strategy within mixed microbial consortia that is associated with, or is an alternative to, interspecies hydrogen (H2) transfer. Microbial fermentation processes and methanogenesis in ruminant animals are highly dependent on the consumption and production of H2in the rumen. Given the crucial role that H2 plays in ruminant digestion, it is desirable to understand the microbial relationships that control H2 partial pressures within the rumen; MFCs may serve as unique tools for studying this complex ecological system. Further, MFC systems offer a novel approach to studying biofilms that form under different redox conditions and may be applied to achieve a greater understanding of how microbial biofilms impact animal health. Here, we present a brief summary of the efforts made towards understanding rumen microbial ecology, microbial biofilms related to animal health, and how MFCs may be further applied in ruminant research. PMID:20024685

  16. Display of wasp venom allergens on the cell surface of Saccharomyces cerevisiae

    PubMed Central

    2010-01-01

    Background Yeast surface display is a technique, where the proteins of interest are expressed as fusions with yeast surface proteins and thus remain attached to the yeast cell wall after expression. Our purpose was to study whether allergens expressed on the cell surface of baker's yeast Saccharomyces cerevisiae preserve their native allergenic properties and whether the yeast native surface glycoproteins interfere with IgE binding. We chose to use the major allergens from the common wasp Vespula vulgaris venom: phospholipase A1, hyaluronidase and antigen 5 as the model. Results The proteins were expressed on the surface as fusions with a-agglutinin complex protein AGA2. The expression was confirmed by fluorescent cytometry (FACS) after staining the cells with antibody against a C-tag attached to the C-terminal end of the allergens. Phospholipase A1 and hyaluronidase retained their enzymatic activities. Phospholipase A1 severely inhibited the growth of the yeast cells. Antigen 5 - expressing yeast cells bound IgE antibodies from wasp venom allergic patient sera but not from control sera as demonstrated by FACS. Moreover, antigen 5 - expressing yeast cells were capable of mediating allergen-specific histamine release from human basophils. Conclusions All the three major wasp venom allergens were expressed on the yeast surface. A high-level expression, which was observed only for antigen 5, was needed for detection of IgE binding by FACS and for induction of histamine release. The non-modified S. cerevisiae cells did not cause any unspecific reaction in FACS or histamine release assay despite the expression of high-mannose oligosaccharides. In perspective the yeast surface display may be used for allergen discovery from cDNA libraries and possibly for sublingual immunotherapy as the cells can serve as good adjuvant and can be produced in large amounts at a low price. PMID:20868475

  17. Yeast and carbon nanotube based biocatalyst developed by synergetic effects of covalent bonding and hydrophobic interaction for performance enhancement of membraneless microbial fuel cell.

    PubMed

    Christwardana, Marcelinus; Kwon, Yongchai

    2017-02-01

    Membraneless microbial fuel cell (MFC) employing new microbial catalyst formed as yeast cultivated from Saccharomyces cerevisiae and carbon nanotube (yeast/CNT) is suggested. To analyze its catalytic activity and performance and stability of MFC, several characterizations are performed. According to the characterizations, the catalyst shows excellent catalytic activities by facile transfer of electrons via reactions of NAD, FAD, cytochrome c and cytochrome a3, while it induces high maximum power density (MPD) (344mW·m(-2)). It implies that adoption of yeast induces increases in catalytic activity and MFC performance. Furthermore, MPD is maintained to 86% of initial value even after eight days, showing excellent MFC stability.

  18. Methanogenesis in membraneless microbial electrolysis cells.

    PubMed

    Clauwaert, Peter; Verstraete, Willy

    2009-04-01

    Operation of microbial electrolysis cells (MECs) without an ion exchange membrane could help to lower the construction costs while lowering the ohmic cell resistance and improving MEC conversion rates by minimizing the pH gradient between anode and cathode. In this research, we demonstrate that membraneless MECs with plain graphite can be operated for methane production without pH adjustment and that the ohmic cell resistance could be lowered with approximately 50% by removing the cation exchange membrane. As a result, the current production increased from 66 +/- 2 to 156 +/- 1 A m(-3) MEC by removing the membrane with an applied voltage of -0.8 V. Methane was the main energetic product despite continuous operation under carbonate-limited and slightly acidified conditions (pH 6.1-6.2). Our results suggest that continuous production of hydrogen in membraneless MECs will be challenging since methane production might not be avoided easily. The electrical energy invested was not always completely recovered under the form of an energy-rich biogas; however, our results indicate that membraneless MECs might be a viable polishing step for the treatment of the effluent of anaerobic digesters as methane was produced under low organic loading conditions and at room temperature.

  19. Changes in reactive oxygen species begin early during replicative aging of Saccharomyces cerevisiae cells.

    PubMed

    Lam, Yuen T; Aung-Htut, May T; Lim, Yu L; Yang, Hongyuan; Dawes, Ian W

    2011-04-15

    Increased reactive oxygen species (ROS) are a feature of aging cells, but little is known about when ROS generation begins as cells age. Here we show how ROS change in Saccharomyces cerevisiae cells throughout their early replicative life span using the fluorescent ROS indicator dihydroethidium (DHE), which has some specificity for the superoxide anion. Cells in a particular age range were heterogeneous with respect to their ROS burden. Surprisingly, some cells as young as 5-7 generations acquired a greatly increased level of ROS detected by DHE relative to virgin cells. By 12 generations 50% of cells had a substantial ROS burden despite being only halfway through their life span. In contrast to the wild type, cells of a sir2 mutant had lower levels of ROS reacting with DHE. Daughters from older mothers had low ROS levels, and this asymmetric distribution of ROS was SIR2-independent. Mitochondrial fragmentation also began to occur in cells after 4 generations and increased markedly as cells aged. Daughter cells regenerated normal tubular mitochondria despite the fragmentation of mitochondria in the mother cells, whereas daughters of the sir2 mutant had fragmented mitochondria at all ages.

  20. Comparative study of stability of soluble and cell wall invertase from Saccharomyces cerevisiae.

    PubMed

    Margetić, Aleksandra; Vujčić, Zoran

    2017-03-16

    Yeast Saccharomyces cerevisiae is the most significant source of enzyme invertase. It is mainly used in the food industry as a soluble or immobilized enzyme. The greatest amount of invertase is located in the periplasmic space in yeast. In this work, it was isolated into two forms of enzyme from yeast S. cerevisiae cell, soluble and cell wall invertase (CWI). Both forms of enzyme showed same temperature optimum (60°C), similar pH optimum, and kinetic parameters. The significant difference between these biocatalysts was observed in their thermal stability, stability in urea and methanol solution. At 60°C, CWI had 1.7 times longer half-life than soluble enzyme, while at 70°C CWI showed 8.7 times longer half-life than soluble enzyme. After 2-hr of incubation in 8 M urea solution, soluble invertase and CWI retained 10 and 60% of its initial activity, respectively. During 22 hr of incubation of both enzymes in 30 and 40% methanol, soluble invertase was completely inactivated, while CWI changed its activity within the experimental error. Therefore, soluble invertase and CWI have not shown any substantial difference, but CWI showed better thermal stability and stability in some of the typical protein-denaturing agents.

  1. Saccharomyces Cerevisiae Cell Wall Components as Tools for Ochratoxin A Decontamination

    PubMed Central

    Piotrowska, Małgorzata; Masek, Anna

    2015-01-01

    The aim of this study was to evaluate the usefulness of Saccharomyces cerevisiae cell wall preparations in the adsorption of ochratoxin A (OTA). The study involved the use of a brewer’s yeast cell wall devoid of protein substances, glucans obtained by water and alkaline extraction, a glucan commercially available as a dietary supplement for animals and, additionally, dried brewer’s yeast for comparison. Fourier Transform Infrared (FTIR) analysis of the obtained preparations showed bands characteristic for glucans in the resulting spectra. The yeast cell wall preparation, water-extracted glucan and the commercial glucan bound the highest amount of ochratoxin A, above 55% of the initial concentration, and the alkaline-extracted glucan adsorbed the lowest amount of this toxin. It has been shown that adsorption is most effective at a close-to-neutral pH, while being considerably limited in alkaline conditions. PMID:25848694

  2. The Saccharomyces cerevisiae Wss1 protein is only present in mother cells.

    PubMed

    van Heusden, G Paul H; Steensma, H Yde

    2008-05-01

    The Saccharomyces cerevisiae WSS1 (Weak Suppressor of Smt3) gene has initially been identified as a multicopy suppressor of a mutation in SMT3 encoding the small ubiquitin-like modifier. Later, multiple functions related to DNA replication and repair have been found for WSS1. Here, we report the subcellular location of the Wss1 protein. Fluorescence microscopy of strains expressing a Wss1p-green fluorescent protein (GFP) fusion shows that the protein is present in a single sharp spot near the nuclear membrane, distinct from the spindle pole bodies and nucleolus. In dividing cells, the spot is exclusively present in the mother cell, suggesting a mother cell-specific function of WSS1.

  3. Microbial Community Analysis of a Single Chamber Microbial Fuel Cell Using Potato Wastewater

    SciTech Connect

    Zhen Li; Rishika Haynes; Eugene Sato; Malcolm Shields; Yoshiko Fujita; Chikashi Sato

    2014-04-01

    Microbial fuel cells (MFCs) convert chemical energy to electrical energy via bioelectrochemical reactions mediated by microorganisms. We investigated the diversity of the microbial community in an air cathode single chamber MFC that utilized potato-process wastewater as substrate. Terminal Restriction Fragment Length Polymorphism (T-RFLP) results indicated that the bacterial communities on the anode, cathode, control electrode, and MFC bulk fluid were similar, but differed dramatically from that of the anaerobic domestic sludge and potato wastewater inoculum. The 16S rDNA sequencing results showed that microbial species detected on the anode were predominantly within the phyla of Proteobacteria, Firmicutes, and Bacteroidetes. Fluorescent microscopy results indicated that there was a clear enhancement of biofilm formation on the anode. Results of this study could help improve understanding of the complexity of microbial communities and optimize the microbial composition for generating electricity by MFCs that utilize potato wastewater.

  4. Microbial community analysis of a single chamber microbial fuel cell using potato wastewater.

    PubMed

    Li, Zhen; Haynes, Rishika; Sato, Eugene; Shields, Malcolm S; Fujita, Yoshiko; Sato, Chikashi

    2014-04-01

    Microbial fuel cells (MFCs) convert chemical energy to electrical energy via bio-electrochemical reactions mediated by microorganisms. This study investigated the diversity of the microbial community in an air cathode single chamber MFC that used potato-process wastewater as substrate. Terminal restriction fragment length polymorphism results indicated that the bacterial communities on the anode, cathode, control electrode, and MFC bulk fluid were similar, but differed dramatically from that of the anaerobic domestic sludge and potato wastewater inoculum. The 16S ribosomal DNA sequencing results showed that microbial species detected on the anode were predominantly within the phyla of Proteobacteria, Firmicutes, and Bacteroidetes. Fluorescent microscopy results indicated that there was a clear enhancement of biofilm formation on the anode. Results of this study could help improve understanding of the complexity of microbial communities and optimize the microbial composition for generating electricity by MFCs that use potato wastewater.

  5. Recovery of Saccharomyces cerevisiae mating-type a cells from G1 arrest by alpha factor.

    PubMed Central

    Chan, R K

    1977-01-01

    Mating-type a cells of the yeast Saccharomyces cerevisiae that had been specifically arrested in the G1 phase of the cell cycle by alpha factor, an oligopeptide pheromone made by alpha cells, recovered and resumed cell division after a period of inhibition which was dependent on the concentration of alpha factor used. These treated a cells were more resistant to alpha factor than untreated a cells, but lost their resistance upon further cell division. However, cells arrested for 6 h were no more resistant to alpha factor than cells arrested for only 2.5 h. Mating-type a strains could inactivate or remove alpha factor from the culture fluid, but two a sterile (nonmating) mutants and an a/alpha diploid strain could not. These results suggest that a cells have a mechanism, which may involve uptake or inactivation of alpha factor, for recovering from alpha factor arrest. However, the results do not distinguish between a recovery mechanism which is constitutive and one which is induced by alpha factor. The loss of alpha factor activity during recovery appeared to be primarily cell contact mediated, although an extracellular, diffusible inhibitor of alpha factor that is labile or that functions stoichiometrically could not be ruled out. PMID:400792

  6. Physiological responses to acid stress by Saccharomyces cerevisiae when applying high initial cell density

    PubMed Central

    Guo, Zhong-peng; Olsson, Lisbeth

    2016-01-01

    High initial cell density is used to increase volumetric productivity and shorten production time in lignocellulosic hydrolysate fermentation. Comparison of physiological parameters in high initial cell density cultivation of Saccharomyces cerevisiae in the presence of acetic, formic, levulinic and cinnamic acids demonstrated general and acid-specific responses of cells. All the acids studied impaired growth and inhibited glycolytic flux, and caused oxidative stress and accumulation of trehalose. However, trehalose may play a role other than protecting yeast cells from acid-induced oxidative stress. Unlike the other acids, cinnamic acid did not cause depletion of cellular ATP, but abolished the growth of yeast on ethanol. Compared with low initial cell density, increasing initial cell density reduced the lag phase and improved the bioconversion yield of cinnamic acid during acid adaptation. In addition, yeast cells were able to grow at elevated concentrations of acid, probable due to the increase in phenotypic cell-to-cell heterogeneity in large inoculum size. Furthermore, the specific growth rate and the specific rates of glucose consumption and metabolite production were significantly lower than at low initial cell density, which was a result of the accumulation of a large fraction of cells that persisted in a viable but non-proliferating state. PMID:27620460

  7. Formaldehyde fixation is detrimental to actin cables in glucose-depleted S. cerevisiae cells

    PubMed Central

    Vasicova, Pavla; Rinnerthaler, Mark; Haskova, Danusa; Novakova, Lenka; Malcova, Ivana; Breitenbach, Michael; Hasek, Jiri

    2016-01-01

    Actin filaments form cortical patches and emanating cables in fermenting cells of Saccharomyces cerevisiae. This pattern has been shown to be depolarized in glucose-depleted cells after formaldehyde fixation and staining with rhodamine-tagged phalloidin. Loss of actin cables in mother cells was remarkable. Here we extend our knowledge on actin in live glucose-depleted cells co-expressing the marker of actin patches (Abp1-RFP) with the marker of actin cables (Abp140-GFP). Glucose depletion resulted in appearance of actin patches also in mother cells. However, even after 80 min of glucose deprivation these cells showed a clear network of actin cables labeled with Abp140-GFP in contrast to previously published data. In live cells with a mitochondrial dysfunction (rho0 cells), glucose depletion resulted in almost immediate appearance of Abp140-GFP foci partially overlapping with Abp1-RFP patches in mother cells. Residual actin cables were clustered in patch-associated bundles. A similar overlapping “patchy” pattern of both actin markers was observed upon treatment of glucose-deprived rho+ cells with FCCP (the inhibitor of oxidative phosphorylation) and upon treatment with formaldehyde. While the formaldehyde-targeted process stays unknown, our results indicate that published data on yeast actin cytoskeleton obtained from glucose-depleted cells after fixation should be considered with caution.

  8. Human lactoferrin triggers a mitochondrial- and caspase-dependent regulated cell death in Saccharomyces cerevisiae.

    PubMed

    Acosta-Zaldívar, M; Andrés, M T; Rego, A; Pereira, C S; Fierro, J F; Côrte-Real, M

    2016-02-01

    We have previously shown that the antifungal activity of human lactoferrin (hLf) against Candida albicans relies on its ability to induce cell death associated with apoptotic markers. To gain a deeper understanding of the mechanisms underlying hLf-induced apoptosis, we characterized this cell death process in the well-established Saccharomyces cerevisiae model. Our results indicate that hLf induces cell death in S. cerevisiae in a manner that requires energy and de novo protein synthesis. Cell death is associated with nuclear chromatin condensation, preservation of plasma membrane integrity, and is Yca1p metacaspase-dependent. Lactoferrin also caused mitochondrial dysfunction associated with ROS accumulation and release of cytochrome c. Pre-incubation with oligomycin, an oxidative phosphorylation inhibitor, increased resistance to hLf and, accordingly, mutants deficient in the F1F0-ATP synthase complex were more resistant to death induced by hLf. This indicates that mitochondrial energetic metabolism plays a key role in the killing effect of hLf, though a direct role of F1F0-ATP synthase cannot be precluded. Overexpression of the anti-apoptotic protein Bcl-xL or pre-incubation with N-acetyl cysteine reduced the intracellular level of ROS and increased resistance to hLf, confirming a ROS-mediated mitochondrial cell death process. Mitochondrial involvement was further reinforced by the higher resistance of cells lacking mitochondrial DNA, or other known yeast mitochondrial apoptosis regulators, such as, Aif1p, Cyc3p and Aac1/2/3p. This study provides new insights into a detailed understanding at the molecular level of hLf-induced apoptosis, which may allow the design of new strategies to overcome the emergence of resistance of clinically relevant fungi to conventional antifungals.

  9. Over-pressurized bioreactors: application to microbial cell cultures.

    PubMed

    Lopes, Marlene; Belo, Isabel; Mota, Manuel

    2014-01-01

    In industrial biotechnology, microbial cultures are exposed to different local pressures inside bioreactors. Depending on the microbial species and strains, the increased pressure may have detrimental or beneficial effects on cellular growth and product formation. In this review, the effects of increased air pressure on various microbial cultures growing in bioreactors under moderate total pressure conditions (maximum, 15 bar) will be discussed. Recent data illustrating the diversity of increased air pressure effects at different levels in microbial cells cultivation will be presented, with particular attention to the effects of oxygen and carbon dioxide partial pressures on cellular growth and product formation, and the concomitant effect of oxygen pressure on antioxidant cellular defense mechanisms.

  10. Relation between cell death progression, reactive oxygen species production and mitochondrial membrane potential in fermenting Saccharomyces cerevisiae cells under heat-shock conditions.

    PubMed

    Pyatrikas, Darya V; Fedoseeva, Irina V; Varakina, Nina N; Rusaleva, Tatyana M; Stepanov, Alexei V; Fedyaeva, Anna V; Borovskii, Gennadii B; Rikhvanov, Eugene G

    2015-06-01

    Moderate heat shock increased reactive oxygen species (ROS) production that led to cell death in glucose-grown Saccharomyces cerevisiae cells. Conditions that disturb mitochondrial functions such as treatment by uncouplers and petite mutation were shown to inhibit ROS production and protects cell from thermal death. Hence, mitochondria are responsible for ROS production and play an active role in cell death. An increase in ROS production was accompanied by hyperpolarization of inner mitochondrial membrane. All agents suppressing hyperpolarization also suppressed heat-induced ROS production. It was supposed that generation of ROS under moderate heat shock in glucose-grown S. cerevisiae cells is driven by the mitochondrial membrane potential.

  11. Power overshoot in two-chambered microbial fuel cell (MFC).

    PubMed

    Nien, Po-Chin; Lee, Chin-Yu; Ho, Kuo-Chuan; Adav, Sunil S; Liu, Lihong; Wang, Aijie; Ren, Nanqi; Lee, Duu-Jong

    2011-04-01

    A two-chamber microbial fuel cell was started using iron-reducing strains as inoculum and acetate as carbon sources. The tested microbial fuel cell had an open-circuit voltage of 0.67 V, and reached 1045 mA m(-2) and a power density of 486 mW m(-2) at 0.46 V before power overshoot occurred. Anodic reactions were identified as the rate-determining steps. Stirring the anolyte insignificantly increased cell performance, suggesting a minimal external mass transfer resistance from the anolyte to the anodic biofilm. Data regression analysis indicates that charge transfer resistance at the biofilm-anode junction was negligible. The order of magnitude estimation of electrical conductance indicates that electron transfer resistance had an insignificant effect on microbial fuel cell performance. Resistance in electrogens for substrate utilization is proposed to induce microbial fuel cell power overshoot.

  12. Visualization of calcium and zinc ions in Saccharomyces cerevisiae cells treated with PEFs (pulse electric fields) by laser confocal microscopy.

    PubMed

    Urszula, Pankiewicz; Jerzy, Jamroz; Sujka, Monika; Kowalski, Radosław

    2015-12-01

    The aim of the present work was to visualize the areas of increased concentration of calcium and zinc ions inside Saccharomyces cerevisiae cells with the use of confocal microscopy and to make an attempt to asses semi-quantitatively their concentration within the limits of the cells. Semi-quantitative analysis revealed that fluorescence inside cells from control samples was three-times lower than that observed for cells from the sample enriched with calcium. Differences in distribution of fluorescence intensity between cells originated from the samples enriched with zinc and control samples were also observed. On the basis of the optical sections, the 3D reconstructions of ion-rich areas distribution in the cell were made. The obtained results showed that confocal microscopy is a useful technique for visualization of the areas in S. cerevisiae cells which contain higher amount of calcium and zinc and it may be also used for semi-quantitative analysis.

  13. Microbial community structure elucidates performance of Glyceria maxima plant microbial fuel cell.

    PubMed

    Timmers, Ruud A; Rothballer, Michael; Strik, David P B T B; Engel, Marion; Schulz, Stephan; Schloter, Michael; Hartmann, Anton; Hamelers, Bert; Buisman, Cees

    2012-04-01

    The plant microbial fuel cell (PMFC) is a technology in which living plant roots provide electron donor, via rhizodeposition, to a mixed microbial community to generate electricity in a microbial fuel cell. Analysis and localisation of the microbial community is necessary for gaining insight into the competition for electron donor in a PMFC. This paper characterises the anode-rhizosphere bacterial community of a Glyceria maxima (reed mannagrass) PMFC. Electrochemically active bacteria (EAB) were located on the root surfaces, but they were more abundant colonising the graphite granular electrode. Anaerobic cellulolytic bacteria dominated the area where most of the EAB were found, indicating that the current was probably generated via the hydrolysis of cellulose. Due to the presence of oxygen and nitrate, short-chain fatty acid-utilising denitrifiers were the major competitors for the electron donor. Acetate-utilising methanogens played a minor role in the competition for electron donor, probably due to the availability of graphite granules as electron acceptors.

  14. Anodic and cathodic microbial communities in single chamber microbial fuel cells.

    PubMed

    Daghio, Matteo; Gandolfi, Isabella; Bestetti, Giuseppina; Franzetti, Andrea; Guerrini, Edoardo; Cristiani, Pierangela

    2015-01-25

    Microbial fuel cells (MFCs) are a rapidly growing technology for energy production from wastewater and biomasses. In a MFC, a microbial biofilm oxidizes organic matter and transfers electrons from reduced compounds to an anode as the electron acceptor by extracellular electron transfer (EET). The aim of this work was to characterize the microbial communities operating in a Single Chamber Microbial Fuel Cell (SCMFC) fed with acetate and inoculated with a biogas digestate in order to gain more insight into anodic and cathodic EET. Taxonomic characterization of the communities was carried out by Illumina sequencing of a fragment of the 16S rRNA gene. Microorganisms belonging to Geovibrio genus and purple non-sulfur (PNS) bacteria were found to be dominant in the anodic biofilm. The alkaliphilic genus Nitrincola and anaerobic microorganisms belonging to Porphyromonadaceae family were the most abundant bacteria in the cathodic biofilm.

  15. The selection of S. cerevisiae mutants defective in the start event of cell division.

    PubMed

    Reed, S I

    1980-07-01

    Thirty-three temperature-sensitive mutations defective in the start event of the cell division cycle of Saccharomyces cerevisiae were isolated and subjected to preliminary characterization. Complementation studies assigned thes mutations to four complementation groups, one of which, cdc28, has been described previously. Genetic analysis revealed that these complementation groups define single nuclear genes, unlinked to one another. One of the three newly identified genes, cdc37, has been located in the yeast linkage map on chromosome IV, two meiotic map units distal to hom2.--Each mutation produces stage-specific arrest of cell division at start, the same point where mating pheromone interrupts division. After synchronization at start by incubation at the restrictive temperature, the mutants retain the capacity to enlarge and to conjugate.

  16. Combining magnetic sorting of mother cells and fluctuation tests to analyze genome instability during mitotic cell aging in Saccharomyces cerevisiae.

    PubMed

    Patterson, Melissa N; Maxwell, Patrick H

    2014-10-16

    Saccharomyces cerevisiae has been an excellent model system for examining mechanisms and consequences of genome instability. Information gained from this yeast model is relevant to many organisms, including humans, since DNA repair and DNA damage response factors are well conserved across diverse species. However, S. cerevisiae has not yet been used to fully address whether the rate of accumulating mutations changes with increasing replicative (mitotic) age due to technical constraints. For instance, measurements of yeast replicative lifespan through micromanipulation involve very small populations of cells, which prohibit detection of rare mutations. Genetic methods to enrich for mother cells in populations by inducing death of daughter cells have been developed, but population sizes are still limited by the frequency with which random mutations that compromise the selection systems occur. The current protocol takes advantage of magnetic sorting of surface-labeled yeast mother cells to obtain large enough populations of aging mother cells to quantify rare mutations through phenotypic selections. Mutation rates, measured through fluctuation tests, and mutation frequencies are first established for young cells and used to predict the frequency of mutations in mother cells of various replicative ages. Mutation frequencies are then determined for sorted mother cells, and the age of the mother cells is determined using flow cytometry by staining with a fluorescent reagent that detects bud scars formed on their cell surfaces during cell division. Comparison of predicted mutation frequencies based on the number of cell divisions to the frequencies experimentally observed for mother cells of a given replicative age can then identify whether there are age-related changes in the rate of accumulating mutations. Variations of this basic protocol provide the means to investigate the influence of alterations in specific gene functions or specific environmental conditions on

  17. AC power generation from microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

    2015-11-01

    Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

  18. Cellular and molecular engineering of yeast Saccharomyces cerevisiae for advanced biobutanol production.

    PubMed

    Kuroda, Kouichi; Ueda, Mitsuyoshi

    2016-02-01

    Butanol is an attractive alternative energy fuel owing to several advantages over ethanol. Among the microbial hosts for biobutanol production, yeast Saccharomyces cerevisiae has a great potential as a microbial host due to its powerful genetic tools, a history of successful industrial use, and its inherent tolerance to higher alcohols. Butanol production by S. cerevisiae was first attempted by transferring the 1-butanol-producing metabolic pathway from native microorganisms or using the endogenous Ehrlich pathway for isobutanol synthesis. Utilizing alternative enzymes with higher activity, eliminating competitive pathways, and maintaining cofactor balance achieved significant improvements in butanol production. Meeting future challenges, such as enhancing butanol tolerance and implementing a comprehensive strategy by high-throughput screening, would further elevate the biobutanol-producing ability of S. cerevisiae toward an ideal microbial cell factory exhibiting high productivity of biobutanol.

  19. Cell-based detection of microbial biomaterial contaminations.

    PubMed

    Roch, Toralf; Ma, Nan; Kratz, Karl; Lendlein, Andreas

    2015-01-01

    A major challenge in biomaterial synthesis and functionalization is the prevention of microbial contaminations such as endotoxins (lipopolysaccharides (LPS)). In addition to LPS, which are exclusively expressed by Gram negative bacteria, also other microbial products derived from fungi or Gram positive bacteria can be found as contaminations in research laboratories. Typically, the Limulus amebocyte lysate (LAL)-test is used to determine the endotoxin levels of medical devices. However, this test fails to detect material-bound LPS and other microbial contaminations and, as demonstrated in this study, detects LPS from various bacterial species with different sensitivities.In this work, a cell-based assay using genetically engineered RAW macrophages, which detect not only soluble but also material-bound microbial contaminations is introduced.The sensitivity of this cell-line towards different LPS species and different heat-inactivated microbes was investigated. As proof of principle a soft hydrophobic poly(n-butyl acrylate) network (cPnBA), which may due to adhesive properties strongly bind microbes, was deliberately contaminated with heat-inactivated bacteria. While the LAL-test failed to detect the microbial contamination, the cell-based assay clearly detected material-bound microbial contaminations. Our data demonstrate that a cell-based detection system should routinely be used as supplement to the LAL-test to determine microbial contaminations of biomaterials.

  20. Invertase activity of intact cells of Saccharomyces cerevisiae growing on sugar cane molasses. 1. Steady-state continuous culture tests

    SciTech Connect

    Vitolo, M.; Vairo, M.L.R.; Borzani, W.

    1985-08-01

    During the steady-state continuous culture of Saccharomyces cerevisiae on sugar cane blackstrap molasses under different experimental conditions, oscillatory variations of the invertase activity of the intact yeast cells were observed. The continuous morphological changes of the cells wall and of the periplasmic space affecting the interaction between invertase and sucrose molecules could be responsible by the observed oscillatory phenomena. The average invertase activity at the steady state is linearly correlated to the cell's growth rate.

  1. Effects of X-ray and carbon ion beam irradiation on membrane permeability and integrity in Saccharomyces cerevisiae cells.

    PubMed

    Cao, Guozhen; Zhang, Miaomiao; Miao, Jianshun; Li, Wenjian; Wang, Jufang; Lu, Dong; Xia, Jiefang

    2015-03-01

    Saccharomyces cerevisiae has served as a eukaryotic model in radiation biology studies of cellular responses to ionizing radiation (IR). Research in this field has thus far mainly been focused on DNA strand breaks, DNA base damage, or inhibition of protein activity. However, the effects of IR on S. cerevisiae cell membranes have barely been studied. Here, we investigated the changes in the permeability and integrity of S. cerevisiae cell membranes induced by high-linear energy transfer carbon ion (CI) beam or low-linear energy transfer X-ray. After CI exposure, protein elution and nucleotide diffusion were more pronounced than after X-ray treatment at the same doses, although these features were most prevalent following irradiation doses of 25-175 Gy. Flow cytometry of forward scatter light versus side scatter light and double-staining with fluorescein diacetate and propidium iodide showed that CI and X-ray irradiation significantly affected S. cerevisiae cell membrane integrity and cellular enzyme activity compared with untreated control cells. The extent of lesions in CI-irradiated cells, which exhibited markedly altered morphology and size, was greater than that in X-ray-irradiated cells. The relationships between permeabilized cells, esterase activity, and non-viable cell numbers furthermore indicated that irradiation-induced increases in cell permeabilization and decreases in esterase activity are dependent on the type of radiation and that these parameters correspond well with cell viability. These results also indicate that the patterns of cell inactivity due to X-ray or CI irradiation may be similar in terms of cell membrane damage.

  2. Microalgae-microbial fuel cell: A mini review.

    PubMed

    Lee, Duu-Jong; Chang, Jo-Shu; Lai, Juin-Yih

    2015-12-01

    Microalgae-microbial fuel cells (mMFCs) are a device that can convert solar energy to electrical energy via biological pathways. This mini-review lists new research and development works on microalgae processes, microbial fuel cell (MFC) processes, and their combined version, mMFC. The substantial improvement and technological advancement are highlighted, with a discussion on the challenges and prospects for possible commercialization of mMFC technologies.

  3. [Biomass energy utilization in microbial fuel cells: potentials and challenges].

    PubMed

    Huang, Liping; Cheng, Shaoan

    2010-07-01

    Microbial fuel cells (MFCs) that can harvest biomass energy from organic wastes through microbial catalysis have garnered more and more attention within the past decade due to its potential benefits to ecological environment. In this article, the updated progress in MFCs is reviewed, with a focus on frontier technologies such as chamber configurations, feedstock varieties and the integration of MFCs with microbial electrolysis cells for hydrogen production. And on the other hand, the challenges like development of cost-effective electrode materials, improvement of biomass energy recovery and power output, design and optimization of commercial MFC devices are presented.

  4. Predictive Potential of Flux Balance Analysis of Saccharomyces cerevisiae Using as Optimization Function Combinations of Cell Compartmental Objectives

    PubMed Central

    García Sánchez, Carlos Eduardo; Vargas García, César Augusto; Torres Sáez, Rodrigo Gonzalo

    2012-01-01

    Background The main objective of flux balance analysis (FBA) is to obtain quantitative predictions of metabolic fluxes of an organism, and it is necessary to use an appropriate objective function to guarantee a good estimation of those fluxes. Methodology In this study, the predictive performance of FBA was evaluated, using objective functions arising from the linear combination of different cellular objectives. This approach is most suitable for eukaryotic cells, owing to their multiplicity of cellular compartments. For this reason, Saccharomyces cerevisiae was used as model organism, and its metabolic network was represented using the genome-scale metabolic model iMM904. As the objective was to evaluate the predictive performance from the FBA using the kind of objective function previously described, substrate uptake and oxygen consumption were the only input data used for the FBA. Experimental information about microbial growth and exchange of metabolites with the environment was used to assess the quality of the predictions. Conclusions The quality of the predictions obtained with the FBA depends greatly on the knowledge of the oxygen uptake rate. For the most of studied classifications, the best predictions were obtained with “maximization of growth”, and with some combinations that include this objective. However, in the case of exponential growth with unknown oxygen exchange flux, the objective function “maximization of growth, plus minimization of NADH production in cytosol, plus minimization of NAD(P)H consumption in mitochondrion” gave much more accurate estimations of fluxes than the obtained with any other objective function explored in this study. PMID:22912775

  5. Implementation of microbial fuel cell in harvesting energy using wastewater

    NASA Astrophysics Data System (ADS)

    Ramli, N. L.; Wahab, M. S. Abdul; Sharif, S. A. Md; Ramly, N. H.

    2016-02-01

    In this century, most of the companies use the electricity from the fossils fuels such as oil, gas and coal. This method will give negative impact to the environment and the fossils fuel will be run out. This project is to develop a microbial fuels cell that can produce electricity. There are several types of the microbial fuel cell, which are a single chamber, double chamber and continuous. In this paper, the double chamber microbial fuel cell was selected to investigate the effect of suspended sludge into the double chamber microbial fuels cell. The salt bridge will construct between both chambers of the double chamber microbial fuels cell. Carbon graphite rod is selected as an electrode at the cathode and anode to transfer the electron from the anode to the cathode. Electricity is generated from the anaerobic oxidation of organic matter by bacteria. At the end of this project, the microbial fuels cell was successful in generating electricity that can be used for a specific application.

  6. Mutants of Saccharomyces cerevisiae unresponsive to cell division control by polypeptide mating hormone

    PubMed Central

    1980-01-01

    Temperature-sensitive mutations that produce insensitivity to division arrest by alpha-factor, a mating pheromone, were isolated in an MATa strain of Saccharomyces cerevisiae and shown by complementation studies to difine eight genes. All of these mutations (designated ste) produce sterility at the restrictive temperature in MATa cells, and mutations in seven of the genes produce sterility in MAT alpha cells. In no case was the sterility associated with these mutations coorectible by including wild-type cells of the same mating type in the mating test nor did nay of the mutants inhibit mating of the wild-type cells; the defect appears to be intrinsic to the cell for mutations in each of the genes. Apparently, none of the mutants is defective exclusively in division arrest by alpha-factor, as the sterility of none is suppressed by a temperature-sensitive cdc 28 mutation (the latter imposes division arrest at the correct cell cycle stage for mating). The mutants were examined for features that are inducible in MATa cells by alpha-factor (agglutinin synthesis as well as division arrest) and for the characteristics that constitutively distinguish MATa from MAT alpha cells (a-factor production, alpha-factor destruction). ste2 Mutants are defective specifically in the two inducible properties, whereas ste4, 5, 7, 8, 9, 11, and 12 mutants are defective, to varying degrees, in constitutive as well as inducible aspects. Mutations in ste8 and 9 assume a polar budding pattern unlike either MATa or MAT alpha cells but characteristic of MATa/alpha cells. This study defines seven genes that function in two cell types (MATa and alpha) to control the differentiation of cell type and one gene, ste2, that functions exclusively in MATa cells to mediate responsiveness to polypeptide hormone. PMID:6993497

  7. Analysis of oxygen reduction and microbial community of air-diffusion biocathode in microbial fuel cells.

    PubMed

    Wang, Zejie; Zheng, Yue; Xiao, Yong; Wu, Song; Wu, Yicheng; Yang, Zhaohui; Zhao, Feng

    2013-09-01

    Microbes play irreplaceable role in oxygen reduction reaction of biocathode in microbial fuel cells (MFCs). In this study, air-diffusion biocathode MFCs were set up for accelerating oxygen reduction and microbial community analysis. Linear sweep voltammetry and Tafel curve confirmed the function of cathode biofilm to catalyze oxygen reduction. Microbial community analysis revealed higher diversity and richness of community in plankton than in biofilm. Proteobacteria was the shared predominant phylum in both biofilm and plankton (39.9% and 49.8%) followed by Planctomycetes (29.9%) and Bacteroidetes (13.3%) in biofilm, while Bacteroidetes (28.2%) in plankton. Minor fraction (534, 16.4%) of the total operational taxonomic units (3252) was overlapped demonstrating the disproportionation of bacterial distribution in biofilm and plankton. Pseudomonadales, Rhizobiales and Sphingobacteriales were exoelectrogenic orders in the present study. The research obtained deep insight of microbial community and provided more comprehensive information on uncultured rare bacteria.

  8. Rapid detection of microbial cell abundance in aquatic systems.

    PubMed

    Rocha, Andrea M; Yuan, Quan; Close, Dan M; O'Dell, Kaela B; Fortney, Julian L; Wu, Jayne; Hazen, Terry C

    2016-11-15

    The detection and quantification of naturally occurring microbial cellular densities is an essential component of environmental systems monitoring. While there are a number of commonly utilized approaches for monitoring microbial abundance, capacitance-based biosensors represent a promising approach because of their low-cost and label-free detection of microbial cells, but are not as well characterized as more traditional methods. Here, we investigate the applicability of enhanced alternating current electrokinetics (ACEK) capacitive sensing as a new application for rapidly detecting and quantifying microbial cellular densities in cultured and environmentally sourced aquatic samples. ACEK capacitive sensor performance was evaluated using two distinct and dynamic systems - the Great Australian Bight and groundwater from the Oak Ridge Reservation in Oak Ridge, TN. Results demonstrate that ACEK capacitance-based sensing can accurately determine microbial cell counts throughout cellular concentrations typically encountered in naturally occurring microbial communities (10(3)-10(6) cells/mL). A linear relationship was observed between cellular density and capacitance change correlations, allowing a simple linear curve fitting equation to be used for determining microbial abundances in unknown samples. This work provides a foundation for understanding the limits of capacitance-based sensing in natural environmental samples and supports future efforts focusing on evaluating the robustness ACEK capacitance-based within aquatic environments.

  9. Vaccinium corymbosum L. (blueberry) extracts exhibit protective action against cadmium toxicity in Saccharomyces cerevisiae cells.

    PubMed

    Oprea, Eliza; Ruta, Lavinia L; Nicolau, Ioana; Popa, Claudia V; Neagoe, Aurora D; Farcasanu, Ileana C

    2014-01-01

    Blueberries (Vaccinium corymbosum L.) are a rich source of antioxidants and their consumption is believed to contribute to food-related protection against oxidative stress. In the present study, the chemoprotective action of blueberry extracts against cadmium toxicity was investigated using a cadmium-hypersensitive strain of Saccharomyces cerevisiae. Four varieties of blueberries were used in the study, and it was found that the extracts with high content of total anthocyanidins exhibited significant protective effect against the toxicity of cadmium and H2O2. Both the blueberry extracts and pure cyanidin exhibited protective effects against cadmium in a dose-dependent manner, but without significantly interfering with the cadmium accumulation by the yeast cells. The results imply that the blueberry extracts might be a potentially valuable food supplement for individuals exposed to high cadmium.

  10. Calcium signaling mediates the response to cadmium toxicity in Saccharomyces cerevisiae cells.

    PubMed

    Ruta, Lavinia L; Popa, Valentina C; Nicolau, Ioana; Danet, Andrei F; Iordache, Virgil; Neagoe, Aurora D; Farcasanu, Ileana C

    2014-08-25

    The involvement of Ca(2+) in the response to high Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Hg(2+) was investigated in Saccharomyces cerevisiae. The yeast cells responded through a sharp increase in cytosolic Ca(2+) when exposed to Cd(2+), and to a lesser extent to Cu(2+), but not to Mn(2+), Co(2+), Ni(2+), Zn(2+), or Hg(2+). The response to high Cd(2+) depended mainly on external Ca(2+) (transported through the Cch1p/Mid1p channel) but also on vacuolar Ca(2+) (released into the cytosol through the Yvc1p channel). The adaptation to high Cd(2+) was influenced by perturbations in Ca(2+) homeostasis. Thus, the tolerance to Cd(2+) often correlated with sharp Cd(2+)-induced cytosolic Ca(2+) pulses, while the Cd(2+) sensitivity was accompanied by the incapacity to rapidly restore the low cytosolic Ca(2+).

  11. Importance of cell damage causing growth delay for high pressure inactivation of Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Nanba, Masaru; Nomura, Kazuki; Nasuhara, Yusuke; Hayashi, Manabu; Kido, Miyuki; Hayashi, Mayumi; Iguchi, Akinori; Shigematsu, Toru; Hirayama, Masao; Ueno, Shigeaki; Fujii, Tomoyuki

    2013-06-01

    A high pressure (HP) tolerant (barotolerant) mutant a2568D8 and a variably barotolerant mutant a1210H12 were generated from Saccharomyces cerevisiae using ultra-violet mutagenesis. The two mutants, a barosensitive mutant a924E1 and the wild-type strain, were pressurized (225 MPa), and pressure inactivation behavior was analyzed. In the wild-type strain, a proportion of the growth-delayed cells were detected after exposure to HP. In a924E1, the proportion of growth-delayed cells significantly decreased compared with the wild-type. In a2568D8, the proportion of growth-delayed cells increased and the proportion of inactivated cells decreased compared with the wild-type. In a1210H12, the growth-delayed cells could not be detected within 120 s of exposure to HP. The proportion of growth-delayed cells, which incurred the damage, would affect the survival ratio by HP. These results suggested that cellular changes in barotolerance caused by mutations are remarkably affected by the ability to recover from cellular damage, which results in a growth delay.

  12. An efficient magnetically modified microbial cell biocomposite for carbazole biodegradation

    NASA Astrophysics Data System (ADS)

    Li, Yufei; Du, Xiaoyu; Wu, Chao; Liu, Xueying; Wang, Xia; Xu, Ping

    2013-12-01

    Magnetic modification of microbial cells enables to prepare smart biocomposites in bioremediation. In this study, we constructed an efficient biocomposite by assembling Fe3O4 nanoparticles onto the surface of Sphingomonas sp. XLDN2-5 cells. The average particle size of Fe3O4 nanoparticles was about 20 nm with 45.5 emu g-1 saturation magnetization. The morphology of Sphingomonas sp. XLDN2-5 cells before and after Fe3O4 nanoparticle loading was verified by scanning electron microscopy and transmission electronic microscopy. Compared with free cells, the microbial cell/Fe3O4 biocomposite had the same biodegradation activity but exhibited remarkable reusability. The degradation activity of the microbial cell/Fe3O4 biocomposite increased gradually during recycling processes. Additionally, the microbial cell/Fe3O4 biocomposite could be easily separated and recycled by an external magnetic field due to the super-paramagnetic properties of Fe3O4 nanoparticle coating. These results indicated that magnetically modified microbial cells provide a promising technique for improving biocatalysts used in the biodegradation of hazardous compounds.

  13. An efficient magnetically modified microbial cell biocomposite for carbazole biodegradation

    PubMed Central

    2013-01-01

    Magnetic modification of microbial cells enables to prepare smart biocomposites in bioremediation. In this study, we constructed an efficient biocomposite by assembling Fe3O4 nanoparticles onto the surface of Sphingomonas sp. XLDN2-5 cells. The average particle size of Fe3O4 nanoparticles was about 20 nm with 45.5 emu g-1 saturation magnetization. The morphology of Sphingomonas sp. XLDN2-5 cells before and after Fe3O4 nanoparticle loading was verified by scanning electron microscopy and transmission electronic microscopy. Compared with free cells, the microbial cell/Fe3O4 biocomposite had the same biodegradation activity but exhibited remarkable reusability. The degradation activity of the microbial cell/Fe3O4 biocomposite increased gradually during recycling processes. Additionally, the microbial cell/Fe3O4 biocomposite could be easily separated and recycled by an external magnetic field due to the super-paramagnetic properties of Fe3O4 nanoparticle coating. These results indicated that magnetically modified microbial cells provide a promising technique for improving biocatalysts used in the biodegradation of hazardous compounds. PMID:24330511

  14. Electricity generation in a microbial fuel cell with a microbially catalyzed cathode.

    PubMed

    Zhang, Jin-Na; Zhao, Qing-Liang; Aelterman, Peter; You, Shi-Jie; Jiang, Jun-Qiu

    2008-10-01

    A microbial fuel cell using aerobic microorganisms as the cathodic catalysts is described. By using anaerobic sludge in the anode and aerobic sludge in the cathode as inocula, the microbial fuel cell could be started up after a short lag time of 9 days, generating a stable voltage of 0.324 V (R (ex) = 500 Omega). At an aeration rate of 300 ml min(-1) in the cathode, a maximum volumetric power density of up to 24.7 W m(-3) (117.2 A m(-3)) was reached. This research demonstrates an economic system for recovering electrical energy from organic compounds.

  15. Efficiency Analysis and Mechanism Insight of that Whole-Cell Biocatalytic Production of Melibiose from Raffinose with Saccharomyces cerevisiae.

    PubMed

    Zhou, Yingbiao; Zhu, Yueming; Dai, Longhai; Men, Yan; Wu, Jinhai; Zhang, Juankun; Sun, Yuanxia

    2017-01-01

    Melibiose is widely used as a functional carbohydrate. Whole-cell biocatalytic production of melibiose from raffinose could reduce its cost. However, characteristics of strains for whole-cell biocatalysis and mechanism of such process are unclear. We compared three different Saccharomyces cerevisiae strains (liquor, wine, and baker's yeasts) in terms of concentration variations of substrate (raffinose), target product (melibiose), and by-products (fructose and galactose) in whole-cell biocatalysis process. Distinct difference was observed in whole-cell catalytic efficiency among three strains. Furthermore, activities of key enzymes (invertase, α-galactosidase, and fructose transporter) involved in process and expression levels of their coding genes (suc2, mel1, and fsy1) were investigated. Conservation of key genes in S. cerevisiae strains was also evaluated. Results show that whole-cell catalytic efficiency of S. cerevisiae in the raffinose substrate was closely related to activity of key enzymes and expression of their coding genes. Finally, we summarized characteristics of producing strain that offered advantages, as well as contributions of key genes to excellent strains. Furthermore, we presented a dynamic mechanism model to achieve some mechanism insight for this whole-cell biocatalytic process. This pioneering study should contribute to improvement of whole-cell biocatalytic production of melibiose from raffinose.

  16. Valproate inhibits MAP kinase signalling and cell cycle progression in S. cerevisiae

    PubMed Central

    Desfossés-Baron, Kristelle; Hammond-Martel, Ian; Simoneau, Antoine; Sellam, Adnane; Roberts, Stephen; Wurtele, Hugo

    2016-01-01

    The mechanism of action of valproate (VPA), a widely prescribed short chain fatty acid with anticonvulsant and anticancer properties, remains poorly understood. Here, the yeast Saccharomyces cerevisiae was used as model to investigate the biological consequences of VPA exposure. We found that low pH strongly potentiates VPA-induced growth inhibition. Transcriptional profiling revealed that under these conditions, VPA modulates the expression of genes involved in diverse cellular processes including protein folding, cell wall organisation, sexual reproduction, and cell cycle progression. We further investigated the impact of VPA on selected processes and found that this drug: i) activates markers of the unfolded protein stress response such as Hac1 mRNA splicing; ii) modulates the cell wall integrity pathway by inhibiting the activation of the Slt2 MAP kinase, and synergizes with cell wall stressors such as micafungin and calcofluor white in preventing yeast growth; iii) prevents activation of the Kss1 and Fus3 MAP kinases of the mating pheromone pathway, which in turn abolishes cellular responses to alpha factor; and iv) blocks cell cycle progression and DNA replication. Overall, our data identify heretofore unknown biological responses to VPA in budding yeast, and highlight the broad spectrum of cellular pathways influenced by this chemical in eukaryotes. PMID:27782169

  17. TOR2 is part of two related signaling pathways coordinating cell growth in Saccharomyces cerevisiae.

    PubMed Central

    Helliwell, S B; Howald, I; Barbet, N; Hall, M N

    1998-01-01

    The Saccharomyces cerevisiae genes TOR1 and TOR2 encode phosphatidylinositol kinase homologs. TOR2 has two essential functions. One function overlaps with TOR1 and mediates protein synthesis and cell cycle progression. The second essential function of TOR2 is unique to TOR2 and mediates the cell-cycle-dependent organization of the actin cytoskeleton. We have isolated temperature-sensitive mutants that are defective for either one or both of the two TOR2 functions. The three classes of mutants were as follows. Class A mutants, lacking only the TOR2-unique function, are defective in actin cytoskeleton organization and arrest within two to three generations as small-budded cells in the G2/M phase of the cell cycle. Class B mutants, lacking only the TOR-shared function, and class C mutants, lacking both functions, exhibit a rapid loss of protein synthesis and a G1 arrest within one generation. To define further the two functions of TOR2, we isolated multicopy suppressors that rescue the class A or B mutants. Overexpression of MSS4, PKC1, PLC1, RHO2, ROM2, or SUR1 suppressed the growth defect of a class A mutant. Surprisingly, overexpression of PLC1 and MSS4 also suppressed the growth defect of a class B mutant. These genes encode proteins that are involved in phosphoinositide metabolism and signaling. Thus, the two functions (readouts) of TOR2 appear to involve two related signaling pathways controlling cell growth. PMID:9475724

  18. Activation of chitin synthetase in permeabilized cells of a Saccharomyces cerevisiae mutant lacking proteinase B.

    PubMed Central

    Fernandez, M P; Correa, J U; Cabib, E

    1982-01-01

    Digitonin treatment at 30 degrees C of a Saccharomyces cerevisiae mutant lacking proteinase B permeabilized the cells and caused rapid and extensive activation of chitin synthetase in situ. The same result was obtained with a mutant generally defective in vacuolar proteases. By lowering the temperature and using different permeabilization procedures, we showed that increases in permeability and activation are distinct processes. Activation was inhibited by the protease inhibitors antipain and leupeptin, but by pepstatin or chymostatin. Metal chelators were also inhibitory, and their effect was reversed by the addition of Ca2+ but not by Mg2+. Antipain added together with Ca2+ after incubation of the cells in the presence of a chelating agent prevented reversal of inhibition, a result that was interpreted as indicating that antipain acts either on the same step affected by Ca2+ or on a subsequent step. Efforts to obtain activation in cell-free extracts were unsuccessful, but it was possible to extract the synthetase, once activated, by breaking permeabilized cells with glass beads. Treatment of the cell-free extracts with trypsin led not only to increased activity of chitin synthetase, but also to a change in the pH-activity curve and a diminished requirement by the enzyme for free N-acetylglucosamine. These observations suggest that the modification undergone by the synthetase during endogenous activation is different from that brought about by trypsin treatment. Images PMID:6216245

  19. Potentiation of gene targeting in human cells by expression of Saccharomyces cerevisiae Rad52

    PubMed Central

    Di Primio, Cristina; Galli, Alvaro; Cervelli, Tiziana; Zoppè, Monica; Rainaldi, Giuseppe

    2005-01-01

    When exogenous DNA is stably introduced in mammalian cells, it is typically integrated in random positions, and only a minor fraction enters a pathway of homologous recombination (HR). The complex Rad51/Rad52 is a major player in the management of exogenous DNA in eukaryotic organisms and plays a critical role in the choice of repair system. In Saccharomyces cerevisiae, the pathway of choice is HR, mediated by Rad52 (ScRad52), which differs slightly from its human homologue. Here, we present an approach that utilizes ScRad52 to enhance HR in human cells containing a specific substrate for recombination. Clones of HeLa cells were produced expressing functional ScRad52. These cells showed enhanced resistance to DNA damaging treatments and revealed a different distribution of Rad51 foci (a marker of recombination complex formation). More significantly, ScRad52 expression resulted in an up to 37-fold increase in gene targeting by HR. In the same cells, random integration of exogenous DNA was significantly reduced, consistent with the view that HR and non-homologous end joining are alternative competing pathways. Expression of ScRad52 could offer a major improvement for experiments requiring gene targeting by HR, both in basic research and in gene therapy studies. PMID:16106043

  20. B cell-helping functions of gut microbial metabolites.

    PubMed

    Kim, Chang H

    2016-09-23

    Commensal microflora profoundly affects the host immune system. It has long been observed that commensal bacteria enhance antibody production in the host by producing antigens for B cell receptors (BCR) and ligands for Toll-like receptors (TLR). We recently reported that the microbial metabolites short-chain fatty acids (SCFAs) regulate the metabolism and gene expression in B cells to promote antibody production (Kim et al. Gut Microbial Metabolites Fuel Host Antibody Responses. Cell Host & Microbe. 2016; 20(2):202-14). The B-cell helping function of SCFAs and its implication in the host immune system are discussed in this article.

  1. B cell-helping functions of gut microbial metabolites

    PubMed Central

    Kim, Chang H.

    2016-01-01

    Commensal microflora profoundly affects the host immune system. It has long been observed that commensal bacteria enhance antibody production in the host by producing antigens for B cell receptors (BCR) and ligands for Toll-like receptors (TLR). We recently reported that the microbial metabolites short-chain fatty acids (SCFAs) regulate the metabolism and gene expression in B cells to promote antibody production (Kim et al. Gut Microbial Metabolites Fuel Host Antibody Responses. Cell Host & Microbe. 2016; 20(2):202-14). The B-cell helping function of SCFAs and its implication in the host immune system are discussed in this article. PMID:28357321

  2. Enrichment of Microbial Electrolysis Cell Biocathodes from Sediment Microbial Fuel Cell Bioanodes

    PubMed Central

    Pisciotta, John M.; Zaybak, Zehra; Call, Douglas F.; Nam, Joo-Youn

    2012-01-01

    Electron-accepting (electrotrophic) biocathodes were produced by first enriching graphite fiber brush electrodes as the anodes in sediment-type microbial fuel cells (sMFCs) using two different marine sediments and then electrically inverting the anodes to function as cathodes in two-chamber bioelectrochemical systems (BESs). Electron consumption occurred at set potentials of −439 mV and −539 mV (versus the potential of a standard hydrogen electrode) but not at −339 mV in minimal media lacking organic sources of energy. Results at these different potentials were consistent with separate linear sweep voltammetry (LSV) scans that indicated enhanced activity (current consumption) below only ca. −400 mV. MFC bioanodes not originally acclimated at a set potential produced electron-accepting (electrotrophic) biocathodes, but bioanodes operated at a set potential (+11 mV) did not. CO2 was removed from cathode headspace, indicating that the electrotrophic biocathodes were autotrophic. Hydrogen gas generation, followed by loss of hydrogen gas and methane production in one sample, suggested hydrogenotrophic methanogenesis. There was abundant microbial growth in the biocathode chamber, as evidenced by an increase in turbidity and the presence of microorganisms on the cathode surface. Clone library analysis of 16S rRNA genes indicated prominent sequences most similar to those of Eubacterium limosum (Butyribacterium methylotrophicum), Desulfovibrio sp. A2, Rhodococcus opacus, and Gemmata obscuriglobus. Transfer of the suspension to sterile cathodes made of graphite plates, carbon rods, or carbon brushes in new BESs resulted in enhanced current after 4 days, demonstrating growth by these microbial communities on a variety of cathode substrates. This report provides a simple and effective method for enriching autotrophic electrotrophs by the use of sMFCs without the need for set potentials, followed by the use of potentials more negative than −400 mV. PMID:22610438

  3. Enrichment of Microbial Electrolysis Cell Biocathodes from Sediment Microbial Fuel Cell Bioanodes

    SciTech Connect

    Pisciotta, JM; Zaybak, Z; Call, DF; Nam, JY; Logan, BE

    2012-07-18

    Electron-accepting (electrotrophic) biocathodes were produced by first enriching graphite fiber brush electrodes as the anodes in sediment-type microbial fuel cells (sMFCs) using two different marine sediments and then electrically inverting the anodes to function as cathodes in two-chamber bioelectrochemical systems (BESs). Electron consumption occurred at set potentials of -439 mV and -539 mV (versus the potential of a standard hydrogen electrode) but not at -339 mV in minimal media lacking organic sources of energy. Results at these different potentials were consistent with separate linear sweep voltammetry (LSV) scans that indicated enhanced activity (current consumption) below only ca. -400 mV. MFC bioanodes not originally acclimated at a set potential produced electron-accepting (electrotrophic) biocathodes, but bioanodes operated at a set potential (+11 mV) did not. CO, was removed from cathode headspace, indicating that the electrotrophic biocathodes were autotrophic. Hydrogen gas generation, followed by loss of hydrogen gas and methane production in one sample, suggested hydrogenotrophic methanogenesis. There was abundant microbial growth in the biocathode chamber, as evidenced by an increase in turbidity and the presence of microorganisms on the cathode surface. Clone library analysis of 16S rRNA genes indicated prominent sequences most similar to those of Eubacterium limosum (Butyribacterium methylotrophicum), Desulfovibrio sp. A2, Rhodococcus opacus, and Gemmata obscuriglobus. Transfer of the suspension to sterile cathodes made of graphite plates, carbon rods, or carbon brushes in new BESs resulted in enhanced current after 4 days, demonstrating growth by these microbial communities on a variety of cathode substrates. This report provides a simple and effective method for enriching autotrophic electrotrophs by the use of sMFCs without the need for set potentials, followed by the use of potentials more negative than -400 mV.

  4. Enrichment of microbial electrolysis cell biocathodes from sediment microbial fuel cell bioanodes.

    PubMed

    Pisciotta, John M; Zaybak, Zehra; Call, Douglas F; Nam, Joo-Youn; Logan, Bruce E

    2012-08-01

    Electron-accepting (electrotrophic) biocathodes were produced by first enriching graphite fiber brush electrodes as the anodes in sediment-type microbial fuel cells (sMFCs) using two different marine sediments and then electrically inverting the anodes to function as cathodes in two-chamber bioelectrochemical systems (BESs). Electron consumption occurred at set potentials of -439 mV and -539 mV (versus the potential of a standard hydrogen electrode) but not at -339 mV in minimal media lacking organic sources of energy. Results at these different potentials were consistent with separate linear sweep voltammetry (LSV) scans that indicated enhanced activity (current consumption) below only ca. -400 mV. MFC bioanodes not originally acclimated at a set potential produced electron-accepting (electrotrophic) biocathodes, but bioanodes operated at a set potential (+11 mV) did not. CO(2) was removed from cathode headspace, indicating that the electrotrophic biocathodes were autotrophic. Hydrogen gas generation, followed by loss of hydrogen gas and methane production in one sample, suggested hydrogenotrophic methanogenesis. There was abundant microbial growth in the biocathode chamber, as evidenced by an increase in turbidity and the presence of microorganisms on the cathode surface. Clone library analysis of 16S rRNA genes indicated prominent sequences most similar to those of Eubacterium limosum (Butyribacterium methylotrophicum), Desulfovibrio sp. A2, Rhodococcus opacus, and Gemmata obscuriglobus. Transfer of the suspension to sterile cathodes made of graphite plates, carbon rods, or carbon brushes in new BESs resulted in enhanced current after 4 days, demonstrating growth by these microbial communities on a variety of cathode substrates. This report provides a simple and effective method for enriching autotrophic electrotrophs by the use of sMFCs without the need for set potentials, followed by the use of potentials more negative than -400 mV.

  5. Expression of a Fungal Hydrophobin in the Saccharomyces cerevisiae Cell Wall: Effect on Cell Surface Properties and Immobilization

    PubMed Central

    Nakari-Setälä, Tiina; Azeredo, Joana; Henriques, Mariana; Oliveira, Rosário; Teixeira, José; Linder, Markus; Penttilä, Merja

    2002-01-01

    The aim of this work was to modify the cell surface properties of Saccharomyces cerevisiae by expression of the HFBI hydrophobin of the filamentous fungus Trichoderma reesei on the yeast cell surface. The second aim was to study the immobilization capacity of the modified cells. Fusion to the Flo1p flocculin was used to target the HFBI moiety to the cell wall. Determination of cell surface characteristics with contact angle and zeta potential measurements indicated that HFBI-producing cells are more apolar and slightly less negatively charged than the parent cells. Adsorption of the yeast cells to different commercial supports was studied. A twofold increase in the binding affinity of the hydrophobin-producing yeast to hydrophobic silicone-based materials was observed, while no improvement in the interaction with hydrophilic carriers could be seen compared to that of the parent cells. Hydrophobic interactions between the yeast cells and the support are suggested to play a major role in attachment. Also, a slight increase in the initial adsorption rate of the hydrophobin yeast was observed. Furthermore, due to the engineered cell surface, hydrophobin-producing yeast cells were efficiently separated in an aqueous two-phase system by using a nonionic polyoxyethylene detergent, C12-18EO5. PMID:12089019

  6. Electricity production from municipal solid waste using microbial fuel cells.

    PubMed

    Chiu, H Y; Pai, T Y; Liu, M H; Chang, C A; Lo, F C; Chang, T C; Lo, H M; Chiang, C F; Chao, K P; Lo, W Y; Lo, S W; Chu, Y L

    2016-07-01

    The organic content of municipal solid waste has long been an attractive source of renewable energy, mainly as a solid fuel in waste-to-energy plants. This study focuses on the potential to use microbial fuel cells to convert municipal solid waste organics into energy using various operational conditions. The results showed that two-chamber microbial fuel cells with carbon felt and carbon felt allocation had a higher maximal power density (20.12 and 30.47 mW m(-2) for 1.5 and 4 L, respectively) than those of other electrode plate allocations. Most two-chamber microbial fuel cells (1.5 and 4 L) had a higher maximal power density than single-chamber ones with corresponding electrode plate allocations. Municipal solid waste with alkali hydrolysis pre-treatment and K3Fe(CN)6 as an electron acceptor improved the maximal power density to 1817.88 mW m(-2) (~0.49% coulomb efficiency, from 0.05-0.49%). The maximal power density from experiments using individual 1.5 and 4 L two-chamber microbial fuel cells, and serial and parallel connections of 1.5 and 4 L two-chamber microbial fuel cells, was found to be in the order of individual 4 L (30.47 mW m(-2)) > serial connection of 1.5 and 4 L (27.75) > individual 1.5 L (20.12) > parallel connection of 1.5 and 4 L (17.04) two-chamber microbial fuel cells . The power density using municipal solid waste microbial fuel cells was compared with information in the literature and discussed.

  7. Modeling of Sustainable Base Production by Microbial Electrolysis Cell.

    PubMed

    Blatter, Maxime; Sugnaux, Marc; Comninellis, Christos; Nealson, Kenneth; Fischer, Fabian

    2016-07-07

    A predictive model for the microbial/electrochemical base formation from wastewater was established and compared to experimental conditions within a microbial electrolysis cell. A Na2 SO4 /K2 SO4 anolyte showed that model prediction matched experimental results. Using Shewanella oneidensis MR-1, a strong base (pH≈13) was generated using applied voltages between 0.3 and 1.1 V. Due to the use of bicarbonate, the pH value in the anolyte remained unchanged, which is required to maintain microbial activity.

  8. Microbial communities involved in electricity generation from sulfide oxidation in a microbial fuel cell.

    PubMed

    Sun, Min; Tong, Zhong-Hua; Sheng, Guo-Ping; Chen, Yong-Zhen; Zhang, Feng; Mu, Zhe-Xuan; Wang, Hua-Lin; Zeng, Raymond J; Liu, Xian-Wei; Yu, Han-Qing; Wei, Li; Ma, Fang

    2010-10-15

    Simultaneous electricity generation and sulfide removal can be achieved in a microbial fuel cell (MFC). In electricity harvesting from sulfide oxidation in such an MFC, various microbial communities are involved. It is essential to elucidate the microbial communities and their roles in the sulfide conversion and electricity generation. In this work, an MFC was constructed to enrich a microbial consortium, which could harvest electricity from sulfide oxidation. Electrochemical analysis demonstrated that microbial catalysis was involved in electricity output in the sulfide-fed MFC. The anode-attached and planktonic communities could perform catalysis independently, and synergistic interactions occurred when the two communities worked together. A 16S rRNA clone library analysis was employed to characterize the microbial communities in the MFC. The anode-attached and planktonic communities shared similar richness and diversity, while the LIBSHUFF analysis revealed that the two community structures were significantly different. The exoelectrogenic, sulfur-oxidizing and sulfate-reducing bacteria were found in the MFC anodic chamber. The discovery of these bacteria was consistent with the community characteristics for electricity generation from sulfide oxidation. The exoelectrogenic bacteria were found both on the anode and in the solution. The sulfur-oxidizing bacteria were present in greater abundance on the anode than in the solution, while the sulfate-reducing bacteria preferably lived in the solution.

  9. Diamagnetic levitation changes growth, cell cycle, and gene expression of Saccharomyces cerevisiae.

    PubMed

    Coleman, Chasity B; Gonzalez-Villalobos, Romer A; Allen, Patricia L; Johanson, Kelly; Guevorkian, Karine; Valles, James M; Hammond, Timothy G

    2007-11-01

    Inhomogeneous magnetic fields are used in magnetic traps to levitate biological specimens by exploiting the natural diamagnetism of virtually all materials. Using Saccharomyces cerevisiae, this report investigates whether magnetic field (B) induces changes in growth, cell cycle, and gene expression. Comparison to the effects of gravity and temperature allowed determination of whether the responses are general pathways or stimulus specific. Growth and cell cycle analysis were examined in wild-type (WT) yeast and strains with deletions in transcription factors Msn4 or Sfp1. Msn4, Sfp1, and Rap1 have been implicated in responses to physical forces, but only Msn4 and Sfp1 deletions are viable. Gene expression changes were examined in strains bearing GFP-tagged reporters for YIL052C (Sfp1-dependent), YST-2 (Sfp1/Rap1-dependent), or SSA4 (Msn4-dependent). The cell growth and gene expression responses were highly stimulus specific. B increased growth only following Msn4 or Sfp1 deletion, associated with decreased G1 and G2/M and increased S phase of the cell cycle. In addition, B suppressed expression of both YIL052C and YST2. Gravity decreased growth in an Sfp1 but not Msn4-dependent manner, in association with decreased G2/M and increased S phase of the cell cycle. Additionally, gravity decreased expression of SSA4 and YIL052C genes. Temperature increased cell growth in an Msn4- and Sfp1-dependent manner in association with increased G1 and G2/M with decreased S phase of the cell cycle. In addition, temperature increased YIL052C gene expression. This study shows that B has selective effects on cell growth, cell cycle, and gene expression that are stimulus specific.

  10. Quantification of cell volume changes upon hyperosmotic stress in Saccharomyces cerevisiae.

    PubMed

    Petelenz-Kurdziel, Elzbieta; Eriksson, Emma; Smedh, Maria; Beck, Caroline; Hohmann, Stefan; Goksör, Mattias

    2011-11-01

    Cell volume is a biophysical property, which is of great importance for quantitative characterisations of biological processes, such as osmotic adaptation. It also is a crucial parameter in the most common type of mathematical description of cellular behaviour-ordinary differential equation (ODE) models, e.g. the integrative model of the osmotic stress response in baker's yeast (E. Klipp, B. Nordlander, R. Kruger, P. Gennemark and S. Hohmann, Nat. Biotechnol., 2005, 23, 975-982). Until recently only rough estimates of this value were available. In this study we measured the mean volume of more than 300 individual yeast cells (Saccharomyces cerevisiae). We quantitatively characterised the dependence between the relative cell volume and the concentration of osmoticum in the cell surrounding. We also followed the recovery of the cellular volume over time, as well as the influence of increased external osmolarity on the nuclear volume. We found that cell shrinkage caused by shifts in the external osmolarity is proportional to the stress intensity only up to 1000 mM NaCl. At this concentration the yeast cells shrink to approximately 55% of their unstressed volume and this volume is maintained even in the case of further osmolarity increase. We observed that returning to the initial, unstressed volume takes more than 45 minutes for stress concentrations exceeding 100 mM NaCl and that only cells treated with the latter concentration are able to fully regain their initial size within the course of the experiment. We postulate that the cytoplasm plays a protective role for the nucleus by buffering the changes in volume caused by external osmolarity shifts. In conclusion, we quantitatively characterised the dynamics of cell volume changes caused by hyperosmotic stress, providing an accurate description of a biophysical cell property, which is crucial for precise mathematical simulations of cellular processes.

  11. Solar energy powered microbial fuel cell with a reversible bioelectrode.

    PubMed

    Strik, David P B T B; Hamelers, Hubertus V M; Buisman, Cees J N

    2010-01-01

    The solar energy powered microbial fuel cell is an emerging technology for electricity generation via electrochemically active microorganisms fueled by solar energy via in situ photosynthesized metabolites from algae, cyanobacteria, or living higher plants. A general problem with microbial fuel cells is the pH membrane gradient which reduces cell voltage and power output. This problem is caused by acid production at the anode, alkaline production at the cathode, and the nonspecific proton exchange through the membrane. Here we report a solution for a new kind of solar energy powered microbial fuel cell via development of a reversible bioelectrode responsible for both biocatalyzed anodic and cathodic electron transfer. Anodic produced protons were used for the cathodic reduction reaction which held the formation of a pH membrane gradient. The microbial fuel cell continuously generated electricity and repeatedly reversed polarity dependent on aeration or solar energy exposure. Identified organisms within biocatalyzing biofilm of the reversible bioelectrode were algae, (cyano)bacteria and protozoa. These results encourage application of solar energy powered microbial fuel cells.

  12. The chromatin structure of Saccharomyces cerevisiae autonomously replicating sequences changes during the cell division cycle.

    PubMed Central

    Brown, J A; Holmes, S G; Smith, M M

    1991-01-01

    The chromatin structures of two well-characterized autonomously replicating sequence (ARS) elements were examined at their chromosomal sites during the cell division cycle in Saccharomyces cerevisiae. The H4 ARS is located near one of the duplicate nonallelic histone H4 genes, while ARS1 is present near the TRP1 gene. Cells blocked in G1 either by alpha-factor arrest or by nitrogen starvation had two DNase I-hypersensitive sites of about equal intensity in the ARS element. This pattern of DNase I-hypersensitive sites was altered in synchronous cultures allowed to proceed into S phase. In addition to a general increase in DNase I sensitivity around the core consensus sequence, the DNase I-hypersensitive site closest to the core consensus became more nuclease sensitive than the distal site. This change in chromatin structure was restricted to the ARS region and depended on replication since cdc7 cells blocked near the time of replication initiation did not undergo the transition. Subsequent release of arrested cdc7 cells restored entry into S phase and was accompanied by the characteristic change in ARS chromatin structure. Images PMID:1922046

  13. Behavior of spindles and spindle plaques in the cell cycle and conjugation of Saccharomyces cerevisiae.

    PubMed Central

    Byers, B; Goetsch, L

    1975-01-01

    The interdependence of spindle plaque with other aspects of cell division and conjugation in Saccharomyces cerevisiae has been investigated. Three forms of the spindle plaque appear sequentially before the formation of the complete, intranuclear spindle. The single plaque is present initially in the mitotic cycle; it becomes transformed into a satellite-bearing single plaque during the latter part of G1. Subsequently, plaque duplication yields the double plaque characteristic of the early phase of budding, which coincides with the period of chromosome replication (S). The eventual separation of these plaques to form a complete spindle, with a single plaque at each pole, is nearly coincident with the completion of S. The form of the plaque differs in two independent cases of G1 arrest: the single plaque is found in a cell in stationary arrest of growth, whereas a cell arrested by mating factors in preparation for conjugation contains a satellite-bearing single plaque. The latter form is retained during zygote formation, where it serves as the initial site of fusion of each prezygotic nuceus with the other. This fusion results in the formation of a single zygotic nucleus with a satellite-bearing single plaque, which is subsequently transformed into a double plaque as the zygote buds. The double plaque is situated adjacent to the site of bud emergence in both vegetative cells and zygotes. Images PMID:1100612

  14. Challenges in microbial fuel cell development and operation.

    PubMed

    Kim, Byung Hong; Chang, In Seop; Gadd, Geoffrey M

    2007-09-01

    A microbial fuel cell (MFC) is a device that converts chemical energy into electricity through the catalytic activities of microorganisms. Although there is great potential of MFCs as an alternative energy source, novel wastewater treatment process, and biosensor for oxygen and pollutants, extensive optimization is required to exploit the maximum microbial potential. In this article, the main limiting factors of MFC operation are identified and suggestions are made to improve performance.

  15. An atypical active cell death process underlies the fungicidal activity of ciclopirox olamine against the yeast Saccharomyces cerevisiae.

    PubMed

    Almeida, Bruno; Sampaio-Marques, Belém; Carvalho, Joana; Silva, Manuel T; Leão, Cecília; Rodrigues, Fernando; Ludovico, Paula

    2007-05-01

    Ciclopirox olamine (CPO), a fungicidal agent widely used in clinical practice, induced in Saccharomyces cerevisiae an active cell death (ACD) process characterized by changes in nuclear morphology and chromatin condensation associated with the appearance of a population in the sub-G(0)/G(1) cell cycle phase and an arrest delay in the G(2)/M phases. This ACD was associated neither with intracellular reactive oxygen species (ROS) signaling, as revealed by the use of different classes of ROS scavengers, nor with a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive phenotype. Furthermore, CPO-induced cell death seems to be dependent on unknown protease activity but independent of the apoptotic regulators Aif1p and Yca1p and of autophagic pathways involving Apg5p, Apg8p and Uth1p. Our results show that CPO triggers in S. cerevisiae an atypical nonapoptotic, nonautophagic ACD with as yet unknown regulators.

  16. Aspergillus oryzae–Saccharomyces cerevisiae Consortium Allows Bio-Hybrid Fuel Cell to Run on Complex Carbohydrates

    PubMed Central

    Jahnke, Justin P.; Hoyt, Thomas; LeFors, Hannah M.; Sumner, James J.; Mackie, David M.

    2016-01-01

    Consortia of Aspergillus oryzae and Saccharomyces cerevisiae are examined for their abilities to turn complex carbohydrates into ethanol. To understand the interactions between microorganisms in consortia, Fourier-transform infrared spectroscopy is used to follow the concentrations of various metabolites such as sugars (e.g., glucose, maltose), longer chain carbohydrates, and ethanol to optimize consortia conditions for the production of ethanol. It is shown that with proper design A. oryzae can digest food waste simulants into soluble sugars that S. cerevisiae can ferment into ethanol. Depending on the substrate and conditions used, concentrations of 13% ethanol were achieved in 10 days. It is further shown that a direct alcohol fuel cell (FC) can be coupled with these A. oryzae-enabled S. cerevisiae fermentations using a reverse osmosis membrane. This “bio-hybrid FC” continually extracted ethanol from an ongoing consortium, enhancing ethanol production and allowing the bio-hybrid FC to run for at least one week. Obtained bio-hybrid FC currents were comparable to those from pure ethanol—water mixtures, using the same FC. The A. oryzae–S. cerevisiae consortium, coupled to a bio-hybrid FC, converted food waste simulants into electricity without any pre- or post-processing. PMID:27681904

  17. The function of chitin synthases 2 and 3 in the Saccharomyces cerevisiae cell cycle

    PubMed Central

    1991-01-01

    The morphology of three Saccharomyces cerevisiae strains, all lacking chitin synthase 1 (Chs1) and two of them deficient in either Chs3 (calR1 mutation) or Chs2 was observed by light and electron microscopy. Cells deficient in Chs2 showed clumpy growth and aberrant shape and size. Their septa were very thick; the primary septum was absent. Staining with WGA-gold complexes revealed a diffuse distribution of chitin in the septum, whereas chitin was normally located at the neck between mother cell and bud and in the wall of mother cells. Strains deficient in Chs3 exhibited minor abnormalities in budding pattern and shape. Their septa were thin and trilaminar. Staining for chitin revealed a thin line of the polysaccharide along the primary septum; no chitin was present elsewhere in the wall. Therefore, Chs2 is specific for primary septum formation, whereas Chs3 is responsible for chitin in the ring at bud emergence and in the cell wall. Chs3 is also required for chitin synthesized in the presence of alpha-pheromone or deposited in the cell wall of cdc mutants at nonpermissive temperature, and for chitosan in spore walls. Genetic evidence indicated that a mutant lacking all three chitin synthases was inviable; this was confirmed by constructing a triple mutant rescued by a plasmid carrying a CHS2 gene under control of a GAL1 promoter. Transfer of the mutant from galactose to glucose resulted in cell division arrest followed by cell death. We conclude that some chitin synthesis is essential for viability of yeast cells. PMID:2050738

  18. Cell-autonomous mechanisms of chronological aging in the yeast Saccharomyces cerevisiae

    PubMed Central

    Arlia-Ciommo, Anthony; Leonov, Anna; Piano, Amanda; Svistkova, Veronika; Titorenko, Vladimir I.

    2014-01-01

    A body of evidence supports the view that the signaling pathways governing cellular aging - as well as mechanisms of their modulation by longevity-extending genetic, dietary and pharmacological interventions - are conserved across species. The scope of this review is to critically analyze recent advances in our understanding of cell-autonomous mechanisms of chronological aging in the budding yeast Saccharomyces cerevisiae. Based on our analysis, we propose a concept of a biomolecular network underlying the chronology of cellular aging in yeast. The concept posits that such network progresses through a series of lifespan checkpoints. At each of these checkpoints, the intracellular concentrations of some key intermediates and products of certain metabolic pathways - as well as the rates of coordinated flow of such metabolites within an intricate network of intercompartmental communications - are monitored by some checkpoint-specific ʺmaster regulatorʺ proteins. The concept envisions that a synergistic action of these master regulator proteins at certain early-life and late-life checkpoints modulates the rates and efficiencies of progression of such processes as cell metabolism, growth, proliferation, stress resistance, macromolecular homeostasis, survival and death. The concept predicts that, by modulating these vital cellular processes throughout lifespan (i.e., prior to an arrest of cell growth and division, and following such arrest), the checkpoint-specific master regulator proteins orchestrate the development and maintenance of a pro- or anti-aging cellular pattern and, thus, define longevity of chronologically aging yeast. PMID:28357241

  19. Saccharomyces cerevisiae STE6 gene product: a novel pathway for protein export in eukaryotic cells.

    PubMed Central

    Kuchler, K; Sterne, R E; Thorner, J

    1989-01-01

    Saccharomyces cerevisiae MATa cells release a lipopeptide mating pheromone, a-factor. Radiolabeling and immunoprecipitation show that MATa ste6 mutants produce pro-a-factor and mature a-factor intracellularly, but little or no extracellular pheromone. Normal MATa cells carrying a multicopy plasmid containing both MFa1 (pro-a-factor structural gene) and the STE6 gene secrete a-factor at least five times faster than the same cells carrying only MFa1 in the same vector. The nucleotide sequence of the STE6 gene predicts a 1290 residue polypeptide with multiple membrane spanning segments and two hydrophilic domains, each strikingly homologous to a set of well-characterized prokaryotic permeases (including hlyB, oppD, hisP, malK and pstB) and sharing even greater identity with mammalian mdr (multiple drug resistance) transporters. These results suggest that the STE6 protein in yeast, and possibly mdr in animals, is a transmembrane translocator that exports polypeptides by a route independent of the classical secretory pathway. Images PMID:2686977

  20. Functional Assembly of Minicellulosomes on the Saccharomyces cerevisiae Cell Surface for Cellulose Hydrolysis and Ethanol Production▿

    PubMed Central

    Tsai, Shen-Long; Oh, Jeongseok; Singh, Shailendra; Chen, Ruizhen; Chen, Wilfred

    2009-01-01

    We demonstrated the functional display of a miniscaffoldin on the Saccharomyces cerevisiae cell surface consisting of three divergent cohesin domains from Clostridium thermocellum (t), Clostridium cellulolyticum (c), and Ruminococcus flavefaciens (f). Incubation with Escherichia coli lysates containing an endoglucanase (CelA) fused with a dockerin domain from C. thermocellum (At), an exoglucanase (CelE) from C. cellulolyticum fused with a dockerin domain from the same species (Ec), and an endoglucanase (CelG) from C. cellulolyticum fused with a dockerin domain from R. flavefaciens (Gf) resulted in the assembly of a functional minicellulosome on the yeast cell surface. The displayed minicellulosome retained the synergistic effect for cellulose hydrolysis. When a β-glucosidase (BglA) from C. thermocellum tagged with the dockerin from R. flavefaciens was used in place of Gf, cells displaying the new minicellulosome exhibited significantly enhanced glucose liberation and produced ethanol directly from phosphoric acid-swollen cellulose. The final ethanol concentration of 3.5 g/liter was 2.6-fold higher than that obtained by using the same amounts of added purified cellulases. The overall yield was 0.49 g of ethanol produced per g of carbohydrate consumed, which corresponds to 95% of the theoretical value. This result confirms that simultaneous and synergistic saccharification and fermentation of cellulose to ethanol can be efficiently accomplished with a yeast strain displaying a functional minicellulosome containing all three required cellulolytic enzymes. PMID:19684173

  1. Raspberry wine fermentation with suspended and immobilized yeast cells of two strains of Saccharomyces cerevisiae.

    PubMed

    Djordjević, Radovan; Gibson, Brian; Sandell, Mari; de Billerbeck, Gustavo M; Bugarski, Branko; Leskošek-Čukalović, Ida; Vunduk, Jovana; Nikićević, Ninoslav; Nedović, Viktor

    2015-01-01

    The objectives of this study were to assess the differences in fermentative behaviour of two different strains of Saccharomyces cerevisiae (EC1118 and RC212) and to determine the differences in composition and sensory properties of raspberry wines fermented with immobilized and suspended yeast cells of both strains at 15 °C. Analyses of aroma compounds, glycerol, acetic acid and ethanol, as well as the kinetics of fermentation and a sensory evaluation of the wines, were performed. All fermentations with immobilized yeast cells had a shorter lag phase and faster utilization of sugars and ethanol production than those fermented with suspended cells. Slower fermentation kinetics were observed in all the samples that were fermented with strain RC212 (suspended and immobilized) than in samples fermented with strain EC1118. Significantly higher amounts of acetic acid were detected in all samples fermented with strain RC212 than in those fermented with strain EC1118 (0.282 and 0.602 g/l, respectively). Slightly higher amounts of glycerol were observed in samples fermented with strain EC1118 than in those fermented with strain RC212.

  2. Proteomic analysis reveals complex metabolic regulation in Saccharomyces cerevisiae cells against multiple inhibitors stress.

    PubMed

    Lv, Ya-Jin; Wang, Xin; Ma, Qian; Bai, Xue; Li, Bing-Zhi; Zhang, Weiwen; Yuan, Ying-Jin

    2014-03-01

    Toxic compounds including acids, furans, and phenols (AFP) were generated from the pretreatment of lignocellulose. We cultivated Saccharomyces cerevisiae cells in a batch mode, besides the cell culture of original yeast strain in AFP-free medium which was referred as C0, three independent subcultures were cultivated under multiple inhibitors AFP and were referred as C1, C2, and C3 in time sequence. Comparing to C0, the cell density was lowered while the ethanol yield was maintained stably in the three yeast cultures under AFP stress, and the lag phase of C1 was extended while the lag phases of C2 and C3 were not extended. In proteomic analysis, 194 and 215 unique proteins were identified as differently expressed proteins at lag phase and exponential phase, respectively. Specifically, the yeast cells co-regulated protein folding and protein synthesis process to prevent the generation of misfolded proteins and to save cellular energy, they increased the activity of glycolysis, redirected metabolic flux towards phosphate pentose pathway and the biosynthesis of ethanol instead of the biosynthesis of glycerol and acetic acid, and they upregulated several oxidoreductases especially at lag phase and induced programmed cell death at exponential phase. When the yeast cells were cultivated under AFP stress, the new metabolism homeostasis in favor of cellular energy and redox homeostasis was generated in C1, then it was inherited and optimized in C2 and C3, enabling the yeast cells in C2 and C3 to enter the exponential phase in a short period after inoculation, which thus significantly shortened the fermentation time.

  3. Nanoparticle Facilitated Extracellular Electron Transfer in Microbial Fuel Cells

    DTIC Science & Technology

    2014-10-13

    KEYWORDS: Bacteria, facilitated electron transport, electrochemically active, iron sulfide, Shewanella Microbial fuel cells (MFCs) are capable of...to MFC technology is the unique capability of electrochemically active bacteria, such as Shewanella and Geobacter, to divert electrons from the... electrochemical studies also demonstra- ted that the current contribution from remote bacterial cells was significantly diminished at longer cell−electrode dis

  4. Functionally stable and phylogenetically diverse microbial enrichments from microbial fuel cells during wastewater treatment.

    PubMed

    Ishii, Shun'ichi; Suzuki, Shino; Norden-Krichmar, Trina M; Nealson, Kenneth H; Sekiguchi, Yuji; Gorby, Yuri A; Bretschger, Orianna

    2012-01-01

    Microbial fuel cells (MFCs) are devices that exploit microorganisms as biocatalysts to recover energy from organic matter in the form of electricity. One of the goals of MFC research is to develop the technology for cost-effective wastewater treatment. However, before practical MFC applications are implemented it is important to gain fundamental knowledge about long-term system performance, reproducibility, and the formation and maintenance of functionally-stable microbial communities. Here we report findings from a MFC operated for over 300 days using only primary clarifier effluent collected from a municipal wastewater treatment plant as the microbial resource and substrate. The system was operated in a repeat-batch mode, where the reactor solution was replaced once every two weeks with new primary effluent that consisted of different microbial and chemical compositions with every batch exchange. The turbidity of the primary clarifier effluent solution notably decreased, and 97% of biological oxygen demand (BOD) was removed after an 8-13 day residence time for each batch cycle. On average, the limiting current density was 1000 mA/m(2), the maximum power density was 13 mW/m(2), and coulombic efficiency was 25%. Interestingly, the electrochemical performance and BOD removal rates were very reproducible throughout MFC operation regardless of the sample variability associated with each wastewater exchange. While MFC performance was very reproducible, the phylogenetic analyses of anode-associated electricity-generating biofilms showed that the microbial populations temporally fluctuated and maintained a high biodiversity throughout the year-long experiment. These results suggest that MFC communities are both self-selecting and self-optimizing, thereby able to develop and maintain functional stability regardless of fluctuations in carbon source(s) and regular introduction of microbial competitors. These results contribute significantly toward the practical application

  5. Batteryless, wireless sensor powered by a sediment microbial fuel cell.

    PubMed

    Donovan, Conrad; Dewan, Alim; Heo, Deukhyoun; Beyenal, Haluk

    2008-11-15

    Sediment microbial fuel cells (SMFCs) are considered to be an alternative renewable power source for remote monitoring. There are two main challenges to using SMFCs as power sources: 1) a SMFC produces a low potential at which most sensor electronics do not operate, and 2) a SMFC cannot provide continuous power, so energy from the SMFC must be stored and then used to repower sensor electronics intermittently. In this study, we developed a SMFC and a power management system (PMS) to power a batteryless, wireless sensor. A SMFC operating with a microbial anode and cathode, located in the Palouse River, Pullman, Washington, U.S.A., was used to demonstrate the utility of the developed system. The designed PMS stored microbial energy and then started powering the wireless sensor when the SMFC potential reached 320 mV. It continued powering until the SMFC potential dropped below 52 mV. The system was repowered when the SMFC potential increased to 320 mV, and this repowering continued as long as microbial reactions continued. We demonstrated that a microbial fuel cell with a microbial anode and cathode can be used as an effective renewable power source for remote monitoring using custom-designed electronics.

  6. COLCEMID INHIBITION OF CELL GROWTH AND THE CHARACTERIZATION OF A COLCEMID-BINDING ACTIVITY IN SACCHAROMYCES CEREVISIAE

    PubMed Central

    Haber, James E.; Peloquin, John G.; Halvorson, Harlyn O.; Borisy, Gary G.

    1972-01-01

    Under restricted culture conditions, the growth and division of Saccharomyces cerevisiae was inhibited by the antimitotic drug Colcemid; in contrast, the related drug colchicine had no effect. The difference in the sensitivity of yeast to these two agents was not dependent on their ability to permeate the cell but rather reflected an inherent difference in the affinity of the two drugs for a cellular-binding site. The binding moiety was characterized by gel filtration as a macromolecule of approximately 110,000 mol wt with an affinity constant for Colcemid of 0.5 x 104 liters per mole; in addition, this macromolecule was retained by diethylaminoethyl (DEAE) ion exchangers. On the basis of these properties, the Colcemid-binding substance in S. cerevisiae cells was provisionally identified as microtubule subunits. PMID:4561943

  7. Characterization of Fluorescent Proteins for Three- and Four-Color Live-Cell Imaging in S. cerevisiae

    PubMed Central

    Higuchi-Sanabria, Ryo; Garcia, Enrique J.; Tomoiaga, Delia; Munteanu, Emilia L.; Feinstein, Paul; Pon, Liza A.

    2016-01-01

    Saccharomyces cerevisiae are widely used for imaging fluorescently tagged protein fusions. Fluorescent proteins can easily be inserted into yeast genes at their chromosomal locus, by homologous recombination, for expression of tagged proteins at endogenous levels. This is especially useful for incorporation of multiple fluorescent protein fusions into a single strain, which can be challenging in organisms where genetic manipulation is more complex. However, the availability of optimal fluorescent protein combinations for 3-color imaging is limited. Here, we have characterized a combination of fluorescent proteins, mTFP1/mCitrine/mCherry for multicolor live cell imaging in S. cerevisiae. This combination can be used with conventional blue dyes, such as DAPI, for potential four-color live cell imaging. PMID:26727004

  8. Polarized Growth Controls Cell Shape and Bipolar Bud Site Selection in Saccharomyces cerevisiae

    PubMed Central

    Sheu, Yi-Jun; Barral, Yves; Snyder, Michael

    2000-01-01

    We examined the relationship between polarized growth and division site selection, two fundamental processes important for proper development of eukaryotes. Diploid Saccharomyces cerevisiae cells exhibit an ellipsoidal shape and a specific division pattern (a bipolar budding pattern). We found that the polarity genes SPA2, PEA2, BUD6, and BNI1 participate in a crucial step of bud morphogenesis, apical growth. Deleting these genes results in round cells and diminishes bud elongation in mutants that exhibit pronounced apical growth. Examination of distribution of the polarized secretion marker Sec4 demonstrates that spa2Δ, pea2Δ, bud6Δ, and bni1Δ mutants fail to concentrate Sec4 at the bud tip during apical growth and at the division site during repolarization just prior to cytokinesis. Moreover, cell surface expansion is not confined to the distal tip of the bud in these mutants. In addition, we found that the p21-activated kinase homologue Ste20 is also important for both apical growth and bipolar bud site selection. We further examined how the duration of polarized growth affects bipolar bud site selection by using mutations in cell cycle regulators that control the timing of growth phases. The grr1Δ mutation enhances apical growth by stabilizing G1 cyclins and increases the distal-pole budding in diploids. Prolonging polarized growth phases by disrupting the G2/M cyclin gene CLB2 enhances the accuracy of bud site selection in wild-type, spa2Δ, and ste20Δ cells, whereas shortening the polarized growth phases by deleting SWE1 decreases the fidelity of bipolar budding. This study reports the identification of components required for apical growth and demonstrates the critical role of polarized growth in bipolar bud site selection. We propose that apical growth and repolarization at the site of cytokinesis are crucial for establishing spatial cues used by diploid yeast cells to position division planes. PMID:10866679

  9. Fast “Feast/Famine” Cycles for Studying Microbial Physiology Under Dynamic Conditions: A Case Study with Saccharomyces cerevisiae

    PubMed Central

    Suarez-Mendez, Camilo A.; Sousa, Andre; Heijnen, Joseph J.; Wahl, Aljoscha

    2014-01-01

    Microorganisms are constantly exposed to rapidly changing conditions, under natural as well as industrial production scale environments, especially due to large-scale substrate mixing limitations. In this work, we present an experimental approach based on a dynamic feast/famine regime (400 s) that leads to repetitive cycles with moderate changes in substrate availability in an aerobic glucose cultivation of Saccharomyces cerevisiae. After a few cycles, the feast/famine produced a stable and repetitive pattern with a reproducible metabolic response in time, thus providing a robust platform for studying the microorganism’s physiology under dynamic conditions. We found that the biomass yield was slightly reduced (−5%) under the feast/famine regime, while the averaged substrate and oxygen consumption as well as the carbon dioxide production rates were comparable. The dynamic response of the intracellular metabolites showed specific differences in comparison to other dynamic experiments (especially stimulus-response experiments, SRE). Remarkably, the frequently reported ATP paradox observed in single pulse experiments was not present during the repetitive perturbations applied here. We found that intracellular dynamic accumulations led to an uncoupling of the substrate uptake rate (up to 9-fold change at 20 s.) Moreover, the dynamic profiles of the intracellular metabolites obtained with the feast/famine suggest the presence of regulatory mechanisms that resulted in a delayed response. With the feast famine setup many cellular states can be measured at high frequency given the feature of reproducible cycles. The feast/famine regime is thus a versatile platform for systems biology approaches, which can help us to identify and investigate metabolite regulations under realistic conditions (e.g., large-scale bioreactors or natural environments). PMID:24957030

  10. Microbial community structure of different electrode materials in constructed wetland incorporating microbial fuel cell.

    PubMed

    Wang, Junfeng; Song, Xinshan; Wang, Yuhui; Abayneh, Befkadu; Ding, Yi; Yan, Denghua; Bai, Junhong

    2016-12-01

    The microbial fuel cell coupled with constructed wetland (CW-MFC) microcosms were operated under fed-batch mode for evaluating the effect of electrode materials on bioelectricity generation and microbial community composition. Experimental results indicated that the bioenergy output in CW-MFC increased with the substrate concentration; maximum average voltage (177mV) was observed in CW-MFC with carbon fiber felt (CFF). In addition, the four different materials resulted in the formation of significantly different microbial community distribution around the anode electrode. The relative abundance of Proteobacteria in CFF and foamed nickel (FN) was significantly higher than that in stainless steel mesh (SSM) and graphite rod (GR) samples. Notably, the findings indicate that CW-MFC utilizing FN anode electrode could apparently improve relative abundance of Dechloromonas, which has been regarded as a denitrifying and phosphate accumulating microorganism.

  11. Simultaneous microbial and electrochemical reductions of vanadium (V) with bioelectricity generation in microbial fuel cells.

    PubMed

    Zhang, Baogang; Tian, Caixing; Liu, Ying; Hao, Liting; Liu, Ye; Feng, Chuanping; Liu, Yuqian; Wang, Zhongli

    2015-03-01

    Simultaneous microbial and electrochemical reductions of vanadium (V) with bioelectricity generation were realized in microbial fuel cells (MFCs). With initial V(V) concentrations of 75 mg/l and 150 mg/l in anolyte and catholyte, respectively, stable power output of 419±11 mW/m(2) was achieved. After 12h operation, V(V) concentration in the catholyte decreased to the value similar to that of the initial one in the anolyte, meanwhile it was nearly reduced completely in the anolyte. V(IV) was the main reduction product, which subsequently precipitated, acquiring total vanadium removal efficiencies of 76.8±2.9%. Microbial community analysis revealed the emergence of the new species of Deltaproteobacteria and Bacteroidetes as well as the enhanced Spirochaetes mainly functioned in the anode. This study opens new pathways to successful remediation of vanadium contamination.

  12. Electricity generation and microbial community changes in microbial fuel cells packed with different anodic materials.

    PubMed

    Sun, Yanmei; Wei, Jincheng; Liang, Peng; Huang, Xia

    2011-12-01

    Four materials, carbon felt cube (CFC), granular graphite (GG), granular activated carbon (GAC) and granular semicoke (GS) were tested as packed anodic materials to seek a potentially practical material for microbial fuel cells (MFCs). The microbial community and its correlation with the electricity generation performance of MFCs were explored. The maximum power density was found in GAC, followed by CFC, GG and GS. In GAC and CFC packed MFCs, Geobacter was the dominating genus, while Azospira was the most populous group in GG. Results further indicated that GAC was the most favorable for Geobacter adherence and growth, and the maximum power densities had positive correlation with the total biomass and the relative abundance of Geobacter, but without apparent correlation with the microbial diversity. Due to the low content of Geobacter in GS, power generated in this system may be attributed to other microorganisms such as Synergistes, Bacteroidetes and Castellaniella.

  13. Protozoan grazing reduces the current output of microbial fuel cells.

    PubMed

    Holmes, Dawn E; Nevin, Kelly P; Snoeyenbos-West, Oona L; Woodard, Trevor L; Strickland, Justin N; Lovley, Derek R

    2015-10-01

    Several experiments were conducted to determine whether protozoan grazing can reduce current output from sediment microbial fuel cells. When marine sediments were amended with eukaryotic inhibitors, the power output from the fuel cells increased 2-5-fold. Quantitative PCR showed that Geobacteraceae sequences were 120 times more abundant on anodes from treated fuel cells compared to untreated fuel cells, and that Spirotrichea sequences in untreated fuel cells were 200 times more abundant on anode surfaces than in the surrounding sediments. Defined studies with current-producing biofilms of Geobacter sulfurreducens and pure cultures of protozoa demonstrated that protozoa that were effective in consuming G. sulfurreducens reduced current production up to 91% when added to G. sulfurreducens fuel cells. These results suggest that anode biofilms are an attractive food source for protozoa and that protozoan grazing can be an important factor limiting the current output of sediment microbial fuel cells.

  14. Recognition of Microbial Glycolipids by Natural Killer T Cells

    PubMed Central

    Zajonc, Dirk M.; Girardi, Enrico

    2015-01-01

    T cells can recognize microbial antigens when presented by dedicated antigen-presenting molecules. While peptides are presented by classical members of the major histocompatibility complex (MHC) family (MHC I and II), lipids, glycolipids, and lipopeptides can be presented by the non-classical MHC member, CD1. The best studied subset of lipid-reactive T cells are type I natural killer T (iNKT) cells that recognize a variety of different antigens when presented by the non-classical MHCI homolog CD1d. iNKT cells have been shown to be important for the protection against various microbial pathogens, including B. burgdorferi, the causative agents of Lyme disease, and S. pneumoniae, which causes pneumococcal meningitis and community-acquired pneumonia. Both pathogens carry microbial glycolipids that can trigger the T cell antigen receptor (TCR), leading to iNKT cell activation. iNKT cells have an evolutionary conserved TCR alpha chain, yet retain the ability to recognize structurally diverse glycolipids. They do so using a conserved recognition mode, in which the TCR enforces a conserved binding orientation on CD1d. TCR binding is accompanied by structural changes within the TCR binding site of CD1d, as well as the glycolipid antigen itself. In addition to direct recognition of microbial antigens, iNKT cells can also be activated by a combination of cytokines (IL-12/IL-18) and TCR stimulation. Many microbes carry TLR antigens, and microbial infections can lead to TLR activation. The subsequent cytokine response in turn lower the threshold of TCR-mediated iNKT cell activation, especially when weak microbial or even self-antigens are presented during the cause of the infection. In summary, iNKT cells can be directly activated through TCR triggering of strong antigens, while cytokines produced by the innate immune response may be necessary for TCR triggering and iNKT cell activation in the presence of weak antigens. Here, we will review the molecular basis of iNKT cell

  15. Continuous bioethanol production from oilseed rape straw hydrosylate using immobilised Saccharomyces cerevisiae cells.

    PubMed

    Mathew, Anil Kuruvilla; Crook, Mitch; Chaney, Keith; Humphries, Andrea Clare

    2014-02-01

    The aim of the study was to evaluate continuous bioethanol production from oilseed rape (OSR) straw hydrolysate using Saccharomyces cerevisiae cells immobilised in Lentikat® discs. The study evaluated the effect of dilution rate (0.25, 0.50, 0.75 and 1.00 h(-1)), substrate concentration (15, 22, 40 and 60 g L(-1)) and cell loading (0.03, 0.16 and 0.24 g d.c.w.mL(-1) Lentikat®) on bioethanol production. Volumetric productivity was found to increase with increasing substrate concentration from 15 g L(-1) to 60 g L(-1). A maximum volumetric productivity of 12.88 g L(-1)h(-1) was achieved at a substrate concentration of 60 g L(-1) and at a dilution rate of 0.5h(-1). An overall mass balance for bioethanol production was created to determine the energy recovery from bioethanol and concluded that a biorefinery approach might be the most appropriate option for maximising the energy recovery from OSR straw.

  16. Modification of thiamine pyrophosphate dependent enzyme activity by oxythiamine in Saccharomyces cerevisiae cells.

    PubMed

    Tylicki, Adam; Czerniecki, Jan; Dobrzyn, Pawel; Matanowska, Agnieszka; Olechno, Anna; Strumilo, Slawomir

    2005-10-01

    Oxythiamine is an antivitamin derivative of thiamine that after phosphorylation to oxythiamine pyro phosphate can bind to the active centres of thiamine-dependent enzymes. In the present study, the effect of oxythiamine on the viability of Saccharomyces cerevisiae and the activity of thiamine pyrophosphate dependent enzymes in yeast cells has been investigated. We observed a decrease in pyruvate decarboxylase specific activity on both a control and an oxythiamine medium after the first 6 h of culture. The cytosolic enzymes transketolase and pyruvate decarboxylase decreased their specific activity in the presence of oxythiamine but only during the beginning of the cultivation. However, after 12 h of cultivation, oxythiamine-treated cells showed higher specific activity of cytosolic enzymes. More over, it was established by SDS-PAGE that the high specific activity of pyruvate decarboxylase was followed by an increase in the amount of the enzyme protein. In contrast, the mitochondrial enzymes, pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes, were inhibited by oxythiamine during the entire experiment. Our results suggest that the observed strong decrease in growth rate and viability of yeast on medium with oxythiamine may be due to stronger inhibition of mitochondrial pyruvate dehydrogenase than of cytosolic enzymes.

  17. Accumulation of phosphorylated sphingoid long chain bases results in cell growth inhibition in Saccharomyces cerevisiae.

    PubMed Central

    Kim, S; Fyrst, H; Saba, J

    2000-01-01

    Sphingolipid metabolites in mammals can function as signaling molecules with cell-specific functions. In Saccharomyces cerevisiae, phosphorylated long chain bases, such as dihydrosphingosine 1-phosphate and phytosphingosine 1-phosphate, have also been implicated in stress responses. To further explore the biological roles of these molecules, we created disruption mutants for LCB4, LCB5, DPL1, YSR2, YSR3, and SUR2. LCB4 and LCB5 encode kinases that phosphorylate long chain bases. DPL1 and YSR2/YSR3 are involved in degradation of the phosphorylated long chain bases. SUR2 catalyzes conversion of dihydrosphingosine to phytosphingosine. We adapted an HPLC method to measure intracellular concentrations of the phosphorylated long chain bases. Double mutants of dpl1 and ysr2 were inviable, whereas dpl1 ysr2 lcb4 triple mutants were viable. Further, growth inhibition associated with accumulated phosphorylated long chain bases was observed in the triple mutant dpl1 ysr2 lcb4 overexpressing LCB4 or LCB5. These results indicate that phosphorylated long chain bases can inhibit cell growth. Mutants defective in both YSR2 and SUR2, which accumulated dihydrosphingosine 1-phosphate only, grew poorly. The phenotypes of the ysr2 sur2 mutants were suppressed by overexpression of DPL1. Our results clearly show that elevated levels of phosphorylated long chain bases have an antiproliferative effect in yeast. PMID:11102354

  18. [Compartmentalization of Spo11p in vegetative cells of yeast Saccharomyces cerevisiae].

    PubMed

    Komakhin, R A; Komakhina, V V

    2008-01-01

    Double-stranded DNA breaks are currently thought to initiate homologous DNA recombination during meiosis. These breaks are mediated by several proteins, the key protein is Spol1p. Spo11 proteins being encoded by the highly conserved orthologs of SPO11 are present in most eukaryotes ranging from plants to man and are structurally similar to the subunit A of the archaea topoisomerase VI. The SPO11 of S. cerevisiae is currently known to be expressed during prophase I. It encodes a topoisomerase II that is apparently active as a dimer. Neither its localization in the native cells nor its nuclear localisation signals have been described in the literature. We report the expression of the coding region of SPO11 and its truncated variants C-terminally tagged by the egfp reporter in yeast. As judged by the EGFP fluorescence, the Spo11 p-EGFP fusion was localized in vegetative yeast nuclei whereas Spo11pdelta-EGFP lacking 25 N-terminal amino acids of Spollp was localized in cytoplasm. Nineteen N-terminal amino acids of Spo11p fused to EGFP made some reporter to be localized in the nucleus. Thus, we conclude that N-terminal part of Spo11p is a nuclear localization signal that is not specific for prophase I and is used to import proteins in vegetative yeast cells.

  19. Physiological and transcriptional responses of Saccharomyces cerevisiae to d-limonene show changes to the cell wall but not to the plasma membrane.

    PubMed

    Brennan, Timothy C R; Krömer, Jens O; Nielsen, Lars K

    2013-06-01

    Monoterpenes can, upon hydrogenation, be used as light-fraction components of sustainable aviation fuels. Fermentative production of monoterpenes in engineered microorganisms, such as Saccharomyces cerevisiae, has gained attention as a potential route to deliver these next-generation fuels from renewable biomass. However, end product toxicity presents a formidable problem for microbial synthesis. Due to their hydrophobicity, monoterpene inhibition has long been attributed to membrane interference, but the molecular mechanism remains largely unsolved. In order to gain a better understanding of the mode of action, we analyzed the composition and structural integrity of the cell envelope as well as the transcriptional response of yeast cells treated with an inhibitory amount of d-limonene (107 mg/liter). We found no alterations in membrane fluidity, structural membrane integrity, or fatty acid composition after the solvent challenge. A 4-fold increase in the mean fluorescence intensity per cell (using calcofluor white stain) and increased sensitivity to cell wall-degrading enzymes demonstrated that limonene disrupts cell wall properties. Global transcript measurements confirmed the membrane integrity observations by showing no upregulation of ergosterol or fatty acid biosynthesis pathways, which are commonly overexpressed in yeast to reinforce membrane rigidity during ethanol exposure. Limonene shock did cause a compensatory response to cell wall damage through overexpression of several genes (ROM1, RLM1, PIR3, CTT1, YGP1, MLP1, PST1, and CWP1) involved with the cell wall integrity signaling pathway. This is the first report demonstrating that cell wall, rather than plasma membrane, deterioration is the main source of monoterpene inhibition. We show that limonene can alter the structure and function of the cell wall, which has a clear effect on cytokinesis.

  20. Physiological and Transcriptional Responses of Saccharomyces cerevisiae to d-Limonene Show Changes to the Cell Wall but Not to the Plasma Membrane

    PubMed Central

    Brennan, Timothy C. R.; Nielsen, Lars K.

    2013-01-01

    Monoterpenes can, upon hydrogenation, be used as light-fraction components of sustainable aviation fuels. Fermentative production of monoterpenes in engineered microorganisms, such as Saccharomyces cerevisiae, has gained attention as a potential route to deliver these next-generation fuels from renewable biomass. However, end product toxicity presents a formidable problem for microbial synthesis. Due to their hydrophobicity, monoterpene inhibition has long been attributed to membrane interference, but the molecular mechanism remains largely unsolved. In order to gain a better understanding of the mode of action, we analyzed the composition and structural integrity of the cell envelope as well as the transcriptional response of yeast cells treated with an inhibitory amount of d-limonene (107 mg/liter). We found no alterations in membrane fluidity, structural membrane integrity, or fatty acid composition after the solvent challenge. A 4-fold increase in the mean fluorescence intensity per cell (using calcofluor white stain) and increased sensitivity to cell wall-degrading enzymes demonstrated that limonene disrupts cell wall properties. Global transcript measurements confirmed the membrane integrity observations by showing no upregulation of ergosterol or fatty acid biosynthesis pathways, which are commonly overexpressed in yeast to reinforce membrane rigidity during ethanol exposure. Limonene shock did cause a compensatory response to cell wall damage through overexpression of several genes (ROM1, RLM1, PIR3, CTT1, YGP1, MLP1, PST1, and CWP1) involved with the cell wall integrity signaling pathway. This is the first report demonstrating that cell wall, rather than plasma membrane, deterioration is the main source of monoterpene inhibition. We show that limonene can alter the structure and function of the cell wall, which has a clear effect on cytokinesis. PMID:23542628

  1. Mating-defective ste mutations are suppressed by cell division cycle start mutations in Saccharomyces cerevisiae.

    PubMed Central

    Shuster, J R

    1982-01-01

    Temperature-sensitive mutants which arrest in the G1 phase of the cell cycle have been described for the yeast Saccharomyces cerevisiae. One class of these mutants (carrying cdc28, cdc36, cdc37, or cdc39) forms a shmoo morphology at restrictive temperature, characteristic of mating pheromone-arrested wild-type cells. Therefore, one hypothesis to explain the control of cell division by mating factors states that mating pheromones arrest wild-type cells by inactivating one or more of these CDC gene products. A class of mutants (carrying ste4, ste5, ste7, ste11, or ste12) which is insensitive to mating pheromone and sterile has also been described. One possible function of the STE gene products is the inactivation of the CDC gene products in the presence of a mating pheromone. A model incorporating these two hypotheses predicts that such STE gene products will not be required for mating in strains carrying an appropriate cdc lesion. This prediction was tested by assaying the mating abilities of double mutants for all of the pairwise combinations of cdc and ste mutations. Lesions in either cdc36 or cdc39 suppressed the mating defect due to ste4 and ste5. Allele specificity was observed in the suppression of both ste4 and ste5. The results indicate that the CDC36, CDC39, STE4, and STE5 gene products interact functionally or physically or both in the regulation of cell division mediated by the presence or absence of mating pheromones. The cdc36 and cdc39 mutations did not suppress ste7, ste11, or ste12. Lesions in cdc28 or cdc37 did not suppress any of the ste mutations. Other models of CDC and STE gene action which predicted that some of the cdc and ste mutations would be alleles of the same locus were tested. None of the cdc mutations was allelic to the ste mutations and, therefore, these models were eliminated. PMID:6757719

  2. Single Cell Protein Production by Saccharomyces cerevisiae Using an Optimized Culture Medium Composition in a Batch Submerged Bioprocess.

    PubMed

    Hezarjaribi, Mehrnoosh; Ardestani, Fatemeh; Ghorbani, Hamid Reza

    2016-08-01

    Saccharomyces cerevisiae PTCC5269 growth was evaluated to specify an optimum culture medium to reach the highest protein production. Experiment design was conducted using a fraction of the full factorial methodology, and signal to noise ratio was used for results analysis. Maximum cell of 8.84 log (CFU/mL) was resulted using optimized culture composed of 0.3, 0.15, 1, and 50 g L(-1) of ammonium sulfate, iron sulfate, glycine, and glucose, respectively at 300 rpm and 35 °C. Glycine concentration (39.32 % contribution) and glucose concentration (36.15 % contribution) were determined as the most effective factors on the biomass production, while Saccharomyces cerevisiae growth had showed the least dependence on ammonium sulfate (5.2 % contribution) and iron sulfate (19.28 % contribution). The most interaction was diagnosed between ammonium sulfate and iron sulfate concentrations with interaction severity index of 50.71 %, while the less one recorded for glycine and glucose concentration was equal to 8.12 %. An acceptable consistency of 84.26 % was obtained between optimum theoretical cell numbers determined by software of 8.91 log (CFU/mL), and experimentally measured one at optimal condition confirms the suitability of the applied method. High protein content of 44.6 % using optimum culture suggests that Saccharomyces cerevisiae is a good commercial case for single cell protein production.

  3. Studies concerning the temporal and genetic control of cell polarity in Saccharomyces cerevisiae

    PubMed Central

    1991-01-01

    The establishment of cell polarity was examined in the budding yeast, S. cerevisiae. The distribution of a polarized protein, the SPA2 protein, was followed throughout the yeast cell cycle using synchronized cells and cdc mutants. The SPA2 protein localizes to a patch at the presumptive bud site of G1 cells. Later it concentrates at the bud tip in budded cells. At cytokinesis, the SPA2 protein is at the neck between the mother and daughter cells. Analysis of unbudded haploid cells has suggested a series of events that occurs during G1. The SPA2 patch is established very early in G1, while the spindle pole body residues on the distal side of the nucleus. Later, microtubules emanating from the spindle pole body intersect the SPA2 crescent, and the nucleus probably rotates towards the SPA2 patch. By middle G1, most cells contain the SPB on the side of the nucleus proximal to the SPA2 patch, and a long extranuclear microtubule bundle intersects this patch. We suggest that a microtubule capture site exists in the SPA2 staining region that stabilizes the long microtubule bundle; this capture site may be responsible for rotation of the nucleus. Cells containing a polarized distribution of the SPA2 protein also possess a polarized distribution of actin spots in the same region, although the actin staining is much more diffuse. Moreover, cdc4 mutants, which form multiple buds at the restrictive temperature, exhibit simultaneous staining of the SPA2 protein and actin spots in a subset of the bud tips. spa2 mutants contain a polarized distribution of actin spots, and act1-1 and act1-2 mutants often contain a polarized distribution of the SPA2 protein suggesting that the SPA2 protein is not required for localization of the actin spots and the actin spots are not required for localization of the SPA2 protein. cdc24 mutants, which fail to form buds at the restrictive temperature, fail to exhibit polarized localization of the SPA2 protein and actin spots, indicating that the CDC

  4. Production Strategies and Applications of Microbial Single Cell Oils

    PubMed Central

    Ochsenreither, Katrin; Glück, Claudia; Stressler, Timo; Fischer, Lutz; Syldatk, Christoph

    2016-01-01

    Polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 class (e.g., α-linolenic acid, linoleic acid) are essential for maintaining biofunctions in mammalians like humans. Due to the fact that humans cannot synthesize these essential fatty acids, they must be taken up from different food sources. Classical sources for these fatty acids are porcine liver and fish oil. However, microbial lipids or single cell oils, produced by oleaginous microorganisms such as algae, fungi and bacteria, are a promising source as well. These single cell oils can be used for many valuable chemicals with applications not only for nutrition but also for fuels and are therefore an ideal basis for a bio-based economy. A crucial point for the establishment of microbial lipids utilization is the cost-effective production and purification of fuels or products of higher value. The fermentative production can be realized by submerged (SmF) or solid state fermentation (SSF). The yield and the composition of the obtained microbial lipids depend on the type of fermentation and the particular conditions (e.g., medium, pH-value, temperature, aeration, nitrogen source). From an economical point of view, waste or by-product streams can be used as cheap and renewable carbon and nitrogen sources. In general, downstream processing costs are one of the major obstacles to be solved for full economic efficiency of microbial lipids. For the extraction of lipids from microbial biomass cell disruption is most important, because efficiency of cell disruption directly influences subsequent downstream operations and overall extraction efficiencies. A multitude of cell disruption and lipid extraction methods are available, conventional as well as newly emerging methods, which will be described and discussed in terms of large scale applicability, their potential in a modern biorefinery and their influence on product quality. Furthermore, an overview is given about applications of microbial lipids or derived fatty

  5. Production Strategies and Applications of Microbial Single Cell Oils.

    PubMed

    Ochsenreither, Katrin; Glück, Claudia; Stressler, Timo; Fischer, Lutz; Syldatk, Christoph

    2016-01-01

    Polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 class (e.g., α-linolenic acid, linoleic acid) are essential for maintaining biofunctions in mammalians like humans. Due to the fact that humans cannot synthesize these essential fatty acids, they must be taken up from different food sources. Classical sources for these fatty acids are porcine liver and fish oil. However, microbial lipids or single cell oils, produced by oleaginous microorganisms such as algae, fungi and bacteria, are a promising source as well. These single cell oils can be used for many valuable chemicals with applications not only for nutrition but also for fuels and are therefore an ideal basis for a bio-based economy. A crucial point for the establishment of microbial lipids utilization is the cost-effective production and purification of fuels or products of higher value. The fermentative production can be realized by submerged (SmF) or solid state fermentation (SSF). The yield and the composition of the obtained microbial lipids depend on the type of fermentation and the particular conditions (e.g., medium, pH-value, temperature, aeration, nitrogen source). From an economical point of view, waste or by-product streams can be used as cheap and renewable carbon and nitrogen sources. In general, downstream processing costs are one of the major obstacles to be solved for full economic efficiency of microbial lipids. For the extraction of lipids from microbial biomass cell disruption is most important, because efficiency of cell disruption directly influences subsequent downstream operations and overall extraction efficiencies. A multitude of cell disruption and lipid extraction methods are available, conventional as well as newly emerging methods, which will be described and discussed in terms of large scale applicability, their potential in a modern biorefinery and their influence on product quality. Furthermore, an overview is given about applications of microbial lipids or derived fatty

  6. Anodic microbial community diversity as a predictor of the power output of microbial fuel cells.

    PubMed

    Stratford, James P; Beecroft, Nelli J; Slade, Robert C T; Grüning, André; Avignone-Rossa, Claudio

    2014-03-01

    The relationship between the diversity of mixed-species microbial consortia and their electrogenic potential in the anodes of microbial fuel cells was examined using different diversity measures as predictors. Identical microbial fuel cells were sampled at multiple time-points. Biofilm and suspension communities were analysed by denaturing gradient gel electrophoresis to calculate the number and relative abundance of species. Shannon and Simpson indices and richness were examined for association with power using bivariate and multiple linear regression, with biofilm DNA as an additional variable. In simple bivariate regressions, the correlation of Shannon diversity of the biofilm and power is stronger (r=0.65, p=0.001) than between power and richness (r=0.39, p=0.076), or between power and the Simpson index (r=0.5, p=0.018). Using Shannon diversity and biofilm DNA as predictors of power, a regression model can be constructed (r=0.73, p<0.001). Ecological parameters such as the Shannon index are predictive of the electrogenic potential of microbial communities.

  7. Enhanced product formation in continuous fermentations with microbial cell recycle

    SciTech Connect

    Bull, D.N.; Young, M.D.

    1981-02-01

    The effect of partial recycle of microbial cells on the operation of a chemostat has been investigated for two fermentations. Stable steady states with and without partial cell recycle were obtained for the conversion of d-sorbitol to L-sorbose by Gluconobacter oxydans subsp. suboxydans 1916B and for the conversion of glucose to 2-ketogluconic acid by Serratia marcescens NRRl B-486. The employment of partial cell recycle dramatically increased product formation rates for both fermentations.

  8. Recent advances in microbial single cell genomics technology and applications

    NASA Astrophysics Data System (ADS)

    Stepanauskas, R.

    2015-12-01

    Single cell genomics is increasingly utilized as a powerful tool to decipher the metabolic potential, evolutionary histories and in situ interactions of environmental microorganisms. I will present several new developments of this exciting technology, which improve genomic data recovery from individual cells and allow its integration with cell's phenotypic properties. I will also demonstrate how these new technical capabilities help understanding the biology of the "microbial dark matter" inhabiting marine and terrestrial subsurface environments.

  9. Defects in Protein Folding Machinery Affect Cell Wall Integrity and Reduce Ethanol Tolerance in S. cerevisiae.

    PubMed

    Narayanan, Aswathy; Pullepu, Dileep; Reddy, Praveen Kumar; Uddin, Wasim; Kabir, M Anaul

    2016-07-01

    The chaperonin complex CCT/TRiC (chaperonin containing TCP-1/TCP-1 ring complex) participates in the folding of many crucial proteins including actin and tubulin in eukaryotes. Mutations in genes encoding its subunits can affect protein folding and in turn, the physiology of the organism. Stress response in Saccharomyces cerevisiae is important in fermentation reactions and operates through overexpression and underexpression of genes, thus altering the protein profile. Defective protein folding machinery can disturb this process. In this study, the response of cct mutants to stress conditions in general and ethanol in specific was investigated. CCT1 mutants showed decreased resistance to different conditions tested including osmotic stress, metal ions, surfactants, reducing and oxidising agents. Cct1-3 mutant with the mutation in the conserved ATP-binding region showed irreversible defects than other mutants. These mutants were found to have inherent cell wall defects and showed decreased ethanol tolerance. This study reveals that cell wall defects and ethanol sensitivity are linked. Genetic and proteomic analyses showed that the yeast genes RPS6A (ribosomal protein), SCL1 (proteasomal subunit) and TDH3 (glyceraldehyde-3-phosphate dehydrogenase) on overexpression, improved the growth of cct1-3 mutant on ethanol. We propose the breakdown of common stress response pathways caused by mutations in CCT complex and the resulting scarcity of functional stress-responsive proteins, affecting the cell's defence against different stress agents in cct mutants. Defective cytoskeleton and perturbed cell wall integrity reduce the ethanol tolerance in the mutants which are rescued by the extragenic suppressors.

  10. Improving flavor metabolism of Saccharomyces cerevisiae by mixed culture with Bacillus licheniformis for Chinese Maotai-flavor liquor making.

    PubMed

    Meng, Xing; Wu, Qun; Wang, Li; Wang, Diqiang; Chen, Liangqiang; Xu, Yan

    2015-12-01

    Microbial interactions could impact the metabolic behavior of microbes involved in food fermentation, and therefore they are important for improving food quality. This study investigated the effect of Bacillus licheniformis, the dominant bacteria in the fermentation process of Chinese Maotai-flavor liquor, on the metabolic activity of Saccharomyces cerevisiae. Results indicated that S. cerevisiae inhibited the growth of B. licheniformis in all mixed culture systems and final viable cell count was lower than 20 cfu/mL. Although growth of S. cerevisiae was barely influenced by B. licheniformis, its metabolism was changed as initial inoculation ratio varied. The maximum ethanol productions were observed in S. cerevisiae and B. licheniformis at 10(6):10(7) and 10(6):10(8) ratios and have increased by 16.8 % compared with single culture of S. cerevisiae. According to flavor compounds, the culture ratio 10(6):10(6) showed the highest level of total concentrations of all different kinds of flavor compounds. Correlation analyses showed that 12 flavor compounds, including 4 fatty acids and their 2 corresponding esters, 1 terpene, and 5 aromatic compounds, that could only be produced by S. cerevisiae were significantly correlated with the initial inoculation amount of B. licheniformis. These metabolic changes in S. cerevisiae were not only a benefit for liquor aroma, but may also be related to its inhibition effect in mixed culture. This study could help to reveal the microbial interactions in Chinese liquor fermentation and provide guidance for optimal arrangement of mixed culture fermentation systems.

  11. Segregation of the Anodic Microbial Communities in a Microbial Fuel Cell Cascade

    PubMed Central

    Hodgson, Douglas M.; Smith, Ann; Dahale, Sonal; Stratford, James P.; Li, Jia V.; Grüning, André; Bushell, Michael E.; Marchesi, Julian R.; Avignone Rossa, C.

    2016-01-01

    Metabolic interactions within microbial communities are essential for the efficient degradation of complex organic compounds, and underpin natural phenomena driven by microorganisms, such as the recycling of carbon-, nitrogen-, and sulfur-containing molecules. These metabolic interactions ultimately determine the function, activity and stability of the community, and therefore their understanding would be essential to steer processes where microbial communities are involved. This is exploited in the design of microbial fuel cells (MFCs), bioelectrochemical devices that convert the chemical energy present in substrates into electrical energy through the metabolic activity of microorganisms, either single species or communities. In this work, we analyzed the evolution of the microbial community structure in a cascade of MFCs inoculated with an anaerobic microbial community and continuously fed with a complex medium. The analysis of the composition of the anodic communities revealed the establishment of different communities in the anodes of the hydraulically connected MFCs, with a decrease in the abundance of fermentative taxa and a concurrent increase in respiratory taxa along the cascade. The analysis of the metabolites in the anodic suspension showed a metabolic shift between the first and last MFC, confirming the segregation of the anodic communities. Those results suggest a metabolic interaction mechanism between the predominant fermentative bacteria at the first stages of the cascade and the anaerobic respiratory electrogenic population in the latter stages, which is reflected in the observed increase in power output. We show that our experimental system represents an ideal platform for optimization of processes where the degradation of complex substrates is involved, as well as a potential tool for the study of metabolic interactions in complex microbial communities. PMID:27242723

  12. Segregation of the Anodic Microbial Communities in a Microbial Fuel Cell Cascade.

    PubMed

    Hodgson, Douglas M; Smith, Ann; Dahale, Sonal; Stratford, James P; Li, Jia V; Grüning, André; Bushell, Michael E; Marchesi, Julian R; Avignone Rossa, C

    2016-01-01

    Metabolic interactions within microbial communities are essential for the efficient degradation of complex organic compounds, and underpin natural phenomena driven by microorganisms, such as the recycling of carbon-, nitrogen-, and sulfur-containing molecules. These metabolic interactions ultimately determine the function, activity and stability of the community, and therefore their understanding would be essential to steer processes where microbial communities are involved. This is exploited in the design of microbial fuel cells (MFCs), bioelectrochemical devices that convert the chemical energy present in substrates into electrical energy through the metabolic activity of microorganisms, either single species or communities. In this work, we analyzed the evolution of the microbial community structure in a cascade of MFCs inoculated with an anaerobic microbial community and continuously fed with a complex medium. The analysis of the composition of the anodic communities revealed the establishment of different communities in the anodes of the hydraulically connected MFCs, with a decrease in the abundance of fermentative taxa and a concurrent increase in respiratory taxa along the cascade. The analysis of the metabolites in the anodic suspension showed a metabolic shift between the first and last MFC, confirming the segregation of the anodic communities. Those results suggest a metabolic interaction mechanism between the predominant fermentative bacteria at the first stages of the cascade and the anaerobic respiratory electrogenic population in the latter stages, which is reflected in the observed increase in power output. We show that our experimental system represents an ideal platform for optimization of processes where the degradation of complex substrates is involved, as well as a potential tool for the study of metabolic interactions in complex microbial communities.

  13. Bioaccumulation of the Selected Metal Ions in Saccharomyces cerevisiae Cells Under Treatment of the Culture with Pulsed Electric Field (PEF).

    PubMed

    Pankiewicz, Urszula; Sujka, Monika; Jamroz, Jerzy

    2015-12-01

    The obtained results demonstrated an influence of PEF on increase in accumulation of various ions in S. cerevisiae cells. Optimization of particular PEF parameters and ions concentrations in the medium caused twofold increase in accumulation of magnesium and zinc ions and 3.5-fold higher accumulation of calcium ions in the cells. In the case of ion couple, accumulation of magnesium and zinc was, respectively, 1.5-fold and twofold higher in comparison to the control cultures. Yeast cells biomass enriched with Mg(2+), Zn(2+), Ca(2+) as well as Mg(2+) and Zn(2+) (simultaneously) may be an alternative for pharmacological supplementation applied in deficiency of these cations.

  14. Magnetic studies of ferrofluid-modified microbial cells.

    PubMed

    Mosiniewicz-Szablewska, Ewa; Safarikova, Mirka; Safarik, Ivo

    2010-04-01

    Microbial cells (Kluyveromyces fragilis and Chlorella vulgaris) efficiently interacted with maghemite nanoparticles stabilized as low-pH ionic magnetic fluid, leading to the formation of magnetically labeled cells. This simple procedure allows to use the prepared materials as new cheap and easy to get magnetic affinity adsorbents to the removal of water-soluble dyes from polluted water sources using magnetic separation techniques. Magnetically modified cells were investigated by means of electron spin resonance spectroscopy and conventional magnetic methods over the temperature range 4-300 K. The magnetic behavior of these materials was dominated by the superparamagnetic relaxation of isolated single domain maghemite particles although a little amount of agglomerates was also present on the cell surface. However, these agglomerates were sufficiently small to show at static conditions the superparamagnetic behavior at room temperature. Therefore, the ferrofluid-modified microbial cells represent new interesting magnetic affinity adsorbents which could be applied for large-scale magnetic separation processes.

  15. Evaluation of industrial Saccharomyces cerevisiae strains as the chassis cell for second-generation bioethanol production

    PubMed Central

    Li, Hongxing; Wu, Meiling; Xu, Lili; Hou, Jin; Guo, Ting; Bao, Xiaoming; Shen, Yu

    2015-01-01

    To develop a suitable Saccharomyces cerevisiae industrial strain as a chassis cell for ethanol production using lignocellulosic materials, 32 wild-type strains were evaluated for their glucose fermenting ability, their tolerance to the stresses they might encounter in lignocellulosic hydrolysate fermentation and their genetic background for pentose metabolism. The strain BSIF, isolated from tropical fruit in Thailand, was selected out of the distinctly different strains studied for its promising characteristics. The maximal specific growth rate of BSIF was as high as 0.65 h−1 in yeast extract peptone dextrose medium, and the ethanol yield was 0.45 g g−1 consumed glucose. Furthermore, compared with other strains, this strain exhibited superior tolerance to high temperature, hyperosmotic stress and oxidative stress; better growth performance in lignocellulosic hydrolysate; and better xylose utilization capacity when an initial xylose metabolic pathway was introduced. All of these results indicate that this strain is an excellent chassis strain for lignocellulosic ethanol production. PMID:25616171

  16. Role of glutathione metabolism status in the definition of some cellular parameters and oxidative stress tolerance of Saccharomyces cerevisiae cells growing as biofilms.

    PubMed

    Gales, Grégoire; Penninckx, Michel; Block, Jean-Claude; Leroy, Pierre

    2008-08-01

    The resistance of Saccharomyces cerevisiae to oxidative stress (H(2)O(2) and Cd(2+)) was compared in biofilms and planktonic cells, with the help of yeast mutants deleted of genes related to glutathione metabolism and oxidative stress. Biofilm-forming cells were found predominantly in the G1 stage of the cell cycle. This might explain their higher tolerance to oxidative stress and the young replicative age of these cells in an old culture. The reduced glutathione status of S. cerevisiae was affected by the growth phase and apparently plays an important role in oxidative stress tolerance in cells growing as a biofilm.

  17. An Endomitotic Effect of a Cell Cycle Mutation of SACCHAROMYCES CEREVISIAE

    PubMed Central

    Schild, David; Ananthaswamy, Honnavara N.; Mortimer, Robert K.

    1981-01-01

    A recessive temperature-sensitive mutation of Saccharomyces cerevisiae has been isolated and shown to cause an increase in ploidy in both haploids and diploids. Genetic analysis revealed that the strain carrying the mutation was an aa diploid, although MNNG mutagenesis had been done on an a haploid strain. When the mutant strain was crossed with an αα diploid and the resultant tetraploid sporulated, some of the meiotic progeny of this tetraploid were themselves tetraploid, as shown by both genetic analysis and DNA measurements, instead of diploid as expected of tetraploid meiosis. The ability of these tetraploids to continue to produce tetraploid meiotic progeny was followed for four generations. Homothallism was excluded as a cause of the increase in ploidy; visual pedigree analysis of spore clones to about the 32-cell stage failed to reveal any zygotes, and haploids that diploidized retained their mating type. An extra round of meiotic DNA synthesis was also considered and excluded. It was found that tetraploidization was independent of sporulation temperature, but was dependent on the temperature of germination and the growth of the spores. Increase in ploidy occurred when the spores were germinated and grown at 30°, but did not occur at 23°. Two cycles of sporulation and growth at 23° resulted in haploids, which were shown to diploidize within 24 hr when grown at 30°. Visual observation of the haploid cells incubated at 36° revealed a cell-division-cycle phenotype characteristic of mutations that affect nuclear division; complementation analysis demonstrated that the mutation, cdc31–2, is allelic to cdc31–1, a mutation isolated by Hartwell et al. (1973) and characterized as causing a temperature-sensitive arrest during late nuclear division. The segregation of cdc31–2 in heterozygous diploids was 2:2 and characteristic of a noncentromere-linked gene. PMID:7028565

  18. Microbial Fuel Cell Performance with a Pressurized Cathode Chamber

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microbial fuel cell (MFC) power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. One important factor for this is the normally low solubility of oxygen in the aqueous cathode solution creating mass transport limitations, which hinder oxygen reduction a...

  19. The Microbial Fuel Cell as an Education Tool

    ERIC Educational Resources Information Center

    Dewan, Alim; Van Wie, Bernard; Beyenal, Haluk; Lewandowski, Zbigniew

    2010-01-01

    Many chemical engineering programs offer courses from a variety of disciplines to teach their students multidisciplinary concepts, but often these courses lack appropriate tools for linking newly learned concepts to principles learned in the core courses. This paper describes our experience of incorporating a microbial fuel cell education module…

  20. The first self-sustainable microbial fuel cell stack.

    PubMed

    Ledezma, Pablo; Stinchcombe, Andrew; Greenman, John; Ieropoulos, Ioannis

    2013-02-21

    This study reports for the first time on the development of a self-sustainable microbial fuel cell stack capable of self-maintenance (feeding, hydration, sensing & reporting). Furthermore, the stack system is producing excess energy, which can be used for improved functionality. The self-maintenance is performed by the stack powering single and multi-channel peristaltic pumps.

  1. Oxygen - Enemy or Friend for Microbial Fuel Cell Anode Performance?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Until recently, scientists and engineers have held a strong belief that oxygen intrusion into the anode chamber of a bioelectrochemical system (BES) is detrimental to microbial fuel cell (MFC) performance because oxygen acts as an alternate electron acceptor. This would, according to recent beliefs...

  2. The Transient Inactivation of the Master Cell Cycle Phosphatase Cdc14 Causes Genomic Instability in Diploid Cells of Saccharomyces cerevisiae

    PubMed Central

    Quevedo, Oliver; Ramos-Pérez, Cristina; Petes, Thomas D.; Machín, Félix

    2015-01-01

    Genomic instability is a common feature found in cancer cells . Accordingly, many tumor suppressor genes identified in familiar cancer syndromes are involved in the maintenance of the stability of the genome during every cell division and are commonly referred to as caretakers. Inactivating mutations and epigenetic silencing of caretakers are thought to be the most important mechanisms that explain cancer-related genome instability. However, little is known of whether transient inactivation of caretaker proteins could trigger genome instability and, if so, what types of instability would occur. In this work, we show that a brief and reversible inactivation, during just one cell cycle, of the key phosphatase Cdc14 in the model organism Saccharomyces cerevisiae is enough to result in diploid cells with multiple gross chromosomal rearrangements and changes in ploidy. Interestingly, we observed that such transient loss yields a characteristic fingerprint whereby trisomies are often found in small-sized chromosomes, and gross chromosome rearrangements, often associated with concomitant loss of heterozygosity, are detected mainly on the ribosomal DNA-bearing chromosome XII. Taking into account the key role of Cdc14 in preventing anaphase bridges, resetting replication origins, and controlling spindle dynamics in a well-defined window within anaphase, we speculate that the transient loss of Cdc14 activity causes cells to go through a single mitotic catastrophe with irreversible consequences for the genome stability of the progeny. PMID:25971663

  3. The Transient Inactivation of the Master Cell Cycle Phosphatase Cdc14 Causes Genomic Instability in Diploid Cells of Saccharomyces cerevisiae.

    PubMed

    Quevedo, Oliver; Ramos-Pérez, Cristina; Petes, Thomas D; Machín, Félix

    2015-07-01

    Genomic instability is a common feature found in cancer cells . Accordingly, many tumor suppressor genes identified in familiar cancer syndromes are involved in the maintenance of the stability of the genome during every cell division and are commonly referred to as caretakers. Inactivating mutations and epigenetic silencing of caretakers are thought to be the most important mechanisms that explain cancer-related genome instability. However, little is known of whether transient inactivation of caretaker proteins could trigger genome instability and, if so, what types of instability would occur. In this work, we show that a brief and reversible inactivation, during just one cell cycle, of the key phosphatase Cdc14 in the model organism Saccharomyces cerevisiae is enough to result in diploid cells with multiple gross chromosomal rearrangements and changes in ploidy. Interestingly, we observed that such transient loss yields a characteristic fingerprint whereby trisomies are often found in small-sized chromosomes, and gross chromosome rearrangements, often associated with concomitant loss of heterozygosity, are detected mainly on the ribosomal DNA-bearing chromosome XII. Taking into account the key role of Cdc14 in preventing anaphase bridges, resetting replication origins, and controlling spindle dynamics in a well-defined window within anaphase, we speculate that the transient loss of Cdc14 activity causes cells to go through a single mitotic catastrophe with irreversible consequences for the genome stability of the progeny.

  4. Significant quantities of the glycolytic enzyme phosphoglycerate mutase are present in the cell wall of yeast Saccharomyces cerevisiae.

    PubMed Central

    Motshwene, Precious; Brandt, Wolf; Lindsey, George

    2003-01-01

    NaOH was used to extract proteins from the cell walls of the yeast Saccharomyces cerevisiae. This treatment was shown not to disrupt yeast cells, as NaOH-extracted cells displayed a normal morphology upon electron microscopy. Moreover, extracted and untreated cells had qualitatively similar protein contents upon disruption. When yeast was grown in the presence of 1 M mannitol, two proteins were found to be present at an elevated concentration in the cell wall. These were found to be the late-embryogenic-abundant-like protein heat-shock protein 12 and the glycolytic enzyme phosphoglycerate mutase. The presence of phosphoglycerate mutase in the cell wall was confirmed by immunocytochemical analysis. Not only was the phosphoglycerate mutase in the yeast cell wall found to be active, but whole yeast cells were also able to convert 3-phosphoglycerate in the medium into ethanol, provided that the necessary cofactors were present. PMID:12238949

  5. Microbial community dynamics in continuous microbial fuel cells fed with synthetic wastewater and pig slurry.

    PubMed

    Sotres, Ana; Tey, Laura; Bonmatí, August; Viñas, Marc

    2016-10-01

    Two-chambered microbial fuel cells (MFCs) operating with synthetic wastewater and pig slurry were assessed. Additionally, the use of 2-bromoethanesulfonate (BES-Inh) was studied. The synthetic wastewater-fed MFC (MFCSW) showed a maximum power density (PDmax) of 2138mWm(-3), and the addition of BES-Inh (10mM) did not show any improvement in its performance (PDmax=2078mWm(-3)). When pig slurry was used as feed (MFCPS), PDmax increased up to 5623mWm(-3). The microbial community composition was affected by the type of substrate used. While, Pseudomonadaceae and Clostridiaceae were the most representative families within the acetate-based medium, Flavobacteriaceae, Chitinophagaceae, Comamonadaceae and Nitrosomonadaceae were predominant when pig slurry was used as feed. Otherwise, only the Eubacterial microbial community composition was strongly modified when adding BES-Inh, thus leading to an enrichment of the Bacteroidetes phylum. Oppositely, the Archaeal community was less affected by the addition of BES-Inh, and Methanosarcina sp., arose as the predominant family in both situations. Despite all the differences in microbial communities, 6 operational taxonomic units (OTUs) belonging to Bacteroidetes (Porphyromonadaceae and Marinilabiaceae) and Firmicutes (Clostridiales) were found to be common to both MFCs, also for different contents of COD and N-NH4(+), and therefore could be considered as the bioanode core microbiome.

  6. Microbial fuel cell treatment of fuel process wastewater

    DOEpatents

    Borole, Abhijeet P; Tsouris, Constantino

    2013-12-03

    The present invention is directed to a method for cleansing fuel processing effluent containing carbonaceous compounds and inorganic salts, the method comprising contacting the fuel processing effluent with an anode of a microbial fuel ell, the anode containing microbes thereon which oxidatively degrade one or more of the carbonaceous compounds while producing electrical energy from the oxidative degradation, and directing the produced electrical energy to drive an electrosorption mechanism that operates to reduce the concentration of one or more inorganic salts in the fuel processing effluent, wherein the anode is in electrical communication with a cathode of the microbial fuel cell. The invention is also directed to an apparatus for practicing the method.

  7. Coastal microbial fuel cell: scaling laws and systems

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Promode R.; McNeilly, Frank J.; Thivierge, Daniel P.; Fredette, Albert R.

    2006-05-01

    Microbes, like Geobacters, have inhabited the seafloors around the world since the early days of earth. Such regions are anaerobic and they gain energy by using the widely prevalent iron oxides and organic matters. Because they appear to colonize conducting surfaces that act as sinks of electrons, microbial fuel cells have been shown to convert organic matter to electricity. A microbial fuel cell system has been deployed in Narragansett Bay in Newport, Rhode Island for a year. Currently, the cathode and anode areas are of the order of that of a small wind mill. Measurements have been carried out to determine the marine scaling laws of power harvesting in passive benthic microbial fuel cells. The focus has been on the ocean engineering aspects such as marine scaling laws and the integration of the biochemical and the electronic systems. The characteristics examined are: the relationship of electrode surface area and power produced, the stabilization rates of ionic paths, that is, the effects of location depth of cathodes on stabilization after deployment, the effects of solar and lunar cycles in the Narragansett Bay on the dynamic components of power produced, and the hysteresis effects between periods of active power harvesting and dormancy; the effects of 'on sediment surface' versus 'in sediment' anode deployment have been examined for smaller electrode areas so far. A capacitance model of power consumption and harvesting has been proposed for the marine environment. It is assumed that the primordial benthic microbe laden layer of the earth acts like a giant capacitor. In the microbial fuel cell, this charged benthic layer acts in series with a smaller constant voltage DC power source. This giant benthic capacitance is a result of untapped accumulated charge from the microbes while the DC source originates from the real-time production due to the microbes. Finally, the microbial fuel cell is integrated with a power conversion system to intermittently energize a

  8. Bioethanol production from mixed sugars by Scheffersomyces stipitis free and immobilized cells, and co-cultures with Saccharomyces cerevisiae.

    PubMed

    De Bari, Isabella; De Canio, Paola; Cuna, Daniela; Liuzzi, Federico; Capece, Angela; Romano, Patrizia

    2013-09-25

    Bioethanol can be produced from several biomasses including lignocellulosic materials. Besides 6-carbon sugars that represent the prevalent carbohydrates, some of these feedstocks contain significant amounts of 5-carbon sugars. One common limit of the major part of the xylose-fermenting yeasts is the diauxic shift between the uptake of glucose and xylose during the fermentation of mixed syrups. Thus, optimized fermentation strategies are required. In this paper the ability of Scheffersomyces stipitis strain NRRLY-11544 to ferment mixed syrups with a total sugar concentration in the range 40-80 g/L was investigated by using mono cultures, co-cultures with Saccharomyces cerevisiae strain Bakers Yeast Type II and single cultures immobilized in silica-hydrogel films. The experimental design for the fermentations with immobilized cells included the process analysis in function of two parameters: the fraction of the gel in the broth and the concentration of the cells loaded in the gel. Furthermore, for each total sugars level, the fermentative course of S. stipitis was analyzed at several glucose-to xylose ratios. The results indicated that the use of S. stipitis and S. cerevisiae in free co-cultures ensured faster processes than single cultures of S. stipitis either free or immobilized. However, the rapid production of ethanol by S. cerevisiae inhibited S. stipitis and caused a stuck of the process. Immobilization of S. stipitis in silica-hydrogel increased the relative consumption rate of xylose-to-glucose by 2-6 times depending on the composition of the fermentation medium. Furthermore the films performances appeared stable over three weeks of continuous operations. However, on the whole, the final process yields obtained with the immobilized cells were not meaningfully different from that of the free cells. This was probably due to concurrent fermentations operated by the cells released in the broth. Optimization of the carrier characteristics could improve the

  9. Microbial Fuel Cell Transformation of Recalcitrant Organic Compounds in Support of Biosensor Research

    DTIC Science & Technology

    2014-03-27

    Microbial Fuel Cell Transformation of Recalcitrant Organic Compounds in Support of Biosensor ...in the United States. AFIT-ENV-14-M-62 Microbial Fuel Cell Transformation of Recalcitrant Organic Compounds in Support of Biosensor Research...DISTRIBUTION UNLIMITED AFIT-ENV-14-M-62 Microbial Fuel Cell Transformation of Recalcitrant Organic Compounds in Support of Biosensor Research Marc

  10. Whole-cell biocatalytic and de novo production of alkanes from free fatty acids in Saccharomyces cerevisiae.

    PubMed

    Foo, Jee Loon; Susanto, Adelia Vicanatalita; Keasling, Jay D; Leong, Susanna Su Jan; Chang, Matthew Wook

    2017-01-01

    Rapid global industrialization in the past decades has led to extensive utilization of fossil fuels, which resulted in pressing environmental problems due to excessive carbon emission. This prompted increasing interest in developing advanced biofuels with higher energy density to substitute fossil fuels and bio-alkane has gained attention as an ideal drop-in fuel candidate. Production of alkanes in bacteria has been widely studied but studies on the utilization of the robust yeast host, Saccharomyces cerevisiae, for alkane biosynthesis have been lacking. In this proof-of-principle study, we present the unprecedented engineering of S. cerevisiae for conversion of free fatty acids to alkanes. A fatty acid α-dioxygenase from Oryza sativa (rice) was expressed in S. cerevisiae to transform C12-18 free fatty acids to C11-17 aldehydes. Co-expression of a cyanobacterial aldehyde deformylating oxygenase converted the aldehydes to the desired alkanes. We demonstrated the versatility of the pathway by performing whole-cell biocatalytic conversion of exogenous free fatty acid feedstocks into alkanes as well as introducing the pathway into a free fatty acid overproducer for de novo production of alkanes from simple sugar. The results from this work are anticipated to advance the development of yeast hosts for alkane production. Biotechnol. Bioeng. 2017;114: 232-237. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

  11. Whole‐cell biocatalytic and de novo production of alkanes from free fatty acids in Saccharomyces cerevisiae

    PubMed Central

    Foo, Jee Loon; Susanto, Adelia Vicanatalita; Keasling, Jay D.; Leong, Susanna Su Jan

    2016-01-01

    ABSTRACT Rapid global industrialization in the past decades has led to extensive utilization of fossil fuels, which resulted in pressing environmental problems due to excessive carbon emission. This prompted increasing interest in developing advanced biofuels with higher energy density to substitute fossil fuels and bio‐alkane has gained attention as an ideal drop‐in fuel candidate. Production of alkanes in bacteria has been widely studied but studies on the utilization of the robust yeast host, Saccharomyces cerevisiae, for alkane biosynthesis have been lacking. In this proof‐of‐principle study, we present the unprecedented engineering of S. cerevisiae for conversion of free fatty acids to alkanes. A fatty acid α‐dioxygenase from Oryza sativa (rice) was expressed in S. cerevisiae to transform C12–18 free fatty acids to C11–17 aldehydes. Co‐expression of a cyanobacterial aldehyde deformylating oxygenase converted the aldehydes to the desired alkanes. We demonstrated the versatility of the pathway by performing whole‐cell biocatalytic conversion of exogenous free fatty acid feedstocks into alkanes as well as introducing the pathway into a free fatty acid overproducer for de novo production of alkanes from simple sugar. The results from this work are anticipated to advance the development of yeast hosts for alkane production. Biotechnol. Bioeng. 2017;114: 232–237. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. PMID:26717118

  12. Cell Surface Display of Four Types of Solanum nigrum Metallothionein on Saccharomyces cerevisiae for Biosorption of Cadmium.

    PubMed

    Wei, Qinguo; Zhang, Honghai; Guo, Dongge; Ma, Shisheng

    2016-05-28

    We displayed four types of Solanum nigrum metallothionein (SMT) for the first time on the surface of Saccharomyces cerevisiae using an α-agglutinin-based display system. The SMT genes were amplified by RT-PCR. The plasmid pYES2 was used to construct the expression vector. Transformed yeast strains were confirmed by PCR amplification and custom sequencing. Surface-expressed metallothioneins were indirectly indicated by the enhanced cadmium sorption capacity. Flame atomic absorption spectrophotometry was used to examine the concentration of Cd(2+) in this study. The transformed yeast strains showed much higher resistance ability to Cd(2+) compared with the control. Strikingly, their Cd(2+) accumulation was almost twice as much as that of the wild-type yeast cells. Furthermore, surface-engineered yeast strains could effectively adsorb ultra-trace cadmium and accumulate Cd(2+) under a wide range of pH levels, from 3 to 7, without disturbing the Cu(2+) and Hg(2+). Four types of surfaceengineered Saccharomyces cerevisiae strains were constructed and they could be used to purify Cd(2+)-contaminated water and adsorb ultra-trace cadmium effectively. The surface-engineered Saccharomyces cerevisiae strains would be useful tools for the bioremediation and biosorption of environmental cadmium contaminants.

  13. Tomato QM-like protein protects Saccharomyces cerevisiae cells against oxidative stress by regulating intracellular proline levels.

    PubMed

    Chen, Changbin; Wanduragala, Srimevan; Becker, Donald F; Dickman, Martin B

    2006-06-01

    Exogenous proline can protect cells of Saccharomyces cerevisiae from oxidative stress. We altered intracellular proline levels by overexpressing the proline dehydrogenase gene (PUT1) of S. cerevisiae. Put1p performs the first enzymatic step of proline degradation in S. cerevisiae. Overexpression of Put1p results in low proline levels and hypersensitivity to oxidants, such as hydrogen peroxide and paraquat. A put1-disrupted yeast mutant deficient in Put1p activity has increased protection from oxidative stress and increased proline levels. Following a conditional life/death screen in yeast, we identified a tomato (Lycopersicon esculentum) gene encoding a QM-like protein (tQM) and found that stable expression of tQM in the Put1p-overexpressing strain conferred protection against oxidative damage from H2O2, paraquat, and heat. This protection was correlated with reactive oxygen species (ROS) reduction and increased proline accumulation. A yeast two-hybrid system assay was used to show that tQM physically interacts with Put1p in yeast, suggesting that tQM is directly involved in modulating proline levels. tQM also can rescue yeast from the lethality mediated by the mammalian proapoptotic protein Bax, through the inhibition of ROS generation. Our results suggest that tQM is a component of various stress response pathways and may function in proline-mediated stress tolerance in plants.

  14. [Microbial fuel cells as an alternative power supply].

    PubMed

    Il'in, V K; Smirnov, I A; Soldatov, P É; Korshunov, D V; Tiurin-Kuz'min, A Iu; Starkova, L V; Chumakov, P E; Emel'ianova, L K; Novikova, L M; Debabov, V G; Voeĭkova, T A

    2012-01-01

    Purpose of the work was designing and prototyping of microbial fuel cells (MFC) and comparative evaluation of the electrogenic activity of wastewater autochthonous microorganisms as well as bacterial monocultures. Objects were model electrogenic strain Shewanella oneidensis MR-1, and an Ochrobactrum sp. strain isolated from the active anode biofilm of MFC composed as an electricity generating system. The study employed the methods typically used for aerobic and anaerobic strains, current measurement, identification of new electrogenic strains in microbial association of wastewater sludge and species definition by rRNA 16-S. As a result, two MFCs prototypes were tried out. Besides, it was shown that electrogenic activity of S. oneidensis MR-1 and Ochrobactrum sp. monocultures is similar but differs from that of the microbial association of the anode biofilm.

  15. Ammodytoxin, a secretory phospholipase A2, inhibits G2 cell-cycle arrest in the yeast Saccharomyces cerevisiae.

    PubMed

    Petrovic, Uros; Sribar, Jernej; Matis, Maja; Anderluh, Gregor; Peter-Katalinić, Jasna; Krizaj, Igor; Gubensek, Franc

    2005-10-15

    Ammodytoxin (Atx), an sPLA2 (secretory phospholipase A2), binds to g and e isoforms of porcine 14-3-3 proteins in vitro. 14-3-3 proteins are evolutionarily conserved eukaryotic regulatory proteins involved in a variety of biological processes, including cell-cycle regulation. We have now shown that Atx binds to yeast 14-3-3 proteins with an affinity similar to that for the mammalian isoforms. Thus yeast Saccharomyces cerevisiae can be used as a model eukaryotic cell, which lacks endogenous phospholipases A2, to assess the in vivo relevance of this interaction. Atx was expressed in yeast cells and shown to be biologically active inside the cells. It inhibited G2 cell-cycle arrest in yeast, which is regulated by 14-3-3 proteins. Interference with the cell cycle indicates a possible mechanism by which sPLA2s are able to cause the opposing effects, proliferation and apoptosis, in mammalian cells.

  16. Rapid Identification and Enumeration of Saccharomyces cerevisiae Cells in Wine by Real-Time PCR

    PubMed Central

    Martorell, P.; Querol, A.; Fernández-Espinar, M. T.

    2005-01-01

    Despite the beneficial role of Saccharomyces cerevisiae in the food industry for food and beverage production, it is able to cause spoilage in wines. We have developed a real-time PCR method to directly detect and quantify this yeast species in wine samples to provide winemakers with a rapid and sensitive method to detect and prevent wine spoilage. Specific primers were designed for S. cerevisiae using the sequence information obtained from a cloned random amplified polymorphic DNA band that differentiated S. cerevisiae from its sibling species Saccharomyces bayanus, Saccharomyces pastorianus, and Saccharomyces paradoxus. The specificity of the primers was demonstrated for typical wine spoilage yeast species. The method was useful for estimating the level of S. cerevisiae directly in sweet wines and red wines without preenrichment when yeast is present in concentrations as low as 3.8 and 5 CFU per ml. This detection limit is in the same order as that obtained from glucose-peptone-yeast growth medium (GPY). Moreover, it was possible to quantify S. cerevisiae in artificially contaminated samples accurately. Limits for accurate quantification in wine were established, from 3.8 × 105 to 3.8 CFU/ml in sweet wine and from 5 × 106 to 50 CFU/ml in red wine. PMID:16269715

  17. Identifying the microbial communities and operational conditions for optimized wastewater treatment in microbial fuel cells.

    PubMed

    Ishii, Shun'ichi; Suzuki, Shino; Norden-Krichmar, Trina M; Wu, Angela; Yamanaka, Yuko; Nealson, Kenneth H; Bretschger, Orianna

    2013-12-01

    Microbial fuel cells (MFCs) are devices that exploit microorganisms as "biocatalysts" to recover energy from organic matter in the form of electricity. MFCs have been explored as possible energy neutral wastewater treatment systems; however, fundamental knowledge is still required about how MFC-associated microbial communities are affected by different operational conditions and can be optimized for accelerated wastewater treatment rates. In this study, we explored how electricity-generating microbial biofilms were established at MFC anodes and responded to three different operational conditions during wastewater treatment: 1) MFC operation using a 750 Ω external resistor (0.3 mA current production); 2) set-potential (SP) operation with the anode electrode potentiostatically controlled to +100 mV vs SHE (4.0 mA current production); and 3) open circuit (OC) operation (zero current generation). For all reactors, primary clarifier effluent collected from a municipal wastewater plant was used as the sole carbon and microbial source. Batch operation demonstrated nearly complete organic matter consumption after a residence time of 8-12 days for the MFC condition, 4-6 days for the SP condition, and 15-20 days for the OC condition. These results indicate that higher current generation accelerates organic matter degradation during MFC wastewater treatment. The microbial community analysis was conducted for the three reactors using 16S rRNA gene sequencing. Although the inoculated wastewater was dominated by members of Epsilonproteobacteria, Gammaproteobacteria, and Bacteroidetes species, the electricity-generating biofilms in MFC and SP reactors were dominated by Deltaproteobacteria and Bacteroidetes. Within Deltaproteobacteria, phylotypes classified to family Desulfobulbaceae and Geobacteraceae increased significantly under the SP condition with higher current generation; however those phylotypes were not found in the OC reactor. These analyses suggest that species

  18. Design of acoustic cell settler for filtering and recycling microbial cells.

    PubMed

    Hwang, Sung-Ho; Koo, Yoon-Mo

    2003-02-01

    An acoustic cell settler (ACS) using ultrasound at cells of 3 MHz was used to recycle Saccharomyces cerevisiae in a fermenter. The locations of both the inlet and outlet in the acoustic cell settler, which have a relatively long distance between the transducer and reflector, were optimized. A tilted settler was designed to make up for the defect in the horizontal ACS, which has a low recovery ratio. The tilted ACS gave a recovery ratio of yeast cells of about 5 during the most period of operation, which was twice that of the horizontal ACS.

  19. Microbial community structure accompanied with electricity production in a constructed wetland plant microbial fuel cell.

    PubMed

    Lu, Lu; Xing, Defeng; Ren, Zhiyong Jason

    2015-11-01

    This study reveals the complex structure of bacterial and archaeal communities associated with a Canna indica plant microbial fuel cell (PMFC) and its electricity production. The PMFC produced a maximum current of 105 mA/m(2) by utilizing rhizodeposits as the sole electron donor without any external nutrient or buffer supplements, which demonstrates the feasibility of PMFCs in practical oligotrophic conditions with low solution conductivity. The microbial diversity was significantly higher in the PMFC than non-plant controls or sediment-only controls, and pyrosequencing and clone library reveal that rhizodeposits conversion to current were carried out by syntrophic interactions between fermentative bacteria (e.g., Anaerolineaceae) and electrochemically active bacteria (e.g., Geobacter). Denitrifying bacteria and acetotrophic methanogens play a minor role in organics degradation, but abundant hydrogenotrophic methanogens and thermophilic archaea are likely main electron donor competitors.

  20. Electricity generation from food wastes and microbial community structure in microbial fuel cells.

    PubMed

    Jia, Jianna; Tang, Yu; Liu, Bingfeng; Wu, Di; Ren, Nanqi; Xing, Defeng

    2013-09-01

    Microbial fuel cell (MFC) was studied as an alternate and a novel way to dispose food wastes (FWs) in a waste-to-energy form. Different organic loading rate obviously affected the performance of MFCs fed with FWs. The maximum power density of ~18 W/m(3) (~556 mW/m(2)) was obtained at COD of 3200±400 mg/L and the maximum coulombic efficiency (CE) was ~27.0% at COD of 4900±350 mg/L. The maximum removals of COD, total carbohydrate (TC) and total nitrogen (TN) were ~86.4%, ~95.9% and ~16.1%, respectively. Microbial community analysis using 454 pyrosequencing of 16S rRNA gene demonstrated the combination of the dominant genera of the exoelectrogenic Geobacter and fermentative Bacteroides effectively drove highly efficient and reliable MFC systems with functions of organic matters degradation and electricity generation.

  1. Microbial fuel cell (MFC) for bioelectricity generation from organic wastes.

    PubMed

    Moqsud, M Azizul; Omine, Kiyoshi; Yasufuku, Noriyuki; Hyodo, Masayuki; Nakata, Yukio

    2013-11-01

    Microbial fuel cells (MFCs) have gained a lot of attention recently as a mode of converting organic matter into electricity. In this study, a compost-based microbial fuel cell that generates bioelectricity by biodegradation of organic matter is developed. Grass cuttings, along with leaf mold, rice bran, oil cake (from mustard plants) and chicken droppings (waste from chickens) were used as organic waste. The electric properties of the MFC under anaerobic fermentation condition were investigated along with the influence of different types of membranes, the mixing of fly ash, and different types of electrode materials. It is observed that the maximum voltage was increased by mixing fly ash. Cellophane showed the highest value of voltage (around 350mV). Bamboo charcoal is good for anode material; however carbon fiber is better for the cathode material in terms of optimization of power generated. This developed MFC is a simple cell to generate electricity from organic waste.

  2. The steady-state level and stability of TLS polymerase eta are cell cycle dependent in the yeast S. cerevisiae.

    PubMed

    Plachta, Michal; Halas, Agnieszka; McIntyre, Justyna; Sledziewska-Gojska, Ewa

    2015-05-01

    Polymerase eta (Pol eta) is a ubiquitous translesion DNA polymerase that is capable of bypassing UV-induced pyrimidine dimers in an error-free manner. However, this specialized polymerase is error prone when synthesizing through an undamaged DNA template. In Saccharomyces cerevisiae, both depletion and overproduction of Pol eta result in mutator phenotypes. Therefore, regulation of the cellular abundance of this enzyme is of particular interest. However, based on the investigation of variously tagged forms of Pol eta, mutually contradictory conclusions have been reached regarding the stability of this polymerase in yeast. Here, we optimized a protocol for the detection of untagged yeast Pol eta and established that the half-life of the native enzyme is 80 ± 14 min in asynchronously growing cultures. Experiments with synchronized cells indicated that the cellular abundance of this translesion polymerase changes throughout the cell cycle. Accordingly, we show that the stability of Pol eta, but not its mRNA level, is cell cycle stage dependent. The half-life of the polymerase is more than fourfold shorter in G1-arrested cells than in those at G2/M. Our results, in concert with previous data for Rev1, indicate that cell cycle regulation is a general property of Y family TLS polymerases in S. cerevisiae.

  3. Development of microbial cell factories for bio-refinery through synthetic bioengineering.

    PubMed

    Kondo, Akihiko; Ishii, Jun; Hara, Kiyotaka Y; Hasunuma, Tomohisa; Matsuda, Fumio

    2013-01-20

    Synthetic bioengineering is a strategy for developing useful microbial strains with innovative biological functions. Novel functions are designed and synthesized in host microbes with the aid of advanced technologies for computer simulations of cellular processes and the system-wide manipulation of host genomes. Here, we review the current status and future prospects of synthetic bioengineering in the yeast Saccharomyces cerevisiae for bio-refinery processes to produce various commodity chemicals from lignocellulosic biomass. Previous studies to improve assimilation of xylose and production of glutathione and butanol suggest a fixed pattern of problems that need to be solved, and as a crucial step, we now need to identify promising targets for further engineering of yeast metabolism. Metabolic simulation, transcriptomics, and metabolomics are useful emerging technologies for achieving this goal, making it possible to optimize metabolic pathways. Furthermore, novel genes responsible for target production can be found by analyzing large-scale data. Fine-tuning of enzyme activities is essential in the latter stage of strain development, but it requires detailed modeling of yeast metabolic functions. Recombinant technologies and genetic engineering are crucial for implementing metabolic designs into microbes. In addition to conventional gene manipulation techniques, advanced methods, such as multicistronic expression systems, marker-recycle gene deletion, protein engineering, cell surface display, genome editing, and synthesis of very long DNA fragments, will facilitate advances in synthetic bioengineering.

  4. Deployable Microbial Fuel Cell and Methods

    DTIC Science & Technology

    2011-09-08

    cells and batteries and in particular to cathodes which are suitable for use in galvanic cells that use an oxidant dissolved in the electrolyte as...is preferably dried so the battery is activated when liquid contacts the electrolyte and separator layer. Water swellable particles are included...required divers to install graphite plates in the marine sediment. As noted above, this is a costly and time consuming process. In addition, the graphite

  5. Microbial Fuel Cells for Powering Navy Devices

    DTIC Science & Technology

    2014-01-20

    they can range in scale from less than 1 W to more than 1 MW. They promise relatively high energy density (Wh/L) compared to lithium batteries and...hydrogen/oxygen fuel cells and relatively high specific energy (Wh/kg) compared to lithium batteries by using nonexplosive biomass-derived organic...high energy density (Wh/L) compared to lithium batteries and hydrogen/oxygen fuel cells and relatively high specific energy (Wh/kg) compared to

  6. Short polyhistidine peptides penetrate effectively into Nicotiana tabacum-cultured cells and Saccharomyces cerevisiae cells.

    PubMed

    Kimura, Sayaka; Kawano, Tsuyoshi; Iwasaki, Takashi

    2017-01-01

    The polyhistidine peptides (PHPs) have been previously reported as novel cell-penetrating peptides and are efficiently internalized into mammal cells; however, penetration of PHPs into other cell types is unknown. In this study, the cellular uptake of PHPs in plant and yeast cells was found to be dependent on the number of histidines, and short PHPs (H6-H10 peptides) showed effective internalization. The H8 peptide showed the highest cell-penetrating capacity and localized to vacuoles in plant and yeast cells. Low-temperature conditions inhibited significantly the cellular uptake of short PHPs by both cells. However, net charge neutralization of PHPs also completely inhibited cellular uptake by plant cells, but not by yeast cells. These results indicate that short PHPs penetrate effectively into plant and yeast cells by similar mechanism with the exception of net charge dependency. The findings show the short PHPs are promising candidates for new delivery tools into plant and yeast cells.

  7. Characterization of microbial fuel cells at microbially and electrochemically meaningful time scales.

    PubMed

    Ren, Zhiyong; Yan, Hengjing; Wang, Wei; Mench, Matthew M; Regan, John M

    2011-03-15

    The variable biocatalyst density in a microbial fuel cell (MFC) anode biofilm is a unique feature of MFCs relative to other electrochemical systems, yet performance characterizations of MFCs typically involve analyses at electrochemically relevant time scales that are insufficient to account for these variable biocatalyst effects. This study investigated the electrochemical performance and the development of anode biofilm architecture under different external loadings, with duplicate acetate-fed single-chamber MFCs stabilized at each resistance for microbially relevant time scales. Power density curves from these steady-state reactors generally showed comparable profiles despite the fact that anode biofilm architectures and communities varied considerably, showing that steady-state biofilm differences had little influence on electrochemical performance until the steady-state external loading was much larger than the reactor internal resistance. Filamentous bacteria were dominant on the anodes under high external resistances (1000 and 5000 Ω), while more diverse rod-shaped cells formed dense biofilms under lower resistances (10, 50, and 265 Ω). Anode charge transfer resistance decreased with decreasing fixed external resistances, but was consistently 2 orders of magnitude higher than the resistance at the cathode. Cell counting showed an inverse exponential correlation between cell numbers and external resistances. This direct link of MFC anode biofilm evolution with external resistance and electricity production offers several operational strategies for system optimization.

  8. Carbon and nitrogen assimilation in deep subseafloor microbial cells.

    PubMed

    Morono, Yuki; Terada, Takeshi; Nishizawa, Manabu; Ito, Motoo; Hillion, François; Takahata, Naoto; Sano, Yuji; Inagaki, Fumio

    2011-11-08

    Remarkable numbers of microbial cells have been observed in global shallow to deep subseafloor sediments. Accumulating evidence indicates that deep and ancient sediments harbor living microbial life, where the flux of nutrients and energy are extremely low. However, their physiology and energy requirements remain largely unknown. We used stable isotope tracer incubation and nanometer-scale secondary ion MS to investigate the dynamics of carbon and nitrogen assimilation activities in individual microbial cells from 219-m-deep lower Pleistocene (460,000 y old) sediments from the northwestern Pacific off the Shimokita Peninsula of Japan. Sediment samples were incubated in vitro with (13)C- and/or (15)N-labeled glucose, pyruvate, acetate, bicarbonate, methane, ammonium, and amino acids. Significant incorporation of (13)C and/or (15)N and growth occurred in response to glucose, pyruvate, and amino acids (∼76% of total cells), whereas acetate and bicarbonate were incorporated without fostering growth. Among those substrates, a maximum substrate assimilation rate was observed at 67 × 10(-18) mol/cell per d with bicarbonate. Neither carbon assimilation nor growth was evident in response to methane. The atomic ratios between nitrogen incorporated from ammonium and the total cellular nitrogen consistently exceeded the ratios of carbon, suggesting that subseafloor microbes preferentially require nitrogen assimilation for the recovery in vitro. Our results showed that the most deeply buried subseafloor sedimentary microbes maintain potentials for metabolic activities and that growth is generally limited by energy but not by the availability of C and N compounds.

  9. Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell

    NASA Astrophysics Data System (ADS)

    Dhar, Bipro Ranjan; Ryu, Hodon; Santo Domingo, Jorge W.; Lee, Hyung-Sool

    2016-11-01

    Multi-anode microbial electrochemical cells (MxCs) are considered as one of the most promising configurations for scale-up of MxCs, but understanding of anode kinetics in multiple anodes is limited in the MxCs. In this study we assessed microbial community and electrochemical kinetic parameters for biofilms on individual anodes in a multi-anode MxC to better comprehend anode fundamentals. Microbial community analysis targeting 16S rRNA Illumina sequencing showed that Geobacter genus was abundant (87%) only on the biofilm anode closest to a reference electrode (low ohmic energy loss) in which current density was the highest among three anodes. In comparison, Geobacter populations were less than 1% for biofilms on other two anodes distant from the reference electrode (high ohmic energy loss), generating small current density. Half-saturation anode potential (EKA) was the lowest at -0.251 to -0.242 V (vs. standard hydrogen electrode) for the closest biofilm anode to the reference electrode, while EKA was as high as -0.134 V for the farthest anode. Our study proves that electric potential of individual anodes changed by ohmic energy loss shifts biofilm communities on individual anodes and consequently influences electron transfer kinetics on each anode in the multi-anode MxC.

  10. Enhanced microbial reduction of vanadium (V) in groundwater with bioelectricity from microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Hao, Liting; Zhang, Baogang; Tian, Caixing; Liu, Ye; Shi, Chunhong; Cheng, Ming; Feng, Chuanping

    2015-08-01

    Bioelectricity generated from the microbial fuel cell (MFC) is applied to the bioelectrical reactor (BER) directly to enhance microbial reduction of vanadium (V) (V(V)) in groundwater. With the maximum power density of 543.4 mW m-2 from the MFC, V(V) removal is accelerated with efficiency of 93.6% during 12 h operation. Higher applied voltage can facilitate this process. V(V) removals decrease with the increase of initial V(V) concentration, while extra addition of chemical oxygen demand (COD) has little effect on performance improvement. Microbial V(V) reduction is enhanced and then suppressed with the increase of conductivity. High-throughput 16S rRNA gene pyrosequencing analysis implies the accumulated Enterobacter and Lactococcus reduce V(V) with products from fermentative microorganisms such as Macellibacteroides. The presentation of electrochemically active bacteria as Enterobacter promotes electron transfers. This study indicates that application of bioelectricity from MFCs is a promising strategy to improve the efficiency of in-situ bioremediation of V(V) polluted groundwater.

  11. Effect of electricity on microbial community of microbial fuel cell simultaneously treating sulfide and nitrate

    NASA Astrophysics Data System (ADS)

    Cai, Jing; Zheng, Ping; Xing, Yajuan; Qaisar, Mahmood

    2015-05-01

    The effect of electric current on microbial community is explored in Microbial Fuel Cells (MFCs) simultaneously treating sulfide and nitrate. The MFCs are operated under four different conditions which exhibited different characteristics of electricity generation. In batch mode, MFCs generate intermittently high current pulses in the beginning, and the current density is instable subsequently, while the current density of MFCs in continuous mode is relatively stable. All operational parameters show good capacity for substrate removal, and nitrogen and sulfate were the main reaction products. Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis is employed to obtain profiles of the bacterial communities present in inoculum and suspension of four MFCs. Based on the community diversity indices and Spearman correlation analyses, significant correlation exists between Richness of the community of anode chamber and the electricity generated, while no strong correlation is evident between other indexes (Shannon index, Simpson index and Equitability index) and the electricity. Additionally, the results of Principal Component Analysis (PCA) suggest that MFCs suffering from current shock have similar suspension communities, while the others have diverse microbial communities.

  12. Microbial cell retention in a melting High Arctic snowpack, Svalbard

    NASA Astrophysics Data System (ADS)

    Zarsky, Jakub; Björkman, Mats; Kühnel, Rafael; Hell, Katherina; Hodson, Andy; Sattler, Birgit; Psenner, Roland

    2014-05-01

    Introduction The melting snow pack represents a highly dynamic system not only for chemical compounds but also for bacterial cells. Microbial activity was found at subzero temperatures in ice veins when liquid water persists due to high concentration of ions on the surface of snow crystals and brine channels between large ice crystals in ice. Several observations also suggest microbial activity under subzero temperatures in seasonal snow. Even with regard to the spatial and temporal relevance of snow ecosystems, microbial activity in such an extreme habitat represents a relatively small proportion in the carbon flux of the global ecosystem and even of the glacial ecosystems specifically. On the other hand, it represents a remarkable piece of mosaic of the microbial activity in glacial ecosystems because the snow pack represents the first contact between the atmosphere and cryosphere. This topic also embodies vital crossovers to biogeochemistry and ecotoxicology, offering a quantitative view of utilization of various substrates relevant for downstream ecosystems. Here we present our study of the dynamics of both solvents and cells suspended in meltwater of the melting snowpack on a high arctic glacier to demonstrate the spatio-temporal constraint of interaction between solvent and bacterial cells in this environment. Method We used 6 lysimeters inserted into the bottom of the snowpack to collect replicated samples of melt water before it comes into contact with basal ice or slush layer at the base of the snow pack. The sampling site was chosen at Midre Lovénbreen (Svalbard, Kongsfjorden, MLB stake 6) where the snow pack showed melting on the surface but the basal ice was still dry. Sampling was conducted in June 2010 for a period of 10 days once per day and the snow profile was sampled according to distinguished layers in the profile at the beginning of the field mission and as bulk at its end. The height of snow above the lysimeters dropped from the initial 74 cm

  13. Simultaneous Alcoholic and Malolactic Fermentations by Saccharomyces cerevisiae and Oenococcus oeni Cells Co-immobilized in Alginate Beads

    PubMed Central

    Bleve, Gianluca; Tufariello, Maria; Vetrano, Cosimo; Mita, Giovanni; Grieco, Francesco

    2016-01-01

    Malolactic fermentation (MLF) usually takes place after the end of alcoholic fermentation (AF). However, the inoculation of lactic acid bacteria together with yeast starter cultures is a promising system to enhance the quality and safety of wine. In recent years, the use of immobilized cell systems has been investigated, with interesting results, for the production of different fermented foods and beverages. In this study we have carried out the simultaneous immobilization of Saccharomyces cerevisiae and Oenococcus oeni in alginate beads and used them in microvinifications tests to produce Negroamaro wine. The process was monitored by chemical and sensorial analyses and dominance of starters and cell leaking from beads were also checked. Co-immobilization of S. cerevisiae and O. oeni allowed to perform an efficient fermentation process, producing low volatile acidity levels and ethanol and glycerol concentrations comparable with those obtained by cell sequential inoculum and co-inoculum of yeast and bacteria cells in free form. More importantly, co-immobilization strategy produced a significant decrease of the time requested to complete AF and MLF. The immobilized cells could be efficiently reused for the wine fermentation at least three times without any apparent loss of cell metabolic activities. This integrated biocatalytic system is able to perform simultaneously AF and MLF, producing wines similar in organoleptic traits in comparison with wines fermented following traditional sequential AF and MLF with free cell starters. The immobilized-cell system, that we here describe for the first time in our knowledge, offers many advantages over conventional free cell fermentations, including: (i) elimination of non-productive cell growth phases; (ii) feasibility of continuous processing; (iii) re-use of the biocatalyst. PMID:27379072

  14. Produced Water Treatment Using Microbial Fuel Cell Technology

    SciTech Connect

    Borole, A. P.; Campbell, R.

    2011-05-20

    ORNL has developed a treatment for produced water using a combination of microbial fuel cells and electrosorption. A collaboration between Campbell Applied Physics and ORNL was initiated to further investigate development of the technology and apply it to treatment of field produced water. The project successfully demonstrated the potential of microbial fuel cells to generate electricity from organics in produced water. A steady voltage was continuously generated for several days using the system developed in this study. In addition to the extraction of electrical energy from the organic contaminants, use of the energy at the representative voltage was demonstrated for salts removal or desalination of the produced water. Thus, the technology has potential to remove organic as well as ionic contaminants with minimal energy input using this technology. This is a novel energy-efficient method to treat produced water. Funding to test the technology at larger scale is being pursued to enable application development.

  15. Composite materials for polymer electrolyte membrane microbial fuel cells.

    PubMed

    Antolini, Ermete

    2015-07-15

    Recently, the feasibility of using composite metal-carbon, metal-polymer, polymer-carbon, polymer-polymer and carbon-carbon materials in microbial fuel cells (MFCs) has been investigated. These materials have been tested as MFC anode catalyst (microorganism) supports, cathode catalysts and membranes. These hybrid materials, possessing the properties of each component, or even with a synergistic effect, would present improved characteristics with respect to the bare components. In this paper we present an overview of the use of these composite materials in microbial fuel cells. The characteristics of the composite materials as well as their effect on MFC performance were compared with those of the individual component and/or the conventionally used materials.

  16. Individual cells of Saccharomyces cerevisiae and Zygosaccharomyces bailii exhibit different short-term intracellular pH responses to acetic acid.

    PubMed

    Arneborg, N; Jespersen, L; Jakobsen, M

    2000-01-01

    The effects of perfusion with 2.7 and 26 mM undissociated acetic acid in the absence or presence of glucose on short-term intracellular pH (pH(i)) changes in individual Saccharormyces cerevisiae and Zygosaccharomyces bailii cells were studied using fluorescence-ratio-imaging microscopy and a perfusion system. In the S. cerevisiae cells, perfusion with acetic acid induced strong short-term pH(i) responses, which were dependent on the undissociated acetic acid concentration and the presence of glucose in the perfusion solutions. In the Z. bailii cells, perfusion with acetic acid induced only very weak short-term pH(i) responses, which were neither dependent on the undissociated acetic acid concentration nor on the presence of glucose in the perfusion solutions. These results clearly show that Z. bailii is more resistant than S. cerevisiae to short-term pH(i) changes caused by acetic acid.

  17. Binding Specificity of Piliated Strains of Escherichia coli and Salmonella typhimurium to Epithelial Cells, Saccharomyces cerevisiae Cells, and Erythrocytes

    PubMed Central

    Korhonen, Timo K.; Leffler, Hakon; Edén, Catharina Svanborg

    1981-01-01

    The binding to mammalian cells of piliated enteric bacteria and the inhibition of the binding by antibodies to purified pili were studied. The target cells were epithelial cells from human bucca and human and rat urinary tracts, erythrocytes from various species, and Saccharomyces cerevisiae cells. The strains were selected to represent the two main agglutination patterns of enteric bacteria: mannose-resistant agglutination of human and other erythrocytes and mannose-sensitive agglutination of guinea pig and other erythrocytes. Escherichia coli 3669 caused only mannose-resistant agglutination, E. coli 6013 caused only mannose-sensitive agglutination, and E. coli 3048 caused both types of agglutination simultaneously. Salmonella typhimurium SH6749 exhibited only mannose-sensitive hemagglutination and was included to allow comparison of its pili with those of E. coli strains. The range of epithelial cells to which the bacteria adhered was related to their agglutination patterns. All four strains attached to human buccal cells. Only E. coli strains 3669 and 3048, which caused mannose-resistant agglutination, adhered to human urinary tract epithelial cells, and only those strains that caused mannose-sensitive agglutination adhered to rat urinary tract epithelial cells. The binding of S. typhimurium SH6749, but not of the other strains with mannose-sensitive agglutination, was significantly inhibited by d-mannose. Globotetraosylceramide, a glycolipid present in the human urinary tract epithelium, inhibited attachment to human uroepithelial cells of the two strains with mannose-resistant hemagglutination. As tested by the enzyme-linked immunosorbent assay, cross-reactions between type 1 pili of the E. coli strains were strong, but those between S. typhimurium and E. coli mannose-sensitive pili were weak. The two pili that induced mannose-resistant hemagglutination on E. coli did not cross-react. Significant inhibition of adhesion of all four strains was obtained with the

  18. New insights in Microbial Fuel Cells: novel solid phase anolyte.

    PubMed

    Tommasi, Tonia; Salvador, Gian Paolo; Quaglio, Marzia

    2016-07-04

    For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system.

  19. Enzyme Amplified Detection of Microbial Cell Wall Components

    NASA Technical Reports Server (NTRS)

    Wainwright, Norman R.

    2004-01-01

    This proposal is MBL's portion of NASA's Johnson Space Center's Astrobiology Center led by Principal Investigator, Dr. David McKay, entitled: 'Institute for the Study of Biomarkers in Astromaterials.' Dr. Norman Wainwright is the principal investigator at MBL and is responsible for developing methods to detect trace quantities of microbial cell wall chemicals using the enzyme amplification system of Limulus polyphemus and other related methods.

  20. New insights in Microbial Fuel Cells: novel solid phase anolyte

    PubMed Central

    Tommasi, Tonia; Salvador, Gian Paolo; Quaglio, Marzia

    2016-01-01

    For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system. PMID:27375205

  1. New insights in Microbial Fuel Cells: novel solid phase anolyte

    NASA Astrophysics Data System (ADS)

    Tommasi, Tonia; Salvador, Gian Paolo; Quaglio, Marzia

    2016-07-01

    For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system.

  2. Electricity generation from synthesis gas by microbial processes: CO fermentation and microbial fuel cell technology.

    PubMed

    Kim, Daehee; Chang, In Seop

    2009-10-01

    A microbiological process was established to harvest electricity from the carbon monoxide (CO). A CO fermenter was enriched with CO as the sole carbon source. The DGGE/DNA sequencing results showed that Acetobacterium spp. were enriched from the anaerobic digester fluid. After the fermenter was operated under continuous mode, the products were then continuously fed to the microbial fuel cell (MFC) to generate electricity. Even though the conversion yield was quite low, this study proved that synthesis gas (syn-gas) can be converted to electricity with the aid of microbes that do not possess the drawbacks of metal catalysts of conventional methods.

  3. Efficacy of beer fermentation residue containing Saccharomyces cerevisiae cells for ameliorating aflatoxicosis in broilers.

    PubMed

    Bovo, F; Franco, L T; Kobashigawa, E; Rottinghaus, G E; Ledoux, D R; Oliveira, C A F

    2015-05-01

    This study aimed to determine the aflatoxin B1 (AFB1) binding capacity of a beer fermentation residue (BFR) containing Saccharomyces cerevisiae cells, and the efficacy of BFR to ameliorate the toxic effects of AFB1 on performance, serum biochemistry, and histology of broilers. The BFR was collected from a microbrewery, and the yeast cells were counted, dried, and milled before it was used in the study. In vitro evaluation of the BFR was conducted using different concentrations of AFB1 (2.0, 4.0, 8.0, 16.0, and 32.0 μg AFB1/mL) and 100 mg/10 mL of BFR at pH 3.0 or 6.0. Two hundred 1-day-old male broilers (Ross 308) were assigned to chick batteries and allowed ad libitum access to feed and water. A completely randomized design was used with 5 replicate pens of 5 chicks assigned to each of 4 dietary treatments from hatch to 21 d, which included: 1) basal diet (BD), with no BFR or AFB1; 2) BD supplemented with 1% BFR; 3) BD supplemented with 2 mg AFB1/kg of feed; and 4) BD supplemented with 2 mg AFB1/kg feed and 1% BFR. Performance variables were determined weekly, while serum analyses were performed on d 14 and 21. At the end of the study, chicks were anesthetized with carbon dioxide, euthanized by cervical dislocation, and the kidney, liver, and bursa of Fabricius were removed for determination of relative weights, and for histological evaluation. In vitro assays showed that the higher the initial AFB1 concentration in solution, the greater the AFB1 amount adsorbed by BFR at both pHs tested. Feed intake, BW gain, and concentrations of albumin, total protein, and globulin increased (P < 0.05) in broilers fed BFR+AFB1 (Diet 4), when compared to the birds receiving only AFB1 (Diet 2). Although BFR was not able to reduce or prevent the effects of AFB1 on relative weights of kidneys and liver, it reduced the severity of histological changes in the liver and kidney caused by AFB1.

  4. A computational model for biofilm-based microbial fuel cells.

    PubMed

    Picioreanu, Cristian; Head, Ian M; Katuri, Krishna P; van Loosdrecht, Mark C M; Scott, Keith

    2007-07-01

    This study describes and evaluates a computational model for microbial fuel cells (MFCs) based on redox mediators with several populations of suspended and attached biofilm microorganisms, and multiple dissolved chemical species. A number of biological, chemical and electrochemical reactions can occur in the bulk liquid, in the biofilm and at the electrode surface. The evolution in time of important MFC parameters (current, charge, voltage and power production, consumption of substrates, suspended and attached biomass growth) has been simulated under several operational conditions. Model calculations evaluated the effect of different substrate utilization yields, standard potential of the redox mediator, ratio of suspended to biofilm cells, initial substrate and mediator concentrations, mediator diffusivity, mass transfer boundary layer, external load resistance, endogenous metabolism, repeated substrate additions and competition between different microbial groups in the biofilm. Two- and three-dimensional model simulations revealed the heterogeneous current distribution over the planar anode surface for younger and patchy biofilms, but becoming uniform in older and more homogeneous biofilms. For uniformly flat biofilms one-dimensional models should give sufficiently accurate descriptions of produced currents. Voltage- and power-current characteristics can also be calculated at different moments in time to evaluate the limiting regime in which the MFC operates. Finally, the model predictions are tested with previously reported experimental data obtained in a batch MFC with a Geobacter biofilm fed with acetate. The potential of the general modeling framework presented here is in the understanding and design of more complex cases of wastewater-fed microbial fuel cells.

  5. [Electricity production from surplus sludge using microbial fuel cells].

    PubMed

    Jia, Bin; Liu, Zhi-Hua; Li, Xiao-Ming; Yang, Yong-Lin; Yang, Qi; Zeng, Guang-Ming; Liu, Yi-Lin; Liu, Qian-Qian; Zheng, Shi-Wen

    2009-04-15

    A single-chamber and membrane-less microbial fuel cells were successfully started up using anaerobic sludge as inoculums without any chemical substance for 20 d. The electricity generation of the microbial fuel cell using surplus sludge as fuel and the change of substrate were investigated. The results showed that the obtained maximum voltage and power density were 495 mV and 44 mW x m(-2) (fixed 1,000 Omega), and the internal resistance was about 300 Omega during steady state. In a cycle, the removal efficiency of SS and VSS were 27.3% and 28.7%, pH was 6.5-8.0. In addition, the COD increased from 617 mg x L(-1) to 1,150 mg x L(-1) and decreased afterwards with time. The change of glucose was similar to that of COD, glucose increased from 47 mg x L(-1) to 60 mg x L(-1) and decreased afterwards with time. Consequently, the microbial fuel cell can transform chemical energy of surplus sludge into the cleanest electrical energy, and it provides a new way of sludge recycling.

  6. Interactions of Condensed Tannins with Saccharomyces cerevisiae Yeast Cells and Cell Walls: Tannin Location by Microscopy.

    PubMed

    Mekoue Nguela, Julie; Vernhet, Aude; Sieczkowski, Nathalie; Brillouet, Jean-Marc

    2015-09-02

    Interactions between grape tannins/red wine polyphenols and yeast cells/cell walls was previously studied within the framework of red wine aging and the use of yeast-derived products as an alternative to aging on lees. Results evidenced a quite different behavior between whole cells (biomass grown to elaborate yeast-derived products, inactivated yeast, and yeast inactivated after autolysis) and yeast cell walls (obtained from mechanical disruption of the biomass). Briefly, whole cells exhibited a high capacity to irreversibly adsorb grape and wine tannins, whereas only weak interactions were observed for cell walls. This last point was quite unexpected considering the literature and called into question the real role of cell walls in yeasts' ability to fix tannins. In the present work, tannin location after interactions between grape and wine tannins and yeast cells and cell walls was studied by means of transmission electron microscopy, light epifluorescence, and confocal microscopy. Microscopy observations evidenced that if tannins interact with cell walls, and especially cell wall mannoproteins, they also diffuse freely through the walls of dead cells to interact with their plasma membrane and cytoplasmic components.

  7. Display of phytase on the cell surface of Saccharomyces cerevisiae to degrade phytate phosphorus and improve bioethanol production.

    PubMed

    Chen, Xianzhong; Xiao, Yan; Shen, Wei; Govender, Algasan; Zhang, Liang; Fan, You; Wang, Zhengxiang

    2016-03-01

    Currently, development of biofuels as an alternative fuel has gained much attention due to resource and environmental challenges. Bioethanol is one of most important and dominant biofuels, and production using corn or cassava as raw materials has become a prominent technology. However, phytate contained in the raw material not only decreases the efficiency of ethanol production, but also leads to an increase in the discharge of phosphorus, thus impacting on the environment. In this study, to decrease phytate and its phosphorus content in an ethanol fermentation process, Saccharomyces cerevisiae was engineered through a surface-displaying system utilizing the C-terminal half of the yeast α-agglutinin protein. The recombinant yeast strain, PHY, was constructed by successfully displaying phytase on the surface of cells, and enzyme activity reached 6.4 U/g wet biomass weight. Ethanol productions using various strains were compared, and the results demonstrated that the specific growth rate and average fermentation rate of the PHY strain were higher 20 and 18 %, respectively, compared to the control strain S. cerevisiae CICIMY0086, in a 5-L bioreactor process by simultaneous saccharification and fermentation. More importantly, the phytate phosphorus concentration decreased by 89.8 % and free phosphorus concentration increased by 142.9 % in dry vinasse compared to the control in a 5-L bioreactor. In summary, we constructed a recombinant S. cerevisiae strain displaying phytase on the cell surface, which could improve ethanol production performance and effectively reduce the discharge of phosphorus. The strain reported here represents a useful novel engineering platform for developing an environment-friendly system for bioethanol production from a corn substrate.

  8. In Situ fuel processing in a microbial fuel cell.

    PubMed

    Bahartan, Karnit; Amir, Liron; Israel, Alvaro; Lichtenstein, Rachel G; Alfonta, Lital

    2012-09-01

    A microbial fuel cell (MFC) was designed in which fuel is generated in the cell by the enzyme glucoamylase, which is displayed on the surface of yeast. The enzyme digests starch specifically into monomeric glucose units and as a consequence enables further glucose oxidation by microorganisms present in the MFC anode. The oxidative enzyme glucose oxidase was coupled to the glucoamylase digestive enzyme. When both enzymes were displayed on the surface of yeast cells in a mixed culture, superior fuel-cell performance was observed in comparison with other combinations of yeast cells, unmodified yeast, or pure enzymes. The feasibility of the use of the green macroalgae Ulva lactuca in such a genetically modified MFC was also demonstrated. Herein, we report the performance of such fuel cells as a proof of concept for the enzymatic digestion of complex organic fuels in the anode of MFCs to render the fuel more available to microorganisms.

  9. Innate immune recognition of microbial cell wall components and microbial strategies to evade such recognitions.

    PubMed

    Sukhithasri, V; Nisha, N; Biswas, Lalitha; Anil Kumar, V; Biswas, Raja

    2013-08-25

    The innate immune system constitutes the first line of defence against invading microbes. The basis of this defence resides in the recognition of defined structural motifs of the microbes called "Microbial associated molecular patterns" that are absent in the host. Cell wall, the outer layer of both bacterial and fungal cells, a unique structure that is absent in the host and is recognized by the germ line encoded host receptors. Nucleotide oligomerization domain proteins, peptidoglycan recognition proteins and C-type lectins are host receptors that are involved in the recognition of bacterial cell wall (usually called peptidoglycan), whereas fungal cell wall components (N- and O-linked mannans, β-glucans etc.) are recognized by host receptors like C-type lectins (Dectin-1, Dectin-2, mannose receptor, DC-SIGN), Toll like receptors-2 and -4 (TLR-2 and TLR-4). These recognitions lead to activation of a variety of host signaling cascades and ultimate production of anti-microbial compounds including phospholipase A2, antimicrobial peptides, lysozyme, reactive oxygen and nitrogen species. These molecules act in cohort against the invading microbes to eradicate infections. Additionally pathogen recognition leads to the production of cytokines, which further activate the adaptive immune system. Both pathogenic and commensal bacteria and fungus use numerous strategies to subvert the host defence. These strategies include bacterial peptidoglycan glycan backbone modifications by O-acetylation, N-deacetylation, N-glycolylation and stem peptide modifications by amidation of meso-Diaminopimelic acid; fungal cell wall modifications by shielding the β-glucan layer with mannoproteins and α-1,3 glucan. This review focuses on the recent advances in understanding the role of bacterial and fungal cell wall in their innate immune recognition and evasion strategies.

  10. Recent Advances in Genetic Technique of Microbial Report Cells and Their Applications in Cell Arrays

    PubMed Central

    Kim, Do Hyun; Kim, Moon Il; Park, Hyun Gyu

    2015-01-01

    Microbial cell arrays have attracted consistent attention for their ability to provide unique global data on target analytes at low cost, their capacity for readily detectable and robust cell growth in diverse environments, their high degree of convenience, and their capacity for multiplexing via incorporation of molecularly tailored reporter cells. To highlight recent progress in the field of microbial cell arrays, this review discusses research on genetic engineering of reporter cells, technologies for patterning live cells on solid surfaces, cellular immobilization in different polymers, and studies on their application in environmental monitoring, disease diagnostics, and other related fields. On the basis of these results, we discuss current challenges and future prospects for novel microbial cell arrays, which show promise for use as potent tools for unraveling complex biological processes. PMID:26436087

  11. Mating type-specific cell-cell recognition of Saccharomyces cerevisiae: cell wall attachment and active sites of a- and alpha-agglutinin.

    PubMed Central

    Cappellaro, C; Baldermann, C; Rachel, R; Tanner, W

    1994-01-01

    Mating type-specific agglutination of Saccharomyces cerevisiae a and alpha cells depends on the heterophilic interaction of two cell surface glycoproteins, the gene products of AG alpha 1 and AGA2. Evidence is presented with immunogold labelling that the alpha-agglutinin is part of the outer fimbrial cell wall coat. The a-agglutinin is bound via two S-S bridges (Cys7 and Cys50) to a cell wall component, most probably the gene product of AGA1. His273 of alpha-agglutinin has previously been shown to be essential for a- and alpha-agglutinin interaction and a model based on two opposing ion-pairs had been proposed. By site-directed mutagenesis this possibility has now been excluded. With the help of various peptides, either chemically synthesized, obtained by proteolysis of intact glycosylated a-agglutinin or prepared from a fusion protein expressed in Escherichia coli, the biologically active region of a-agglutinin was located at the C-terminus of the molecule. A peptide consisting of the C-terminal 10 amino acids (GSPIN-TQYVF) was active in nanomolar concentrations. Saccharide moieties, therefore, are not essential for the mating type-specific cell-cell interaction; glycosylated peptides are, however, four to five times more active than non-glycosylated ones. Comparisons of the recognition sequences of the S. cerevisiae agglutinins with that of the Dictyostelium contact site A glycoprotein (gp80), as well as with those of the various families of cell adhesion molecules of higher eucaryotes, have been made and are discussed. Images PMID:7957044

  12. Sustainable wastewater treatment: how might microbial fuel cells contribute.

    PubMed

    Oh, Sung T; Kim, Jung Rae; Premier, Giuliano C; Lee, Tae Ho; Kim, Changwon; Sloan, William T

    2010-01-01

    The need for cost-effective low-energy wastewater treatment has never been greater. Clean water for our expanding and predominantly urban global population will be expensive to deliver, eats into our diminishing carbon-based energy reserves and consequently contributes to green house gases in the atmosphere and climate change. Thus every potential cost and energy cutting measure for wastewater treatment should be explored. Microbial fuel cells (MFCs) could potentially yield such savings but, to achieve this, requires significant advances in our understanding in a few critical areas and in our designs of the overall systems. Here we review the research which might accelerate our progress towards sustainable wastewater treatment using MFCs: system control and modelling and the understanding of the ecology of the microbial communities that catalyse the generation of electricity.

  13. Recent Progress of Nanostructure Modified Anodes in Microbial Fuel Cells.

    PubMed

    Kim, Marie; Kim, Hyeon Woo; Nam, Joo-Youn; In, Su-Il

    2015-09-01

    Microbial fuel cell (MFC) is a bio-electrochemical system which converts chemical energy into electrical energy by catalytic activity of microorganisms. Electrons produced by microbial oxidation from substrates such as organic matter, complex or renewable biomass are transferred to the anode. Protons produced at the anode migrate to the cathode via the wire and combine with oxygen to form water. Therefore MFC technologies are promising approach for generating electricity or hydrogen gas and wastewater treatment. Electrode materials are one of the keys to increase the power output of MFCs. To improve the cost effective performance of MFCs, various electrodes materials, modifications and configurations have been developed. In this paper, among other recent advances of nanostructured electrodes, especially carbon based anodes, are highlighted. The properties of these electrodes, in terms of surface characteristics, conductivity, modifications, and options were reviewed. The applications, challenges and perspectives of the current MFCs electrode for future development in bio or medical field are briefly discussed.

  14. Perchlorate reduction in microbial electrolysis cell with polyaniline modified cathode.

    PubMed

    Li, Jia-Jia; Gao, Ming-Ming; Zhang, Gang; Wang, Xin-Hua; Wang, Shu-Guang; Song, Chao; Xu, Yan-Yan

    2015-02-01

    Excellent perchlorate reduction was obtained under various initial concentrations in a non-membrane microbial electrolysis cell with polyaniline (PANI) modified graphite cathode as sole electron donor. PANI modification is conducive to the formation of biofilm due to its porous structure and good electrocatalytic performance. Compared with cathode without biofilm, over 12% higher reduction rates were acquired in the presence of biocathode. The study demonstrates that, instead of perchlorate reduction, the main contribution of biofilm is involved in facilitate electron transfer from cathode to electrolyte. Interestingly, hairlike structure, referred as to pili-like, was observed in the biofilm as well as in the electrolyte. Additionally, the results show that pili were prone to formation under the condition of external electron field as sole electron donor. Analysis of microbial community suggests that perchlorate reduction bacteria community was most consistent with Azospiraoryzae strain DSM 13638 in the subdivision of the class Proteobacteria.

  15. A hybrid biocathode: surface display of O2-reducing enzymes for microbial fuel cell applications.

    PubMed

    Szczupak, Alon; Kol-Kalman, Dan; Alfonta, Lital

    2012-01-04

    Laccase and bilirubin oxidase were successfully displayed on the surface of yeast cells. Subsequently, these modified yeast cells were used in the cathode compartment of a microbial fuel cell. The performance of the fuel cells is compared.

  16. Molecular Analysis of the Candida albicans Homolog of Saccharomyces cerevisiae MNN9, Required for Glycosylation of Cell Wall Mannoproteins

    PubMed Central

    Southard, Susan B.; Specht, Charles A.; Mishra, Chitra; Chen-Weiner, Joan; Robbins, Phillips W.

    1999-01-01

    The fungal cell wall has generated interest as a potential target for developing antifungal drugs, and the genes encoding glucan and chitin in fungal pathogens have been studied to this end. Mannoproteins, the third major component of the cell wall, contain mannose in either O- or N-glycosidic linkages. Here we describe the molecular analysis of the Candida albicans homolog of Saccharomyces cerevisiae MNN9, a gene required for the synthesis of N-linked outer-chain mannan in yeast, and the phenotypes associated with its disruption. CaMNN9 has significant homology with S. cerevisiae MNN9, including a putative N-terminal transmembrane domain, and represents a member of a similar gene family in Candida. CaMNN9 resides on chromosome 3 and is expressed at similar levels in both yeast and hyphal cells. Disruption of both copies of CaMNN9 leads to phenotypic effects characteristic of cell wall defects including poor growth in liquid media and on solid media, formation of aggregates in liquid culture, osmotic sensitivity, aberrant hyphal formation, and increased sensitivity to lysis after treatment with β-1,3-glucanase. Like all members of the S. cerevisiae MNN9 gene family the Camnn9Δ strain is resistant to sodium orthovanadate and sensitive to hygromycin B. Analysis of cell wall-associated carbohydrates showed the Camnn9Δ strain to contain half the amount of mannan present in cell walls derived from the wild-type parent strain. Reverse transcription-PCR and Northern analysis of the expression of MNN9 gene family members CaVAN1 and CaANP1 in the Camnn9Δ strain showed that transcription of those genes is not affected in the absence of CaMNN9 transcription. Our results suggest that, while the role MNN9 plays in glycosylation in both Candida and Saccharomyces is conserved, loss of MNN9 function in C. albicans leads to phenotypes that are inconsistent with the pathogenicity of the organism and thus identify CaMnn9p as a potential drug target. PMID:10601199

  17. Energy generation by fermentation of glucose in a batch flow microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Badea, Silviu-Laurentiu; Enache, Stanica; Tamaian, Radu; Buga, Mihaela-Ramona; Pirvu, Cristian; Varlam, Mihai

    2016-04-01

    In the last years, microbial fuel cells (MFCs) have emerged like a novel research technologies for production of sustainable and clean electricity energy through bioxidation of organic materials, representing a promising alternative to combustion energy sources. In this study, production of bioelectricity in MFC in batch system (dual chambered MFC) was investigated. A dual chambered MFC from glass was built for this purpose. Saccharomyces cerevisiae as an active biocatalyst was explored for power generation. Graphite plates were used as electrodes and glucose as substrate. Saccharomyces cerevisiae was initially grown on a period of 72h at 30 degree Celsius, on medium of modified Sabouraud liquid medium containing 30 g glucose/L. A volume of inoculated medium (80 mL) was transferred in the anode compartment of MFC together with 20 mL glucose 1M, while neutral red was used as mediator (electron shuttle) in concentration of 200 μM in anaerobic anode chamber. Potassium permanganate (KMnO4) was used as oxidizing agent in the cathode in wide concentration range (400 μM-40 000 μM). Cathodic compartment was loaded initially with 40 mM potassium permanganate, and afterwards was supplied two times more with KMnO4 of the same concentration, in order to maintain MFC functionality. The MFC was operated on a water bath heated by a combined hot-plate magnetic-stirrer device at 30 degree Celsius and mixed at 180 rpm. The maximum open circuit potential (OCV) recorded of about 0.6 V was reached after the 3rd loading with 40 milimolles of potassium permanganate. Using a potentiostat, the polarization curve was recorded by varying the potential between 0.5 V and 0.0 V, while the intensity of current increased from 0.0 to about 1.5 mA respectively, corresponding to an anodic current density of about 0.81 A/m2. In order to optimize the design and performance of the MFC, the goal of the further research is to use variously concentrations of potassium permanganate. Furthermore, a dual

  18. Vacuolar H+-ATPase Protects Saccharomyces cerevisiae Cells against Ethanol-Induced Oxidative and Cell Wall Stresses

    PubMed Central

    Charoenbhakdi, Sirikarn; Dokpikul, Thanittra; Burphan, Thanawat; Techo, Todsapol

    2016-01-01

    ABSTRACT During fermentation, increased ethanol concentration is a major stress for yeast cells. Vacuolar H+-ATPase (V-ATPase), which plays an important role in the maintenance of intracellular pH homeostasis through vacuolar acidification, has been shown to be required for tolerance to straight-chain alcohols, including ethanol. Since ethanol is known to increase membrane permeability to protons, which then promotes intracellular acidification, it is possible that the V-ATPase is required for recovery from alcohol-induced intracellular acidification. In this study, we show that the effects of straight-chain alcohols on membrane permeabilization and acidification of the cytosol and vacuole are strongly dependent on their lipophilicity. These findings suggest that the membrane-permeabilizing effect of straight-chain alcohols induces cytosolic and vacuolar acidification in a lipophilicity-dependent manner. Surprisingly, after ethanol challenge, the cytosolic pH in Δvma2 and Δvma3 mutants lacking V-ATPase activity was similar to that of the wild-type strain. It is therefore unlikely that the ethanol-sensitive phenotype of vma mutants resulted from severe cytosolic acidification. Interestingly, the vma mutants exposed to ethanol exhibited a delay in cell wall remodeling and a significant increase in intracellular reactive oxygen species (ROS). These findings suggest a role for V-ATPase in the regulation of the cell wall stress response and the prevention of endogenous oxidative stress in response to ethanol. IMPORTANCE The yeast Saccharomyces cerevisiae has been widely used in the alcoholic fermentation industry. Among the environmental stresses that yeast cells encounter during the process of alcoholic fermentation, ethanol is a major stress factor that inhibits yeast growth and viability, eventually leading to fermentation arrest. This study provides evidence for the molecular mechanisms of ethanol tolerance, which is a desirable characteristic for yeast strains

  19. Engineering microbial fuels cells: recent patents and new directions.

    PubMed

    Biffinger, Justin C; Ringeisen, Bradley R

    2008-01-01

    Fundamental research into how microbes generate electricity within microbial fuel cells (MFCs) has far outweighed the practical application and large scale development of microbial energy harvesting devices. MFCs are considered alternatives to standard commercial polymer electrolyte membrane (PEM) fuel cell technology because the fuel supply does not need to be purified, ambient operating temperatures are maintained with biologically compatible materials, and the biological catalyst is self-regenerating. The generation of electricity during wastewater treatment using MFCs may profoundly affect the approach to anaerobic treatment technologies used in wastewater treatment as a result of developing this energy harvesting technology. However, the materials and engineering designs for MFCs were identical to commercial fuel cells until 2003. Compared to commercial fuel cells, MFCs will remain underdeveloped as long as low power densities are generated from the best systems. The variety of designs for MFCs has expanded rapidly in the last five years in the literature, but the patent protection has lagged behind. This review will cover recent and important patents relating to MFC designs and progress.

  20. Osteoprotegerin Regulates Pancreatic β-Cell Homeostasis upon Microbial Invasion

    PubMed Central

    Kuroda, Yukiko; Maruyama, Kenta; Fujii, Hideki; Sugawara, Isamu; Ko, Shigeru B. H.; Yasuda, Hisataka; Matsui, Hidenori; Matsuo, Koichi

    2016-01-01

    Osteoprotegerin (OPG), a decoy receptor for receptor activator of NF-κB ligand (RANKL), antagonizes RANKL’s osteoclastogenic function in bone. We previously demonstrated that systemic administration of lipopolysaccharide (LPS) to mice elevates OPG levels and reduces RANKL levels in peripheral blood. Here, we show that mice infected with Salmonella, Staphylococcus, Mycobacteria or influenza virus also show elevated serum OPG levels. We then asked whether OPG upregulation following microbial invasion had an effect outside of bone. To do so, we treated mice with LPS and observed OPG production in pancreas, especially in β-cells of pancreatic islets. Insulin release following LPS administration was enhanced in mice lacking OPG, suggesting that OPG inhibits insulin secretion under acute inflammatory conditions. Consistently, treatment of MIN6 pancreatic β-cells with OPG decreased their insulin secretion following glucose stimulation in the presence of LPS. Finally, our findings suggest that LPS-induced OPG upregulation is mediated in part by activator protein (AP)-1 family transcription factors, particularly Fos proteins. Overall, we report that acute microbial infection elevates serum OPG, which maintains β-cell homeostasis by restricting glucose-stimulated insulin secretion, possibly preventing microbe-induced exhaustion of β-cell secretory capacity. PMID:26751951

  1. Design and development of synthetic microbial platform cells for bioenergy

    PubMed Central

    Lee, Sang Jun; Lee, Sang-Jae; Lee, Dong-Woo

    2013-01-01

    The finite reservation of fossil fuels accelerates the necessity of development of renewable energy sources. Recent advances in synthetic biology encompassing systems biology and metabolic engineering enable us to engineer and/or create tailor made microorganisms to produce alternative biofuels for the future bio-era. For the efficient transformation of biomass to bioenergy, microbial cells need to be designed and engineered to maximize the performance of cellular metabolisms for the production of biofuels during energy flow. Toward this end, two different conceptual approaches have been applied for the development of platform cell factories: forward minimization and reverse engineering. From the context of naturally minimized genomes,non-essential energy-consuming pathways and/or related gene clusters could be progressively deleted to optimize cellular energy status for bioenergy production. Alternatively, incorporation of non-indigenous parts and/or modules including biomass-degrading enzymes, carbon uptake transporters, photosynthesis, CO2 fixation, and etc. into chassis microorganisms allows the platform cells to gain novel metabolic functions for bioenergy. This review focuses on the current progress in synthetic biology-aided pathway engineering in microbial cells and discusses its impact on the production of sustainable bioenergy. PMID:23626588

  2. Design and development of synthetic microbial platform cells for bioenergy.

    PubMed

    Lee, Sang Jun; Lee, Sang-Jae; Lee, Dong-Woo

    2013-01-01

    The finite reservation of fossil fuels accelerates the necessity of development of renewable energy sources. Recent advances in synthetic biology encompassing systems biology and metabolic engineering enable us to engineer and/or create tailor made microorganisms to produce alternative biofuels for the future bio-era. For the efficient transformation of biomass to bioenergy, microbial cells need to be designed and engineered to maximize the performance of cellular metabolisms for the production of biofuels during energy flow. Toward this end, two different conceptual approaches have been applied for the development of platform cell factories: forward minimization and reverse engineering. From the context of naturally minimized genomes,non-essential energy-consuming pathways and/or related gene clusters could be progressively deleted to optimize cellular energy status for bioenergy production. Alternatively, incorporation of non-indigenous parts and/or modules including biomass-degrading enzymes, carbon uptake transporters, photosynthesis, CO2 fixation, and etc. into chassis microorganisms allows the platform cells to gain novel metabolic functions for bioenergy. This review focuses on the current progress in synthetic biology-aided pathway engineering in microbial cells and discusses its impact on the production of sustainable bioenergy.

  3. β-Galactomannan and Saccharomyces cerevisiae var. boulardii modulate the immune response against Salmonella enterica serovar Typhimurium in porcine intestinal epithelial and dendritic cells.

    PubMed

    Badia, Roger; Brufau, M Teresa; Guerrero-Zamora, Ana Maria; Lizardo, Rosil; Dobrescu, Irina; Martin-Venegas, Raquel; Ferrer, Ruth; Salmon, Henri; Martínez, Paz; Brufau, Joaquim

    2012-03-01

    Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that causes inflammation, necrosis, and diarrhea in pigs, as well as being an important source of food-borne diseases in humans. Probiotics and prebiotics are promising alternatives to antibiotics to control and prevent intestinal infections. The present work investigated a recently developed β-galactomannan (βGM) prebiotic compared to the proven probiotic Saccharomyces cerevisiae var. boulardii on porcine ileum intestinal epithelial cells (IECs) of the IPI-2I line and monocyte-derived dendritic cells (DCs) cocultured in vitro with Salmonella. We observed that both S. cerevisiae var. boulardii and βGM inhibited the association of Salmonella with IECs in vitro. Our data indicated that βGM has a higher ability than S. cerevisiae var. boulardii to inhibit Salmonella-induced proinflammatory mRNA (cytokines tumor necrosis factor alpha [TNF-α], interleukin-1α [IL-1α], IL-6, and granulocyte-macrophage colony-stimulating factor [GM-CSF] and chemokines CCL2, CCL20, and CXCL8) and at protein levels (IL-6 and CXCL8). Additionally, βGM and S. cerevisiae var. boulardii induced some effects on DCs that were not observed on IECs: βGM and S. cerevisiae var. boulardii showed slight upregulation of mRNA for TNF-α, GM-CSF, and CCR7 receptor on porcine monocyte-derived dendritic cells (DCs). Indeed, the addition of βGM or S. cerevisiae var. boulardii on DCs cocultured with Salmonella showed higher gene expression (mRNA) for TNF-α, GM-CSF, and CXCL8 compared to that of the control with Salmonella. In conclusion, the addition of βGM inhibits Salmonella-induced proinflammatory profiles in IECs but may promote DC activation, although associated molecular mechanisms remain to be elucidated.

  4. Deletion of AIF1 but not of YCA1/MCA1 protects Saccharomyces cerevisiae and Candida albicans cells from caspofungin-induced programmed cell death

    PubMed Central

    Chin, Christopher; Donaghey, Faith; Helming, Katherine; McCarthy, Morgan; Rogers, Stephen; Austriaco, Nicanor

    2014-01-01

    Caspofungin was the first member of a new class of antifungals called echinocandins to be approved by a drug regulatory authority. Like the other echinocandins, caspofungin blocks the synthesis of β(1,3)-D-glucan of the fungal cell wall by inhibiting the enzyme, β(1,3)-D-glucan synthase. Loss of β(1,3)-D-glucan leads to osmotic instability and cell death. However, the precise mechanism of cell death associated with the cytotoxicity of caspofungin was unclear. We now provide evidence that Saccharomyces cerevisiae cells cultured in media containing caspofungin manifest the classical hallmarks of programmed cell death (PCD) in yeast, including the generation of reactive oxygen species (ROS), the fragmentation of mitochondria, and the production of DNA strand breaks. Our data also suggests that deleting AIF1 but not YCA1/MCA1 protects S. cerevisiae and Candida albicans from caspofungin-induced cell death. This is not only the first time that AIF1 has been specifically tied to cell death in Candida but also the first time that caspofungin resistance has been linked to the cell death machinery in yeast.

  5. Microbial electricity generation in rice paddy fields: recent advances and perspectives in rhizosphere microbial fuel cells.

    PubMed

    Kouzuma, Atsushi; Kaku, Nobuo; Watanabe, Kazuya

    2014-12-01

    Microbial fuel cells (MFCs) are devices that use living microbes for the conversion of organic matter into electricity. MFC systems can be applied to the generation of electricity at water/sediment interfaces in the environment, such as bay areas, wetlands, and rice paddy fields. Using these systems, electricity generation in paddy fields as high as ∼80 mW m(-2) (based on the projected anode area) has been demonstrated, and evidence suggests that rhizosphere microbes preferentially utilize organic exudates from rice roots for generating electricity. Phylogenetic and metagenomic analyses have been conducted to identify the microbial species and catabolic pathways that are involved in the conversion of root exudates into electricity, suggesting the importance of syntrophic interactions. In parallel, pot cultures of rice and other aquatic plants have been used for rhizosphere MFC experiments under controlled laboratory conditions. The findings from these studies have demonstrated the potential of electricity generation for mitigating methane emission from the rhizosphere. Notably, however, the presence of large amounts of organics in the rhizosphere drastically reduces the effect of electricity generation on methane production. Further studies are necessary to evaluate the potential of these systems for mitigating methane emission from rice paddy fields. We suggest that paddy-field MFCs represent a promising approach for harvesting latent energy of the natural world.

  6. Ammonia inhibition and microbial adaptation in continuous single-chamber microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Woo; Nam, Joo-Youn; Shin, Hang-Sik

    2011-08-01

    Here, we report that a continuous single-chamber microbial fuel cell (MFC) is applicable to wastewaters containing a high nitrogen concentration using a process of adaptation. Continuous experiments are conducted to investigate the inhibitory effect of total ammonia nitrogen (TAN) on the MFC using influents with various concentrations of TAN ranged from 84 to 10,000 mg N L-1. As the TAN concentration increases up to 3500 mg N L-1, the maximum power density remains at 6.1 W m-3. However, as the concentration further increases, TAN significantly inhibits the maximum power density, which is reduced at saturation to 1.4 W m-3 at 10,000 mg N L-1. We confirm that the adapted electrical performance of a continuous MFC can generate approximately 44% higher power density than the conductivity control. A comparative study reveals that the power densities obtained from a continuous MFC can sustain 7-fold higher TAN concentration than that of previous batch MFCs. TAN removal efficiencies are limited to less than 10%, whereas acetate removal efficiencies remain as high as 93-99%. The increased threshold TAN of the continuous MFC suggests that microbial acclimation in a continuous MFC can allow the electrochemical functioning of the anode-attached bacteria to resist ammonia inhibition.

  7. Performance and microbial ecology of air-cathode microbial fuel cells with layered electrode assemblies.

    PubMed

    Butler, Caitlyn S; Nerenberg, Robert

    2010-05-01

    Microbial fuel cells (MFCs) can be built with layered electrode assemblies, where the anode, proton exchange membrane (PEM), and cathode are pressed into a single unit. We studied the performance and microbial community structure of MFCs with layered assemblies, addressing the effect of materials and oxygen crossover on the community structure. Four MFCs with layered assemblies were constructed using Nafion or Ultrex PEMs and a plain carbon cloth electrode or a cathode with an oxygen-resistant polytetrafluoroethylene diffusion layer. The MFC with Nafion PEM and cathode diffusion layer achieved the highest power density, 381 mW/m(2) (20 W/m(3)). The rates of oxygen diffusion from cathode to anode were three times higher in the MFCs with plain cathodes compared to those with diffusion-layer cathodes. Microsensor studies revealed little accumulation of oxygen within the anode cloth. However, the abundance of bacteria known to use oxygen as an electron acceptor, but not known to have exoelectrogenic activity, was greater in MFCs with plain cathodes. The MFCs with diffusion-layer cathodes had high abundance of exoelectrogenic bacteria within the genus Geobacter. This work suggests that cathode materials can significantly influence oxygen crossover and the relative abundance of exoelectrogenic bacteria on the anode, while PEM materials have little influence on anode community structure. Our results show that oxygen crossover can significantly decrease the performance of air-cathode MFCs with layered assemblies, and therefore limiting crossover may be of particular importance for these types of MFCs.

  8. Comparative analysis of microbial community between different cathode systems of microbial fuel cells for denitrification.

    PubMed

    Li, Chao; Xu, Ming; Lu, Yi; Fang, Fang; Cao, Jiashun

    2016-01-01

    Two types of cathodic biofilm in microbial fuel cells (MFC) were established for comparison on their performance and microbial communities. Complete autotrophic simultaneous nitrification and denitrification (SND) without organics addition was achieved in nitrifying-MFC (N-MFC) with a total nitrogen (TN) removal rate of 0.35 mg/(L·h), which was even higher than that in denitrifying-MFC (D-MFC) at same TN level. Integrated denaturing gradient gel electrophoresis analysis based on both 16S rRNA and nirK genes showed that Alpha-, Gammaproteobacteria were the main denitrifier communities. Some potential autotrophic denitrifying bacteria which can use electrons and reducing power from cathodes, such as Shewanella oneidensis, Shewanella loihica, Pseudomonas aeruginosa, Starkeya novella and Rhodopseudomonas palustris were identified and selectively enriched on cathode biofilms. Further, relative abundance of denitrifying bacteria characterized by nirK/16S ratios was much higher in biofilm than suspended sludge according to real-time polymerase chain reaction. The highest enrichment efficiency for denitrifiers was obtained in N-MFC cathode biofilms, which confirmed autotrophic denitrifying bacteria enrichment is the key factor for a D-MFC system.

  9. Size and Carbon Content of Sub-seafloor Microbial Cells

    NASA Astrophysics Data System (ADS)

    Braun, S.; Morono, Y.; Littmann, S.; Jørgensen, B. B.; Lomstein, B. A.

    2015-12-01

    Into the seafloor, a radical decline in nutrient and energy availability poses strong metabolic demands to any residing life. However, a sedimentary microbial ecosystem seems to maintain itself close to what we understand to be the energetic limit of life. Since a complex sediment matrix is interfering with the analysis of whole cells and sub-cellular compounds such as cell wall and membrane molecules, little is known about the physiological properties of cells in the deep biosphere. Here we focus on the size and carbon content of cells from a 90-m sediment drill core retrieved in October 2013 at Landsort Deep, Baltic Sea, in 437 meters water depth. To determine their shape and volume, cells were separated from the sediment matrix by multi-layer density centrifugation and visualized via fluorescence microscopy (FM), scanning electron microscopy (SEM), and stimulated emission depletion microscopy (STED). Total cell-carbon was calculated from amino acid-carbon, which was analyzed by high-performance liquid chromatography after cells had additionally been purified by fluorescence activated cell sorting (FACS). Cell-carbon turnover times were estimated using an amino acid racemization model that is based on the built-in molecular clock of aspartic acid, which due to racemization alternates between the D- and L-isomeric configurations over timescales of thousands of years at low in-situ temperatures (≈4˚C). We find that the majority of microbial cells in the sediment have coccoid or rod-shaped morphology, and that absolute values for cell volume are strongly dependent on the method used, spanning three orders of magnitude from approximately 0.001 to 1 µm3 for both coccoid and rod-shaped cells. From the surface to the deepest sample measured (≈60 mbsf), cell volume decreases by an order of magnitude, and carbon content is in the lower range (<20 fg C cell-1) of what has been reported in the literature as conversion factors. Cell-carbon is turned over approximately

  10. An essential gene, ESR1, is required for mitotic cell growth, DNA repair and meiotic recombination in Saccharomyces cerevisiae.

    PubMed Central

    Kato, R; Ogawa, H

    1994-01-01

    A new mutant, which was sensitive to both methyl-methanesulfonate (MMS) and ultra-violet light (UV) and defective in meiotic recombination, was isolated from Saccharomyces cerevisiae. The gene, ESR1, was cloned by complementation of the MMS sensitivity of the mutant and found to be essential for cell growth, as the deleted haploid strain was lethal. The ESR1 gene was adjacent to the CKS1 gene on chromosome II and encoded a putative 2368-amino acid protein with a molecular weight of 273 k. The ESR1 transcript was 8.0 kb long and was induced during meiosis. The predicted Esr1 protein had a mosaic structure composed of homologous regions and showed amino acid sequence similarities to Schizosaccharomyces pombe rad3+ protein, which monitors completion of DNA repair synthesis, and cut1+ protein, which is required for spindle pole body (SPB) duplication. The Esr1 protein was also similar to phosphatidylinositol (PI) 3-kinases, including Saccharomyces cerevisiae TOR2 (and DRR1), which are involved in G1 progression. These results suggest that ESR1 is multi-functional throughout mitosis and meiosis. Images PMID:8065923

  11. Construction of engineered Saccharomyces cerevisiae strain to improve that whole-cell biocatalytic production of melibiose from raffinose.

    PubMed

    Zhou, Yingbiao; Zhu, Yueming; Men, Yan; Dong, Caixia; Sun, Yuanxia; Zhang, Juankun

    2017-01-18

    There are excessive by-products in the biocatalysis process of this whole-cell biocatalytic production of melibiose from raffinose with current Saccharomyces cerevisiae strains. To solve this problem, we constructed engineered strains based on a liquor yeast (S. cerevisiae) via gene deletion (mel1 gene), heterologous integration (fsy1 or/and ffzi1 gene from Candida magnoliae), and gene overexpression (gcr1 gene). Functional verification showed that deletion of the mel1 gene led to elimination of the reactions catalyzed by α-galactosidase, as well as elimination of the degradation of melibiose and the formation of galactose by-product. Insertion of the fsy1 or/and ffzi1 gene and overexpression of the gcr1 gene could contribute to fructose transport for enhancing the biopurification rate of the fructose by-product. Compared with the wild-type strain, the optimal engineered strain of MP8 (Δmel1::fsy1 cm ::ffzi1 cm ::gcr1 sc ) had improved about 30% on yield, 31% on productivity, and 36% on purity of the melibiose product.

  12. Saccharomyces cerevisiae decreases inflammatory responses induced by F4+ enterotoxigenic Escherichia coli in porcine intestinal epithelial cells.

    PubMed

    Zanello, Galliano; Meurens, François; Berri, Mustapha; Chevaleyre, Claire; Melo, Sandrine; Auclair, Eric; Salmon, Henri

    2011-05-15

    Probiotic yeasts may provide protection against intestinal inflammation induced by enteric pathogens. In piglets, infection with F4+ enterotoxigenic Escherichia coli (ETEC) leads to inflammation, diarrhea and intestinal damage. In this study, we investigated whether the yeast strains Saccharomyces cerevisiae (Sc, strain CNCM I-3856) and S. cerevisiae variety boulardii (Sb, strain CNCM I-3799) decreased the expression of pro-inflammatory cytokines and chemokines in intestinal epithelial IPI-2I cells cultured with F4+ ETEC. Results showed that viable Sc inhibited the ETEC-induced TNF-α gene expression whereas Sb did not. In contrast, killed Sc failed to inhibit the expression of pro-inflammatory genes. This inhibition was dependent on secreted soluble factors. Sc culture supernatant decreased the TNF-α, IL-1α, IL-6, IL-8, CXCL2 and CCL20 ETEC-induced mRNA. Furthermore, Sc culture supernatant filtrated fraction < 10 kDa displayed the same effects excepted for TNF-α. Thus, our results extended to Sc (strain CNCM I-3856) the inhibitory effects of some probiotic yeast strains onto inflammation.

  13. Microbial solar cells: applying photosynthetic and electrochemically active organisms.

    PubMed

    Strik, David P B T B; Timmers, Ruud A; Helder, Marjolein; Steinbusch, Kirsten J J; Hamelers, Hubertus V M; Buisman, Cees J N

    2011-01-01

    Microbial solar cells (MSCs) are recently developed technologies that utilize solar energy to produce electricity or chemicals. MSCs use photoautotrophic microorganisms or higher plants to harvest solar energy, and use electrochemically active microorganisms in the bioelectrochemical system to generate electrical current. Here, we review the principles and performance of various MSCs in an effort to identify the most promising systems, as well as the bottlenecks and potential solutions, for "real-life" MSC applications. We present an outlook on future applications based on the intrinsic advantages of MSCs, specifically highlighting how these living energy systems can facilitate the development of an electricity-producing green roof.

  14. Application of living microbial cells entrapped with synthetic resin prepolymers.

    PubMed

    Fukui, S; Tanaka, A

    1989-12-01

    Living and growing microbial cells were immobilized by entrapping in synthetic resin gels prepared from their prepolymers, and used in the production of various useful substances. The production of the desired metabolites and also both the activity and the stability of the catalytic systems were seriously affected by the physico-chemical properties of the prepolymers, and those of the resin gels subsequently formed, such as gel network, hydrophilicity-hydrophobicity balance and ionic nature, as well as by the type of bioreactors. Hydroxylation of steroids and production of antibiotics, polypeptides and other biologically active substances, and the effects of gel properties on them are discussed as examples.

  15. Multi-population model of a microbial electrolysis cell.

    PubMed

    Pinto, R P; Srinivasan, B; Escapa, A; Tartakovsky, B

    2011-06-01

    This work presents a multi-population dynamic model of a microbial electrolysis cell (MEC). The model describes the growth and metabolic activity of fermentative, electricigenic, methanogenic acetoclastic, and methanogenic hydrogenophilic microorganisms and is capable of simulating hydrogen production in a MEC fed with complex organic matter, such as wastewater. The model parameters were estimated with the experimental results obtained in continuous flow MECs fed with acetate or synthetic wastewater. Following successful model validation with an independent data set, the model was used to analyze and discuss the influence of applied voltage and organic load on hydrogen production and COD removal.

  16. Design of a microbial fuel cell and its transition to microbial electrolytic cell for hydrogen production by electrohydrogenesis.

    PubMed

    Gupta, Pratima; Parkhey, Piyush; Joshi, Komal; Mahilkar, Anjali

    2013-10-01

    Anaerobic bacteria were isolated from industrial wastewater and soil samples and tested for exoelectrogenic activity by current production in double chambered microbial fuel cell (MFC), which was further transitioned into a single chambered microbial electrolytic cell to test hydrogen production by electrohydrogenesis. Of all the cultures, the isolate from industrial water sample showed the maximum values for current = 0.161 mA, current density = 108.57 mA/m2 and power density = 48.85 mW/m2 with graphite electrode. Maximum voltage across the cell, however, was reported by the isolate from sewage water sample (506 mv) with copper as electrode. Tap water with KMnO4 was the best cathodic electrolyte as the highest values for all the measured MFC parameters were reported with it. Once the exoelectrogenic activity of the isolates was confirmed by current production, these were tested for hydrogen production in a single chambered microbial electrolytic cell (MEC) modified from the MFC. Hydrogen production was reported positive from co-culture of isolates of both the water samples and co-culture of one soil and one water sample. The maximum rate and yield of hydrogen production was 0.18 m3H2/m3/d and 3.2 mol H2/mol glucose respectively with total hydrogen production of 42.4 mL and energy recovery of 57.4%. Cumulative hydrogen production for a five day cycle of MEC operation was 0.16 m3H2/m3/d.

  17. Photosynthetic microbial fuel cells with positive light response.

    PubMed

    Zou, Yongjin; Pisciotta, John; Billmyre, R Blake; Baskakov, Ilia V

    2009-12-01

    The current study introduces an aerobic single-chamber photosynthetic microbial fuel cell (PMFC). Evaluation of PMFC performance using naturally growing fresh-water photosynthetic biofilm revealed a weak positive light response, that is, an increase in cell voltage upon illumination. When the PMFC anodes were coated with electrically conductive polymers, the rate of voltage increased and the amplitude of the light response improved significantly. The rapid immediate positive response to light was consistent with a mechanism postulating that the photosynthetic electron-transfer chain is the source of the electrons harvested on the anode surface. This mechanism is fundamentally different from the one exploited in previously designed anaerobic microbial fuel cells (MFCs), sediment MFCs, or anaerobic PMFCs, where the electrons are derived from the respiratory electron-transfer chain. The power densities produced in PMFCs were substantially lower than those that are currently reported for conventional MFC (0.95 mW/m(2) for polyaniline-coated and 1.3 mW/m(2) for polypyrrole-coated anodes). However, the PMFC did not depend on an organic substrate as an energy source and was powered only by light energy. Its operation was CO(2)-neutral and did not require buffers or exogenous electron transfer shuttles.

  18. Stacked microbial desalination cells to enhance water desalination efficiency.

    PubMed

    Chen, Xi; Xia, Xue; Liang, Peng; Cao, Xiaoxin; Sun, Haotian; Huang, Xia

    2011-03-15

    Microbial desalination cell (MDC) is a new method to obtain clean water from brackish water using electricity generated from organic matters by exoelectrogenic bacteria. Anions and cations, derived from salt solution filled in the desalination chamber between the anode and cathode, move to the anode and cathode chambers under the force of electrical field, respectively. On the basis of the primitive single-desalination-chambered MDC, stacked microbial desalination cells (SMDCs) were developed in order to promote the desalination rate in the present study. The effects of desalination chamber number and external resistance were investigated. Results showed that a remarkable increase in the total desalination rate (TDR) could be obtained by means of increasing the desalination cell number and reducing the external resistance, which caused the charge transfer efficiency increased since the SMDCs enabled more pairs of ions separated while one electron passed through the external circuit. The maximum TDR of 0.0252 g/h was obtained using a two-desalination-chambered SMDC with an external resistance of 10 Ω, which was 1.4 times that of single-desalination-chambered MDC. SMDCs proved to be an effective approach to increase the total water desalination rate if provided a proper desalination chamber number and external resistance.

  19. Environmental sensing of heavy metals through whole cell microbial biosensors: a synthetic biology approach.

    PubMed

    Bereza-Malcolm, Lara Tess; Mann, Gülay; Franks, Ashley Edwin

    2015-05-15

    Whole cell microbial biosensors are offering an alternative means for rapid, on-site heavy metal detection. Based in microorganisms, biosensing constructs are designed and constructed to produce both qualitative and quantitative outputs in response to heavy metal ions. Previous microbial biosensors designs are focused on single-input constructs; however, development of multiplexed systems is resulting in more flexible designs. The movement of microbial biosensors from laboratory based designs toward on-site, functioning heavy metal detectors has been hindered by the toxic nature of heavy metals, along with the lack of specificity of heavy metals promoter elements. Applying a synthetic biology approach with alternative microbial chassis may increase the robustness of microbial biosensors and mitigate these issues. Before full applications are achieved, further consideration has to be made regarding the risk and regulations of whole cell microbial biosensor use in the environment. To this end, a standard framework for future whole cell microbial biosensor design and use is proposed.

  20. Using S. cerevisiae as a Model System to Investigate V. cholerae VopX-Host Cell Protein Interactions and Phenotypes.

    PubMed

    Seward, Christopher H; Manzella, Alexander; Alam, Ashfaqul; Butler, J Scott; Dziejman, Michelle

    2015-10-14

    Most pathogenic, non-O1/non-O139 serogroup Vibrio cholerae strains cause diarrheal disease in the absence of cholera toxin. Instead, many use Type 3 Secretion System (T3SS) mediated mechanisms to disrupt host cell homeostasis. We identified a T3SS effector protein, VopX, which is translocated into mammalian cells during in vitro co-culture. In a S. cerevisiae model system, we found that expression of VopX resulted in a severe growth defect that was partially suppressed by a deletion of RLM1, encoding the terminal transcriptional regulator of the Cell Wall Integrity MAP kinase (CWI) regulated pathway. Growth of yeast cells in the presence of sorbitol also suppressed the defect, supporting a role for VopX in destabilizing the cell wall. Expression of VopX activated expression of β-galactosidase from an RLM1-reponsive element reporter fusion, but failed to do so in cells lacking MAP kinases upstream of Rlm1. The results suggest that VopX inhibits cell growth by stimulating the CWI pathway through Rlm1. Rlm1 is an ortholog of mammalian MEF2 transcription factors that are proposed to regulate cell differentiation, proliferation, and apoptosis. The collective findings suggest that VopX contributes to disease by activating MAP kinase cascades that elicit changes in cellular transcriptional programs.

  1. Glucose-dependent cell size is regulated by a G protein-coupled receptor system in yeast Saccharomyces cerevisiae.

    PubMed

    Tamaki, Hisanori; Yun, Cheol-Won; Mizutani, Tomohiro; Tsuzuki, Takahiro; Takagi, Yukinobu; Shinozaki, Makiko; Kodama, Yukiko; Shirahige, Katsuhiko; Kumagai, Hidehiko

    2005-03-01

    In the yeast, Saccharomyces cerevisiae, cell size is affected by the kind of carbon source in the medium. Here, we present evidence that the Gpr1 receptor and Gpa2 Galpha subunit are required for both maintenance and modulation of cell size in response to glucose. In the presence of glucose, mutants lacking GPR1 or GPA2 gene showed smaller cells than the wild-type strain. Physiological studies revealed that protein synthesis rate was reduced in the mutant strains indicating that reduced growth rate, while the level of mRNAs for CLN1, 2 and 3 was not affected in all strains. Gene chip analysis also revealed a down-regulation in the expression of genes related to biosynthesis of not only protein but also other cellular component in the mutant strains. We also show that GPR1 and GPA2 are required for a rapid increase in cell size in response to glucose. Wild-type cells grown in ethanol quickly increased in size by addition of glucose, while little change was observed in the mutant strains, in which glucose-dependent cell cycle arrest caused by CLN1 repression was somewhat alleviated. Our study indicates that the yeast G-protein coupled receptor system consisting of Gpr1 and Gpa2 regulates cell size by affecting both growth rate and cell division.

  2. Using S. cerevisiae as a Model System to Investigate V. cholerae VopX-Host Cell Protein Interactions and Phenotypes

    PubMed Central

    Seward, Christopher H.; Manzella, Alexander; Alam, Ashfaqul; Butler, J. Scott; Dziejman, Michelle

    2015-01-01

    Most pathogenic, non-O1/non-O139 serogroup Vibrio cholerae strains cause diarrheal disease in the absence of cholera toxin. Instead, many use Type 3 Secretion System (T3SS) mediated mechanisms to disrupt host cell homeostasis. We identified a T3SS effector protein, VopX, which is translocated into mammalian cells during in vitro co-culture. In a S. cerevisiae model system, we found that expression of VopX resulted in a severe growth defect that was partially suppressed by a deletion of RLM1, encoding the terminal transcriptional regulator of the Cell Wall Integrity MAP kinase (CWI) regulated pathway. Growth of yeast cells in the presence of sorbitol also suppressed the defect, supporting a role for VopX in destabilizing the cell wall. Expression of VopX activated expression of β-galactosidase from an RLM1-reponsive element reporter fusion, but failed to do so in cells lacking MAP kinases upstream of Rlm1. The results suggest that VopX inhibits cell growth by stimulating the CWI pathway through Rlm1. Rlm1 is an ortholog of mammalian MEF2 transcription factors that are proposed to regulate cell differentiation, proliferation, and apoptosis. The collective findings suggest that VopX contributes to disease by activating MAP kinase cascades that elicit changes in cellular transcriptional programs. PMID:26473925

  3. Characterization of the Cell Surface Properties of Drinking Water Pathogens by Microbial Adhesion to Hydrocarbon and Electrophoretic Mobility Measurements

    EPA Science Inventory

    The surface characteristics of microbial cells directly influence their mobility and behavior within aqueous environments. The cell surface hydrophobicity (CSH) and electrophoretic mobility (EPM) of microbial cells impact a number of interactions and processes including aggregati...

  4. Single-cell analysis of S. cerevisiae growth recovery after a sublethal heat-stress applied during an alcoholic fermentation.

    PubMed

    Tibayrenc, Pierre; Preziosi-Belloy, Laurence; Ghommidh, Charles

    2011-06-01

    Interest in bioethanol production has experienced a resurgence in the last few years. Poor temperature control in industrial fermentation tanks exposes the yeast cells used for this production to intermittent heat stress which impairs fermentation efficiency. Therefore, there is a need for yeast strains with improved tolerance, able to recover from such temperature variations. Accordingly, this paper reports the development of methods for the characterization of Saccharomyces cerevisiae growth recovery after a sublethal heat stress. Single-cell measurements were carried out in order to detect cell-to-cell variability. Alcoholic batch fermentations were performed on a defined medium in a 2 l instrumented bioreactor. A rapid temperature shift from 33 to 43 °C was applied when ethanol concentration reached 50 g l⁻¹. Samples were collected at different times after the temperature shift. Single cell growth capability, lag-time and initial growth rate were determined by monitoring the growth of a statistically significant number of cells after agar medium plating. The rapid temperature shift resulted in an immediate arrest of growth and triggered a progressive loss of cultivability from 100 to 0.0001% within 8 h. Heat-injured cells were able to recover their growth capability on agar medium after a lag phase. Lag-time was longer and more widely distributed as the time of heat exposure increased. Thus, lag-time distribution gives an insight into strain sensitivity to heat-stress, and could be helpful for the selection of yeast strains of technological interest.

  5. Construction of a xylan-fermenting yeast strain through codisplay of xylanolytic enzymes on the surface of xylose-utilizing Saccharomyces cerevisiae cells.

    PubMed

    Katahira, Satoshi; Fujita, Yasuya; Mizuike, Atsuko; Fukuda, Hideki; Kondo, Akihiko

    2004-09-01

    Hemicellulose is one of the major forms of biomass in lignocellulose, and its essential component is xylan. We used a cell surface engineering system based on alpha-agglutinin to construct a Saccharomyces cerevisiae yeast strain codisplaying two types of xylan-degrading enzymes, namely, xylanase II (XYNII) from Trichoderma reesei QM9414 and beta-xylosidase (XylA) from Aspergillus oryzae NiaD300, on the cell surface. In a high-performance liquid chromatography analysis, xylose was detected as the main product of the yeast strain codisplaying XYNII and XylA, while xylobiose and xylotriose were detected as the main products of a yeast strain displaying XYNII on the cell surface. These results indicate that xylan is sequentially hydrolyzed to xylose by the codisplayed XYNII and XylA. In a further step toward achieving the simultaneous saccharification and fermentation of xylan, a xylan-utilizing S. cerevisiae strain was constructed by codisplaying XYNII and XylA and introducing genes for xylose utilization, namely, those encoding xylose reductase and xylitol dehydrogenase from Pichia stipitis and xylulokinase from S. cerevisiae. After 62 h of fermentation, 7.1 g of ethanol per liter was directly produced from birchwood xylan, and the yield in terms of grams of ethanol per gram of carbohydrate consumed was 0.30 g/g. These results demonstrate that the direct conversion of xylan to ethanol is accomplished by the xylan-utilizing S. cerevisiae strain.

  6. The Role of Soil Organic Matter, Nutrients, and Microbial Community Structure on the Performance of Microbial Fuel Cells

    NASA Astrophysics Data System (ADS)

    Rooney-Varga, J. N.; Dunaj, S. J.; Vallino, J. J.; Hines, M. E.; Gay, M.; Kobyljanec, C.

    2011-12-01

    Microbial fuel cells (MFCs) offer the potential for generating electricity, mitigating greenhouse gas emissions, and bioremediating pollutants through utilization of a plentiful, natural, and renewable resource: soil organic carbon. In the current study, we analyzed microbial community structure, MFC performance, and soil characteristics in different microhabitats (bulk soil, anode, and cathode) within MFCs constructed from agricultural or forest soils in order to determine how soil type and microbial dynamics influence MFC performance. MFCs were constructed with soils from agricultural and hardwood forest sites at Harvard Forest (Petersham, MA). The bulk soil characteristics were analyzed, including polyphenols, short chain fatty acids, total organic C and N, abiotic macronutrients, N and P mineralization rates, CO2 respiration rates, and MFC power output. Microbial community structure of the anodes, cathodes, and bulk soils was determined with molecular fingerprinting methods, which included terminal restriction length polymorphism (T-RFLP) analysis and 16S rRNA gene sequencing analysis. Our results indicated that MFCs constructed from agricultural soil had power output about 17 times that of forest soil-based MFCs and respiration rates about 10 times higher than forest soil MFCs. Agricultural soil MFCs had lower C:N ratios, polyphenol content, and acetate concentrations than forest soil MFCs, suggesting that active agricultural MFC microbial communities were supported by higher quality organic carbon. Microbial community profile data indicate that the microbial communities at the anode of the high power MFCs were less diverse than in low power MFCs and were dominated by Deltaproteobacteria, Geobacter, and, to a lesser extent, Clostridia, while low-power MFC anode communities were dominated by Clostridia. These data suggest that the presence of organic carbon substrate (acetate) was not the major limiting factor in selecting for highly electrogenic microbial

  7. Proliferating cell nuclear antigen (PCNA) contributes to the high-order structure and stability of heterochromatin in Saccharomyces cerevisiae.

    PubMed

    Bi, Xin; Ren, Yue; Kath, Morgan

    2016-12-16

    Heterochromatin plays important roles in the structure, maintenance, and function of the eukaryotic genome. It is associated with special histone modifications and specialized non-histone proteins and assumes a more compact structure than euchromatin. Genes embedded in heterochromatin are generally transcriptionally silent. It was found previously that several mutations of proliferating cell nuclear antigen (PCNA), a DNA replication processivity factor, reduce transcriptional silencing at heterochromatin loci in Saccharomyces cerevisiae. However, the notion that PCNA plays a role in transcriptional silencing was recently questioned because of a potential problem concerning the silencing assays used in prior studies. To determine if PCNA is a bona fide contributor to heterochromatin-mediated transcriptional silencing, we examined the effects of PCNA mutations on heterochromatin structure. We found evidence implicating PCNA in the maintenance of the high-order structure and stability of heterochromatin, which indicates a role of DNA replication in heterochromatin maintenance.

  8. Scanning electrochemical microscopy based evaluation of influence of pH on bioelectrochemical activity of yeast cells - Saccharomyces cerevisiae.

    PubMed

    Ramanavicius, A; Morkvenaite-Vilkonciene, I; Kisieliute, A; Petroniene, J; Ramanaviciene, A

    2017-01-01

    In this research scanning electrochemical microscopy was applied for the investigation of immobilized yeast Saccharomyces cerevisiae cells. Two redox mediators based system was applied in order to increase the efficiency of charge transfer from yeast cells. 9,10-phenanthrenequinone (PQ) was applied as a lipophilic redox mediator, which has the ability to cross the cell's membrane; another redox mediator was ferricyanide, which acted as a hydrophylic electron acceptor able to transfer electrons from the PQ to the working electrode of SECM. Hill's function was applied to determine the optimal pH for this described SECM-based system. The influence of pH on cell viability could be well described by Hill's function. It was determined that at pH 6.5 the PQ has a minimal toxic influence on yeast cells, and the kinetics of metabolic processes in cells as well as electron transfer rate achieved in consecutive action of both redox mediators were appropriate to achieve optimal current signals.

  9. Chemical modulation of the ultra-weak photon emission from Saccharomyces cerevisiae and differentiated HL-60 cells

    NASA Astrophysics Data System (ADS)

    Červinková, Kateřina; Nerudová, Michaela; Hašek, Jiří; Cifra, Michal

    2015-01-01

    The ultra-weak photon emission (UPE) is a universal phenomenon common to all cells with active oxidative metabolism. Generally accepted mechanism of the origin of the ultra-weak photon emission considers reactions of radical or nonradical reactive oxygen species (ROS) with biomolecules such as lipids and proteins which lead to the formation of electron excited species. During the transition to the ground state the excess energy is released as a photon with a wavelength in the visible range of the electromagnetic spectrum. Since the intensity of the light is very low it is possible to be measured only by highly sensitive devices. We used Hamamatsu Photonics PMT module H7360-01 mounted into a light-tight chamber for the purposes of this work. The goal of our research is to delineate an origin of UPE from two model organisms; differentiated HL-60 cells (human promyelocytic leukemia) and yeast cells Saccharomyces cerevisiae. While the UPE from the yeast cells arises spontaneously during the growth without any external stimuli, UPE from HL-60 is induced by phorbol 12-myristate, 13-acetate (PMA). It is possible to modulate the UPE production by certain antioxidants which scavenge ROS formed during the metabolism (yeast cells) or respiratory burst (HL-60 cells). The experiments are focused on the description of effects caused by antioxidants. Several kinds of antioxidants (ascorbic acid, mannitol, glutathione) with different concentration were used and we studied the changes in the UPE intensities of and the temporal developments of the optical signal.

  10. Strengths and weaknesses in the determination of Saccharomyces cerevisiae cell viability by ATP-based bioluminescence assay.

    PubMed

    Paciello, Lucia; Falco, Francesco Cristino; Landi, Carmine; Parascandola, Palma

    2013-03-05

    Due to its sensitivity and speed of execution, detection of ATP by luciferin-luciferase reaction is a widely spread system to highlight cell viability. The paper describes the methodology followed to successfully run the assay in the presence of yeast cells of two strains of the yeast Saccharomyces cerevisiae, BY4741 and CEN.PK2-1C and emphasizes the importance of correctly determining the contact time between the lysing agent and the yeast cells. Once this was established, luciferin-luciferase reaction was exploited to determine the maximum specific rate of growth, as well as cell viability in a series of routine tests. The results obtained in this preliminary study highlighted that using luciferin-luciferase can imply an over-estimation of maximum specific growth rate with respect to that determined by optical density and/or viable count. On the contrary, the bioluminescence assay gave the possibility to highlight, if employed together with viable count, physiological changes occurring in yeast cells as response to stressful environmental conditions such as those deriving from exposure of yeast cells to high temperature or those depending on the operative conditions applied during fed-batch operations.

  11. The Cytosolic pH of Individual Saccharomyces cerevisiae Cells Is a Key Factor in Acetic Acid Tolerance.

    PubMed

    Fernández-Niño, Miguel; Marquina, Maribel; Swinnen, Steve; Rodríguez-Porrata, Boris; Nevoigt, Elke; Ariño, Joaquín

    2015-11-01

    It was shown recently that individual cells of an isogenic Saccharomyces cerevisiae population show variability in acetic acid tolerance, and this variability affects the quantitative manifestation of the trait at the population level. In the current study, we investigated whether cell-to-cell variability in acetic acid tolerance could be explained by the observed differences in the cytosolic pHs of individual cells immediately before exposure to the acid. Results obtained with cells of the strain CEN.PK113-7D in synthetic medium containing 96 mM acetic acid (pH 4.5) showed a direct correlation between the initial cytosolic pH and the cytosolic pH drop after exposure to the acid. Moreover, only cells with a low initial cytosolic pH, which experienced a less severe drop in cytosolic pH, were able to proliferate. A similar correlation between initial cytosolic pH and cytosolic pH drop was also observed in the more acid-tolerant strain MUCL 11987-9. Interestingly, a fraction of cells in the MUCL 11987-9 population showed initial cytosolic pH values below the minimal cytosolic pH detected in cells of the strain CEN.PK113-7D; consequently, these cells experienced less severe drops in cytosolic pH. Although this might explain in part the difference between the two strains with regard to the number of cells that resumed proliferation, it was observed that all cells from strain MUCL 11987-9 were able to proliferate, independently of their initial cytosolic pH. Therefore, other factors must also be involved in the greater ability of MUCL 11987-9 cells to endure strong drops in cytosolic pH.

  12. Flow dependent performance of microfluidic microbial fuel cells.

    PubMed

    Vigolo, Daniele; Al-Housseiny, Talal T; Shen, Yi; Akinlawon, Fiyinfoluwa O; Al-Housseiny, Saif T; Hobson, Ronald K; Sahu, Amaresh; Bedkowski, Katherine I; DiChristina, Thomas J; Stone, Howard A

    2014-06-28

    The integration of Microbial Fuel Cells (MFCs) in a microfluidic geometry can significantly enhance the power density of these cells, which would have more active bacteria per unit volume. Moreover, microfluidic MFCs can be operated in a continuous mode as opposed to the traditional batch-fed mode. Here we investigate the effect of fluid flow on the performance of microfluidic MFCs. The growth and the structure of the bacterial biofilm depend to a large extent on the shear stress of the flow. We report the existence of a range of flow rates for which MFCs can achieve maximum voltage output. When operated under these optimal conditions, the power density of our microfluidic MFC is about 15 times that of a similar-size batch MFC. Furthermore, this optimum suggests a correlation between the behaviour of bacteria and fluid flow.

  13. Nitrite as a candidate substrate in microbial fuel cells.

    PubMed

    Faraghi, Neda; Ebrahimi, Sirous

    2012-08-01

    Current generation using nitrite as substrate (pH 6.9, 40 mgN l(-1)) in a nitrite-fed microbial fuel cell was investigated under anaerobic and aerobic anodic conditions as an alternative to the biological nitrite oxidation process. Cell current, coulombic efficiency (CE) and power generation of 0.04 mA, 30 ± 2 % and 19.3 ± 3.3 μW m(-2), respectively, were observed under anaerobic conditions while complete nitrite degradation (no current) was obtained under aerobic conditions. Switching from aerobic to anaerobic anode enhanced the CE and power generation (39 ± 1 % and 29 ± 4.3 μW m(-2)).

  14. Analysis of the microbial community of the biocathode of a hydrogen-producing microbial electrolysis cell.

    PubMed

    Croese, Elsemiek; Pereira, Maria Alcina; Euverink, Gert-Jan W; Stams, Alfons J M; Geelhoed, Jeanine S

    2011-12-01

    The microbial electrolysis cell (MEC) is a promising system for hydrogen production. Still, expensive catalysts such as platinum are needed for efficient hydrogen evolution at the cathode. Recently, the possibility to use a biocathode as an alternative for platinum was shown. The microorganisms involved in hydrogen evolution in such systems are not yet identified. We analyzed the microbial community of a mixed culture biocathode that was enriched in an MEC bioanode. This biocathode produced 1.1 A m(-2) and 0.63 m3 H2 m(-3) cathode liquid volume per day. The bacterial population consisted of 46% Proteobacteria, 25% Firmicutes, 17% Bacteroidetes, and 12% related to other phyla. The dominant ribotype belonged to the species Desulfovibrio vulgaris. The second major ribotype cluster constituted a novel taxonomic group at the genus level, clustering within uncultured Firmicutes. The third cluster belonged to uncultured Bacteroidetes and grouped in a taxonomic group from which only clones were described before; most of these clones originated from soil samples. The identified novel taxonomic groups developed under environmentally unusual conditions, and this may point to properties that have not been considered before. A pure culture of Desulfovibrio strain G11 inoculated in a cathode of an MEC led to a current development from 0.17 to 0.76 A m(-2) in 9 days, and hydrogen gas formation was observed. On the basis of the known characteristics of Desulfovibrio spp., including its ability to produce hydrogen, we propose a mechanism for hydrogen evolution through Desulfovibrio spp. in a biocathode system.

  15. Probabilistic Model of Microbial Cell Growth, Division, and Mortality ▿

    PubMed Central

    Horowitz, Joseph; Normand, Mark D.; Corradini, Maria G.; Peleg, Micha

    2010-01-01

    After a short time interval of length δt during microbial growth, an individual cell can be found to be divided with probability Pd(t)δt, dead with probability Pm(t)δt, or alive but undivided with the probability 1 − [Pd(t) + Pm(t)]δt, where t is time, Pd(t) expresses the probability of division for an individual cell per unit of time, and Pm(t) expresses the probability of mortality per unit of time. These probabilities may change with the state of the population and the habitat's properties and are therefore functions of time. This scenario translates into a model that is presented in stochastic and deterministic versions. The first, a stochastic process model, monitors the fates of individual cells and determines cell numbers. It is particularly suitable for small populations such as those that may exist in the case of casual contamination of a food by a pathogen. The second, which can be regarded as a large-population limit of the stochastic model, is a continuous mathematical expression that describes the population's size as a function of time. It is suitable for large microbial populations such as those present in unprocessed foods. Exponential or logistic growth with or without lag, inactivation with or without a “shoulder,” and transitions between growth and inactivation are all manifestations of the underlying probability structure of the model. With temperature-dependent parameters, the model can be used to simulate nonisothermal growth and inactivation patterns. The same concept applies to other factors that promote or inhibit microorganisms, such as pH and the presence of antimicrobials, etc. With Pd(t) and Pm(t) in the form of logistic functions, the model can simulate all commonly observed growth/mortality patterns. Estimates of the changing probability parameters can be obtained with both the stochastic and deterministic versions of the model, as demonstrated with simulated data. PMID:19915038

  16. Enhancement of Electricity Production by Graphene Oxide in Soil Microbial Fuel Cells and Plant Microbial Fuel Cells

    PubMed Central

    Goto, Yuko; Yoshida, Naoko; Umeyama, Yuto; Yamada, Takeshi; Tero, Ryugo; Hiraishi, Akira

    2015-01-01

    The effects of graphene oxide (GO) on electricity generation in soil microbial fuel cells (SMFCs) and plant microbial fuel cell (PMFCs) were investigated. GO at concentrations ranging from 0 to 1.9 g⋅kg−1 was added to soil and reduced for 10 days under anaerobic incubation. All SMFCs (GO-SMFCs) utilizing the soils incubated with GO produced electricity at a greater rate and in higher quantities than the SMFCs which did not contain GO. In fed-batch operations, the overall average electricity generation in GO-SMFCs containing 1.0 g⋅kg−1 of GO was 40 ± 19 mW⋅m−2, which was significantly higher than the value of 6.6 ± 8.9 mW⋅m−2 generated from GO-free SMFCs (p < 0.05). The increase in catalytic current at the oxidative potential was observed by cyclic voltammetry (CV) for GO-SMFC, with the CV curve suggesting the enhancement of electron transfer from oxidation of organic substances in the soil by the reduced form of GO. The GO-containing PMFC also displayed a greater generation of electricity compared to the PMFC with no added GO, with GO-PMFC producing 49 mW⋅m−2 of electricity after 27 days of operation. Collectively, this study demonstrates that GO added to soil can be microbially reduced in soil, and facilitates electron transfer to the anode in both SMFCs and PMFCs. PMID:25883931

  17. Enhancement of electricity production by graphene oxide in soil microbial fuel cells and plant microbial fuel cells.

    PubMed

    Goto, Yuko; Yoshida, Naoko; Umeyama, Yuto; Yamada, Takeshi; Tero, Ryugo; Hiraishi, Akira

    2015-01-01

    The effects of graphene oxide (GO) on electricity generation in soil microbial fuel cells (SMFCs) and plant microbial fuel cell (PMFCs) were investigated. GO at concentrations ranging from 0 to 1.9 g⋅kg(-1) was added to soil and reduced for 10 days under anaerobic incubation. All SMFCs (GO-SMFCs) utilizing the soils incubated with GO produced electricity at a greater rate and in higher quantities than the SMFCs which did not contain GO. In fed-batch operations, the overall average electricity generation in GO-SMFCs containing 1.0 g⋅kg(-1) of GO was 40 ± 19 mW⋅m(-2), which was significantly higher than the value of 6.6 ± 8.9 mW⋅m(-2) generated from GO-free SMFCs (p < 0.05). The increase in catalytic current at the oxidative potential was observed by cyclic voltammetry (CV) for GO-SMFC, with the CV curve suggesting the enhancement of electron transfer from oxidation of organic substances in the soil by the reduced form of GO. The GO-containing PMFC also displayed a greater generation of electricity compared to the PMFC with no added GO, with GO-PMFC producing 49 mW⋅m(-2) of electricity after 27 days of operation. Collectively, this study demonstrates that GO added to soil can be microbially reduced in soil, and facilitates electron transfer to the anode in both SMFCs and PMFCs.

  18. Antiapoptotic role of S-adenosyl-l-methionine against hydrochloric acid induced cell death in Saccharomyces cerevisiae.

    PubMed

    Malakar, Dipankar; Dey, Anindya; Basu, Arghya; Ghosh, Anil K

    2008-01-01

    Exposure of stationary phase cells of Saccharomyces cerevisiae to 10 mM HCl (pH approximately 2) resulted in cell death as a function of time (up to 6 h) with most (about 40%-65%) of the cells showing apoptotic features including chromatin condensation along the nuclear envelope, exposure of phosphatidylserine on the outer leaflet of cytoplasmic membrane, and DNA fragmentation. During the first 2 h of acid exposure there was an increase in reactive oxygen species (ROS) level inside cells, with subsequent elevation in the level of lipid peroxidation and decrease in reducing equivalents culminating in loss of mitochondrial membrane potential (DeltaPsi(m)). An initial (1 h) event of mitochondrial hyper-polarization with subsequent elevation of ROS level of the acid treated cells was also observed. S-adenosyl-l-methionine (AdoMet; 1 mM) treatment increased the cell survival of the acid stressed cells. It partially scavenged the increased intracellular ROS level by supplementing glutathione through the transsulfuration pathway. It also inhibited acid mediated lipid peroxidation, partially recovered acid evoked loss of DeltaPsi(m) and protected the cells from apoptotic cell death. S-adenosyl di-aldehyde, an indirect inhibitor of the AdoMet metabolic pathway, increased mortality of the acid treated cells. Incubation of acid stressed cells with the antioxidant, N-acetyl-cysteine (1 mM), decreased the cellular mortality, but the same concentration of AdoMet offered more protection by scavenging the free radicals. The ability of AdoMet to scavenge ROS mediated apoptosis may be an important function of this molecule in responding to cellular stress. The study could open a new avenue for detailed investigation on the curative potential of AdoMet against gastric ulcer.

  19. Cell-to-cell contact and antimicrobial peptides play a combined role in the death of Lachanchea thermotolerans during mixed-culture alcoholic fermentation with Saccharomyces cerevisiae.

    PubMed

    Kemsawasd, Varongsiri; Branco, Patrícia; Almeida, Maria Gabriela; Caldeira, Jorge; Albergaria, Helena; Arneborg, Nils

    2015-07-01

    The roles of cell-to-cell contact and antimicrobial peptides in the early death of Lachanchea thermotolerans CBS2803 during anaerobic, mixed-culture fermentations with Saccharomyces cerevisiae S101 were investigated using a commercially available, double-compartment fermentation system separated by cellulose membranes with different pore sizes, i.e. 1000 kDa for mixed- and single-culture fermentations, and 1000 and 3.5-5 kDa for compartmentalized-culture fermentations. SDS-PAGE and gel filtration chromatography were used to determine an antimicrobial peptidic fraction in the fermentations. Our results showed comparable amounts of the antimicrobial peptidic fraction in the inner compartments of the mixed-culture and 1000 kDa compartmentalized-culture fermentations containing L. thermotolerans after 4 days of fermentation, but a lower death rate of L. thermotolerans in the 1000 kDa compartmentalized-culture fermentation than in the mixed-culture fermentation. Furthermore, L. thermotolerans died off even more slowly in the 3.5-5 kDa than in the 1000 kDa compartmentalized-culture fermentation, which coincided with the presence of less of the antimicrobial peptidic fraction in the inner compartment of that fermentation than of the 1000 kDa compartmentalized-culture fermentation. Taken together, these results indicate that the death of L. thermotolerans in mixed cultures with S. cerevisiae is caused by a combination of cell-to-cell contact and antimicrobial peptides.

  20. Integrated hydrogen production process from cellulose by combining dark fermentation, microbial fuel cells, and a microbial electrolysis cell.

    PubMed

    Wang, Aijie; Sun, Dan; Cao, Guangli; Wang, Haoyu; Ren, Nanqi; Wu, Wei-Min; Logan, Bruce E

    2011-03-01

    Hydrogen gas production from cellulose was investigated using an integrated hydrogen production process consisting of a dark fermentation reactor and microbial fuel cells (MFCs) as power sources for a microbial electrolysis cell (MEC). Two MFCs (each 25 mL) connected in series to an MEC (72 mL) produced a maximum of 0.43 V using fermentation effluent as a feed, achieving a hydrogen production rate from the MEC of 0.48 m(3) H(2)/m(3)/d (based on the MEC volume), and a yield of 33.2 mmol H(2)/g COD removed in the MEC. The overall hydrogen production for the integrated system (fermentation, MFC and MEC) was increased by 41% compared with fermentation alone to 14.3 mmol H(2)/g cellulose, with a total hydrogen production rate of 0.24 m(3) H(2)/m(3)/d and an overall energy recovery efficiency of 23% (based on cellulose removed) without the need for any external electrical energy input.

  1. Self-sustained reduction of multiple metals in a microbial fuel cell-microbial electrolysis cell hybrid system.

    PubMed

    Li, Yan; Wu, Yining; Liu, Bingchuan; Luan, Hongwei; Vadas, Timothy; Guo, Wanqian; Ding, Jie; Li, Baikun

    2015-09-01

    A self-sustained hybrid bioelectrochemical system consisting of microbial fuel cell (MFC) and microbial electrolysis cell (MEC) was developed to reduce multiple metals simultaneously by utilizing different reaction potentials. Three heavy metals representing spontaneous reaction (chromium, Cr) and unspontaneous reaction (lead, Pb and nickel, Ni) were selected in this batch-mode study. The maximum power density of the MFC achieved 189.4 mW m(-2), and the energy recovery relative to the energy storage circuit (ESC) was ∼ 450%. At the initial concentration of 100 mg L(-1), the average reduction rate of Cr(VI) was 30.0 mg L(-1) d(-1), Pb(II) 32.7 mg L(-1) d(-1), and Ni(II) 8.9 mg L(-1) d(-1). An electrochemical model was developed to predict the change of metal concentration over time. The power output of the MFC was sufficient to meet the requirement of the ESC and MEC, and the "self-sustained metal reduction" was achieved in this hybrid system.

  2. A comparison of simultaneous organic carbon and nitrogen removal in microbial fuel cells and microbial electrolysis cells.

    PubMed

    Hussain, Abid; Manuel, Michelle; Tartakovsky, Boris

    2016-05-15

    This study demonstrates simultaneous carbon and nitrogen removal in laboratory-scale continuous flow microbial fuel cell (MFC) and microbial electrolysis cell (MEC) and provides side-by side comparison of these bioelectrochemical systems. The maximum organic carbon removal rates in MFC and MEC tests were similar at 5.1 g L(-1) d(-1) and 4.16 g L(-1) d(-1), respectively, with a near 100% carbon removal efficiency at an organic load of 3.3 g L(-1) d(-1). An ammonium removal efficiency of 30-55% with near-zero nitrite and nitrate concentrations was observed in the MFC operated at an optimal external resistance, while open-circuit MFC operation resulted in a reduced carbon and ammonium removal of 53% and 21%, respectively. In the MEC ammonium removal was limited to 7-12% under anaerobic conditions, while micro-aerobic conditions increased the removal efficiency to 31%. Also, at zero applied voltage both carbon and ammonium removal efficiencies were reduced to 42% and 4%, respectively. Based on the observed performance under different operating conditions, it was concluded that simultaneous carbon and nitrogen removal was facilitated by concurrent anaerobic and aerobic biotransformation pathways at the anode and cathode, which balanced bioelectrochemical nitrification and denitrification reactions.

  3. Stress-tolerance of baker's-yeast (Saccharomyces cerevisiae) cells: stress-protective molecules and genes involved in stress tolerance.

    PubMed

    Shima, Jun; Takagi, Hiroshi

    2009-05-29

    During the fermentation of dough and the production of baker's yeast (Saccharomyces cerevisiae), cells are exposed to numerous environmental stresses (baking-associated stresses) such as freeze-thaw, high sugar concentrations, air-drying and oxidative stresses. Cellular macromolecules, including proteins, nucleic acids and membranes, are seriously damaged under stress conditions, leading to the inhibition of cell growth, cell viability and fermentation. To avoid lethal damage, yeast cells need to acquire a variety of stress-tolerant mechanisms, for example the induction of stress proteins, the accumulation of stress protectants, changes in membrane composition and repression of translation, and by regulating the corresponding gene expression via stress-triggered signal-transduction pathways. Trehalose and proline are considered to be critical stress protectants, as is glycerol. It is known that these molecules are effective for providing protection against various types of environmental stresses. Modifications of the metabolic pathways of trehalose and proline by self-cloning methods have significantly increased tolerance to baking-associated stresses. To clarify which genes are required for stress tolerance, both a comprehensive phenomics analysis and a functional genomics analysis were carried out under stress conditions that simulated those occurring during the commercial baking process. These analyses indicated that many genes are involved in stress tolerance in yeast. In particular, it was suggested that vacuolar H+-ATPase plays important roles in yeast cells under stress conditions.

  4. High-cell-density fed-batch culture of Saccharomyces cerevisiae KV-25 using molasses and corn steep liquor.

    PubMed

    Vu, Van Hanh; Kim, Keun

    2009-12-01

    High-cell-density cultivation of yeast was investigated using the agricultural waste products corn steep liquor (CSL) and molasses. The Saccharomyces cerevisiae KV-25 cell mass was significantly dependent on the ratio between C and N sources. The concentrations of molasses and CSL in the culture medium were statistically optimized at 10.25% (v/v) and 16.87% (v/v), respectively, by response surface methodology (RSM). Batch culture in a 5-l stirred tank reactor using the optimized medium resulted in a cell mass production of 36.5 g/l. In the fed-batch culture, the feed phase was preceded by a batch phase using the optimized medium, and a very high dried-cell-mass yield of 187.63 g/l was successfully attained by feeding a mixture of 20% (v/v) molasses and 80% (v/v) CSL at a rate of 22 ml/h. In this system, the production of cell mass depended mainly on the agitation speed, the composition of the feed medium, and the glucose level in the medium, but only slightly on the aeration rate.

  5. Saccharomyces cerevisiae Shuttle vectors.

    PubMed

    Gnügge, Robert; Rudolf, Fabian

    2017-01-10

    Yeast shuttle vectors are indispensable tools in yeast research. They enable cloning of defined DNA sequences in Escherichia coli and their direct transfer into Saccharomyces cerevisiae cells. There are three types of commonly used yeast shuttle vectors: centromeric plasmids, episomal plasmids and integrating plasmids. In this review, we discuss the different plasmid systems and their characteristic features. We focus on their segregational stability and copy number and indicate how to modify these properties. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Genomic Sequencing of Single Microbial Cells from Environmental Samples

    SciTech Connect

    Ishoey, Thomas; Woyke, Tanja; Stepanauskas, Ramunas; Novotny, Mark; Lasken, Roger S.

    2008-02-01

    Recently developed techniques allow genomic DNA sequencing from single microbial cells [Lasken RS: Single-cell genomic sequencing using multiple displacement amplification, Curr Opin Microbiol 2007, 10:510-516]. Here, we focus on research strategies for putting these methods into practice in the laboratory setting. An immediate consequence of single-cell sequencing is that it provides an alternative to culturing organisms as a prerequisite for genomic sequencing. The microgram amounts of DNA required as template are amplified from a single bacterium by a method called multiple displacement amplification (MDA) avoiding the need to grow cells. The ability to sequence DNA from individual cells will likely have an immense impact on microbiology considering the vast numbers of novel organisms, which have been inaccessible unless culture-independent methods could be used. However, special approaches have been necessary to work with amplified DNA. MDA may not recover the entire genome from the single copy present in most bacteria. Also, some sequence rearrangements can occur during the DNA amplification reaction. Over the past two years many research groups have begun to use MDA, and some practical approaches to single-cell sequencing have been developed. We review the consensus that is emerging on optimum methods, reliability of amplified template, and the proper interpretation of 'composite' genomes which result from the necessity of combining data from several single-cell MDA reactions in order to complete the assembly. Preferred laboratory methods are considered on the basis of experience at several large sequencing centers where >70% of genomes are now often recovered from single cells. Methods are reviewed for preparation of bacterial fractions from environmental samples, single-cell isolation, DNA amplification by MDA, and DNA sequencing.

  7. Atomic Force Microscopy in Microbiology: New Structural and Functional Insights into the Microbial Cell Surface

    PubMed Central

    2014-01-01

    ABSTRACT Microbial cells sense and respond to their environment using their surface constituents. Therefore, understanding the assembly and biophysical properties of cell surface molecules is an important research topic. With its ability to observe living microbial cells at nanometer resolution and to manipulate single-cell surface molecules, atomic force microscopy (AFM) has emerged as a powerful tool in microbiology. Here, we survey major breakthroughs made in cell surface microbiology using AFM techniques, emphasizing the most recent structural and functional insights. PMID:25053785

  8. A Role for Programmed Cell Death in the Microbial Loop

    PubMed Central

    Durand, Pierre M.; Whitehead, Kenia; Baliga, Nitin S.

    2013-01-01

    The microbial loop is the conventional model by which nutrients and minerals are recycled in aquatic eco-systems. Biochemical pathways in different organisms become metabolically inter-connected such that nutrients are utilized, processed, released and re-utilized by others. The result is that unrelated individuals end up impacting each others' fitness directly through their metabolic activities. This study focused on the impact of programmed cell death (PCD) on a population's growth as well as its role in the exchange of carbon between two naturally co-occurring halophilic organisms. Flow cytometric, biochemical, 14C radioisotope tracing assays, and global transcriptomic analyses show that organic algal photosynthate released by Dunalliela salina cells undergoing PCD complements the nutritional needs of other non-PCD D. salina cells. This occurs in vitro in a carbon limited environment and enhances the growth of the population. In addition, a co-occurring heterotroph Halobacterium salinarum re-mineralizes the carbon providing elemental nutrients for the mixoheterotrophic chlorophyte. The significance of this is uncertain and the archaeon can also subsist entirely on the lysate of apoptotic algae. PCD is now well established in unicellular organisms; however its ecological relevance has been difficult to decipher. In this study we found that PCD in D. salina causes the release of organic nutrients such as glycerol, which can be used by others in the population as well as a co-occurring halophilic archaeon. H. salinarum also re-mineralizes the dissolved material promoting algal growth. PCD in D. salina was the mechanism for the flow of dissolved photosynthate between unrelated organisms. Ironically, programmed death plays a central role in an organism's own population growth and in the exchange of nutrients in the microbial loop. PMID:23667496

  9. Integrated Microfluidic Flow-Through Microbial Fuel Cells.

    PubMed

    Jiang, Huawei; Ali, Md Azahar; Xu, Zhen; Halverson, Larry J; Dong, Liang

    2017-01-25

    This paper reports on a miniaturized microbial fuel cell with a microfluidic flow-through configuration: a porous anolyte chamber is formed by filling a microfluidic chamber with three-dimensional graphene foam as anode, allowing nutritional medium to flow through the chamber to intimately interact with the colonized microbes on the scaffolds of the anode. No nutritional media flow over the anode. This allows sustaining high levels of nutrient utilization, minimizing consumption of nutritional substrates, and reducing response time of electricity generation owing to fast mass transport through pressure-driven flow and rapid diffusion of nutrients within the anode. The device provides a volume power density of 745 μW/cm(3) and a surface power density of 89.4 μW/cm(2) using Shewanella oneidensis as a model biocatalyst without any optimization of bacterial culture. The medium consumption and the response time of the flow-through device are reduced by 16.4 times and 4.2 times, respectively, compared to the non-flow-through counterpart with its freeway space volume six times the volume of graphene foam anode. The graphene foam enabled microfluidic flow-through approach will allow efficient microbial conversion of carbon-containing bioconvertible substrates to electricity with smaller space, less medium consumption, and shorter start-up time.

  10. New applications of carbon nanostructures in microbial fuel cells (MFC)

    NASA Astrophysics Data System (ADS)

    Kaca, W.; Żarnowiec, P.; Keczkowska, Justyna; Suchańska, M.; Czerwosz, E.; Kozłowski, M.

    2014-11-01

    In the studies presented we proposed a new application for nanocomposite carbon films (C-Pd). These films were evaluated as an anode material for Microbial Fuel Cells (MFCs) used for electrical current generation. The results of characterization of C-Pd films composed of carbon and palladium nanograins were obtained using the Physical Vapor Deposition (PVD) method. The film obtained by this method exhibits a multiphase structure composed of fullerene nanograins, amorphous carbon and palladium nanocrystals. Raman Spectroscopy (RS) and scanning electron microscopy (SEM) are used to characterize the chemical composition, morphology and topography of these films. We observed, for MFC with C-Pd anode, the highest electrochemical activity and maximal voltage density - 458 mV (20,8 mV/cm2) for Proteus mirabilis, 426 mV (19,4 mV/cm2) for Pseudomonas aeruginosa and 652 mV (29,6 mV/cm2) for sewage bacteria as the microbial catalyst.

  11. Stimulating sediment bioremediation with benthic microbial fuel cells.

    PubMed

    Li, Wen-Wei; Yu, Han-Qing

    2015-01-01

    Efficient and sustainable technologies for cleaning up of contaminated sediments are under urgent demand. Bioremediation by utilizing the natural metabolic activities of sediment-inhabited microorganisms has been widely accepted as a viable option, but the relatively low efficiency and poor controllability severely limite its application. Here, we bring out the concept that electrochemical approaches may be used as an efficient means to stimulate sediment bioremediation. Although still at the very beginning, benthic microbial fuel cells (BMFC) as a remediation technology show many potential benefits, such as accelerated decontamination, self-sustained operation, relatively easy deployment and control, and environmental benignity. The unique features of BMFC setup and operation also give rise to substantially different challenges compared to conventional MFCs. In this review, we present a critical overview on the characteristics, possible application niches, and state-of-the-art progress of this technology. Especially, the current limitations in respect of system design, electrode selection, microbial control and selection of deployment environment are discussed in details, and the needed future research endeavors to promote its practical application are highlighted.

  12. Control of malodorous hydrogen sulfide compounds using microbial fuel cell.

    PubMed

    Eaktasang, Numfon; Min, Hyeong-Sik; Kang, Christina; Kim, Han S

    2013-10-01

    In this study, a microbial fuel cell (MFC) was used to control malodorous hydrogen sulfide compounds generated from domestic wastewaters. The electricity production demonstrated a distinct pattern of a two-step increase during 170 h of system run: the first maximum current density was 118.6 ± 7.2 mA m⁻² followed by a rebound of current density increase, reaching the second maximum of 176.8 ± 9.4 mA m⁻². The behaviors of the redox potential and the sulfate level in the anode compartment indicated that the microbial production of hydrogen sulfide compounds was suppressed in the first stage, and the hydrogen sulfide compounds generated from the system were removed effectively as a result of their electrochemical oxidation, which contributed to the additional electricity production in the second stage. This was also directly supported by sulfur deposits formed on the anode surface, which was confirmed by analyses on those solids using a scanning electron microscope equipped with energy dispersive X-ray spectroscopy as well as an elemental analyzer. To this end, the overall reduction efficiencies for HS⁻ and H₂S(g) were as high as 67.5 and 96.4 %, respectively. The correlations among current density, redox potential, and sulfate level supported the idea that the electricity signal generated in the MFC can be utilized as a potential indicator of malodor control for the domestic wastewater system.

  13. Electricity generation from tetrathionate in microbial fuel cells by acidophiles.

    PubMed

    Sulonen, Mira L K; Kokko, Marika E; Lakaniemi, Aino-Maija; Puhakka, Jaakko A

    2015-03-02

    Inorganic sulfur compounds, such as tetrathionate, are often present in mining process and waste waters. The biodegradation of tetrathionate was studied under acidic conditions in aerobic batch cultivations and in anaerobic anodes of two-chamber flow-through microbial fuel cells (MFCs). All four cultures originating from biohydrometallurgical process waters from multimetal ore heap bioleaching oxidized tetrathionate aerobically at pH below 3 with sulfate as the main soluble metabolite. In addition, all cultures generated electricity from tetrathionate in MFCs at pH below 2.5 with ferric iron as the terminal cathodic electron acceptor. The maximum current and power densities during MFC operation and in the performance analysis were 79.6 mA m(-2) and 13.9 mW m(-2) and 433 mA m(-2) and 17.6 mW m(-2), respectively. However, the low coulombic efficiency (below 5%) indicates that most of the electrons were directed to other processes, such as aerobic oxidation of tetrathionate and unmeasured intermediates. The microbial community analysis revealed that the dominant species both in the anolyte and on the anode electrode surface of the MFCs were Acidithiobacillus spp. and Ferroplasma spp. This study provides a proof of concept that tetrathionate serves as electron donor for biological electricity production in the pH range of 1.2-2.5.

  14. Integrated Microfluidic Flow-Through Microbial Fuel Cells

    NASA Astrophysics Data System (ADS)

    Jiang, Huawei; Ali, Md. Azahar; Xu, Zhen; Halverson, Larry J.; Dong, Liang

    2017-01-01

    This paper reports on a miniaturized microbial fuel cell with a microfluidic flow-through configuration: a porous anolyte chamber is formed by filling a microfluidic chamber with three-dimensional graphene foam as anode, allowing nutritional medium to flow through the chamber to intimately interact with the colonized microbes on the scaffolds of the anode. No nutritional media flow over the anode. This allows sustaining high levels of nutrient utilization, minimizing consumption of nutritional substrates, and reducing response time of electricity generation owing to fast mass transport through pressure-driven flow and rapid diffusion of nutrients within the anode. The device provides a volume power density of 745 μW/cm3 and a surface power density of 89.4 μW/cm2 using Shewanella oneidensis as a model biocatalyst without any optimization of bacterial culture. The medium consumption and the response time of the flow-through device are reduced by 16.4 times and 4.2 times, respectively, compared to the non-flow-through counterpart with its freeway space volume six times the volume of graphene foam anode. The graphene foam enabled microfluidic flow-through approach will allow efficient microbial conversion of carbon-containing bioconvertible substrates to electricity with smaller space, less medium consumption, and shorter start-up time.

  15. Integrated Microfluidic Flow-Through Microbial Fuel Cells

    PubMed Central

    Jiang, Huawei; Ali, Md. Azahar; Xu, Zhen; Halverson, Larry J.; Dong, Liang

    2017-01-01

    This paper reports on a miniaturized microbial fuel cell with a microfluidic flow-through configuration: a porous anolyte chamber is formed by filling a microfluidic chamber with three-dimensional graphene foam as anode, allowing nutritional medium to flow through the chamber to intimately interact with the colonized microbes on the scaffolds of the anode. No nutritional media flow over the anode. This allows sustaining high levels of nutrient utilization, minimizing consumption of nutritional substrates, and reducing response time of electricity generation owing to fast mass transport through pressure-driven flow and rapid diffusion of nutrients within the anode. The device provides a volume power density of 745 μW/cm3 and a surface power density of 89.4 μW/cm2 using Shewanella oneidensis as a model biocatalyst without any optimization of bacterial culture. The medium consumption and the response time of the flow-through device are reduced by 16.4 times and 4.2 times, respectively, compared to the non-flow-through counterpart with its freeway space volume six times the volume of graphene foam anode. The graphene foam enabled microfluidic flow-through approach will allow efficient microbial conversion of carbon-containing bioconvertible substrates to electricity with smaller space, less medium consumption, and shorter start-up time. PMID:28120875

  16. Flow cytometry and cell sorting of heterogeneous microbial populations: the importance of single-cell analyses.

    PubMed Central

    Davey, H M; Kell, D B

    1996-01-01

    The most fundamental questions such as whether a cell is alive, in the sense of being able to divide or to form a colony, may sometimes be very hard to answer, since even axenic microbial cultures are extremely heterogeneous. Analyses that seek to correlate such things as viability, which is a property of an individual cell, with macroscopic measurements of culture variables such as ATP content, respiratory activity, and so on, must inevitably fail. It is therefore necessary to make physiological measurements on individual cells. Flow cytometry is such a technique, which allows one to analyze cells rapidly and individually and permits the quantitative analysis of microbial heterogeneity. It therefore offers many advantages over conventional measurements for both routine and more exploratory analyses of microbial properties. While the technique has been widely applied to the study of mammalian cells, is use in microbiology has until recently been much more limited, largely because of the smaller size of microbes and the consequently smaller optical signals obtainable from them. Since these technical barriers no longer hold, flow cytometry with appropriate stains has been used for the rapid discrimination and identification of microbial cells, for the rapid assessment of viability and of the heterogeneous distributions of a wealth of other more detailed physiological properties, for the analysis of antimicrobial drug-cell interactions, and for the isolation of high-yielding strains of biotechnological interest. Flow cytometric analyses provide an abundance of multivariate data, and special methods have been devised to exploit these. Ongoing advances mean that modern flow cytometers may now be used by nonspecialists to effect a renaissance in our understanding of microbial heterogeneity. PMID:8987359

  17. DNA Damage Response Checkpoint Activation Drives KP1019 Dependent Pre-Anaphase Cell Cycle Delay in S. cerevisiae

    PubMed Central

    Bierle, Lindsey A.; Reich, Kira L.; Taylor, Braden E.; Blatt, Eliot B.; Middleton, Sydney M.; Burke, Shawnecca D.; Stultz, Laura K.; Hanson, Pamela K.; Partridge, Janet F.; Miller, Mary E.

    2015-01-01

    Careful regulation of the cell cycle is required for proper replication, cell division, and DNA repair. DNA damage–including that induced by many anticancer drugs–results in cell cycle delay or arrest, which can allow time for repair of DNA lesions. Although its molecular mechanism of action remains a matter of debate, the anticancer ruthenium complex KP1019 has been shown to bind DNA in biophysical assays and to damage DNA of colorectal and ovarian cancer cells in vitro. KP1019 has also been shown to induce mutations and induce cell cycle arrest in Saccharomyces cerevisiae, suggesting that budding yeast can serve as an appropriate model for characterizing the cellular response to the drug. Here we use a transcriptomic approach to verify that KP1019 induces the DNA damage response (DDR) and find that KP1019 dependent expression of HUG1 requires the Dun1 checkpoint; both consistent with KP1019 DDR in budding yeast. We observe a robust KP1019 dependent delay in cell cycle progression as measured by increase in large budded cells, 2C DNA content, and accumulation of Pds1 which functions to inhibit anaphase. Importantly, we also find that deletion of RAD9, a gene required for the DDR, blocks drug-dependent changes in cell cycle progression, thereby establishing a causal link between the DDR and phenotypes induced by KP1019. Interestingly, yeast treated with KP1019 not only delay in G2/M, but also exhibit abnormal nuclear position, wherein the nucleus spans the bud neck. This morphology correlates with short, misaligned spindles and is dependent on the dynein heavy chain gene DYN1. We find that KP1019 creates an environment where cells respond to DNA damage through nuclear (transcriptional changes) and cytoplasmic (motor protein activity) events. PMID:26375390

  18. DNA Damage Response Checkpoint Activation Drives KP1019 Dependent Pre-Anaphase Cell Cycle Delay in S. cerevisiae.

    PubMed

    Bierle, Lindsey A; Reich, Kira L; Taylor, Braden E; Blatt, Eliot B; Middleton, Sydney M; Burke, Shawnecca D; Stultz, Laura K; Hanson, Pamela K; Partridge, Janet F; Miller, Mary E

    2015-01-01

    Careful regulation of the cell cycle is required for proper replication, cell division, and DNA repair. DNA damage--including that induced by many anticancer drugs--results in cell cycle delay or arrest, which can allow time for repair of DNA lesions. Although its molecular mechanism of action remains a matter of debate, the anticancer ruthenium complex KP1019 has been shown to bind DNA in biophysical assays and to damage DNA of colorectal and ovarian cancer cells in vitro. KP1019 has also been shown to induce mutations and induce cell cycle arrest in Saccharomyces cerevisiae, suggesting that budding yeast can serve as an appropriate model for characterizing the cellular response to the drug. Here we use a transcriptomic approach to verify that KP1019 induces the DNA damage response (DDR) and find that KP1019 dependent expression of HUG1 requires the Dun1 checkpoint; both consistent with KP1019 DDR in budding yeast. We observe a robust KP1019 dependent delay in cell cycle progression as measured by increase in large budded cells, 2C DNA content, and accumulation of Pds1 which functions to inhibit anaphase. Importantly, we also find that deletion of RAD9, a gene required for the DDR, blocks drug-dependent changes in cell cycle progression, thereby establishing a causal link between the DDR and phenotypes induced by KP1019. Interestingly, yeast treated with KP1019 not only delay in G2/M, but also exhibit abnormal nuclear position, wherein the nucleus spans the bud neck. This morphology correlates with short, misaligned spindles and is dependent on the dynein heavy chain gene DYN1. We find that KP1019 creates an environment where cells respond to DNA damage through nuclear (transcriptional changes) and cytoplasmic (motor protein activity) events.

  19. A comparative evaluation of different types of microbial electrolysis desalination cells for malic acid production.

    PubMed

    Liu, Guangli; Zhou, Ying; Luo, Haiping; Cheng, Xing; Zhang, Renduo; Teng, Wenkai

    2015-12-01

    The aim of this study was to investigate different microbial electrolysis desalination cells for malic acid production. The systems included microbial electrolysis desalination and chemical-production cell (MEDCC), microbial electrolysis desalination cell (MEDC) with bipolar membrane and anion exchange membrane (BP-A MEDC), MEDC with bipolar membrane and cation exchange membrane (BP-C MEDC), and modified microbial desalination cell (M-MDC). The microbial electrolysis desalination cells performed differently in terms of malic acid production and energy consumption. The MEDCC performed best with the highest malic acid production rate (18.4 ± 0.6 mmol/Lh) and the lowest energy consumption (0.35 ± 0.14 kWh/kg). The best performance of MEDCC was attributable to the neutral pH condition in the anode chamber, the lowest internal resistance, and the highest Geobacter percentage of the anode biofilm population among all the reactors.

  20. Optimization of ethanol production from carob pod extract using immobilized Saccharomyces cerevisiae cells in a stirred tank bioreactor.

    PubMed

    Ercan, Yatmaz; Irfan, Turhan; Mustafa, Karhan

    2013-05-01

    In this study, optimization of ethanol production from carob pod extract was carried out by immobilized Saccharomyces cerevisiae. Results showed that Ca-alginate concentration and the amount of immobilized cells had significant effects on yield. Optimum conditions for ethanol fermentation were determined to be 2% Ca-alginate concentration, 150 rpm agitation rate, 5% yeast cells entrapped in beads and pH 5.5. After validation experiments; ethanol concentration, yield, production rate and sugar utilization rate were respectively 40.10 g/L, 46.32%, 3.19 g/L/h and 90.66%; and the fermentation time was decreased to 24 h. In addition, the immobilized cells were shown to be reusable for five cycles, though a decrease in yield was observed. Finally, carob pod extract was used for ethanol fermentation by controlled and uncontrolled pH without any enrichment, and the results suggest that carob extract can be utilized effectively by immobilized-cell fermentation without the use of enrichments to facilitate yeast growth.

  1. Superoxide Triggers an Acid Burst in Saccharomyces cerevisiae to Condition the Environment of Glucose-starved Cells*

    PubMed Central

    Baron, J. Allen; Laws, Kaitlin M.; Chen, Janice S.; Culotta, Valeria C.

    2013-01-01

    Although yeast cells grown in abundant glucose tend to acidify their extracellular environment, they raise the pH of the environment when starved for glucose or when grown strictly with non-fermentable carbon sources. Following prolonged periods in this alkaline phase, Saccharomyces cerevisiae cells will switch to producing acid. The mechanisms and rationale for this “acid burst” were unknown. Herein we provide strong evidence for the role of mitochondrial superoxide in initiating the acid burst. Yeast mutants lacking the mitochondrial matrix superoxide dismutase (SOD2) enzyme, but not the cytosolic Cu,Zn-SOD1 enzyme, exhibited marked acceleration in production of acid on non-fermentable carbon sources. Acid production is also dramatically enhanced by the superoxide-producing agent, paraquat. Conversely, the acid burst is eliminated by boosting cellular levels of Mn-antioxidant mimics of SOD. We demonstrate that the acid burst is dependent on the mitochondrial aldehyde dehydrogenase Ald4p. Our data are consistent with a model in which mitochondrial superoxide damage to Fe-S enzymes in the tricarboxylic acid (TCA) cycle leads to acetate buildup by Ald4p. The resultant expulsion of acetate into the extracellular environment can provide a new carbon source to glucose-starved cells and enhance growth of yeast. By triggering production of organic acids, mitochondrial superoxide has the potential to promote cell population growth under nutrient depravation stress. PMID:23281478

  2. Compromised cellular responses to DNA damage accelerate chronological aging by incurring cell wall fragility in Saccharomyces cerevisiae.

    PubMed

    Yu, Shanshan; Zhang, Xian-En; Chen, Guanjun; Liu, Weifeng

    2012-04-01

    Elevated levels of reactive oxygen species (ROS) can attack almost all cell components including genomic DNA to induce many types of DNA damage. In this study, we used Saccharomyces cerevisiae with various mutations in a biological network supposed to prevent deleterious effects of endogenous ROS to test the effect of such a network on yeast chronological aging. Our results showed that cells with defects in cellular antioxidation, DNA repair and DNA damage checkpoints displayed a mutation rate higher than that of wild-type strain. Moreover, the chronological life span of most mutants as determined by colony formation was found to be shorter than that of wild-type cells, especially for the mutants defective in DNA replication and DNA damage checkpoints, although the observed cell number was almost the same for wild-type and mutant strains. The mutants were finally found to be more sensitive to SDS and lysing enzyme treatment, and that the degree of sensitivity was correlated with their chronological life span.

  3. Scaling up microbial fuel cells and other bioelectrochemical systems.

    PubMed

    Logan, Bruce E

    2010-02-01

    Scientific research has advanced on different microbial fuel cell (MFC) technologies in the laboratory at an amazing pace, with power densities having reached over 1 kW/m(3) (reactor volume) and to 6.9 W/m(2) (anode area) under optimal conditions. The main challenge is to bring these technologies out of the laboratory and engineer practical systems for bioenergy production at larger scales. Recent advances in new types of electrodes, a better understanding of the impact of membranes and separators on performance of these systems, and results from several new pilot-scale tests are all good indicators that commercialization of the technology could be possible within a few years. Some of the newest advances and future challenges are reviewed here with respect to practical applications of these MFCs for renewable energy production and other applications.

  4. Microbial Fuel Cell Possibilities on American Indian Tribal Lands

    SciTech Connect

    Cameron, Kimberlynn

    2016-10-01

    The purpose of this paper is to present a brief background of tribal reservations, the process of how Microbial Fuel Cells (MFCs) work, and the potential benefits of using MFCs on tribal reservations to convert waste water to energy as a means to sustainably generate electricity. There have been no known studies conducted on tribal lands that would be able to add to the estimated percentage of all renewable energy resources identified. Not only does MFC technology provide a compelling, innovative solution, it could also address better management of wastewater, using it as a form of energy generation. Using wastewater for clean energy generation could provide a viable addition to community infrastructure systems improvements.

  5. Carbon nanotube modification of microbial fuel cell electrodes.

    PubMed

    Yazdi, Alireza Ahmadian; D'Angelo, Lorenzo; Omer, Nada; Windiasti, Gracia; Lu, Xiaonan; Xu, Jie

    2016-11-15

    The use of carbon nanotubes (CNTs) for energy harvesting devices is preferable due to their unique mechanical, thermal, and electrical properties. On the other hand, microbial fuel cells (MFCs) are promising devices to recover carbon-neutral energy from the organic matters, and have been hindered with major setbacks towards commercialization. Nanoengineered CNT-based materials show remarkable electrochemical properties, and therefore have provided routes towards highly effective modification of MFC compartments to ultimately reach the theoretical limits of biomass energy recovery, low-cost power production, and thus the commercialization of MFCs. Moreover, these CNT-based composites offer significant flexibility in the design of MFCs that enable their use for a broad spectrum of applications ranging from scaled-up power generation to medically related devices. This article reviews the recent advances in the modification of MFCs using CNTs and CNT-based composites, and the extent to which each modification route impacts MFC power and current generation.

  6. Performance of Denitrifying Microbial Fuel Cell with Biocathode over Nitrite

    PubMed Central

    Zhao, Huimin; Zhao, Jianqiang; Li, Fenghai; Li, Xiaoling

    2016-01-01

    Microbial fuel cell (MFC) with nitrite as an electron acceptor in cathode provided a new technology for nitrogen removal and electricity production simultaneously. The influences of influent nitrite concentration and external resistance on the performance of denitrifying MFC were investigated. The optimal effectiveness were obtained with the maximum total nitrogen (TN) removal rate of 54.80 ± 0.01 g m−3 d−1. It would be rather desirable for the TN removal than electricity generation at lower external resistance. Denaturing gradient gel electrophoresis suggested that Proteobacteria was the predominant phylum, accounting for 35.72%. Thiobacillus and Afipia might benefit to nitrite removal. The presence of nitrifying Devosia indicated that nitrite was oxidized to nitrate via a biochemical mechanism in the cathode. Ignavibacterium and Anaerolineaceae was found in the cathode as a heterotrophic bacterium with sodium acetate as substrate, which illustrated that sodium acetate in anode was likely permeated through proton exchange membrane to the cathode. PMID:27047462

  7. Bi-directional electrical characterisation of microbial fuel cell.

    PubMed

    Degrenne, N; Ledezma, P; Bevilacqua, P; Buret, F; Allard, B; Greenman, J; Ieropoulos, I A

    2013-01-01

    The electrical performance of microbial fuel cells in steady-state is usually investigated by standard characterisation methods that reveal many important parameters e.g. maximum power. This paper introduces a novel "bi-directional" method to study how the acquisition parameters (i.e. sweep rate and sweep regime) can influence measurements and consequently performance estimations. The investigation exhibited considerable differences (hysteresis) between the forward and backward characterisation regimes, indicating a difficulty to reach steady-state under certain conditions. Moreover, it is found that fast sweep rates (time-step of 2 min) can lead to an overestimation of the short-circuit currents, while prolonged operation with high external loads leads to maximum power overestimation and extended conditioning at high currents can result in its underestimation.

  8. Microbial fuel cells: novel biotechnology for energy generation.

    PubMed

    Rabaey, Korneel; Verstraete, Willy

    2005-06-01

    Microbial fuel cells (MFCs) provide new opportunities for the sustainable production of energy from biodegradable, reduced compounds. MFCs function on different carbohydrates but also on complex substrates present in wastewaters. As yet there is limited information available about the energy metabolism and nature of the bacteria using the anode as electron acceptor; few electron transfer mechanisms have been established unequivocally. To optimize and develop energy production by MFCs fully this knowledge is essential. Depending on the operational parameters of the MFC, different metabolic pathways are used by the bacteria. This determines the selection and performance of specific organisms. Here we discuss how bacteria use an anode as an electron acceptor and to what extent they generate electrical output. The MFC technology is evaluated relative to current alternatives for energy generation.

  9. Microbial fuel cell treatment of ethanol fermentation process water

    DOEpatents

    Borole, Abhijeet P [Knoxville, TN

    2012-06-05

    The present invention relates to a method for removing inhibitor compounds from a cellulosic biomass-to-ethanol process which includes a pretreatment step of raw cellulosic biomass material and the production of fermentation process water after production and removal of ethanol from a fermentation step, the method comprising contacting said fermentation process water with an anode of a microbial fuel cell, said anode containing microbes thereon which oxidatively degrade one or more of said inhibitor compounds while producing electrical energy or hydrogen from said oxidative degradation, and wherein said anode is in electrical communication with a cathode, and a porous material (such as a porous or cation-permeable membrane) separates said anode and cathode.

  10. Light energy to bioelectricity: photosynthetic microbial fuel cells.

    PubMed

    Rosenbaum, Miriam; He, Zhen; Angenent, Largus T

    2010-06-01

    Here, we reviewed five different approaches that integrate photosynthesis with microbial fuel cells (MFCs)-photoMFCs. Until now, no conclusive report has been published that identifies direct electron transfer (DET) between a photosynthetic biocatalyst and the anode of a MFC. Therefore, most recent research has been performed to generate sufficient electric current from sunlight with either electrocatalysts or heterotrophic bacteria on the anode to convert photosynthetic products indirectly. The most promising photoMFCs to date are electrocatalytic bioelectrochemical systems (BESs) that convert hydrogen from photosynthesis and sediment-based BESs that can convert excreted organics from cyanobacteria or plants. In addition, illumination on the cathode may provide either oxygen for an electrocatalytic reduction reaction or a promising anoxygenic biocathode.

  11. Increased power density from a spiral wound microbial fuel cell.

    PubMed

    Jia, Boyang; Hu, Dawei; Xie, Beizhen; Dong, Kun; Liu, Hong

    2013-03-15

    Using Microbial fuel cell (MFC) to convert organic and inorganic matter into electricity is of great interest for powering portable devices, which is now still limited by the output of MFC. In this study, a spiral wound MFC (SWMFC) with relatively large volume normalized surface area of separator (4.2 cm(2)/ml) was fabricated to enhance power generation. Compared with double-membrane MFC (DMMFC) and conventional double chamber MFC (DCMFC), the power density of SWMFC increased by 42% and 99% resulted from its lower internal resistance. Besides larger separator area, the better performance of SWMFC benefited from its structure sandwiching the cathodes between two separators. This point was proved again by a comparison of another DCMFC and a triple chamber MFC (TCMFC) as well as a simulation using finite element method. Moreover, the feature of SWMFC was more convenient and compact to scale up. Therefore, SWMFC provides a promising configuration for high power output as a portable power source.

  12. Microfluidic microbial fuel cells: from membrane to membrane free

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Ye, Dingding; Li, Jun; Zhu, Xun; Liao, Qiang; Zhang, Biao

    2016-08-01

    Microfluidic microbial fuel cells (MMFCs) are small carbon-neutral devices that use self-organized bacteria to degrade organic substrates and harness energy from the waste water. Conventional MMFCs have made great strides in the past decade and have overcome some limitations, such as high capital costs and low energy output. A co-laminar flow MFC has been first proposed in 2011 with the potential to be an attractively power source to niche applications. Co-laminar MFCs typically operate without any physical membranes separating the reactants, and bacterial ecosystems can be easily manipulated by regulating the inlet conditions. This paper highlights recent accomplishments in the development of co-laminar MFCs, emphasizing basic principles, mass transport and fluid dynamics including boundary layer theory, entrance conditions and mixing zone issues. Furthermore, the development of current techniques, major challenges and the potential research directions are discussed.

  13. Fade to Green: A Biodegradable Stack of Microbial Fuel Cells.

    PubMed

    Winfield, Jonathan; Chambers, Lily D; Rossiter, Jonathan; Stinchcombe, Andrew; Walter, X Alexis; Greenman, John; Ieropoulos, Ioannis

    2015-08-24

    The focus of this study is the development of biodegradable microbial fuel cells (MFCs) able to produce useful power. Reactors with an 8 mL chamber volume were designed using all biodegradable products: polylactic acid for the frames, natural rubber as the cation-exchange membrane and egg-based, open-to-air cathodes coated with a lanolin gas diffusion layer. Forty MFCs were operated in various configurations. When fed with urine, the biodegradable stack was able to power appliances and was still operational after six months. One useful application for this truly sustainable MFC technology includes onboard power supplies for biodegradable robotic systems. After operation in remote ecological locations, these could degrade harmlessly into the surroundings to leave no trace when the mission is complete.

  14. Experimenting with microbial fuel cells for powering implanted biomedical devices.

    PubMed

    Roxby, Daniel N; Nham Tran; Pak-Lam Yu; Nguyen, Hung T

    2015-08-01

    Microbial Fuel Cell (MFC) technology has the ability to directly convert sugar into electricity by using bacteria. Such a technology could be useful for powering implanted biomedical devices that require a surgery to replace their batteries every couple of years. In steps towards this, parameters such as electrode configuration, inoculation size, stirring of the MFC and single versus dual chamber reactor configuration were tested for their effect on MFC power output. Results indicate that a Top-Bottom electrode configuration, stirring and larger amounts of bacteria in single chamber MFCs, and smaller amounts of bacteria in dual chamber MFCs give increased power outputs. Finally, overall dual chamber MFCs give several fold larger MFC power outputs.

  15. An insight into cathode options for microbial fuel cells.

    PubMed

    Lefebvre, O; Al-Mamun, A; Ooi, W K; Tang, Z; Chua, D H C; Ng, H Y

    2008-01-01

    Microbial fuel cell (MFC) is an emerging and promising technology, particularly in the field of wastewater treatment. The MFC capability of achieving organic removal and generating in situ electricity could make it an attractive alternative wastewater treatment technology over conventional treatment technologies. However, MFC is still far from being economically viable, especially because of the cost of the platinum (Pt) catalyst that makes possible the reaction at the cathode. In this study, we tested alternative cathode catalysts, namely sputter-deposited Cobalt (Co) and denitrifying bacteria (biocathode). The performance of these innovative cathodes was compared with that of classic Pt-cathodes. Co competed well with Pt, but further research is still required for biocathodes. However, biocathodes MFC have showed promise.

  16. Application of conductive polymers in biocathode of microbial fuel cells and microbial community.

    PubMed

    Li, Chao; Ding, Lili; Cui, Hao; Zhang, Libin; Xu, Ke; Ren, Hongqiang

    2012-07-01

    Four kinds of conductive polymers, polyaniline (PANI) and its co-polymers poly (aniline-co-o-aminophenol) (PANOA), poly (aniline-co-2, 4-diaminophenol) (PANDAP) and poly (aniline-1, 8-diaminonaphthalene) (PANDAN) were applied to modify carbon felts as the aerobic abiotic cathodes and biocathodes in microbial fuel cells (MFC). Compare to unmodified, all the four polymers can significantly improve the power densities for both abiotic cathodes (increased by 300%) and biocathodes (increased by 180%). The co-polymers with different functional groups introduction had further special advantages in MFC performance: PANOA and PANDAP with -OH showed less sensitivity to DO and pH change in cathode; PANDAP and PANDAN with -NH(3) provided better attachment condition for biofilm which endowed them higher power output. With the help of conductive polymer coats, the cathode biofilm became thicker, and according to biodiversity analysis, the predominated phyla changed from β-Proteobacteria (unmodified) to α, γ-Proteobacteria (modified), which may be responsible for the superiority of the modified MFCs.

  17. Enrichment, performance, and microbial diversity of a thermophilic mediatorless microbial fuel cell.

    PubMed

    Jong, Bor Chyan; Kim, Byung Hong; Chang, In Seop; Liew, Pauline Woan Ying; Choo, Yeng Fung; Kang, Gi Su

    2006-10-15

    A thermophilic mediatorless microbial fuel cell (ML-MFC) was developed for continuous electricity production while treating artificial wastewater concurrently. A maximum power density of 1030 +/- 340 mW/m2 was generated continuously at 55 degrees C with an anode retention time of 27 min (11 mL h(-1)) and continuous pumping of air-saturated phosphate buffer into the cathode compartment at the retention time of 0.7 min (450 mL h(-1)). Meanwhile, about 80% of the electrons available from acetate oxidation were recovered as current. Denaturing gradient gel electrophoresis (DGGE) and direct 16S-rRNA gene analysis revealed that the bacterial diversity in this ML-MFC system was lower than the inoculum. Direct 16S rDNA analysis showed that the dominant bacteria representing 57.8% of total population in anode compartment was phylogenetically very closely related to an uncultured clone, clone E4. Two sheets of graphite used as the anode showed different dominant bacterial population. For the first time, it is shown that thermophilic electrochemically active bacteria can be enriched to concurrently generate electricity and treat artificial wastewater in a thermophilic ML-MFC.

  18. Electricity generation and microbial community analysis of alcohol powered microbial fuel cells.

    PubMed

    Kim, Jung Rae; Jung, Sok Hee; Regan, John M; Logan, Bruce E

    2007-09-01

    Two different microbial fuel cell (MFC) configurations were investigated for electricity production from ethanol and methanol: a two-chambered, aqueous-cathode MFC; and a single-chamber direct-air cathode MFC. Electricity was generated in the two-chamber system at a maximum power density typical of this system (40+/-2 mW/m2) and a Coulombic efficiency (CE) ranging from 42% to 61% using ethanol. When bacteria were transferred into a single-chamber MFC known to produce higher power densities with different substrates, the maximum power density increased to 488+/-12 mW/m2 (CE = 10%) with ethanol. The voltage generated exhibited saturation kinetics as a function of ethanol concentration in the two-chambered MFC, with a half-saturation constant (Ks) of 4.86 mM. Methanol was also examined as a possible substrate, but it did not result in appreciable electricity generation. Analysis of the anode biofilm and suspension from a two-chamber MFC with ethanol using 16S rDNA-based techniques indicated that bacteria with sequences similar to Proteobacterium Core-1 (33.3% of clone library sequences), Azoarcus sp. (17.4%), and Desulfuromonas sp. M76 (15.9%) were significant members of the anode chamber community. These results indicate that ethanol can be used for sustained electricity generation at room temperature using bacteria on the anode in a MFC.

  19. Microbial fuel cells for clogging assessment in constructed wetlands.

    PubMed

    Corbella, Clara; García, Joan; Puigagut, Jaume

    2016-11-01

    Clogging in HSSF CW may result in a reduction of system's life-span or treatment efficiency. Current available techniques to assess the degree of clogging in HSSF CW are time consuming and cannot be applied on a continuous basis. Main objective of this work was to assess the potential applicability of microbial fuel cells for continuous clogging assessment in HSSF CW. To this aim, two replicates of a membrane-less microbial fuel cell (MFC) were built up and operated under laboratory conditions for five weeks. The MFC anode was gravel-based to simulate the filter media of HSSF CW. MFC were weekly loaded with sludge that had been accumulating for several years in a pilot HSSF CW treating domestic wastewater. Sludge loading ranged from ca. 20kgTS·m(-3)CW·year(-1) at the beginning of the study period up to ca. 250kgTS·m(-3)CW·year(-1) at the end of the study period. Sludge loading applied resulted in sludge accumulated within the MFC equivalent to a clogging degree ranging from 0.2years (ca. 0.5kgTS·m(-3)CW) to ca. 5years (ca. 10kgTS·m(-3)CW). Results showed that the electric charge was negatively correlated to the amount of sludge accumulated (degree of clogging). Electron transference (expressed as electric charge) almost ceased when accumulated sludge within the MFC was equivalent to ca. 5years of clogging (ca. 10kgTS·m(-3)CW). This result suggests that, although longer study periods under more realistic conditions shall be further performed, HSSF CW operated as a MFC has great potential for clogging assessment.

  20. A new method for water desalination using microbial desalination cells.

    PubMed

    Cao, Xiaoxin; Huang, Xia; Liang, Peng; Xiao, Kang; Zhou, Yingjun; Zhang, Xiaoyuan; Logan, Bruce E

    2009-09-15

    Current water desalination techniques are energy intensive and some use membranes operated at high pressures. It is shown here that water desalination can be accomplished without electrical energy input or high water pressure by using a source of organic matter as the fuel to desalinate water. A microbial fuel cell was modified by placing two membranes between the anode and cathode, creating a middle chamber for water desalination between the membranes. An anion exchange membrane was placed adjacent to the anode, and a cation exchange membrane was positioned next to the cathode. When current was produced by bacteria on the anode, ionic species in the middle chamber were transferred into the two electrode chambers, desalinating the water in the middle chamber. Proof-of-concept experiments for this approach, using what we call a microbial desalination cell (MDC), was demonstrated using water at different initial salt concentrations (5, 20, and 35 g/L) with acetate used as the substrate for the bacteria. The MDC produced a maximum of 2 W/m2 (31 W/m3) while at the same time removing about 90% of the salt in a single desalination cycle. As the salt was removed from the middle chamber the ohmic resistance of the MDC (measured using electrochemical impedance spectroscopy) increased from 25 Omega to 970 Omega at the end of the cycle. This increased resistance was reflected by a continuous decrease in the voltage produced over the cycle. These results demonstrate for the first time the possibility for a new method for water desalination and power production that uses only a source of biodegradable organic matter and bacteria.

  1. Molecular Basis for Strain Variation in the Saccharomyces cerevisiae Adhesin Flo11p

    PubMed Central

    Li, Li; Lipke, Peter N.; Dranginis, Anne M.

    2016-01-01

    ABSTRACT FLO11 encodes a yeast cell wall flocculin that mediates a variety of adhesive phenotypes in Saccharomyces cerevisiae. Flo11p is implicated in many developmental processes, including flocculation, formation of pseudohyphae, agar invasion, and formation of microbial mats and biofilms. However, Flo11p mediates different processes in different yeast strains. To investigate the mechanisms by which FLO11 determines these differences in colony morphology, flocculation, and invasion, we studied gene structure, function, and expression levels. Nonflocculent Saccharomyces cerevisiae Σ1278b cells exhibited significantly higher FLO11 mRNA expression, especially in the stationary phase, than highly flocculent S. cerevisiae var. diastaticus. The two strains varied in cell surface hydrophobicity, and Flo11p contributed significantly to surface hydrophobicity in S. cerevisiae var. diastaticus but not in strain Σ1278b. Sequencing of the FLO11 gene in S. cerevisiae var. diastaticus revealed strain-specific differences, including a 15-amino-acid insertion in the adhesion domain. Flo11p adhesion domains from strain Σ1278b and S. cerevisiae var. diastaticus were expressed and used to coat magnetic beads. The adhesion domain from each strain bound preferentially to homologous cells, and the preferences were independent of the cells in which the adhesion domains were produced. These results are consistent with the idea that strain-specific variations in the amino acid sequences in the adhesion domains cause different Flo11p flocculation activities. The results also imply that strain-specific differences in expression levels, posttranslational modifications, and allelic differences outside the adhesion domains have little effect on flocculation. IMPORTANCE As a nonmotile organism, Saccharomyces cerevisiae employs the cell surface flocculin Flo11/Muc1 as an important means of adapting to environmental change. However, there is a great deal of strain variation in the

  2. Regulation of Cdc28 Cyclin-Dependent Protein Kinase Activity during the Cell Cycle of the Yeast Saccharomyces cerevisiae

    PubMed Central

    Mendenhall, Michael D.; Hodge, Amy E.

    1998-01-01

    The cyclin-dependent protein kinase (CDK) encoded by CDC28 is the master regulator of cell division in the budding yeast Saccharomyces cerevisiae. By mechanisms that, for the most part, remain to be delineated, Cdc28 activity controls the timing of mitotic commitment, bud initiation, DNA replication, spindle formation, and chromosome separation. Environmental stimuli and progress through the cell cycle are monitored through checkpoint mechanisms that influence Cdc28 activity at key cell cycle stages. A vast body of information concerning how Cdc28 activity is timed and coordinated with various mitotic events has accrued. This article reviews that literature. Following an introduction to the properties of CDKs common to many eukaryotic species, the key influences on Cdc28 activity—cyclin-CKI binding and phosphorylation-dephosphorylation events—are examined. The processes controlling the abundance and activity of key Cdc28 regulators, especially transcriptional and proteolytic mechanisms, are then discussed in detail. Finally, the mechanisms by which environmental stimuli influence Cdc28 activity are summarized. PMID:9841670

  3. Methanol extracts from the resurrection plant Haberlea rhodopensis ameliorate cellular vitality in chronologically ageing Saccharomyces cerevisiae cells.

    PubMed

    Georgieva, Milena; Moyankova, Daniela; Djilianov, Dimitar; Uzunova, Katya; Miloshev, George

    2015-08-01

    Bioactive substances that are found in many natural plant extracts are very important for the cosmetics, pharmaceutical industry and biotechnology. Especially interesting for these industries are the substances that possess cell revitalizing and anti-ageing properties. The endemic plant Haberlea rhodopensis is known for its ability to withstand drought and to revitalize when returned to optimal conditions after a long time in desiccation. It is a mere fact that this plant not only can completely resurrect from a dried state but is also able to bring back the natural biochemical compositions of its cells. As a result H. rhodopensis offers a wide field for investigation of the exact mechanisms of the revitalization process as well as broadens the search for unique bioactive chemical substances in its cells. Here, by using the yeast Saccharomyces cerevisiae as a model we have demonstrated that methanol extracts from the plant H. rhodopensis hold specific properties to revitalize and ameliorate cellular growth as well as to balance intracellular metabolic states. Our results add valuable knowledge on the effects of natural compounds on ageing and reinforce the idea of using yeast as a model organism in the development of rapid tests for studying the efficacy of different bioactive substances.

  4. Saccharomyces cerevisiae cells execute a default pathway to select a mate in the absence of pheromone gradients

    PubMed Central

    1995-01-01

    During conjugation, haploid S. cerevisiae cells find one another by polarizing their growth toward each other along gradients of pheromone (chemotropism). We demonstrate that yeast cells exhibit a second mating behavior: when their receptors are saturated with pheromone, wild-type a cells execute a default pathway and select a mate at random. These matings are less efficient than chemotropic matings, are induced by the same dose of pheromone that induces shmoo formation, and appear to use a site near the incipient bud site for polarization. We show that the SPA2 gene is specifically required for the default pathway: spa2 delta mutants cannot mate if pheromone concentrations are high and gradients are absent, but can mate if gradients are present. ste2 delta, sst2 delta, and far1 delta mutants are chemotropism-defective and therefore must choose a mate by using a default pathway; consistent with this deduction, these strains require SPA2 to mate. In addition, our results suggest that far1 mutants are chemotropism-defective because their mating polarity is fixed at the incipient bud site, suggesting that the FAR1 gene is required for inhibiting the use of the incipient bud site during chemotropic mating. These observations reveal a molecular relationship between the mating and budding polarity pathways. PMID:7490289

  5. Effect of dissolved oxygen, temperature, initial cell count, and sugar concentration on the viability of Saccharomyces cerevisiae in rapid fermentations.

    PubMed

    Nagodawithana, T W; Castellano, C; Steinkraus, K H

    1974-09-01

    By using 7 x 10(8) cells of Saccharomyces cerevisiae per ml with which 25 degrees Brix honey solutions were fermented to 9.5% (wt/vol; 12% vol/vol) ethanol in 2.5 to 3 h at 30 C, i.e., rapid fermentation, the death rate was found to be high, with only 2.1% of the yeast cells surviving at the end of 3 h under anaerobic conditions. As the dissolved oxygen in the medium was increased from 0 to 13 to 20 to 100% in rapid fermentations at 30 C, there was a progressive increase in the percentage of cells surviving. The ethanol production rate and total were not seriously affected by a dissolved oxygen concentration of 13%, but fermentation was retarded by 20% dissolved oxygen and still further decreased as the dissolved oxygen content reached 100%. When the fermentation temperature was decreased to 15 C (at 13% dissolved oxygen), the rate of fermentation decreased, and the fermentation time to 9.5% ethanol (wt/vol) increased to 6 h. It was found that the higher the temperature between 15 and 30 C, the greater the rate of death as initial cell counts were increased from 1.1 x 10(7) to 7.8 x 10(8) cells per ml. At the lowest level of inoculum, 1.1 x 10(7) cells per ml, there was actual multiplication, even at 30 C; however, the fermentation was no longer rapid. The addition of 15% sugar, initially followed after an hour by the remaining 10%, or addition of the sugar in increments of 2.5 or 5% yielded a better survival rate of yeast cells than when the fermentation was initiated with 25% sugar.

  6. Enhancement of gene targeting in human cells by intranuclear permeation of the Saccharomyces cerevisiae Rad52 protein

    PubMed Central

    Kalvala, Arjun; Rainaldi, Giuseppe; Di Primio, Cristina; Liverani, Vania; Falaschi, Arturo; Galli, Alvaro

    2010-01-01

    The introduction of exogenous DNA in human somatic cells results in a frequency of random integration at least 100-fold higher than gene targeting (GT), posing a seemingly insurmountable limitation for gene therapy applications. We previously reported that, in human cells, the stable over-expression of the Saccharomyces cerevisiae Rad52 gene (yRAD52), which plays the major role in yeast homologous recombination (HR), caused an up to 37-fold increase in the frequency of GT, indicating that yRAD52 interacts with the double-strand break repair pathway(s) of human cells favoring homologous integration. In the present study, we tested the effect of the yRad52 protein by delivering it directly to the human cells. To this purpose, we fused the yRAD52 cDNA to the arginine-rich domain of the TAT protein of HIV (tat11) that is known to permeate the cell membranes. We observed that a recombinant yRad52tat11 fusion protein produced in Escherichia coli, which maintains its ability to bind single-stranded DNA (ssDNA), enters the cells and the nuclei, where it is able to increase both intrachromosomal recombination and GT up to 63- and 50-fold, respectively. Moreover, the non-homologous plasmid DNA integration decreased by 4-fold. yRAD52tat11 proteins carrying point mutations in the ssDNA binding domain caused a lower or nil increase in recombination proficiency. Thus, the yRad52tat11 could be instrumental to increase GT in human cells and a ‘protein delivery approach’ offers a new tool for developing novel strategies for genome modification and gene therapy applications. PMID:20519199

  7. From microbial fuel cell (MFC) to microbial electrochemical snorkel (MES): maximizing chemical oxygen demand (COD) removal from wastewater.

    PubMed

    Erable, Benjamin; Etcheverry, Luc; Bergel, Alain

    2011-03-01

    The paper introduces the concept of the microbial electrochemical snorkel (MES), a simplified design of a "short-circuited" microbial fuel cell (MFC). The MES cannot provide current but it is optimized for wastewater treatment. An electrochemically active biofilm (EAB) was grown on graphite felt under constant polarization in an urban wastewater. Controlling the electrode potential and inoculating the bioreactor with a suspension of an established EAB improved the performance and the reproducibility of the anodes. Anodes, colonized by an EAB were tested for the chemical oxygen demand (COD) removal from urban wastewater using a variety of bio-electrochemical processes (microbial electrolysis, MFC, MES). The MES technology, as well as a short-circuited MFC, led to a COD removal 57% higher than a 1000 Ω-connected MFC, confirming the potential for wastewater treatment.

  8. Unravelling the active microbial community in a thermophilic anaerobic digester-microbial electrolysis cell coupled system under different conditions.

    PubMed

    Cerrillo, Míriam; Viñas, Marc; Bonmatí, August

    2017-03-01

    Thermophilic anaerobic digestion (AD) of pig slurry coupled to a microbial electrolysis cell (MEC) with a recirculation loop was studied at lab-scale as a strategy to increase AD stability when submitted to organic and nitrogen overloads. The system performance was studied, with the recirculation loop both connected and disconnected, in terms of AD methane production, chemical oxygen demand removal (COD) and volatile fatty acid (VFA) concentrations. Furthermore, the microbial population was quantitatively and qualitatively assessed through DNA and RNA-based qPCR and high throughput sequencing (MiSeq), respectively to identify the RNA-based active microbial populations from the total DNA-based microbial community composition both in the AD and MEC reactors under different operational conditions. Suppression of the recirculation loop reduced the AD COD removal efficiency (from 40% to 22%) and the methane production (from 0.32 to 0.03 m(3) m(-3) d(-1)). Restoring the recirculation loop led to a methane production of 0.55 m(3) m(-3) d(-1) concomitant with maximum MEC COD and ammonium removal efficiencies of 29% and 34%, respectively. Regarding microbial analysis, the composition of the AD and MEC anode populations differed from really active microorganisms. Desulfuromonadaceae was revealed as the most active family in the MEC (18%-19% of the RNA relative abundance), while hydrogenotrophic methanogens (Methanobacteriaceae) dominated the AD biomass.

  9. Inhibition of microbial growth on air cathodes of single chamber microbial fuel cells by incorporating enrofloxacin into the catalyst layer.

    PubMed

    Liu, Weifeng; Cheng, Shaoan; Sun, Dan; Huang, Haobin; Chen, Jie; Cen, Kefa

    2015-10-15

    The inevitable growth of aerobic bacteria on the surface of air cathodes is an important factor reducing the performance stability of air cathode single-chamber membrane-free microbial fuel cells (MFCs). Thus searching for effective methods to inhibit the cathodic microbial growth is critical for the practical application of MFCs. In this study, enrofloxacin (ENR), a broad spectrum fluoroquinolone antibiotic, was incorporated into the catalyst layer of activated carbon air cathodes (ACACs) to inhibit the cathodic microbial growth. The biomass content on ACACs was substantially reduced by 60.2% with ENR treatment after 91 days of MFCs operation. As a result of the inhibited microbial growth, the oxygen reduction catalytic performance of the ENR treated ACACs was much stable compared to the fast performance decline of the untreated control. Consequently, a quite stable electricity production was obtained for the MFCs with the ENR treated ACACs, in contrast with a 22.5% decrease in maximum power density of the MFCs with the untreated cathode. ENR treatment of ACACs showed minimal effects on the anode performance. These results indicate that incorporating antibiotics into ACACs should be a simple and effective strategy to inhibit the microbial growth and improve the long-term stability of the performance of air cathode and the electricity production of MFCs.

  10. The Wsc1p Cell Wall Signaling Protein Controls Biofilm (Mat) Formation Independently of Flo11p in Saccharomyces cerevisiae

    PubMed Central

    Sarode, Neha; Davis, Sarah E.; Tams, Robert N.; Reynolds, Todd B.

    2013-01-01

    Saccharomyces cerevisiae strains of the ∑1278b background generate biofilms, referred to as mats, on low-density agar (0.3%) plates made with rich media (YPD). Mat formation involves adhesion of yeast cells to the surface of the agar substrate and each other as the biofilm matures, resulting in elaborate water channels that create filigreed patterns of cells. The cell wall adhesion protein Flo11p is required for mat formation; however, genetic data indicate that other unknown effectors are also required. For example, mutations in vacuolar protein sorting genes that affect the multivesicular body pathway, such as vps27∆, cause mat formation defects independently of Flo11p, presumably by affecting an unidentified signaling pathway. A cell wall signaling protein, Wsc1p, found at the plasma membrane is affected for localization and function by vps27∆. We found that a wsc1∆ mutation disrupted mat formation in a Flo11p-independent manner. Wsc1p appears to impact mat formation through the Rom2p-Rho1p signaling module, by which Wsc1p also regulates the cell wall. The Bck1p, Mkk1/Mkk2, Mpk1p MAP kinase signaling cascade is known to regulate the cell wall downstream of Wsc1p-Rom2p-Rho1p but, surprisingly, these kinases do not affect mat formation. In contrast, Wsc1p may impact mat formation by affecting Skn7p instead. Skn7p can also receive signaling inputs from the Sln1p histidine kinase; however, mutational analysis of specific histidine kinase receiver residues in Skn7p indicate that Sln1p does not play an important role in mat formation, suggesting that Skn7p primarily acts downstream of Wsc1p to regulate mat formation. PMID:24318926

  11. Transcriptional regulation of changes in growth, cell cycle, and gene expression of Saccharomyces cerevisiae due to changes in buoyancy.

    PubMed

    Coleman, Chasity B; Allen, Patricia L; Valles, James M; Hammond, Timothy G

    2008-06-01

    To understand the cellular effects of magnetic traps requires independent analysis of the effects of magnetic field, gravity, and buoyancy. In the current study, buoyancy is manipulated by addition of Ficoll, a viscous substance that can create gradients of buoyancy without significantly affecting osmolality. Specifically, we investigated whether Ficoll induces concentration dependent changes in cell growth, cell cycle, and gene expression in Saccharomyces cerevisiae, with special attention paid to the neutrally buoyant concentration of 35% Ficoll. Cell growth and cell cycle analysis were examined in three strains: wild-type (WT) yeast and strains with deletions in transcription factors Msn4 (Msn4Delta) or Sfp1 (Sfp1Delta). Changes in growth were observed in all three strains with WT and Msn4Delta strains showing strong concentration dependence. In addition, these changes in growth were supported by changes in the cell cycle of all three strains. Gene expression changes were observed in seven GFP-reporter strains including: SSA4, YIL052C, YST2, Msn4DeltaSSA4, Sfp1DeltaSSA4, Msn4DeltaYIL052C, and Sfp1DeltaYIL052C. Buoyancy forces had selective concentration dependent effects on gene expression of SSA4 and YIL052C with transcription factor dependence on Msn4. Additionally, SSA4 expression was dependent on Sfp1. YST2 gene expression was not dependent on changes in buoyancy force. This study shows that buoyancy has selective and concentration dependent effects on growth, cell cycle and gene expression, some of which are Msn4 and Sfp1 dependent. For the first time, SSA4 gene expression is shown to be dependent on Sfp1 and YIL052C gene expression is dependent on Msn4.

  12. Chromosome or chromatin condensation leads to meiosis or apoptosis in stationary yeast (Saccharomyces cerevisiae) cells.

    PubMed

    Yang, Hui; Ren, Qun; Zhang, Zhaojie

    2006-12-01

    When starved of essential nutrients, yeast cells cease mitotic division and enter an alternative state called the 'stationary phase'. In this paper, we report that stationary cells enter two major pathways: meiosis and apoptosis. Using transmission electron microscopy, five types of cell were identified in the stationary phase: (1) cells with chromosome condensed nuclei; (2) cells with normal, homogeneously stained nuclei; (3) sporulated cells; (4) apoptotic cells, in which chromatin, but not individual chromosomes, was condensed; and (5) dead cells, in which nuclei and cytoplasm were degraded. Further evidence using live cell imaging and mutation analysis suggested that cells with condensed chromosomes underwent meiosis, whereas chromatin condensed cells underwent apoptotic cell death. Cells with homogeneous nuclei are believed to be in the true resting state and undergo cell death when starvation continues. Chromosome or chromatin condensation may serve as a hallmark of life or death for stationary cells.

  13. Transcriptome analysis of a microbial coculture in which the cell populations are separated by a membrane.

    PubMed

    Hosoda, Kazufumi; Ono, Naoaki; Suzuki, Shingo; Yomo, Tetsuya

    2014-01-01

    The microbial coculture of multiple cell populations is used to study community evolution and for bioengineering applications. The cells in coculture undergo dynamic changes because of cell-cell and cell-environment interactions. Transcriptome analysis allows us to study the molecular basis of these changes in cell physiology. For transcriptome analysis, it is essential that the cell populations in the coculture are harvested separately. Here, we describe a method for transcriptome analysis of a microbial coculture in which two different cell populations are separated by a porous membrane.

  14. The effect of trehalose on the fermentation performance of aged cells of Saccharomyces cerevisiae.

    PubMed

    Trevisol, Eduardo T V; Panek, Anita D; Mannarino, Sergio Cantu; Eleutherio, Elis C A

    2011-04-01

    The fermentation process offers a wide variety of stressors for yeast, such as temperature, aging, and ethanol. To evaluate a possible beneficial effect of trehalose on ethanol production, we used mutant strains of Saccharomyces cerevisiae possessing different deficiencies in the metabolism of this disaccharide: in synthesis, tps1; in transport, agt1; and in degradation, ath1 and nth1. According to our results, the tps1 mutant, the only strain tested unable to synthesize trehalose, showed the lowest fermentation yield, indicating that this sugar is important to improve ethanol production. At the end of the first fermentation cycle, only the strains deficient in transport and degradation maintained a significant level of the initial trehalose. The agt1, ath1, and nth1 strains showed the highest survival rates and the highest proportions of non-petites. Accumulation of petites during fermentation has been correlated to low ethanol production. When recycled back for a subsequent fermentation, those mutant strains produced the highest ethanol yields, suggesting that trehalose is required for improving fermentative capacity and longevity of yeasts, as well as their ability to withstand stressful industrial conditions. Finally, according to our results, the mechanism by which trehalose improves ethanol production seems to involve mainly protection against protein oxidation.

  15. Convergent development of anodic bacterial communities in microbial fuel cells

    PubMed Central

    Yates, Matthew D; Kiely, Patrick D; Call, Douglas F; Rismani-Yazdi, Hamid; Bibby, Kyle; Peccia, Jordan; Regan, John M; Logan, Bruce E

    2012-01-01

    Microbial fuel cells (MFCs) are often inoculated from a single wastewater source. The extent that the inoculum affects community development or power production is unknown. The stable anodic microbial communities in MFCs were examined using three inocula: a wastewater treatment plant sample known to produce consistent power densities, a second wastewater treatment plant sample, and an anaerobic bog sediment. The bog-inoculated MFCs initially produced higher power densities than the wastewater-inoculated MFCs, but after 20 cycles all MFCs on average converged to similar voltages (470±20 mV) and maximum power densities (590±170 mW m−2). The power output from replicate bog-inoculated MFCs was not significantly different, but one wastewater-inoculated MFC (UAJA3 (UAJA, University Area Joint Authority Wastewater Treatment Plant)) produced substantially less power. Denaturing gradient gel electrophoresis profiling showed a stable exoelectrogenic biofilm community in all samples after 11 cycles. After 16 cycles the predominance of Geobacter spp. in anode communities was identified using 16S rRNA gene clone libraries (58±10%), fluorescent in-situ hybridization (FISH) (63±6%) and pyrosequencing (81±4%). While the clone library analysis for the underperforming UAJA3 had a significantly lower percentage of Geobacter spp. sequences (36%), suggesting that a predominance of this microbe was needed for convergent power densities, the lower percentage of this species was not verified by FISH or pyrosequencing analyses. These results show that the predominance of Geobacter spp. in acetate-fed systems was consistent with good MFC performance and independent of the inoculum source. PMID:22572637

  16. Optical manipulation of Saccharomyces cerevisiae cells reveals that green light protection against UV irradiation is favored by low Ca2+ and requires intact UPR pathway.

    PubMed

    Farcasanu, Ileana C; Mitrica, Radu; Cristache, Ligia; Nicolau, Ioana; Ruta, Lavinia L; Paslaru, Liliana; Comorosan, Sorin

    2013-11-01

    Optical manipulation of Saccharomyces cerevisiae cells with high density green photons conferred protection against the deleterious effects of UV radiation. Combining chemical screening with UV irradiation of yeast cells, it was noted that the high density green photons relied on the presence of intact unfolded protein response (UPR) pathway to exert their protective effect and that the low Ca(2+) conditions boosted the effect. UPR chemical inducers tunicamycin, dithiotreitol and calcium chelators augmented the green light effect in a synergic action against UV-induced damage. Photo-manipulation of cells was a critical factor since the maximum protection was achieved only when cells were pre-exposed to green light.

  17. Adhesion-dependent rupturing of Saccharomyces cerevisiae on biological antimicrobial nanostructured surfaces

    PubMed Central

    Nowlin, Kyle; Boseman, Adam; Covell, Alan; LaJeunesse, Dennis

    2015-01-01

    Recent studies have shown that some nanostructured surfaces (NSS), many of which are derived from surfaces found on insect cuticles, rupture and kill adhered prokaryotic microbes. Most important, the nanoscale topography is directly responsible for this effect. Although parameters such as cell adhesion and cell wall rigidity have been suggested to play significant roles in this process, there is little experimental evidence regarding the underlying mechanisms involving NSS-induced microbial rupture. In this work, we report the NSS-induced rupturing of a eukaryotic microorganism, Saccharomyces cerevisiae. We show that the amount of NSS-induced rupture of S. cerevisiae is dependent on both the adhesive qualities of the yeast cell and the nanostructure geometry of the NSS. Thus, we are providing the first empirical evidence that these parameters play a direct role in the rupturing of microbes on NSS. Our observations of this phenomenon with S. cerevisiae, particularly the morphological changes, are strikingly similar to that reported for bacteria despite the differences in the yeast cell wall structure. Consequently, NSS provide a novel approach for the control of microbial growth and development of broad-spectrum microbicidal surfaces. PMID:25551144

  18. Predicting complex phenotype-genotype interactions to enable yeast engineering: Saccharomyces cerevisiae as a model organism and a cell factory.

    PubMed

    Dikicioglu, Duygu; Pir, Pınar; Oliver, Stephen G

    2013-09-01

    There is an increasing use of systems biology approaches in both "red" and "white" biotechnology in order to enable medical, medicinal, and industrial applications. The intricate links between genotype and phenotype may be explained through the use of the tools developed in systems biology, synthetic biology, and evolutionary engineering. Biomedical and biotechnological research are among the fields that could benefit most from the elucidation of this complex relationship. Researchers have studied fitness extensively to explain the phenotypic impacts of genetic variations. This elaborate network of dependencies and relationships so revealed are further complicated by the influence of environmental effects that present major challenges to our achieving an understanding of the cellular mechanisms leading to healthy or diseased phenotypes or optimized production yields. An improved comprehension of complex genotype-phenotype interactions and their accurate prediction should enable us to more effectively engineer yeast as a cell factory and to use it as a living model of human or pathogen cells in intelligent screens for new drugs. This review presents different methods and approaches undertaken toward improving our understanding and prediction of the growth phenotype of the yeast Saccharomyces cerevisiae as both a model and a production organism.

  19. Cell surface engineering of Saccharomyces cerevisiae combined with membrane separation technology for xylitol production from rice straw hydrolysate.

    PubMed

    Guirimand, Gregory; Sasaki, Kengo; Inokuma, Kentaro; Bamba, Takahiro; Hasunuma, Tomohisa; Kondo, Akihiko

    2016-04-01

    Xylitol, a value-added polyol deriving from D-xylose, is widely used in both the food and pharmaceutical industries. Despite extensive studies aiming to streamline the production of xylitol, the manufacturing cost of this product remains high while demand is constantly growing worldwide. Biotechnological production of xylitol from lignocellulosic waste may constitute an advantageous and sustainable option to address this issue. However, to date, there have been few reports of biomass conversion to xylitol. In the present study, xylitol was directly produced from rice straw hydrolysate using a recombinant Saccharomyces cerevisiae YPH499 strain expressing cytosolic xylose reductase (XR), along with β-glucosidase (BGL), xylosidase (XYL), and xylanase (XYN) enzymes (co-)displayed on the cell surface; xylitol production by this strain did not require addition of any commercial enzymes. All of these enzymes contributed to the consolidated bioprocessing (CBP) of the lignocellulosic hydrolysate to xylitol to produce 5.8 g/L xylitol with 79.5 % of theoretical yield from xylose contained in the biomass. Furthermore, nanofiltration of the rice straw hydrolysate provided removal of fermentation inhibitors while simultaneously increasing sugar concentrations, facilitating high concentration xylitol production (37.9 g/L) in the CBP. This study is the first report (to our knowledge) of the combination of cell surface engineering approach and membrane separation technology for xylitol production, which could be extended to further industrial applications.

  20. Proteomic Analyses Reveal that Sky1 Modulates Apoptosis and Mitophagy in Saccharomyces cerevisiae Cells Exposed to Cisplatin

    PubMed Central

    Rodríguez-Lombardero, Silvia; Rodríguez-Belmonte, M. Esther; González-Siso, M. Isabel; Vizoso-Vázquez, Ángel; Valdiglesias, Vanessa; Laffón, Blanca; Cerdán, M. Esperanza

    2014-01-01

    Sky1 is the only member of the SR (Serine–Arginine) protein kinase family in Saccharomyces cerevisiae. When yeast cells are treated with the anti-cancer drug cisplatin, Sky1 kinase activity is necessary to produce the cytotoxic effect. In this study, proteome changes in response to this drug and/or SKY1 deletion have been evaluated in order to understand the role of Sky1 in the response of yeast cells to cisplatin. Results reveal differential expression of proteins previously related to the oxidative stress response, DNA damage, apoptosis and mitophagy. With these precedents, the role of Sky1 in apoptosis, necrosis and mitophagy has been evaluated by flow-cytometry, fluorescence microscopy, biosensors and fluorescence techniques. After cisplatin treatment, an apoptotic-like process diminishes in the ∆sky1 strain in comparison to the wild-type. The treatment does not affect mitophagy in the wild-type strain, while an increase is observed in the ∆sky1 strain. The increased resistance to cisplatin observed in the ∆sky1 strain may be attributable to a decrease of apoptosis and an increase of mitophagy. PMID:25029545

  1. Whole-cell imaging of the budding yeast Saccharomyces cerevisiae by high-voltage scanning transmission electron tomography.

    PubMed

    Murata, Kazuyoshi; Esaki, Masatoshi; Ogura, Teru; Arai, Shigeo; Yamamoto, Yuta; Tanaka, Nobuo

    2014-11-01

    Electron tomography using a high-voltage electron microscope (HVEM) provides three-dimensional information about cellular components in sections thicker than 1 μm, although in bright-field mode image degradation caused by multiple inelastic scattering of transmitted electrons limit the attainable resolution. Scanning transmission electron microscopy (STEM) is believed to give enhanced contrast and resolution compared to conventional transmission electron microscopy (CTEM). Samples up to 1 μm in thickness have been analyzed with an intermediate-voltage electron microscope because inelastic scattering is not a critical limitation, and probe broadening can be minimized. Here, we employed STEM at 1 MeV high-voltage to extend the useful specimen thickness for electron tomography, which we demonstrate by a seamless tomographic reconstruction of a whole, budding Saccharomyces cerevisiae yeast cell, which is ~3 μm in thickness. High-voltage STEM tomography, especially in the bright-field mode, demonstrated sufficiently enhanced contrast and intensity, compared to CTEM tomography, to permit segmentation of major organelles in the whole cell. STEM imaging also reduced specimen shrinkage during tilt-series acquisition. The fidelity of structural preservation was limited by cytoplasmic extraction, and the spatial resolution was limited by the relatively large convergence angle of the scanning probe. However, the new technique has potential to solve longstanding problems of image blurring in biological specimens beyond 1 μm in thickness, and may facilitate new research in cellular structural biology.

  2. A cell-free system for reconstitution of transport between prevacuolar compartments and vacuoles in Saccharomyces cerevisiae.

    PubMed

    Vida, Thomas A

    2008-01-01

    Genetic approaches have revealed more than 50 genes involved in the delivery of soluble zymogens like carboxypeptidase Y (CPY) to the lysosome-like vacuole in Saccharomyces cerevisiae. At least 20 of these genes function in transport between the prevacuolar endosome-like compartment (PVC) and the vacuole. To gain biochemical access to these functions, the authors developed a cell-free assay that measures transport-coupled proteolytic maturation of soluble zymogens in vitro. A polycarbonate filter with a defined pore size is used to lyse yeast spheroplasts after pulse-chase radiolabeling. Differential centrifugation enriches for PVCs containing proCPY (p2CPY) in a 125,000 g membrane pellet and is used as donor membranes. Nonradiolabeled spheroplasts are also lysed with a polycarbonate filter but a 15,000 g membrane pellet enriched for vacuoles is collected and used as acceptor membranes. When these two crude membrane pellets are incubated together with adenosine triphosphate and cytosolic protein extracts, nearly 50% of the radiolabeled p2CPY can be processed to the mature vacuolar form, mCPY. This cell-free system allows reconstitution of intercompartmental transport coupled to the function of VPS gene products.

  3. Predicting complex phenotype–genotype interactions to enable yeast engineering: Saccharomyces cerevisiae as a model organism and a cell factory

    PubMed Central

    Dikicioglu, Duygu; Pir, Pınar; Oliver, Stephen G

    2013-01-01

    There is an increasing use of systems biology approaches in both “red” and “white” biotechnology in order to enable medical, medicinal, and industrial applications. The intricate links between genotype and phenotype may be explained through the use of the tools developed in systems biology, synthetic biology, and evolutionary engineering. Biomedical and biotechnological research are among the fields that could benefit most from the elucidation of this complex relationship. Researchers have studied fitness extensively to explain the phenotypic impacts of genetic variations. This elaborate network of dependencies and relationships so revealed are further complicated by the influence of environmental effects that present major challenges to our achieving an understanding of the cellular mechanisms leading to healthy or diseased phenotypes or optimized production yields. An improved comprehension of complex genotype–phenotype interactions and their accurate prediction should enable us to more effectively engineer yeast as a cell factory and to use it as a living model of human or pathogen cells in intelligent screens for new drugs. This review presents different methods and approaches undertaken toward improving our understanding and prediction of the growth phenotype of the yeast Saccharomyces cerevisiae as both a model and a production organism. PMID:24031036

  4. The effect of intracellular amino acids on GSH production by high-cell-density cultivation of Saccharomyces cerevisiae.

    PubMed

    Wang, Miaomiao; Sun, Jingfeng; Xue, Feiyan; Shang, Fei; Wang, Zheng; Tan, Tianwei

    2012-09-01

    The present paper studies the effects of precursor amino acids, i.e., L-glutamic acid (Glu), L-glycine (Gly), and L-cysteine (Cys), on the glutathione (GSH) production. The three amino acids were added during the fermentations. The GSH production was analyzed by gas chromatography-mass spectrometry (GC-MS). It was observed that the cell content of Cys reduced continually, Gly maintained a fairly constant concentration, while Glu remained at a high concentration compared with Cys and Gly. The synthesis of GSH was found to significantly increase after 28 h of fermentation upon addition of 6 mmol l(-1) of each of the three amino acids. Under these conditions, the GSH yields reached 2,250±50 mg l(-1) at 34 h from 1,050±50 mg l(-1) at 28 h. The GC-MS analyses on the effect caused by the addition of amino acids indicated that the addition of Glu was not necessary to improve the GSH production by high-cell-density cultivation of Saccharomyces cerevisiae. The addition of Cys or Gly individually enhances the production of GSH.

  5. Determination of Microbial Growth by Protein Assay in an Air-Cathode Single Chamber Microbial Fuel Cell.

    PubMed

    Li, Na; Kakarla, Ramesh; Moon, Jung Mi; Min, Booki

    2015-07-01

    Microbial fuel cells (MFCs) have gathered attention as a novel bioenergy technology to simultaneously treat wastewater with less sludge production than the conventional activated sludge system. In two different operations of the MFC and aerobic process, microbial growth was determined by the protein assay method and their biomass yields using real wastewater were compared. The biomass yield on the anode electrode of the MFC was 0.02 g-COD-cell/g- COD-substrate and the anolyte planktonic biomass was 0.14 g-COD-cell/g-COD-substrate. An MFC without anode electrode resulted in the biomass yield of 0.07 ± 0.03 g-COD-cell/g-COD-substrate, suggesting that oxygen diffusion from the cathode possibly supported the microbial growth. In a comparative test, the biomass yield under aerobic environment was 0.46 ± 0.07 g-COD-cell/g-COD-substrate, which was about 3 times higher than the total biomass value in the MFC operation.

  6. Critical analysis of the maximum non inhibitory concentration (MNIC) method in quantifying sub-lethal injury in Saccharomyces cerevisiae cells exposed to either thermal or pulsed electric field treatments.

    PubMed

    Kethireddy, V; Oey, I; Jowett, Tim; Bremer, P

    2016-09-16

    Sub-lethal injury within a microbial population, due to processing treatments or environmental stress, is often assessed as the difference in the number of cells recovered on non-selective media compared to numbers recovered on a "selective media" containing a predetermined maximum non-inhibitory concentration (MNIC) of a selective agent. However, as knowledge of cell metabolic response to injury, population diversity and dynamics increased, the rationale behind the conventional approach of quantifying sub-lethal injury must be scrutinized further. This study reassessed the methodology used to quantify sub-lethal injury for Saccharomyces cerevisiae cells (≈ 4.75 Log CFU/mL) exposed to either a mild thermal (45°C for 0, 10 and 20min) or a mild pulsed electric field treatment (field strengths of 8.0-9.0kV/cm and energy levels of 8, 14 and 21kJ/kg). Treated cells were plated onto either Yeast Malt agar (YM) or YM containing NaCl, as a selective agent at 5-15% in 1% increments. The impact of sub-lethal stress due to initial processing, the stress due to selective agents in the plating media, and the subsequent variation of inhibition following the treatments was assessed based on the CFU count (cell numbers). ANOVA and a generalised least squares model indicated significant effects of media, treatments, and their interaction effects (P<0.05) on cell numbers. It was shown that the concentration of the selective agent used dictated the extent of sub-lethal injury recorded owing to the interaction effects of the selective component (NaCl) in the recovery media. Our findings highlight a potential common misunderstanding on how culture conditions impact on sub-lethal injury. Interestingly for S. cerevisiae cells the number of cells recovered at different NaCl concentrations in the media appears to provide valuable information about the mode of injury, the comparative efficacy of different processing regimes and the inherent degree of resistance within a population. This

  7. Genetic analysis reveals that FLO11 upregulation and cell polarization independently regulate invasive growth in Saccharomyces cerevisiae.

    PubMed Central

    Palecek, S P; Parikh, A S; Kron, S J

    2000-01-01

    Under inducing conditions, haploid Saccharomyces cerevisiae perform a dimorphic transition from yeast-form growth on the agar surface to invasive growth, where chains of cells dig into the solid growth medium. Previous work on signaling cascades that promote agar invasion has demonstrated upregulation of FLO11, a cell-surface flocculin involved in cell-cell adhesion. We find that increasing FLO11 transcription is sufficient to induce both invasive and filamentous growth. A genetic screen for repressors of FLO11 isolated mutant strains that dig into agar (dia) and identified mutations in 35 different genes: ELM1, HSL1, HSL7, BUD3, BUD4, BUD10, AXL1, SIR2, SIR4, BEM2, PGI1, GND1, YDJ1, ARO7, GRR1, CDC53, HSC82, ZUO1, ADH1, CSE2, GCR1, IRA1, MSN5, SRB8, SSN3, SSN8, BPL1, GTR1, MED1, SKN7, TAF25, DIA1, DIA2, DIA3, and DIA4. Indeed, agar invasion in 20 dia mutants requires upregulation of the endogenous FLO11 promoter. However, 13 mutants promote agar invasion even with FLO11 clamped at a constitutive low-expression level. These FLO11 promoter-independent dia mutants establish distinct invasive growth pathways due to polarized bud site selection and/or cell elongation. Epistasis with the STE MAP kinase cascade and cytokinesis/budding checkpoint shows these pathways are targets of DIA genes that repress agar invasion by FLO11 promoter-dependent and -independent mechanisms, respectively. PMID:11063681

  8. Importance of OH(-) transport from cathodes in microbial fuel cells.

    PubMed

    Popat, Sudeep C; Ki, Dongwon; Rittmann, Bruce E; Torres, César I

    2012-06-01

    Cathodic limitation in microbial fuel cells (MFCs) is considered an important hurdle towards practical application as a bioenergy technology. The oxygen reduction reaction (ORR) needs to occur in MFCs under significantly different conditions compared to chemical fuel cells, including a neutral pH. The common reason cited for cathodic limitation is the difficulty in providing protons to the catalyst sites. Here, we show that it is not the availability of protons, but the transport of OH(-) from the catalyst layer to the bulk liquid that largely governs cathodic potential losses. OH(-) is a product of an ORR mechanism that has not been considered dominant before. The accumulation of OH(-) at the catalyst sites results in an increase in the local cathode pH, resulting in Nernstian concentration losses. For Pt-based gas-diffusion cathodes, using polarization curves developed in unbuffered and buffered solutions, we quantified this loss to be >0.3 V at a current density of 10 Am(-2) . We show that this loss can be partially overcome by replacing the Nafion binder used in the cathode catalyst layer with an anion-conducting binder and by providing additional buffer to the cathode catalyst directly in the form of CO(2) , which results in enhanced OH(-) transport. Our results provide a comprehensive analysis of cathodic limitations in MFCs and should allow researchers to develop and select materials for the construction of MFC cathodes and identify operational conditions that will help minimize Nernstian concentration losses due to pH gradients.

  9. Microbial fuel cells with highly active aerobic biocathodes

    NASA Astrophysics Data System (ADS)

    Milner, Edward M.; Popescu, Dorin; Curtis, Tom; Head, Ian M.; Scott, Keith; Yu, Eileen H.

    2016-08-01

    Microbial fuel cells (MFCs), which convert organic waste to electricity, could be used to make the wastewater infrastructure more energy efficient and sustainable. However, platinum and other non-platinum chemical catalysts used for the oxygen reduction reaction (ORR) at the cathode of MFCs are unsustainable due to their high cost and long-term degradation. Aerobic biocathodes, which use microorganisms as the biocatalysts for cathode ORR, are a good alternative to chemical catalysts. In the current work, high-performing aerobic biocathodes with an onset potential for the ORR of +0.4 V vs. Ag/AgCl were enriched from activated sludge in electrochemical half-cells poised at -0.1 and + 0.2 V vs. Ag/AgCl. Gammaproteobacteria, distantly related to any known cultivated gammaproteobacterial lineage, were identified as dominant in these working electrode biofilms (23.3-44.3% of reads in 16S rRNA gene Ion Torrent libraries), and were in very low abundance in non-polarised control working electrode biofilms (0.5-0.7%). These Gammaproteobacteria were therefore most likely responsible for the high activity of biologically catalysed ORR. In MFC tests, a high-performing aerobic biocathode increased peak power 9-fold from 7 to 62 μW cm-2 in comparison to an unmodified carbon cathode, which was similar to peak power with a platinum-doped cathode at 70 μW cm-2.

  10. Compost in plant microbial fuel cell for bioelectricity generation.

    PubMed

    Moqsud, M A; Yoshitake, J; Bushra, Q S; Hyodo, M; Omine, K; Strik, David

    2015-02-01

    Recycling of organic waste is an important topic in developing countries as well as developed countries. Compost from organic waste has been used for soil conditioner. In this study, an experiment has been carried out to produce green energy (bioelectricity) by using paddy plant microbial fuel cells (PMFCs) in soil mixed with compost. A total of six buckets filled with the same soil were used with carbon fiber as the electrodes for the test. Rice plants were planted in five of the buckets, with the sixth bucket containing only soil and an external resistance of 100 ohm was used for all cases. It was observed that the cells with rice plants and compost showed higher values of voltage and power density with time. The highest value of voltage showed around 700 mV when a rice plant with 1% compost mixed soil was used, however it was more than 95% less in the case of no rice plant and without compost. Comparing cases with and without compost but with the same number of rice plants, cases with compost depicted higher voltage to as much as 2 times. The power density was also 3 times higher when the compost was used in the paddy PMFCs which indicated the influence of compost on bio-electricity generation.

  11. Increased electrical output when a bacterial ABTS oxidizer is used in a microbial fuel cell

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microbial fuel cells (MFCs) are a technology that provides electrical energy from the microbial oxidation of organic compounds. Most MFCs use oxygen as the oxidant in the cathode chamber. The present study examined the formation in culture of an unidentified bacterial oxidant and investigated the ...

  12. Enrichment of microbial community generating electricity using a fuel-cell-type electrochemical cell.

    PubMed

    Kim, B H; Park, H S; Kim, H J; Kim, G T; Chang, I S; Lee, J; Phung, N T

    2004-02-01

    A fuel cell was used to enrich a microbial consortium generating electricity, using organic wastewater as the fuel. Within 30 days of enrichment the maximum current of 0.2 mA was generated with a resistance of 1 kOhms. Current generation was coupled to a fall in chemical oxygen demand from over 1,700 mg l(-1) down to 50 mg l(-1). Denaturing gradient gel electrophoresis showed a different microbial population in the enriched electrode from that in the sludge used as the inoculum. Electron microscopic observation showed a biofilm on the electrode surface and microbial clumps. Nanobacteria-like particles were present on the biofilm surface. Metabolic inhibitors and electron acceptors inhibited the current generation. 16S ribosomal RNA gene analysis showed a diverse bacterial population in the enrichment culture. These findings demonstrate that an electricity-generating microbial consortium can be enriched using a fuel cell and that the electrochemical activity is a form of anaerobic electron transfer.

  13. Process intensification through microbial strain evolution: mixed glucose-xylose fermentation in wheat straw hydrolyzates by three generations of recombinant Saccharomyces cerevisiae

    PubMed Central

    2014-01-01

    Background Lignocellulose hydrolyzates present difficult substrates for ethanol production by the most commonly applied microorganism in the fermentation industries, Saccharomyces cerevisiae. High resistance towards inhibitors released during pretreatment and hydrolysis of the feedstock as well as efficient utilization of hexose and pentose sugars constitute major challenges in the development of S. cerevisiae strains for biomass-to-ethanol processes. Metabolic engineering and laboratory evolution are applied, alone and in combination, to adduce desired strain properties. However, physiological requirements for robust performance of S. cerevisiae in the conversion of lignocellulose hydrolyzates are not well understood. The herein presented S. cerevisiae strains IBB10A02 and IBB10B05 are descendants of strain BP10001, which was previously derived from the widely used strain CEN.PK 113-5D through introduction of a largely redox-neutral oxidoreductive xylose assimilation pathway. The IBB strains were obtained by a two-step laboratory evolution that selected for fast xylose fermentation in combination with anaerobic growth before (IBB10A02) and after adaption in repeated xylose fermentations (IBB10B05). Enzymatic hydrolyzates were prepared from up to 15% dry mass pretreated (steam explosion) wheat straw and contained glucose and xylose in a mass ratio of approximately 2. Results With all strains, yield coefficients based on total sugar consumed were high for ethanol (0.39 to 0.40 g/g) and notably low for fermentation by-products (glycerol: ≤0.10 g/g; xylitol: ≤0.08 g/g; acetate: 0.04 g/g). In contrast to the specific glucose utilization rate that was similar for all strains (qGlucose ≈ 2.9 g/gcell dry weight (CDW)/h), the xylose consumption rate was enhanced by a factor of 11.5 (IBB10A02; qXylose = 0.23 g/gCDW/h) and 17.5 (IBB10B05; qXylose = 0.35 g/gCDW/h) as compared to the qXylose of the non-evolved strain BP10001. In xylose-supplemented (50

  14. High-cell-density fermentation of Saccharomyces cerevisiae for the optimisation of mead production.

    PubMed

    Pereira, A P; Mendes-Ferreira, A; Oliveira, J M; Estevinho, L M; Mendes-Faia, A

    2013-02-01

    Mead is a traditional drink that contains 8%-18% (v/v) of ethanol, resulting from the alcoholic fermentation of diluted honey by yeasts. Mead fermentation is a time-consuming process and the quality of the final product is highly variable. Therefore, the present investigation had two main objectives: first, to determine the adequate inoculum size of two commercial wine-making strains of Saccharomyces cerevisiae for the optimisation of mead fermentation; and second, to determine if an increase in yeast pitching rates in batch fermentations altered the resulting aroma profiles. Minor differences were detected in the growth kinetics between the two strains at the lowest pitching rate. With increasing pitching rates net growth of the strain ICV D47 progressively decreased, whereas for the QA23 the increasing inoculum size had no influence on its net growth. The time required to reach the same stage of fermentation ranged from 24 to 96 h depending on the inoculum size. The final aroma composition was dependent on the yeast strain and inoculum size. Fourteen of the twenty-seven volatile compounds quantified could contribute to mead aroma and flavour because their concentrations rose above their respective thresholds. The formation of these compounds was particularly pronounced at low pitching rates, except in mead fermented by strain ICV D47, at 10(6) CFUs/mL. The esters isoamyl acetate, ethyl octanoate and ethyl hexanoate were the major powerful odourants found in the meads. The results obtained in this study demonstrate that yeast strain and inoculum size can favourably impact mead's flavour and aroma profiles.

  15. Type 2C protein phosphatase Ptc6 participates in activation of the Slt2-mediated cell wall integrity pathway in Saccharomyces cerevisiae.

    PubMed

    Sharmin, Dilruba; Sasano, Yu; Sugiyama, Minetaka; Harashima, Satoshi

    2015-04-01

    The phosphorylation status of cellular proteins results from an equilibrium between the activities of protein kinases and protein phosphatases (PPases). Reversible protein phosphorylation is an important aspect of signal transduction that regulate many biological processes in eukaryotic cells. The Saccharomyces cerevisiae genome encodes 40 PPases, including seven members of the protein phosphatase 2C subfamily (PTC1 to PTC7). In contrast to other PPases, the cellular roles of PTCs have not been investigated in detail. Here, we sought to determine the cellular role of PTC6 in S. cerevisiae with disruption of PTC genes. We found that cells with Δptc6 disruption were tolerant to the cell wall-damaging agents Congo red (CR) and calcofluor white (CFW); however, cells with simultaneous disruption of PTC1 and PTC6 were very sensitive to these agents. Thus, simultaneous disruption of PTC1 and PTC6 gave a synergistic response to cell wall damaging agents. The level of phosphorylated Slt2 increased significantly after CR treatment in Δptc1 cells and more so in Δptc1Δptc6 cells; therefore, deletion of PTC6 enhanced Slt2 phosphorylation in the Δptc1 disruptant. The level of transcription of KDX1 upon exposure to CR increased to a greater extent in the Δptc1Δptc6 double disruptant than the Δptc1 single disruptant. The Δptc1Δptc6 double disruptant cells showed normal vacuole formation under standard growth conditions, but fragmented vacuoles were present in the presence of CR or CFW. Our analyses indicate that S. cerevisiae PTC6 participates in the negative regulation of Slt2 phosphorylation and vacuole morphogenesis under cell wall stress conditions.

  16. Single Cell Synchrotron FT-IR Microspectroscopy Reveals a Link between Neutral Lipid and Storage Carbohydrate Fluxes in S. cerevisiae

    PubMed Central

    Jamme, Frédéric; Vindigni, Jean-David; Méchin, Valérie; Cherifi, Tamazight; Chardot, Thierry; Froissard, Marine

    2013-01-01

    In most organisms, storage lipids are packaged into specialized structures called lipid droplets. These contain a core of neutral lipids surrounded by a monolayer of phospholipids, and various proteins which vary depending on the species. Hydrophobic structural proteins stabilize the interface between the lipid core and aqueous cellular environment (perilipin family of proteins, apolipoproteins, oleosins). We developed a genetic approach using heterologous expression in Saccharomyces cerevisiae of the Arabidopsis thaliana lipid droplet oleosin and caleosin proteins AtOle1 and AtClo1. These transformed yeasts overaccumulate lipid droplets, leading to a specific increase in storage lipids. The phenotype of these cells was explored using synchrotron FT-IR microspectroscopy to investigate the dynamics of lipid storage and cellular carbon fluxes reflected as changes in spectral fingerprints. Multivariate statistical analysis of the data showed a clear effect on storage carbohydrates and more specifically, a decrease in glycogen in our modified strains. These observations were confirmed by biochemical quantification of the storage carbohydrates glycogen and trehalose. Our results demonstrate that neutral lipid and storage carbohydrate fluxes are tightly connected and co-regulated. PMID:24040242

  17. Identification of sequence elements that confer cell-type-specific control of MF alpha 1 expression in Saccharomyces cerevisiae.

    PubMed Central

    Inokuchi, K; Nakayama, A; Hishinuma, F

    1987-01-01

    The MF alpha 1 gene of Saccharomyces cerevisiae, a major structural gene for mating pheromone alpha factor, is an alpha-specific gene whose expression is regulated by the mating-type locus. To study the role of sequences upstream of MF alpha 1 in its expression and regulation, we generated two sets of promoter deletions: upstream deletions and internal deletions. By analyzing these deletions, we have identified a TATA box and two closely related, tandemly arranged upstream activation sites as necessary elements for MF alpha 1 expression. Two upstream activation sites were located ca. 300 and 250 base pairs upstream of the MF alpha 1 transcription start points, which were also determined in this study. Each site contained a homologous 22-base-pair sequence, and both sites were required for maximum transcription level. The distance between the upstream activation sites and the transcription start points could be altered without causing loss of transcription efficiency, and the sites were active in either orientation with respect to the coding region. These elements conferred cell type-specific expression on a heterologous promoter. Analysis with host mating-type locus mutants indicates that these sequences are the sites through which the MAT alpha 1 product exerts its action to activate the MF alpha 1 gene. Homologous sequences with these elements were found in other alpha-specific genes, MF alpha 2 and STE3, and may mediate activation of this set of genes by MAT alpha 1. Images PMID:2959859

  18. Dietary Saccharomyces cerevisiae Cell Wall Extract Supplementation Alleviates Oxidative Stress and Modulates Serum Amino Acids Profiles in Weaned Piglets

    PubMed Central

    Yu, Lei; Martínez, Yordan

    2017-01-01

    This research aims to evaluate the effects of dietary supplementation with Saccharomyces cerevisiae cell wall extract (SCCWE) on growth performance, oxidative stress, intestinal morphology, and serum amino acid concentration in weaned piglets. Utilizing a completely randomized design, 40 healthy piglets weaned at 21 d were grouped into 4 experimental treatments with 10 pigs per treatment group. Treatments consisted of a basal diet (T0), a basal diet with a 0.05% SCCWE (T1), a basal diet with a 0.10% SCCWE (T2), and a basal diet with a 0.15% SCCWE (T3). SCCWE supplementation increased the average daily gain and final body weight compared with T0 (P < 0.05). SCCWE in T2 and T3 improved the average daily feed intake and decreased the feed/gain ratio compared with T1 and T2 (P < 0.05). SCCWE decreased serum malondialdehyde (MDA) and increased activities of catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) significantly compared to T0 (P < 0.05). SCCWE increased the concentration of Ile compared to T0 (P < 0.05). Moreover, the concentrations of Leu, Phe, and Arg were higher in T2 and T3 (P < 0.05). These findings indicate beneficial effects of SCCWE supplementation on growth performance, the concentration of some essential amino acids, and alleviation of oxidative stress in weaned piglets. PMID:28386308

  19. Identification of two hydrophilins that contribute to the desiccation and freezing tolerance of yeast (Saccharomyces cerevisiae) cells.

    PubMed

    Dang, Nghiem X; Hincha, Dirk K

    2011-06-01

    Hydrophilins are a group of proteins that are present in all organisms and that have been defined as being highly hydrophilic and rich in glycine. They are assumed to play important roles in cellular dehydration tolerance. There are 12 genes in the yeast Saccharomyces cerevisiae that encode hydrophilins and most of these genes are stress responsive. However, the functional role of yeast hydrophilins, especially in desiccation and freezing tolerance, is largely unknown. Here, we selected six candidate hydrophilins for further analysis. All six proteins were predicted to be intrinsically disordered, i.e. to have no stable structure in solution. The contribution of these proteins to the desiccation and freezing tolerance of yeast was investigated in the respective knock-out strains. Only the disruption of the genes YJL144W and YMR175W (SIP18) resulted in significantly reduced desiccation tolerance, while none of the strains was affected in its freezing tolerance under our experimental conditions. Complementation experiments showed that yeast cells overexpressing these two genes were both more desiccation and freezing tolerant, confirming the role of these two hydrophilins in yeast dehydration stress tolerance.

  20. Effects of increased transaldolase activity on D-xylulose and D-glucose metabolism in Saccharomyces cerevisiae cell extracts.

    PubMed Central

    Senac, T; Hahn-Hägerdal, B

    1991-01-01

    In vitro metabolism of D-xylulose and D-glucose in extracts obtained from D-glucose- and D-xylulose-fermenting Saccharomyces cerevisiae cells was investigated with 10- and 100-fold-increased activity of the enzyme transaldolase (EC 2.2.1.2). The rate of sugar consumption was the same in most cases, whereas the rate of ethanol formation decreased with increased levels of transaldolase. The formation of glycerol, pentitols, and acetic acid was not dependent on added transaldolase but was dependent on the sugar used as the growth substrate and on the sugar used in the in vitro metabolism experiments. The carbon balance showed that the dissimilated carbon could not be accounted for in products when transaldolase was added. The concentration of D-fructose-1,6.-diphosphate in the extracts was not influenced by added transaldolase but was higher with D-xylulose than with D-glucose. Levels of pyruvate, comparable with the two substrates, decreased with increasing levels of transaldolase. Exogenously added transaldolase decreased D-sedoheptulose-7-phosphate levels when D-xylulose was the substrate. The results are discussed in relation to the dissimilation of carbon through the upper part of glycolysis and the pentose phosphate pathway. PMID:1831338

  1. Microbial desalination cells for improved performance in wastewater treatment, electricity production, and desalination.

    PubMed

    Luo, Haiping; Xu, Pei; Roane, Timberley M; Jenkins, Peter E; Ren, Zhiyong

    2012-02-01

    The low conductivity and alkalinity in municipal wastewater significantly limit power production from microbial fuel cells (MFCs). This study integrated desalination with wastewater treatment and electricity production in a microbial desalination cell (MDC) by utilizing the mutual benefits among the above functions. When using wastewater as the sole substrate, the power output from the MDC (8.01 W/m(3)) was four times higher than a control MFC without desalination function. In addition, the MDC removed 66% of the salts and improved COD removal by 52% and Coulombic efficiency by 131%. Desalination in MDCs improved wastewater characteristics by increasing the conductivity by 2.5 times and stabilizing anolyte pH, which therefore reduced system resistance and maintained microbial activity. Microbial community analysis revealed a more diverse anode microbial structure in the MDC than in the MFC. The results demonstrated that MDC can serve as a viable option for integrated wastewater treatment, energy production, and desalination.

  2. Is resistance futile? Changing external resistance does not improve microbial fuel cell performance.

    PubMed

    Lyon, Delina Y; Buret, Francois; Vogel, Timothy M; Monier, Jean-Michel

    2010-04-01

    Microbial fuel cells (MFCs) show promise as an alternative to conventional batteries for point source electricity generation. A better understanding of the relationship between the microbiological and electrical aspects of fuels cells is needed prior to successful MFC application. Here, we observed the effects of external resistance on power production and the anodic biofilm community structure. Large differences in the external resistance affected both power production and microbial community structure. After the establishment of the anodic microbial community, change in external resistance (from low to high and vice versa) changed the anodic microbial community structure, but the resulting community did not resemble the communities established at that same external resistance. Different microbial community structures, established under different external resistances, resulted in similar power production, demonstrating the flexibility of the MFC system.

  3. A novel microbial fuel cell sensor with biocathode sensing element.

    PubMed

    Jiang, Yong; Liang, Peng; Liu, Panpan; Wang, Donglin; Miao, Bo; Huang, Xia

    2017-03-02

    The traditional microbial fuel cell (MFC) sensor with bioanode as sensing element delivers limited sensitivity to toxicity monitoring, restricted application to only anaerobic and organic rich water body, and increased potential fault warning to the combined shock of organic matter/toxicity. In this study, the biocathode for oxygen reduction reaction was employed for the first time as the sensing element in MFC sensor for toxicity monitoring. The results shown that the sensitivity of MFC sensor with biocathode sensing element (7.4±2.0 to 67.5±4.0mA%(-1)cm(-2)) was much greater than that showed by bioanode sensing element (3.4±1.5 to 5.5±0.7mA%(-1)cm(-2)). The biocathode sensing element achieved the lowest detection limit reported to date using MFC sensor for formaldehyde detection (0.0005%), while the bioanode was more applicable for higher concentration (>0.0025%). There was a quicker response of biocathode sensing element with the increase of conductivity and dissolved oxygen (DO). The biocathode sensing element made the MFC sensor directly applied to clean water body monitoring, e.g., drinking water and reclaimed water, without the amending of background organic matter, and it also decreased the warning failure when challenged by a combined shock of organic matter/toxicity.

  4. Polymer coatings as separator layers for microbial fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Watson, Valerie J.; Saito, Tomonori; Hickner, Michael A.; Logan, Bruce E.

    2011-03-01

    Membrane separators reduce oxygen flux from the cathode into the anolyte in microbial fuel cells (MFCs), but water accumulation and pH gradients between the separator and cathode reduces performance. Air cathodes were spray-coated (water-facing side) with anion exchange, cation exchange, and neutral polymer coatings of different thicknesses to incorporate the separator into the cathode. The anion exchange polymer coating resulted in greater power density (1167 ± 135 mW m-2) than a cation exchange coating (439 ± 2 mW m-2). This power output was similar to that produced by a Nafion-coated cathode (1114 ± 174 mW m-2), and slightly lower than the uncoated cathode (1384 ± 82 mW m-2). Thicker coatings reduced oxygen diffusion into the electrolyte and increased coulombic efficiency (CE = 56-64%) relative to an uncoated cathode (29 ± 8%), but decreased power production (255-574 mW m-2). Electrochemical characterization of the cathodes ex situ to the MFC showed that the cathodes with the lowest charge transfer resistance and the highest oxygen reduction activity produced the most power in MFC tests. The results on hydrophilic cathode separator layers revealed a trade off between power and CE. Cathodes coated with a thin coating of anion exchange polymer show promise for controlling oxygen transfer while minimally affecting power production.

  5. Capacitive bioanodes enable renewable energy storage in microbial fuel cells.

    PubMed

    Deeke, Alexandra; Sleutels, Tom H J A; Hamelers, Hubertus V M; Buisman, Cees J N

    2012-03-20

    We developed an integrated system for storage of renewable electricity in a microbial fuel cell (MFC). The system contained a capacitive electrode that was inserted into the anodic compartment of an MFC to form a capacitive bioanode. This capacitive bioanode was compared with a noncapacitive bioanode on the basis of performance and storage capacity. The performance and storage capacity were investigated during polarization curves and charge-discharge experiments. During polarization curves the capacitive electrode reached a maximum current density of 1.02 ± 0.04 A/m(2), whereas the noncapacitive electrode reached a current density output of only 0.79 ± 0.03 A/m(2). During the charge-discharge experiment with 5 min of charging and 20 min of discharging, the capacitive electrode was able to store a total of 22,831 C/m(2), whereas the noncapacitive electrode was only able to store 12,195 C/m(2). Regarding the charge recovery of each electrode, the capacitive electrode was able to recover 52.9% more charge during each charge-discharge experiment compared with the noncapacitive electrode. The capacitive electrode outperformed the noncapacitive electrode throughout each charge-discharge experiment. With a capacitive electrode it is possible to use the MFC simultaneously for production and storage of renewable electricity.

  6. Effective ammonium removal by anaerobic oxidation in microbial fuel cells.

    PubMed

    Jadhav, Dipak A; Ghangrekar, Makarand M

    2015-01-01

    Dual-chamber microbial fuel cells (MFCs), made of clayware cylinder, were operated at different chemical oxygen demands: ammonium-nitrogen (COD:NH4+) ratio (1:1, 10:1 and 5:1) under batch mode for simultaneous removal of ammonia and organic matter from wastewater. Ammonium-N removal efficiencies of 63-32.66% were obtained for COD:NH4+ ratio of 1:10, respectively. Average COD removal efficiencies demonstrated by these MFCs were about 88%; indicating effective use of MFCs for treatment of wastewater containing organic matter and high ammonia concentration. MFCs operated with COD:NH4+ ratio of 10:1 produced highest volumetric power density of 752.88 mW/m3. The ammonium-N removal slightly increased when microbes were exposed to only ammonium as a source of electron when organic source was not supplemented. When this MFC was operated with imposed potential on cathode and without aeration in the cathode chamber, oxidation of ammonium ions at a faster rate confirmed anaerobic oxidation. During the non-turnover condition of cyclic voltammetry, MFC operated with COD:NH4+ ratio of 10:1 gave higher oxidative and reductive currents than MFC operated with COD:NH4+ ratio of 1:1 due to higher redox species. Successful application of such an anammox process for ammonium oxidation in MFCs will be useful for treatment of wastewater containing higher ammonium concentration and harvesting energy in the form of electricity.

  7. High performance spiral wound microbial fuel cell with hydraulic characterization.

    PubMed

    Haeger, Alexander; Forrestal, Casey; Xu, Pei; Ren, Zhiyong Jason

    2014-12-01

    The understanding and development of functioning systems are crucial steps for microbial fuel cell (MFC) technology advancement. In this study, a compact spiral wound MFC (swMFC) was developed and hydraulic residence time distribution (RTD) tests were conducted to investigate the flow characteristics in the systems. Results show that two-chamber swMFCs have high surface area to volume ratios of 350-700m(2)/m(3), and by using oxygen cathode without metal-catalysts, the maximum power densities were 42W/m(3) based on total volume and 170W/m(3) based on effective volume. The hydraulic step-input tracer study identified 20-67% of anodic flow dead space, which presents new opportunities for system improvement. Electrochemical tools revealed very low ohmic resistance but high charge transfer and diffusion resistance due to catalyst-free oxygen reduction. The spiral wound configuration combined with RTD tool offers a holistic approach for MFC development and optimization.

  8. Electricity production coupled to ammonium in a microbial fuel cell.

    PubMed

    He, Zhen; Kan, Jinjun; Wang, Yanbing; Huang, Yuelong; Mansfeld, Florian; Nealson, Kenneth H

    2009-05-01

    The production of electricity from ammonium was examined using a rotating-cathode microbial fuel cell (MFC). The addition of ammonium chloride, ammonium sulfate, or ammonium phosphate (monobasic) resulted in electricity generation, while adding sodium chloride, nitrate, or nitrite did not cause any increase in current production. The peak current increased with increasing amount of ammonium addition up to 62.3 mM of ammonium chloride, suggesting that ammonium was involved in electricity generation either directly as the anodic fuel or indirectly as substrates for nitrifiers to produce organic compounds for heterotrophs. Adding nitrate or nitrite with ammonium increased current production compared to solely ammonium addition. Using 16S rRNA-linked molecular analyses, we found ammonium-oxidizing bacteria and denitrifying bacteria on both the anode and cathode electrodes, whereas no anammox bacteria were detected. The dominant ammonium-oxidizing bacteria were closely related to Nitrosomonas europaea. The present MFC achieved an ammonium removal efficiency of 49.2 +/- 5.9 or 69.7 +/- 3.6%, depending on hydraulic retention time, but exhibited a very low Coulombic efficiency.

  9. Electricity generation from rapeseed straw hydrolysates using microbial fuel cells.

    PubMed

    Jablonska, Milena A; Rybarczyk, Maria K; Lieder, Marek

    2016-05-01

    Rapeseed straw is an attractive fuel material for microbial fuel cells (MFCs) due to its high content of carbohydrates (more than 60% carbohydrates). This study has demonstrated that reducing sugars can be efficiently extracted from raw rapeseed straw by combination of hydrothermal pretreatment and enzymatic hydrolysis followed by utilization as a fuel in two-chamber MFCs for electrical power generation. The most efficient method of saccharification of this lignocellulosic biomass (17%) turned out hydrothermal pretreatment followed by enzymatic hydrolysis. Electricity was produced using hydrolysate concentrations up to 150 mg/dm(3). The power density reached 54 mW/m(2), while CEs ranged from 60% to 10%, corresponding to the initial reducing sugar concentrations of 10-150 mg/dm(3). The COD degradation rates based on charge calculation increased from 0.445 g COD/m(2)/d for the hydrolysate obtained with the microwave treatment to 0.602 g COD/m(2)/d for the most efficient combination of hydrothermal treatment followed by enzymatic hydrolysis.

  10. Submersible microbial fuel cell for electricity production from sewage sludge.

    PubMed

    Zhang, Yifeng; Olias, Lola Gonzalez; Kongjan, Prawit; Angelidaki, Irini

    2011-01-01

    A submersible microbial fuel cell (SMFC) was utilized to treat sewage sludge and simultaneously generate electricity. Stable power generation (145 +/- 5 mW/m2, 470 omega) was produced continuously from raw sewage sludge for 5.5 days. The maximum power density reached 190 +/- 5 mW/m2. The corresponding total chemical oxygen demand (TCOD) removal efficiency was 78.1 +/- 0.2% with initial TCOD of 49.7 g/L. The power generation of SMFC was depended on the sludge concentration, while dilution of the raw sludge resulted in higher power density. The maximum power density was saturated at sludge concentration of 17 g-TCOD/L, where 290 mw/m2 was achieved. When effluents from an anaerobic digester that was fed with raw sludge were used as substrate in the SMFC, a maximum power density of 318 mW/m2, and a final TCOD removal of 71.9 +/- 0.2% were achieved. These results have practical implications for development of an effective system to treat sewage sludge and simultaneously recover energy.

  11. Continuous flowing membraneless microbial fuel cells with separated electrode chambers.

    PubMed

    Du, Fangzhou; Xie, Beizhen; Dong, Wenbo; Jia, Boyang; Dong, Kun; Liu, Hong

    2011-10-01

    Microbial fuel cell (MFC) is an emerging technology in the energy and environment field. Its application is limited due to its high cost caused by the utilization of membranes and noble metal catalysts. In this paper, a membraneless MFC, with separated electrode chambers, was designed. The two separated chambers are connected via a channel and the continuous electrolyte flow from anode to cathode drives proton transfer. The proton mass transfer coefficiency in this MFC is 0.9086 cm/s, which is higher than reported MFCs with membranes, such as J-cloth and glass fiber. The maximum output voltage is 160.7 mV, with 1000 Ω resistor. Its peak power density is 24.33 mW/m³. SCOD removal efficiency can reach 90.45% via this MFC. If the connection between the two electrode chambers is blocked, the performance of MFC will decrease severely. All the above results prove the feasibility and advantages of this special MFC model.

  12. Tubular bamboo charcoal for anode in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Li, Jun; Ye, Dingding; Zhu, Xun; Liao, Qiang; Zhang, Biao

    2014-12-01

    The anode material plays a significant role in determining the performance of microbial fuel cells (MFCs). In this study, the bamboo charcoal tube is proposed as a novel anode substrate by carbonizing the natural bamboo. Its surface functional groups, biocompatibility and internal resistance are thoroughly investigated. Performance of the MFCs with a conventional graphite tube anode and a bamboo charcoal tube anode is also compared. The results indicate that the tubular bamboo charcoal anode exhibits advantages over the graphite tube anode in terms of rougher surface, superior biocompatibility and smaller total internal resistance. Moreover, the X-ray photoelectron spectroscopy (XPS) analysis for the bamboo charcoal reveals that the introduced C-N bonds facilitate the electron transfer between the biofilm and electrodes. As a result, the MFC with a bamboo charcoal tube anode achieves a 50% improvement in the maximum power density over the graphite tube case. Furthermore, scale-up of the bamboo charcoal tube anode is demonstrated by employing a bundle of tubular bamboo charcoal to reach higher power output.

  13. Carbon Material Optimized Biocathode for Improving Microbial Fuel Cell Performance

    PubMed Central

    Tursun, Hairti; Liu, Rui; Li, Jing; Abro, Rashid; Wang, Xiaohui; Gao, Yanmei; Li, Yuan

    2016-01-01

    To improve the performance of microbial fuel cells (MFCs), the biocathode electrode material of double-chamber was optimized. Alongside the basic carbon fiber brush, three carbon materials namely graphite granules, activated carbon granules (ACG) and activated carbon powder, were added to the cathode-chambers to improve power generation. The result shows that the addition of carbon materials increased the amount of available electroactive microbes on the electrode surface and thus promote oxygen reduction rate, which improved the generation performance of the MFCs. The Output current (external resistance = 1000 Ω) greatly increased after addition of the three carbon materials and maximum power densities in current stable phase increased by 47.4, 166.1, and 33.5%, respectively. Additionally, coulombic efficiencies of the MFC increased by 16.3, 64.3, and 20.1%, respectively. These results show that MFC when optimized with ACG show better power generation, higher chemical oxygen demands removal rate and coulombic efficiency. PMID:26858695

  14. Microbial fuel cell energy harvesting using synchronous flyback converter

    NASA Astrophysics Data System (ADS)

    Alaraj, Muhannad; Ren, Zhiyong Jason; Park, Jae-Do

    2014-02-01

    Microbial Fuel Cells (MFCs) use biodegradable substrates, such as wastewater and marine sediments to generate electrical energy. To harvest more energy from an MFC, power electronic converters have recently been used to replace resistors or charge pumps, because they have superior controllability on MFC's operating point and higher efficiency in energy storage for different applications. Conventional diode-based energy harvesters suffer from low efficiency because of the energy losses through the diode. Replacing the diode with a MOSFET can reduce the conduction loss, but it requires an isolated gate signal to control the floating secondary MOSFET, which makes the control circuitry complex. This study presents a new MFC energy harvesting regime using a synchronous flyback converter, which implements a transformer-based harvester with much simpler configuration and improves harvesting efficiency by 37.6% compared to a diode based boost converter, from 33.5% to 46.1%. The proposed harvester was able to store 2.27 J in the output capacitor out of 4.91 J generated energy from the MFC, while the boost converter can capture 1.67 J from 4.95 J.

  15. Microbial fuel cells using Cellulomonas spp. with cellulose as fuel.

    PubMed

    Takeuchi, Yuya; Khawdas, Wichean; Aso, Yuji; Ohara, Hitomi

    2017-03-01

    Cellulomonas fimi, Cellulomonas biazotea, and Cellulomonas flavigena are cellulose-degrading microorganisms chosen to compare the degradation of cellulose. C. fimi degraded 2.5 g/L of cellulose within 4 days, which was the highest quantity among the three microorganisms. The electric current generation by the microbial fuel cell (MFC) using the cellulose-containing medium with C. fimi was measured over 7 days. The medium in the MFC was sampled every 24 h to quantify the degradation of cellulose, and the results showed that the electric current increased with the degradation of cellulose. The maximum electric power generated by the MFC was 38.7 mW/m(2), and this numeric value was 63% of the electric power generated by an MFC with Shewanella oneidensis MR-1, a well-known current-generating microorganism. Our results showed that C. fimi was an excellent candidate to produce the electric current from cellulose via MFCs.

  16. Shift of voltage reversal in stacked microbial fuel cells

    NASA Astrophysics Data System (ADS)

    An, Junyeong; Kim, Bongkyu; Chang, In Seop; Lee, Hyung-Sool

    2015-03-01

    We proved that sluggish kinetics on the cathode and the imbalance of cathode kinetics cause voltage reversal in a stacked microbial fuel cell (MFC) equipped with a non-Pt cathode. Catholyte aeration to a unit MFC against passive air diffusion to the cathode in the other unit MFC shifted voltage reversal between the two units, due to improved mass transport and O2 concentration effects in the aerated MFC. The shifted voltage reversal returned to an original status when catholyte aeration was stopped. A Pt-coated cathode increased the rate of oxygen reduction reaction (ORR) by a factor of ∼20, as compared to the non-Pt cathode. As a result, the anodic reaction rate that became slower than the rate on the Pt-cathode limited current density to overpotential in the stacked MFC equipped with the Pt-cathode. This work shows that dominant kinetic bottlenecks, which are the primary cause of voltage reversal, can be shifted between individual MFCs of stacked MFCs or electrodes depending on relative kinetics.

  17. Cadmium recovery by coupling double microbial fuel cells.

    PubMed

    Choi, Chansoo; Hu, Naixu; Lim, Bongsu

    2014-10-01

    Cr(VI)-MFC of the double microbial fuel cell (d-MFC) arrangement could successfully complement the insufficient voltage and power needed to recover cadmium metal from Cd(II)-MFC, which operated as a redox-flow battery. It was also possible to drain electrical energy from the d-MFC by an additional passage. The highest maximum utilization power density (22.5Wm(-2)) of Cr(VI)-MFC, with the cathode optimized with sulfate buffer, was 11.3times higher than the highest power density directly supplied to Cd(II)-MFC (2.0Wm(-2)). Cr(VI)-MFC could generate 3times higher power with the additional passage than without it; and the current density for the former was 4.2times higher than the latter at the same maximum power point (38.0Am(-2) vs. 9.0Am(-2)). This boosting phenomenon could be explained by the Le Chatelier's principle, which addresses the rate of electron-hole pair formation that can be accelerated by quickly removing electrons generated by microorganisms.

  18. Carbon fiber enhanced bioelectricity generation in soil microbial fuel cells.

    PubMed

    Li, Xiaojing; Wang, Xin; Zhao, Qian; Wan, Lili; Li, Yongtao; Zhou, Qixing

    2016-11-15

    The soil microbial fuel cell (MFC) is a promising biotechnology for the bioelectricity recovery as well as the remediation of organics contaminated soil. However, the electricity production and the remediation efficiency of soil MFC are seriously limited by the tremendous internal resistance of soil. Conductive carbon fiber was mixed with petroleum hydrocarbons contaminated soil and significantly enhanced the performance of soil MFC. The maximum current density, the maximum power density and the accumulated charge output of MFC mixed carbon fiber (MC) were 10, 22 and 16 times as high as those of closed circuit control due to the carbon fiber productively assisted the anode to collect the electron. The internal resistance of MC reduced by 58%, 83% of which owed to the charge transfer resistance, resulting in a high efficiency of electron transfer from soil to anode. The degradation rates of total petroleum hydrocarbons enhanced by 100% and 329% compared to closed and opened circuit controls without the carbon fiber respectively. The effective range of remediation and the bioelectricity recovery was extended from 6 to 20cm with the same area of air-cathode. The mixed carbon fiber apparently enhanced the bioelectricity generation and the remediation efficiency of soil MFC by means of promoting the electron transfer rate from soil to anode. The use of conductively functional materials (e.g. carbon fiber) is very meaningful for the remediation and bioelectricity recovery in the bioelectrochemical remediation.

  19. Cathodic and anodic biofilms in Single Chamber Microbial Fuel Cells.

    PubMed

    Cristiani, P; Carvalho, M L; Guerrini, E; Daghio, M; Santoro, C; Li, B

    2013-08-01

    The oxygen reduction due to microaerophilic biofilms grown on graphite cathodes (biocathodes) in Single Chamber Microbial Fuel Cells (SCMFCs) is proved and analysed in this paper. Pt-free cathode performances are compared with those of different platinum-loaded cathodes, before and after the biofilm growth. Membraneless SCMFCs were operating in batch-mode, filled with wastewater. A substrate (fuel) of sodium acetate (0.03 M) was periodically added and the experiment lasted more than six months. A maximum of power densities, up to 0.5 W m(-2), were reached when biofilms developed on the electrodes and the cathodic potential decreased (open circuit potential of 50-200 mV vs. SHE). The power output was almost constant with an acetate concentration of 0.01-0.05 M and it fell down when the pH of the media exceeded 9.5, independently of the Pt-free/Pt-loading at the cathodes. Current densities varied in the range of 1-5 Am(-2) (cathode area of 5 cm(2)). Quasi-stationary polarization curves performed with a three-electrode configuration on cathodic and anodic electrodes showed that the anodic overpotential, more than the cathodic one, may limit the current density in the SCMFCs for a long-term operation.

  20. Bioelectricity production from soil using microbial fuel cells.

    PubMed

    Wolińska, Agnieszka; Stępniewska, Zofia; Bielecka, Arletta; Ciepielski, Jakub

    2014-08-01

    Microbial fuel cells (MFCs) are a device using microorganisms as biocatalysts for transforming chemical energy into bioelectricity. As soil is an environment with the highest number of microorganisms and diversity, we hypothesized that it should have the potential for energy generation. The soil used for the study was Mollic Gleysol collected from the surface layer (0-20 cm). Four combinations of soil MFC differing from each other in humidity (full water holding capacity [WHC] and flooding) and the carbon source (glucose and straw) were constructed. Voltage (mV) and current intensity (μA) produced by the MFCs were recorded every day or at 2-day intervals. The fastest and the most effective MFCs in voltage generation (372.2 ± 5 mV) were those constructed on the basis of glucose (MFC-G). The efficiency of straw MFCs (MFC-S) was noticeable after 2 weeks (319.3 ± 4 mV). Maximal power density (P max = 32 mW m(-2)) was achieved by the MFC-G at current density (CD) of 100 mA m(-2). Much lower values of P max (10.6-10.8 mW m(-2)) were noted in the MFC-S at CD of ca. 60-80 mA m(-2). Consequently, soil has potential for production of renewable energy.

  1. Microbial fuel cells for robotics: energy autonomy through artificial symbiosis.

    PubMed

    Ieropoulos, Ioannis A; Greenman, John; Melhuish, Chris; Horsfield, Ian

    2012-06-01

    The development of the microbial fuel cell (MFC) technology has seen an enormous growth over the last hundred years since its inception by Potter in 1911. The technology has reached a level of maturity that it is now considered to be a field in its own right with a growing scientific community. The highest level of activity has been recorded over the last decade and it is perhaps considered commonplace that MFCs are primarily suitable for stationary, passive wastewater treatment applications. Sceptics have certainly not considered MFCs as serious contenders in the race for developing renewable energy technologies. Yet this is the only type of alternative system that can convert organic waste-widely distributed around the globe-directly into electricity, and therefore, the only technology that will allow artificial agents to autonomously operate in a plethora of environments. This Minireview describes the history and current state-of-the-art regarding MFCs in robotics and their vital role in artificial symbiosis and autonomy. Furthermore, the article demonstrates how pursuing practical robotic applications can provide insights of the core MFC technology in general.

  2. Tubular microbial fuel cells for efficient electricity generation.

    PubMed

    Rabaey, Korneel; Clauwaert, Peter; Aelterman, Peter; Verstraete, Willy

    2005-10-15

    A tubular, single-chambered, continuous microbial fuel cell (MFC) that generates high power outputs using a granular graphite matrix as the anode and a ferricyanide solution as the cathode is described. The maximal power outputs obtained were 90 and 66 W m(-3) net anodic compartment (NAC) (48 and 38 W m(-3) total anodic compartment (TAC)) for feed streams based on acetate and glucose, respectively, and 59 and 48 W m(-3) NAC for digester effluent and domestic wastewater, respectively. For acetate and glucose, the total Coulombic conversion efficiencies were 75 +/- 5% and 59 +/- 4%, respectively, at loading rates of 1.1 kg chemical oxygen demand m(-3) NAC volume day(-1). When wastewater was used, of the organic matter effectively removed (i.e., 22% at a loading of 2 kg organic matter m(-3) NAC day(-1)), up to 96% was converted to electricity on a Coulombic basis. The lower overall efficiency of the wastewater-treating reactors is related to the presence of nonreadily biodegradable organics and the interference of alternative electron acceptors such as sulfate present in the wastewater. To further improve MFCs, focus has to be placed on the enhanced conversion of nonrapidly biodegradable material and the better directing of the anode flow toward the electrode instead of to alternative electron acceptors. Also the use of sustainable, open-air cathodes is a critical issue for practical implementation.

  3. Impact of tobramycin on the performance of microbial fuel cell

    PubMed Central

    2014-01-01

    Background The release of antibiotics into aquatic environments has made the treatment of wastewater containing antibiotics a world-wide public health problem. The ability of microbial fuel cells (MFCs) to harvest electricity from organic waste and renewable biomass is attracting increased interest in wastewater treatment. In this paper we investigated the bioelectrochemical response of an electroactive mixed-culture biofilm in MFC to different tobramycin concentrations. Results The electroactive biofilms showed a high degree of robustness against tobramycin at the level of μg/L. The current generation responses of the biofilms were affected by the presence of tobramycin. The inhibition ratio of the MFC increased exponentially with the tobramycin concentrations in the range of 0.1-1.9 g/L. The bacterial communities of the biofilms vary with the concentrations of tobramycin, the equilibrium of which is critical for the stability of electroactive biofilms based-MFC. Conclusions Experimental results demonstrate that the electroactive biofilm-based MFC is robust against antibiotics at the level of μg/L, but sensitive to changes in antibiotic concentration at the level of g/L. These results could provide significant information about the effects of antibiotics on the performance MFC as a waste-treatment technology. PMID:24993129

  4. Impact of volatile fatty acids on microbial electrolysis cell performance.

    PubMed

    Yang, Nan; Hafez, Hisham; Nakhla, George

    2015-10-01

    This study investigated the performance of microbial electrolysis cells (MECs) fed with three common fermentation products: acetate, butyrate, and propionate. Each substrate was fed to the reactor for three consecutive-batch cycles. The results showed high current densities for acetate, but low current densities for butyrate and propionate (maximum values were 6.0 ± 0.28, 2.5 ± 0.06, 1.6 ± 0.14 A/m(2), respectively). Acetate also showed a higher coulombic efficiency of 87 ± 5.7% compared to 72 ± 2.0 and 51 ± 6.4% for butyrate and propionate, respectively. This paper also revealed that acetate could be easily oxidized by anode respiring bacteria in MEC, while butyrate and propionate could not be oxidized to the same degree. The utilization rate of the substrates in MEC followed the order: acetate > butyrate > propionate. The ratio of suspended biomass to attached biomass was approximately 1:4 for all the three substrates.

  5. Energy-dependent, carrier-mediated extrusion of carboxyfluorescein from Saccharomyces cerevisiae allows rapid assessment of cell viability by flow cytometry.

    PubMed Central

    Breeuwer, P; Drocourt, J L; Rombouts, F M; Abee, T

    1994-01-01

    Carboxyfluorescein diacetate is a nonfluorescent compound which can be used in combination with flow cytometry for vital staining of yeasts and bacteria. The basis of this method is the assumption that, once inside the cell, carboxyfluorescein diacetate is hydrolyzed by nonspecific esterases to produce the fluorescent carboxyfluorescein (cF). cF is retained by cells with intact membranes (viable cells) and lost by cells with damaged membranes. In this report, we show that Saccharomyces cerevisiae extrudes cF in an energy-dependent manner. This efflux was studied in detail, and several indications that a transport system is involved were found. Efflux of cF was stimulated by the addition of glucose and displayed Michaelis-Menten kinetics. A Km for cF transport of 0.25 mM could be determined. The transport of cF was inhibited by the plasma membrane H(+)-ATPase inhibitors N,N'-dicyclohexylcarbodiimide and diethylstilbestrol and by high concentrations of tetraphenylphosphonium ions. These treatments resulted in a dissipation of the proton motive force, whereas the intracellular ATP concentration remained high. Transport of cF is therefore most probably driven by the membrane potential and/or the pH gradient. The viability of S. cerevisiae was determined by a two-step procedure consisting of loading the cells with cF followed by incubation at 40 degrees C in the presence of glucose. Subsequently, the fluorescence intensity of the cells was analyzed by flow cytometry. The efflux experiments showed an excellent correlation between the viability of S. cerevisiae cells and the ability to translocate cF. This method should prove of general utility for the rapid assessment of yeast vitality and viability. PMID:8017931

  6. Poly iron sulfate flocculant as an effective additive for improving the performance of microbial fuel cells.

    PubMed

    Miyahara, Morio; Sakamoto, Akihiro; Kouzuma, Atsushi; Watanabe, Kazuya

    2016-12-01

    Laboratory microbial fuel cells were supplied with artificial wastewater and used to examine how supplementation with poly iron sulfate, an inorganic polymer flocculant widely used in wastewater-treatment plants, affects electricity generation and anode microbiomes. It is shown that poly iron sulfate substantially increases electric outputs from microbial fuel cells. Microbiological analyses show that iron and sulfate separately affect anode microbiomes, and the increase in power output is associated with the increases in bacteria affiliated with the families Geobacteraceae and/or Desulfuromonadaceae. We suggest that poly iron sulfate is an effective additive for increasing the electric output from microbial fuel cells. Other utilities of poly iron sulfate in microbial fuel cells are also discussed.

  7. Comparison of electrogenic capabilities of microbial fuel cell with different light power on algae grown cathode.

    PubMed

    Juang, D F; Lee, C H; Hsueh, S C

    2012-11-01

    Electricity generation capabilities of microbial fuel cell with different light power on algae grown cathode were compared. Results showed that microbial fuel cell with 6 and 12W power of light always produced higher voltage and power density than with 18 and 26W. Similarly, microbial fuel cell with 6 and 12W of light power always displayed higher Coulombic efficiency and specific power than the one with 18 and 26W. The results also showed that microbial fuel cell with covered anodic chamber always displayed higher voltage, power density, Coulombic efficiency and specific power than the one without covered anodic chamber. Binary quadratic equations can be used to express the relationships between the light power and the voltage, power density, Coulombic efficiency and specific power. Although lower power of light on algae grown cathode and covering anodic chamber will increase system's electricity production, they will not significantly reduce its internal resistance.

  8. Scale-up of phosphate remobilization from sewage sludge in a microbial fuel cell.

    PubMed

    Happe, Manuel; Sugnaux, Marc; Cachelin, Christian Pierre; Stauffer, Marc; Zufferey, Géraldine; Kahoun, Thomas; Salamin, Paul-André; Egli, Thomas; Comninellis, Christos; Grogg, Alain-François; Fischer, Fabian

    2016-01-01

    Phosphate remobilization from digested sewage sludge containing iron phosphate was scaled-up in a microbial fuel cell (MFC). A 3litre triple chambered MFC was constructed. This reactor was operated as a microbial fuel cell and later as a microbial electrolysis cell to accelerate cathodic phosphate remobilization. Applying an additional voltage and exceeding native MFC power accelerated chemical base formation and the related phosphate remobilization rate. The electrolysis approach was extended using a platinum-RVC cathode. The pH rose to 12.6 and phosphate was recovered by 67% in 26h. This was significantly faster than using microbial fuel cell conditions. Shrinking core modelling particle fluid kinetics showed that the reaction resistance has to move inside the sewage sludge particle for considerable rate enhancement. Remobilized phosphate was subsequently precipitated as struvite and inductively coupled plasma mass spectrometry indicated low levels of cadmium, lead, and other metals as required by law for recycling fertilizers.

  9. Silicon-based microfabricated microbial fuel cell toxicity sensor.

    PubMed

    Dávila, D; Esquivel, J P; Sabaté, N; Mas, J

    2011-01-15

    Microbial fuel cells (MFCs) have been used for several years as biosensors for measuring environmental parameters such as biochemical oxygen demand and water toxicity. The present study is focused on the detection of toxic matter using a novel silicon-based MFC. Like other existing toxicity sensors based on MFCs, this device is capable of detecting the variation on the current produced by the cell when toxic compounds are present in the medium. The MFC approach presented in this work aims to obtain a simple, compact and planar device for its further application as a biosensor in the design and fabrication of equipment for toxicity monitoring. It consists on a proton exchange membrane placed between two microfabricated silicon plates that act as current collectors. An array of square 80 μm × 80 μm vertical channels, 300 μm deep, have been defined trough the plates over an area of 6 mm × 6 mm. The final testing assembly incorporates two perspex pieces positioned onto the plates as reservoirs with a working volume of 144 μL per compartment. The operation of the microdevice as a direct electron transfer MFC has been validated by comparing its performance against a larger scale MFC, run under the same conditions. The device has been tested as a toxicity sensor by setting it at a fixed current while monitoring changes in the output power. A drop in the power production is observed when a toxic compound is added to the anode compartment. The compact design of the device makes it suitable for its incorporation into measurement equipment either as an individual device or as an array of sensors for high throughput processing.

  10. Enhanced power production from microbial fuel cells with high cell density culture.

    PubMed

    Zhai, Dan-Dan; Li, Bing; Sun, Jian-Zhong; Sun, De-Zhen; Si, Rong-Wei; Yong, Yang-Chun

    2016-01-01

    Improvement of power production in a microbial fuel cell (MFC) with a high cell density culture strategy was developed. By using high cell density culture, the voltage output and power density output of the MFC were enhanced about 0.6 and 1.6 times compared to the control, respectively. Further analysis showed that riboflavin concentration in the MFC was dramatically increased from 0.1 mg/L to 1.2 mg/L by high cell density culture. Moreover, the biofilm formation on the anode surface was significantly enhanced by this new strategy. The increased accumulation of electron shuttle (riboflavin) as well as enhanced biofilm formation contributed to the improvement in anodic electrochemical activity and these factors were the underlying mechanism for MFC performance improvement by high cell density culture. This work demonstrated that high cell density culture would be a simple and practical strategy for MFC manipulation.

  11. Metabolite Analysis of Clostridium acetobutylicum: Fermentation in a Microbial Fuel Cell

    DTIC Science & Technology

    2010-01-01

    Metabolite analysis of Clostridium acetobutylicum : Fermentation in a microbial fuel cell Amethist S. Finch, Timothy D. Mackie, Christian J. Sund...Fermentation products Clostridium acetobutylicum Current generation a b s t r a c t Microbial fuel cells (MFCs) were used to monitor metabolism...changes in Clostridium acetobutylicum fer- mentations. When MFCs were inoculated with C. acetobutylicum , they generated a unique voltage output pattern

  12. Flow cytometric assessment of cell structural and functional changes induced by acetic acid in the yeasts Zygosaccharomyces bailii and Saccharomyces cerevisiae.

    PubMed

    Prudêncio, C; Sansonetty, F; Côrte-Real, M

    1998-04-01

    Flow cytometry (FCM) was used with different viability dyes to assess changes in cell structure and function induced by acetic acid (AA) in populations of Zygosaccharomyces bailii (AA resistant) and Saccharomyces cerevisiae (AA sensitive). Kinetic changes in esterase activity, intracellular dye processing, and membrane integrity were monitored, and to detect those changes we used three assays involving fluorescein diacetate hydrolysis, FUN-1 processing, and propidium iodide exclusion, respectively. In S. cerevisiae, the decrease in the ability to process FUN-1 preceded the decrease in esterase activity, and there was loss of cell membrane integrity after incubation with AA. In Z. bailii, with higher AA concentrations, there was a similar decrease in the ability to process FUN-1, which also preceded the loss of cell membrane integrity. Changes in esterase activity in this yeast induced by AA treatment could not be monitored because the changes occurred independently of the presence of the acid. For control samples (untreated cells killed with 10% v/v of AA), the percentages of nonaltered cells as estimated by FCM and percentages of viable cells as estimated by colony forming unit (CFU) counts were identical. However, for cell samples treated for short periods with 3% (v/v) or less of AA, none of the dyes produced FCM results comparable to those produced by CFU counts.

  13. Anhydrobiosis in yeast: cell wall mannoproteins are important for yeast Saccharomyces cerevisiae resistance to dehydration.

    PubMed

    Borovikova, Diana; Teparić, Renata; Mrša, Vladimir; Rapoport, Alexander

    2016-08-01

    The state of anhydrobiosis is linked with the reversible delay of metabolism as a result of strong dehydration of cells, and is widely distributed in nature. A number of factors responsible for the maintenance of organisms' viability in these conditions have been revealed. This study was directed to understanding how changes in cell wall structure may influence the resistance of yeasts to dehydration-rehydration. Mutants lacking various cell wall mannoproteins were tested to address this issue. It was revealed that mutants lacking proteins belonging to two structurally and functionally unrelated groups (proteins non-covalently attached to the cell wall, and Pir proteins) possessed significantly lower cell resistance to dehydration-rehydration than the mother wild-type strain. At the same time, the absence of the GPI-anchored cell wall protein Ccw12 unexpectedly resulted in an increase of cell resistance to this treatment; this phenomenon is explained by the compensatory synthesis of chitin. The results clearly indicate that the cell wall structure/composition relates to parameters strongly influencing yeast viability during the processes of dehydration-rehydration, and that damage to cell wall proteins during yeast desiccation can be an important factor leading to cell death. Copyright © 2016 John Wiley & Sons, Ltd.

  14. Long-term performance of a plant microbial fuel cell with Spartina anglica.

    PubMed

    Timmers, Ruud A; Strik, David P B T B; Hamelers, Hubertus V M; Buisman, Cees J N

    2010-04-01

    The plant microbial fuel cell is a sustainable and renewable way of electricity production. The plant is integrated in the anode of the microbial fuel cell which consists of a bed of graphite granules. In the anode, organic compounds deposited by plant roots are oxidized by electrochemically active bacteria. In this research, salt marsh species Spartina anglica generated current for up to 119 days in a plant microbial fuel cell. Maximum power production was 100 mW m(-2) geometric anode area, highest reported power output for a plant microbial fuel cell. Cathode overpotential was the main potential loss in the period of oxygen reduction due to slow oxygen reduction kinetics at the cathode. Ferricyanide reduction improved the kinetics at the cathode and increased current generation with a maximum of 254%. In the period of ferricyanide reduction, the main potential loss was transport loss. This research shows potential application of microbial fuel cell technology in salt marshes for bio-energy production with the plant microbial fuel cell.

  15. Protein haze formation in white wines: effect of saccharomyces cerevisiae cell wall components prepared with different procedures.

    PubMed

    Lomolino, Giovanna; Curioni, Andrea

    2007-10-17

    Cell wall material was extracted by five different methods from an oenological strain of Saccharomyces cerevisiae. Enzyme preparations containing beta-glucanase activity (Zymolyase, Glucanex, and Finizym 250L) allowed a better extraction yield compared to that of dithiothreitol (DTT) and EDTA. The yeast extracts were only soluble in part in wine. The wine-soluble fraction (WSF) of the five extracts, differing in both protein and sugar contents, when added in increasing amounts to white wine differently affected protein haze formation, as determined by the heat test, giving dose/response curves of different shapes. The curves obtained with the WSF derived from DDT and Zymolyase extracts showed a plateau value corresponding to 90% and 80% of wine haze reduction, respectively. In contrast, addition of the WSF derived from the other extracts resulted in increased turbidity with respect to the original wine. The mannoproteins (MP), isolated from each yeast extract by Concanavalin-A chromatography, gave dose/response curves showing shapes more similar among them than those obtained with the whole WSFs. The best wine stabilization was obtained with the MP of the DTT and Zymolyase extracts. The supernatants obtained after heating the MP of the different extracts were also tested. The stabilizing effect of the heat-stable MP (HSMP) was always larger than that of the corresponding total (un-heated) MP. The HSMP obtained starting from the DTT and Zymolyase extracts showed the best haze-protecting effect, which was, however, lower than that obtained with their corresponding WSF. This result suggests that wine protein stabilization by compounds of the yeast cell wall could be related, in addition to the action of the MP, also to the presence of other substances of different nature.

  16. Endolysosomal membrane trafficking complexes drive nutrient-dependent TORC1 signaling to control cell growth in Saccharomyces cerevisiae.

    PubMed

    Kingsbury, Joanne M; Sen, Neelam D; Maeda, Tatsuya; Heitman, Joseph; Cardenas, Maria E

    2014-04-01

    The rapamycin-sensitive and endomembrane-associated TORC1 pathway controls cell growth in response to nutrients in eukaryotes. Mutations in class C Vps (Vps-C) complexes are synthetically lethal with tor1 mutations and confer rapamycin hypersensitivity in Saccharomyces cerevisiae, suggesting a role for these complexes in TORC1 signaling. Vps-C complexes are required for vesicular trafficking and fusion and comprise four distinct complexes: HOPS and CORVET and their minor intermediaries (i)-CORVET and i-HOPS. We show that at least one Vps-C complex is required to promote TORC1 activity, with the HOPS complex having the greatest input. The vps-c mutants fail to recover from rapamycin-induced growth arrest and show low levels of TORC1 activity. TORC1 promotes cell growth via Sch9, a p70(S6) kinase ortholog. Constitutively active SCH9 or hyperactive TOR1 alleles restored rapamycin recovery and TORC1 activity of vps-c mutants, supporting a role for the Vps-C complexes upstream of TORC1. The EGO GTPase complex Exit from G0 Complex (EGOC) and its homologous Rag-GTPase complex convey amino acid signals to TORC1 in yeast and mammals, respectively. Expression of the activated EGOC GTPase subunits Gtr1(GTP) and Gtr2(GDP) partially suppressed vps-c mutant rapamycin recovery defects, and this suppression was enhanced by increased amino acid concentrations. Moreover, vps-c mutations disrupted EGOC-TORC1 interactions. TORC1 defects were more severe for vps-c mutants than those observed in EGOC mutants. Taken together, our results support a model in which distinct endolysosomal trafficking Vps-C complexes promote rapamycin-sensitive TORC1 activity via multiple inputs, one of which involves maintenance of amino acid homeostasis that is sensed and transmitted to TORC1 via interactions with EGOC.

  17. A combined cell-free transcription-translation system from Saccharomyces cerevisiae for rapid and robust protein synthe.

    PubMed

    Gan, Rui; Jewett, Michael C

    2014-05-01

    Cell-free protein synthesis (CFPS) provides a valuable platform for understanding, using, and expanding the capabilities of the translation apparatus. For example, high-throughput CFPS is helping to address the increasing discrepancy between genome sequence data and their translation products. Here, we report the development of a combined cell-free transcription-translation (Tx/Tl) system from Saccharomyces cerevisiae that is suitable for such efforts. First, we show the ability to enable translation initiation in a cap-independent manner. The performance of various genetic elements was assessed, including 5'-UTR, 3'-UTR, and length of poly(A) tail. A specific vector harboring the 5'-UTR fragment of the Ω sequence from the tobacco mosaic virus and a poly(A) tail of 50 nucleotides led to optimal performance. Second, we developed a simple, two-step polymerase chain reaction (PCR) method for high-throughput production of linear templates for yeast CFPS. This procedure allows all functional elements needed for Tx/Tl to be added to an open-reading frame directly by overlap extension PCR. Our two-step PCR method was successfully applied to three reporter proteins: luciferase, green fluorescence protein, and chloramphenicol acetyl transferase, yielding 7 to 12.5 μg mL-1 active protein after 1.5-h batch reactions. Surprisingly, the linear templates outperformed plasmid DNA by up to 60%. Hence, the presented CFPS method has the potential to rapidly prepare tens to thousands of DNA templates without time-consuming cloning work. Further, it holds promise for fast and convenient optimization of expression constructs, study of internal ribosome entry site, and production of protein libraries for genome-scale studies. See accompanying commentary by Russ and Dueber DOI: 10.1002/biot.201400071.

  18. Water metabolism in cells of Saccharomyces cerevisiae of races Y-3137 and Y-3327, according to pulsed-field gradient NMR data

    NASA Astrophysics Data System (ADS)

    Avilova, I. A.; Vasil'ev, S. G.; Rimareva, L. V.; Serba, E. M.; Volkova, L. D.; Volkov, V. I.

    2015-04-01

    The self-diffusion of water in cells of Saccharomyces cerevisiae of races Y-3137 and Y-3327 is studied by means of pulsed-field gradient (PFG) NMR. Three types of water are detected that differ by their self-diffusion coefficients (SDCs): free, intercellular, and intracellular. It is found that the self-diffusion of intercellular and intracellular water is restricted. The size and permeability of the cells of yeasts with different cultivation times (24 and 48 h) is determined by analyzing the dependences of the self-diffusion coefficients of intracellular water on the interval between pulses of the magnetic field gradient.

  19. Tracking heavy water (D2O) incorporation for identifying and sorting active microbial cells.

    PubMed

    Berry, David; Mader, Esther; Lee, Tae Kwon; Woebken, Dagmar; Wang, Yun; Zhu, Di; Palatinszky, Marton; Schintlmeister, Arno; Schmid, Markus C; Hanson, Buck T; Shterzer, Naama; Mizrahi, Itzhak; Rauch, Isabella; Decker, Thomas; Bocklitz, Thomas; Popp, Jürgen; Gibson, Christopher M; Fowler, Patrick W; Huang, Wei E; Wagner, Michael

    2015-01-13

    Microbial communities are essential to the function of virtually all ecosystems and eukaryotes, including humans. However, it is still a major challenge to identify microbial cells active under natural conditions in complex systems. In this study, we developed a new method to identify and sort active microbes on the single-cell level in complex samples using stable isotope probing with heavy water (D2O) combined with Raman microspectroscopy. Incorporation of D2O-derived D into the biomass of autotrophic and heterotrophic bacteria and archaea could be unambiguously detected via C-D signature peaks in single-cell Raman spectra, and the obtained labeling pattern was confirmed by nanoscale-resolution secondary ion MS. In fast-growing Escherichia coli cells, label detection was already possible after 20 min. For functional analyses of microbial communities, the detection of D incorporation from D2O in individual microbial cells via Raman microspectroscopy can be directly combined with FISH for the identification of active microbes. Applying this approach to mouse cecal microbiota revealed that the host-compound foragers Akkermansia muciniphila and Bacteroides acidifaciens exhibited distinctive response patterns to amendments of mucin and sugars. By Raman-based cell sorting of active (deuterated) cells with optical tweezers and subsequent multiple displacement amplification and DNA sequencing, novel cecal microbes stimulated by mucin and/or glucosamine were identified, demonstrating the potential of the nondestructive D2O-Raman approach for targeted sorting of microbial cells with defined functional properties for single-cell genomics.

  20. Effect of HXT1 and HXT7 hexose transporter overexpression on wild-type and lactic acid producing Saccharomyces cerevisiae cells

    PubMed Central

    2010-01-01

    Background Since about three decades, Saccharomyces cerevisiae can be engineered to efficiently produce proteins and metabolites. Even recognizing that in baker's yeast one determining step for the glucose consumption rate is the sugar uptake, this fact has never been conceived to improve the metabolite(s) productivity. In this work we compared the ethanol and/or the lactic acid production from wild type and metabolically engineered S. cerevisiae cells expressing an additional copy of one hexose transporter. Results Different S. cerevisiae strains (wild type and metabolically engineered for lactic acid production) were transformed with the HXT1 or the HXT7 gene encoding for hexose transporters. Data obtained suggest that the overexpression of an Hxt transporter may lead to an increase in glucose uptake that could result in an increased ethanol and/or lactic acid productivities. As a consequence of the increased productivity and of the reduced process timing, a higher production was measured. Conclusion Metabolic pathway manipulation for improving the properties and the productivity of microorganisms is a well established concept. A high production relies on a multi-factorial system. We showed that by modulating the first step of the pathway leading to lactic acid accumulation an improvement of about 15% in lactic acid production can be obtained in a yeast strain already developed for industrial application. PMID:20214823

  1. Cytoplasmic proteasomes are not indispensable for cell growth in Saccharomyces cerevisiae

    SciTech Connect

    Tsuchiya, Hikaru; Arai, Naoko; Tanaka, Keiji Saeki, Yasushi

    2013-07-05

    Highlights: •We succeeded to control the proteasome localization by the anchor-away technique. •Nuclear proteasome-depleted cells showed a lethal phenotype. •Cytoplasmic proteasomes are not indispensable for cell growth in dividing cells. -- Abstract: The 26S proteasome is an essential protease complex responsible for the degradation of ubiquitinated proteins in eukaryotic cells. In rapidly proliferating yeast cells, proteasomes are mainly localized in the nucleus, but the biological significance of the proteasome localization is still unclear. In this study, we investigated the relationship between the proteasome localization and the functions by the anchor-away technique, a ligand-dependent sequestration of a target protein into specific compartment(s). Anchoring of the proteasome to the plasma membrane or the ribosome resulted in conditional depletion of the nuclear proteasomes, whereas anchoring to histone resulted in the proteasome sequestration into the nucleus. We observed that the accumulation of ubiquitinated proteins in all the proteasome-targeted cells, suggesting that both the nuclear and cytoplasmic proteasomes have proteolytic functions and that the ubiquitinated proteins are produced and degraded in each compartment. Consistent with previous studies, the nuclear proteasome-depleted cells exhibited a lethal phenotype. In contrast, the nuclear sequestration of the proteasome resulted only in a mild growth defect, suggesting that the cytoplasmic proteasomes are not basically indispensable for cell growth in rapidly growing yeast cells.

  2. Continuous power generation and microbial community structure of the anode biofilms in a three-stage microbial fuel cell system.

    PubMed

    Chung, Kyungmi; Okabe, Satoshi

    2009-07-01

    A mediator-less three-stage two-chamber microbial fuel cell (MFC) system was developed and operated continuously for more than 1.5 years to evaluate continuous power generation while treating artificial wastewater containing glucose (10 mM) concurrently. A stable power density of 28 W/m(3) was attained with an anode hydraulic retention time of 4.5 h and phosphate buffer as the cathode electrolyte. An overall dissolved organic carbon removal ratio was about 85%, and coulombic efficiency was about 46% in this MFC system. We also analyzed the microbial community structure of anode biofilms in each MFC. Since the environment in each MFC was different due to passing on the products to the next MFC in series, the microbial community structure was different accordingly. The anode biofilm in the first MFC consisted mainly of bacteria belonging to the Gammaproteobacteria, identified as Aeromonas sp., while the Firmicutes dominated the anode biofilms in the second and third MFCs that were mainly fed with acetate. Cyclic voltammetric results supported the presence of a redox compound(s) associated with the anode biofilm matrix, rather than mobile (dissolved) forms, which could be responsible for the electron transfer to the anode. Scanning electron microscopy revealed that the anode biofilms were comprised of morphologically different cells that were firmly attached on the anode surface and interconnected each other with anchor-like filamentous appendages, which might support the results of cyclic voltammetry.

  3. Analysis of long-term performance and microbial community structure in bio-cathode microbial desalination cells.

    PubMed

    Zhang, Huichao; Wen, Qinxue; An, Zhongyi; Chen, Zhiqiang; Nan, Jun

    2016-03-01

    A microbial desalination cell (MDC) could desalinate salt water without energy consumption and simultaneously generate bioenergy. Compared with an abiotic cathode MDC, an aerobic bio-cathode MDC is more sustainable and is less expensive to operate. In this study, the long-term operation (5500 h) performance of a bio-cathode MDC was investigated in which the power density, Coulombic efficiency, and salt removal rate were decreased by 71, 44, and 27 %, respectively. The primary reason for the system performance decrease was biofouling on the membranes, which increased internal resistance and reduced the ionic transfer and energy conversion efficiency. Changing membranes was an effective method to recover the MDC performance. The microbial community diversity in the MDC anode was low compared with that of the reported microbial fuel cell (MFC), while the abundance of Proteobacteria was 30 % higher. The content of Planctomycetes in the cathode biofilm sample was much higher than that in biofouling on the cation exchange membrane (CEM), indicating that Planctomycetes were relevant to cathode oxygen reduction.

  4. Method for immobilizing microbial cells on gel surface for dynamic AFM studies.

    PubMed Central

    Gad, M; Ikai, A

    1995-01-01

    The processes of cell growth and budding of the yeast cells Saccharomyces cerevisiae, which were gently immobilized on 3% agar and submerged in culture medium, were successfully imaged with an atomic force microscope for 6-7 h. Similar experiments on chemically fixed cells did not detect any appreciable change in their appearance except in a few scannings at the very beginning, indicating that the dissolution of agar and/or scraping of its surface by the scanning tip, if any, did not significantly interfere with the images taken thereafter. The increment in the height of many of the untreated cells, accompanied by their lateral enlargement, was taken as an indication of successful imaging of the growth process of yeast cells, together with an image of a growing daughter cell attached to its mother cell. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 FIGURE 7 FIGURE 8 PMID:8599630

  5. Microbial community analysis in a long-term membrane-less microbial electrolysis cell with hydrogen and methane production.

    PubMed

    Rago, Laura; Ruiz, Yolanda; Baeza, Juan A; Guisasola, Albert; Cortés, Pilar

    2015-12-01

    A single-chamber microbial electrolysis cell (MEC) aiming at hydrogen production with acetate as sole carbon source failed due to methanogenesis build-up despite the significant amount of 2-bromoethanesulfonate (BES) dosage, 50 mM. Specific batch experiments and a thorough microbial community analysis, pyrosequencing and qPCR, of cathode, anode and medium were performed to understand these observations. The experimental data rebuts different hypothesis and shows that methanogenesis at high BES concentration was likely due to the capacity of some Archaea (hydrogen-oxidizing genus Methanobrevibacter) to resist high BES concentration up to 200 mM. Methanobrevibacter, of the Methanobacteriales order, represented almost the 98% of the total Archaea in the cathode whereas Geobacter was highly abundant in the anode (72% of bacteria). Moreover, at higher BES concentration (up to 200 mM), methanogenesis activity decreased resulting in an increase of homoacetogenic activity, which challenged the performance of the MEC for H2 production.

  6. Arabidopsis Bax Inhibitor-1 inhibits cell death induced by pokeweed antiviral protein in Saccharomyces cerevisiae

    PubMed Central

    Çakır, Birsen; Tumer, Nilgun E.

    2015-01-01

    Apoptosis is an active form of programmed cell death (PCD) that plays critical roles in the development, differentiation and resistance to pathogens in multicellular organisms. Ribosome inactivating proteins (RIPs) are able to induce apoptotic cell death in mammalian cells. In this study, using yeast as a model system, we showed that yeast cells expressing pokeweed antiviral protein (PAP), a single-chain ribosome-inactivating protein, exhibit apoptotic-like features, such as nuclear fragmentation and ROS production. We studied the interaction between PAP and AtBI-1 (Arabidopsis thaliana Bax Inhibitor-1), a plant anti-apoptotic protein, which inhibits Bax induced cell death. Cells expressing PAP and AtBI-1 were able to survive on galactose media compared to PAP alone, indicating a reduction in the cytotoxicity of PAP in yeast. However, PAP was able to depurinate the ribosomes and to inhibit total translation in the presence of AtBI-1. A C-terminally deleted AtBI-1 was able to reduce the cytotoxicity of PAP. Since anti-apoptotic proteins form heterodimers to inhibit the biological activity of their partners, we used a co-immunoprecipitation assay to examine the binding of AtBI-1 to PAP. Both full length and C-terminal deleted AtBI-1 were capable of binding to PAP. These findings indicate that PAP induces cell death in yeast and AtBI-1 inhibits cell death induced by PAP without affecting ribosome depurination and translation inhibition. PMID:28357275

  7. Stackable and submergible microbial fuel cell modules for wastewater treatment.

    PubMed

    Kim, Minsoo; Cha, Jaehwan; Yu, Jaecheul; Kim, Changwon

    2016-08-01

    The stackable and submergible microbial fuel cell (SS-MFC) system was fabricated consisting of three MFC modules (#1, #2 and #3) that were immersed in an anaerobic tank as a 30 L anode compartment. Each module consisted of the anion exchange membrane-membrane electrode assembly (A-MEA) and cation exchange membrane-MEA (C-MEA). Two MEAs shared a cathode compartment in the module and the three modules shared a anode compartment The SS-MFC system was operated with two phase. After batch feeding (phase I), the system was operated under continuous mode (phase II) with different organic concentrations (from 50 to 1000 mg/L) and different hydraulic retention times (HRT; from 3.4 to 7.2 h). The SS-MFC system successfully produced a stable voltage. A-MEA generated a lower power density than the C-MEA because of the former's high activation and resistance loss. C-MEA showed a higher average maximum power density (3.16 W/m(3)) than A-MEA (2.82 W/m(3)) at 70 mL/min (HRT of 7.2 h). The current density increased as the organic concentration was increased from 70 to 1000 mg/L in a manner consistent with Monod kinetics. When the HRT was increased from 3.4 to 7.2 h, the power densities of the C-MEAs increased from 34.3-40.9 to 40.7-45.7 mW/m(2), but those of the A-MEAs decreased from 25.3-48.0 to 27.7-40.9 mW/m(2). Although power generation was affected by HRT, organic concentrations, and separator types, the proposed SS-MFC modules can be applied to existing wastewater treatment plants.

  8. Power generation from furfural using the microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Luo, Yong; Liu, Guangli; Zhang, Renduo; Zhang, Cuiping

    Furfural is a typical inhibitor in the ethanol fermentation process using lignocellulosic hydrolysates as raw materials. In the literature, no report has shown that furfural can be utilized as the fuel to produce electricity in the microbial fuel cell (MFC), a device that uses microbes to convert organic compounds to generate electricity. In this study, we demonstrated that electricity was successfully generated using furfural as the sole fuel in both the ferricyanide-cathode MFC and the air-cathode MFC. In the ferricyanide-cathode MFC, the maximum power densities reached 45.4, 81.4, and 103 W m -3, respectively, when 1000 mg L -1 glucose, a mixture of 200 mg L -1 glucose and 5 mM furfural, and 6.68 mM furfural were used as the fuels in the anode solution. The corresponding Coulombic efficiencies (CE) were 4.0, 7.1, and 10.2% for the three treatments, respectively. For pure furfural as the fuel, the removal efficiency of furfural reached up to 95% within 12 h. In the air-cathode MFC using 6.68 mM furfural as the fuel, the maximum values of power density and CE were 361 mW m -2 (18 W m -3) and 30.3%, respectively, and the COD removal was about 68% at the end of the experiment (about 30 h). Increase in furfural concentrations from 6.68 to 20 mM resulted in increase in the maximum power densities from 361 to 368 mW m -2, and decrease in CEs from 30.3 to 20.6%. These results indicated that some toxic and biorefractory organics such as furfural might still be suitable resources for electricity generation using the MFC technology.

  9. Hydrogen production from proteins via electrohydrogenesis in microbial electrolysis cells.

    PubMed

    Lu, Lu; Xing, Defeng; Xie, Tianhui; Ren, Nanqi; Logan, Bruce E

    2010-08-15

    Microorganisms can produce hydrogen gas (H(2)) at high rates by fermentation of carbohydrates, but not from proteins. However, it is possible to produce H(2) at high rates and yields from proteins by electrohydrogenesis in microbial electrolysis cells (MECs). Hydrogen gas was generated using bovine serum albumin (BSA, 700 mg/L) in a single-chamber MEC at a rate of Q=0.42+/-0.07 m(3)/m(3)/day and a yield of Y(H2) = 21.0 +/- 5.0 mmol-H2/g-COD, with an energy recovery (relative to electrical input) of eta(E)=75+/-12% (applied voltage of 0.6 V). Hydrogen production was substantially reduced using a complex protein (peptone) under the same conditions, to Q=0.05+/-0.01 m(3)/m(3)/day, YH2 = 2.6 +/- 0.1 mmol-H2/g-COD, and eta(E)=14+/-3%. There was good removal of organic matter for both substrates in terms of either protein (87+/-6 -97 +/-2%) or total COD (86+/-2 - 91+/-2%). Electron recycling likely occurred as Coulombic efficiencies exceeded 100% using BSA. The use of a two-chamber design, with either a CEM or AEM membrane, reduced the hydrogen production rate, but did not appreciably affect the hydrogen yield or energy efficiency. When an MEC was first acclimated to acetate, and then switched to BSA, performance was substantially reduced and was similar to that obtained using peptone. These results demonstrate that electrohydrogenesis can be used to produce H(2) from proteins, and it can also be used as a method for treatment of protein-containing wastewaters.

  10. Electricity production from twelve monosaccharides using microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Catal, Tunc; Li, Kaichang; Bermek, Hakan; Liu, Hong

    Direct generation of electricity from monosaccharides of lignocellulosic biomass was examined using air cathode microbial fuel cells (MFCs). Electricity was generated from all carbon sources tested, including six hexoses (D-glucose, D-galactose, D(-)-levulose (fructose), L-fucose, L-rhamnose, and D-mannose), three pentoses (D-xylose, D(-)-arabinose, and D(-)-ribose), two uronic acids (D-galacturonic acid and D-glucuronic acid) and one aldonic acid (D-gluconic acid). The mixed bacterial culture, which was enriched using acetate as a carbon source, adapted well to all carbon sources tested, although the adaptation times varied from 1 to 70 h. The maximum power density obtained from these carbon sources ranged from 1240 ± 10 to 2770 ± 30 mW m -2 at current density range of 0.76-1.18 mA cm -2. D-Mannose resulted in the lowest maximum power density, whereas D-glucuronic acid generated the highest one. Coulombic efficiency ranged from 21 to 37%. For all carbon sources tested, the relationship between the maximum voltage output and the substrate concentration appeared to follow saturation kinetics at 120 Ω external resistance. The estimated maximum voltage output ranged between 0.26 and 0.44 V and half-saturation kinetic constants ranged from 111 to 725 mg L -1. Chemical oxygen demand (COD) removal was over 80% for all carbon sources tested. Results from this study indicated that lignocellulosic biomass-derived monosaccharides might be a suitable resource for electricity generation using MFC technology.

  11. Bioconversion of cellulose into electrical energy in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Rismani-Yazdi, Hamid

    In microbial fuel cells (MFCs), bacteria generate electricity by mediating the oxidation of organic compounds and transferring the resulting electrons to an anode electrode. The first objective of this study was to test the possibility of generating electricity with rumen microorganisms as biocatalysts and cellulose as the electron donor in two-compartment MFCs. Maximum power density reached 55 mW/m2 (1.5 mA, 313 mV) with cellulose as the electron donor. Cellulose hydrolysis and electrode reduction were shown to support the production of current. The electrical current was sustained for over two months with periodic cellulose addition. Clarified rumen fluid and a soluble carbohydrate mixture, serving as the electron donors, could also sustain power output. The second objective was to analyze the composition of the bacterial communities enriched in the cellulose-fed MFCs. Denaturing gradient gel electrophoresis of PCR amplified 16S rRNA genes revealed that the microbial communities differed when different substrates were used in the MFCs. The anode-attached and the suspended consortia were shown to be different within the same MFC. Cloning and analysis of 16S rRNA gene sequences indicated that the most predominant bacteria in the anode-attached consortia were related to Clostridium spp., while Comamonas spp. was abundant in the suspended consortia. The external resistance affects the characteristic outputs of MFCs by controlling the flow of electrons from the anode to the cathode. The third objective of this study was to determine the effect of various external resistances on power output and coulombic efficiency of cellulose-fed MFCs. Four external resistances (20, 249, 480, and 1000 ohms) were tested with a systematic approach of operating parallel MFCs independently at constant circuit loads for three months. A maximum power density of 66 mWm-2 was achieved by MFCs with 20 ohms circuit load, while MFCs with 249, 480 and1000 ohms external resistances produced 57

  12. Acrolein-Induced Oxidative Stress and Cell Death Exhibiting Features of Apoptosis in the Yeast Saccharomyces cerevisiae Deficient in SOD1.

    PubMed

    Kwolek-Mirek, Magdalena; Zadrąg-Tęcza, Renata; Bednarska, Sabina; Bartosz, Grzegorz

    2015-04-01

    The yeast Saccharomyces cerevisiae is a useful eukaryotic model to study the toxicity of acrolein, an important environmental toxin and endogenous product of lipid peroxidation. The study was aimed at elucidation of the cytotoxic effect of acrolein on the yeast deficient in SOD1, Cu, Zn-superoxide dismutase which is hypersensitive to aldehydes. Acrolein generated within the cell from its precursor allyl alcohol caused growth arrest and cell death of the yeast cells. The growth inhibition involved an increase in production of reactive oxygen species and high level of protein carbonylation. DNA condensation and fragmentation, exposition of phosphatidylserine at the cell surface as well as decreased dynamic of actin microfilaments and mitochondria disintegration point to the induction of apoptotic-type cell death besides necrotic cell death.

  13. Searches for Microbial Cells with Fluorescence Loggers with Single-cell Sensitivity

    NASA Astrophysics Data System (ADS)

    Price, P. B.; Rohde, R. A.; Bay, R. C.

    2007-12-01

    Two known habitats for microbial metabolism in ice are surfaces of mineral grains and liquid veins along three- grain boundaries. Several problems suggest the need for a third habitat: veins usually contain toxic liquid; some microorganisms are too large to fit into a vein; veins may not be present at all depths; and the oxygen concentration in veins does not permit the coexistence of both strict anaerobes and aerobes in the same region. We show that a more general habitat avoids these problems. Isolated microbes frozen in ice and not in contact with a vein or grain can metabolize by redox reactions with dissolved small molecules diffusing through the ice lattice. The two requirements are that the gaseous reactants have sufficiently high equilibrium concentrations and diffusion coefficients to provide enough metabolic energy to repair macromolecular damage as it occurs. Molecules with less than ~6 atoms (e.g., H2, O2, N2¬, CO, CO2, CH4, H2S, NH3, HNO3, HCHO, and HCOOH) have values of diffusion coefficient D(T) that exceed ~10- 15 m2 s-1, which is sufficient to sustain microbial life in ice. For terrestrial environments, we show that there is an adequate supply of such molecules diffusing throughout deep glacial ice to sustain metabolism for millions of years. Our recent noninvasive observations of ice cores from GISP2 and WAIS Divide provide evidence for this habitat. Using scanning fluorimetry to map proteins (a proxy for cells) and F420 (a proxy for methanogens) in ice cores, we find isolated spikes of fluorescence consistent with as few as one microbial cell in a volume 0.16 microliter with the protein mapper and in 1.9 microliter with the methanogen mapper. With such precise localization one could use a nanomanipulator to extract single cells for molecular identification. Low- power, miniaturized versions of these instruments could search for single cells in subglacial lakes, Martian ice- rich permafrost, and Europan ice.

  14. Mitochondrial inheritance is delayed in Saccharomyces cerevisiae cells lacking the serine/threonine phosphatase PTC1.

    PubMed

    Roeder, A D; Hermann, G J; Keegan, B R; Thatcher, S A; Shaw, J M

    1998-04-01

    In wild-type yeast mitochondrial inheritance occurs early in the cell cycle concomitant with bud emergence. Cells lacking the PTC1 gene initially produce buds without a mitochondrial compartment; however, these buds later receive part of the mitochondrial network from the mother cell. Thus, the loss of PTC1 causes a delay, but not a complete block, in mitochondrial transport. PTC1 encodes a serine/threonine phosphatase in the high-osmolarity glycerol response (HOG) pathway. The mitochondrial inheritance delay in the ptc1 mutant is not attributable to changes in intracellular glycerol concentrations or defects in the organization of the actin cytoskeleton. Moreover, epistasis experiments with ptc1delta and mutations in HOG pathway kinases reveal that PTC1 is not acting through the HOG pathway to control the timing of mitochondrial inheritance. Instead, PTC1 may be acting either directly or through a different signaling pathway to affect the mitochondrial transport machinery in the cell. These studies indicate that the timing of mitochondrial transport in wild-type cells is genetically controlled and provide new evidence that mitochondrial inheritance does not depend on a physical link between the mitochondrial network and the incipient bud site.

  15. Enantioselective bioconversion using Escherichia coli cells expressing Saccharomyces cerevisiae reductase and Bacillus subtilis glucose dehydrogenase.

    PubMed

    Park, Hyun Joo; Jung, Jihye; Choi, Hyejeong; Uhm, Ki-Nam; Kim, Hyung Kwoun

    2010-09-01

    Ethyl (R, S)-4-chloro-3-hydroxybutanoate (ECHB) is a useful chiral building block for the synthesis of L-carnitine and hypercholesterolemia drugs. The yeast reductase, YOL151W (GenBank locus tag), exhibits an enantioselective reduction activity, converting ethyl-4-chlorooxobutanoate (ECOB) exclusively into (R)-ECHB. YOL151W was generated in Escherichia coli cells and purified via Ni- NTA and desalting column chromatography. It evidenced an optimum temperature of 45 degrees C and an optimum pH of 6.5-7.5. Bacillus subtilis glucose dehydrogenase (GDH) was also expressed in Escherichia coli, and was used for the recycling of NADPH, required for the reduction reaction. Thereafter, Escherichia coli cells co-expressing YOL151W and GDH were constructed. After permeablization treatment, the Escherichia coli whole cells were utilized for ECHB synthesis. Through the use of this system, the 30 mM ECOB substrate could be converted to (R)-ECHB.

  16. Set anode potentials affect the electron fluxes and microbial community structure in propionate-fed microbial electrolysis cells.

    PubMed

    Hari, Ananda Rao; Katuri, Krishna P; Logan, Bruce E; Saikaly, Pascal E

    2016-12-09

    Anode potential has been shown to be a critical factor in the rate of acetate removal in microbial electrolysis cells (MECs), but studies with fermentable substrates and set potentials are lacking. Here, we examined the impact of three different set anode potentials (SAPs; -0.25, 0, and 0.25 V vs. standard hydrogen electrode) on the electrochemical performance, electron flux to various sinks, and anodic microbial community structure in two-chambered MECs fed with propionate. Electrical current (49-71%) and CH4 (22.9-41%) were the largest electron sinks regardless of the potentials tested. Among the three SAPs tested, 0 V showed the highest electron flux to electrical current (71 ± 5%) and the lowest flux to CH4 (22.9 ± 1.2%). In contrast, the SAP of -0.25 V had the lowest electron flux to current (49 ± 6%) and the highest flux to CH4 (41.1 ± 2%). The most dominant genera detected on the anode of all three SAPs based on 16S rRNA gene sequencing were Geobacter, Smithella and Syntrophobacter, but their relative abundance varied among the tested SAPs. Microbial community analysis implies that complete degradation of propionate in all the tested SAPs was facilitated by syntrophic interactions between fermenters and Geobacter at the anode and ferementers and hydrogenotrophic methanogens in suspension.

  17. Set anode potentials affect the electron fluxes and microbial community structure in propionate-fed microbial electrolysis cells

    PubMed Central

    Hari, Ananda Rao; Katuri, Krishna P.; Logan, Bruce E.; Saikaly, Pascal E.

    2016-01-01

    Anode potential has been shown to be a critical factor in the rate of acetate removal in microbial electrolysis cells (MECs), but studies with fermentable substrates and set potentials are lacking. Here, we examined the impact of three different set anode potentials (SAPs; −0.25, 0, and 0.25 V vs. standard hydrogen electrode) on the electrochemical performance, electron flux to various sinks, and anodic microbial community structure in two-chambered MECs fed with propionate. Electrical current (49–71%) and CH4 (22.9–41%) were the largest electron sinks regardless of the potentials tested. Among the three SAPs tested, 0 V showed the highest electron flux to electrical current (71 ± 5%) and the lowest flux to CH4 (22.9 ± 1.2%). In contrast, the SAP of −0.25 V had the lowest electron flux to current (49 ± 6%) and the highest flux to CH4 (41.1 ± 2%). The most dominant genera detected on the anode of all three SAPs based on 16S rRNA gene sequencing were Geobacter, Smithella and Syntrophobacter, but their relative abundance varied among the tested SAPs. Microbial community analysis implies that complete degradation of propionate in all the tested SAPs was facilitated by syntrophic interactions between fermenters and Geobacter at the anode and ferementers and hydrogenotrophic methanogens in suspension. PMID:27934925

  18. Response of microbial community structure to pre-acclimation strategies in microbial fuel cells for domestic wastewater treatment.

    PubMed

    Park, Younghyun; Cho, Hyunwoo; Yu, Jaechul; Min, Booki; Kim, Hong Suck; Kim, Byung Goon; Lee, Taeho

    2017-02-27

    Microbial community structures and performance of air-cathode microbial fuel cells (MFCs) inoculated with activated sludge from domestic wastewater were investigated to evaluate the effects of three substrate pre-acclimation strategies: 1, serial pre-acclimation with acetate and glucose before supplying domestic wastewater; 2, one step pre-acclimation with acetate before supplying domestic wastewater; and 3, direct supply of domestic wastewater without any pre-acclimation. Strategy 1 showed much higher current generation (1.4mA) and Coulombic efficiency (33.5%) than strategies 2 (0.7mA and 9.4%) and 3 (0.9mA and 10.3%). Pyrosequencing showed that microbial communities were significantly affected by pre-acclimation strategy. Although Proteobacteria was the dominant phylum with all strategies, Actinobacteria was abundant when MFCs were pre-acclimated with glucose after acetate. Not only anode-respiring bacteria (ARB) in the genus Geobacter but also non-ARB belonging to the family Anaerolinaceae seemed to play important roles in air-cathode MFCs to produce electricity from domestic wastewater.

  19. The fungicide Mancozeb induces metacaspase-dependent apoptotic cell death in Saccharomyces cerevisiae BY4741.

    PubMed

    Scariot, F J; Jahn, L M; Maianti, J P; Delamare, A P L; Echeverrigaray, S

    2016-07-01

    Mancozeb (MZ), a mixture of ethylene-bis-dithiocarbamate manganese and zinc salts, is one of the most widely used fungicides in agriculture. Toxicologic studies in mammals and mammalian cells indicate that this fungicide can cause neurological and cytological disorders, putatively associated with pro-oxidant and apoptotic effects. Yeast adaptation to sub-inhibitory concentrations of MZ has been correlated with oxidative response, proteins degradation, and energy metabolism, and its main effect on yeast has been attributed to its high reactivity with thiol groups in proteins. Herein, we show that acute MZ treatments on aerobic exponentially growing yeast of wild type (BY4741) and deletion mutant strains, coupled with multiplex flow cytometry analysis, conclusively demonstrated that MZ displays the typical features of pro-oxidant activity on Saccharomyces, elevating mitochondrial ROS, and causing hyper-polarization of mitochondrial membranes leading to apoptosis. A drastic reduction of cellular viability associated with the maintenance of cell membrane integrity, as well as phosphatidyl serine externalization on yeast cells exposed to MZ, also supports an apoptotic mode of action. Moreover, abrogation of the apoptotic response in yca1 deficient mutants indicates that metacaspase-1 is involved in the programmed cell death mechanism induced by MZ in yeast.

  20. Pyrosequencing reveals highly diverse microbial communities in microbial electrolysis cells involved in enhanced H2 production from waste activated sludge.

    PubMed

    Lu, Lu; Xing, Defeng; Ren, Nanqi

    2012-05-01

    Renewable H(2) production from a plentiful biomass, waste activated sludge (WAS), can be achieved by fermentation, but the yields are low. The use of a microbial electrolysis cell (MEC) can increase the H(2) production yields to several times that of fermentation. We have proved that the enhancement of H(2) production was due to the ability of MECs to use a wider range of organic matter in WAS than in fermentation. To support this result strongly, we here investigated the microbial community structures of WAS and anode biofilms in WAS-fed MECs. A pyrosequencing analysis based on the bacterial 16S rRNA gene showed that dominant populations in MECs were more diverse than those in WAS (inoculum and substrate) after enrichment, and there was a clear distinction between MECs and WAS in microbial community structure. Diverse acid-producing bacteria and exoelectrogens (predominance of Geobacter) were detected in MECs but they were only rarely found in WAS. It has been reported that these acid-producing bacteria can ferment various sugars and amines with acetate, propionate, and butyrate as their major by-products. This was consistent with our chemical analyses. Detected exoelectrogens are known to use these organic acids (mainly acetate) and certain sugars to directly produce current for H(2) generation at the cathodes in the MECs. Using quantitative real-time PCR, we demonstrated that a consistent feed of alkaline-pretreated WAS containing large amounts of acetate led to a predominance of acetoclastic methanogens, while hydrogenotrophic methanogens were abundant in MECs fed both raw and alkaline-pretreated WAS. Syntrophic interactions between phylogenetically diverse microbial populations in anodophilic biofilms were found to drive the efficient cascade utilization of organic matter in WAS.

  1. Effects of yeast (Saccharomyces cerevisiae) cell components on growth performance, meat quality, and ileal mucosa development of broiler chicks.

    PubMed

    Zhang, A W; Lee, B D; Lee, S K; Lee, K W; An, G H; Song, K B; Lee, C H

    2005-07-01

    An experiment was conducted with 240, 1-d-old, male broilers to investigate the effects of Saccharomyces cerevisiae (SC) cell components on the growth performance, meat quality, and ileal mucosa development. There were 4 dietary treatments, each consisting of 6 replicates. Whole yeast (WY), SC extract (YE), and SC cell wall (CW) were added at 0.5, 0.3, and 0.3%, respectively, to the control starter and finisher diets. From 0 to 3 wk of age, a lower feed/gain ratio (P < or = 0.05) was observed with CW, whereas the WY-fed birds at 4 to 5 wk of age showed a lower feed/gain ratio compared with the control. From 0 to 5 wk of age, WY and CW gave higher BW gains than did the control. The shear force of raw drumstick decreased in the WY treatment relative to the control, and YE and CW treatments were intermediate. The shear forces in cooked breast and drumstick in treatments WY and YE decreased when compared with the control. The amount of 2-thiobarbituric acid-reactive substances (TBARS) in the breast meats of WY, YE, and CW were lower than the control at 10 d of incubation. In raw drumstick meats, TBARS values were lower in treatments WY and YE than that of the control at 6 and 10 d of incubation. At 10 d of incubation, skins from YE and CW treatments had lower TBARS values than did the control. Villus height was greater in WY and CW compared with those in control and YE. No differences were found in crypt depth among the 4 treatments. The villus height/ crypt depth ratios in WY and CW were greater than those of the control and YE. It could be concluded that dietary yeast components, such as WY or CW supplementation improved growth performance. Meat tenderness could be improved by the WY or YE. Both YE and CW had oxidation-reducing effects. Yeast cell wall may improve ileal villus development.

  2. Dimethyl sulfoxide elevates hydrogen peroxide-mediated cell death in Saccharomyces cerevisiae by inhibiting the antioxidant function of methionine sulfoxide reductase A.

    PubMed

    Kwak, Geun-Hee; Choi, Seung Hee; Kim, Hwa-Young

    2010-09-01

    Dimethyl sulfoxide (DMSO) can be reduced to dimethyl sulfide by MsrA, which stereospecifically catalyzes the reduction of methionine-S-sulfoxide to methionine. Our previous study showed that DMSO can competitively inhibit methionine sulfoxide reduction ability of yeast and mammalian MsrA in both in vitro and in vivo, and also act as a non-competitive inhibitor for mammalian MsrB2, specific for the reduction of methionine-R-sulfoxide, with lower inhibition effects. The present study investigated the effects of DMSO on the physiological antioxidant functions of methionine sulfoxide reductases. DMSO elevated hydrogen peroxide-mediated Saccharomyces cerevisiae cell death, whereas it protected human SK-Hep1 cells against oxidative stress. DMSO reduced the protein-carbonyl content in yeast cells in normal conditions, but markedly increased protein-carbonyl accumulation under oxidative stress. Using Msr deletion mutant yeast cells, we demonstrated the DMSO's selective inhibition of the antioxidant function of MsrA in S. cerevisiae, resulting in an increase in oxidative stress-induced cytotoxicity.

  3. The fraction of cells that resume growth after acetic acid addition is a strain-dependent parameter of acetic acid tolerance in Saccharomyces cerevisiae.

    PubMed

    Swinnen, Steve; Fernández-Niño, Miguel; González-Ramos, Daniel; van Maris, Antonius J A; Nevoigt, Elke

    2014-06-01

    High acetic acid tolerance of Saccharomyces cerevisiae is a relevant phenotype in industrial biotechnology when using lignocellulosic hydrolysates as feedstock. A screening of 38 S. cerevisiae strains for tolerance to acetic acid revealed considerable differences, particularly with regard to the duration of the latency phase. To understand how this phenotype is quantitatively manifested, four strains exhibiting significant differences were studied in more detail. Our data show that the duration of the latency phase is primarily determined by the fraction of cells within the population that resume growth. Only this fraction contributed to the exponential growth observed after the latency phase, while all other cells persisted in a viable but non-proliferating state. A remarkable variation in the size of the fraction was observed among the tested strains differing by several orders of magnitude. In fact, only 11 out of 10(7)  cells of the industrial bioethanol production strain Ethanol Red resumed growth after exposure to 157 mM acetic acid at pH 4.5, while this fraction was 3.6 × 10(6) (out of 10(7)  cells) in the highly acetic acid tolerant isolate ATCC 96581. These strain-specific differences are genetically determined and represent a valuable starting point to identify genetic targets for future strain improvement.

  4. Candidate regulatory sequence elements for cell cycle-dependent transcription in Saccharomyces cerevisiae.

    PubMed

    Wolfsberg, T G; Gabrielian, A E; Campbell, M J; Cho, R J; Spouge, J L; Landsman, D

    1999-08-01

    Recent developments in genome-wide transcript monitoring have led to a rapid accumulation of data from gene expression studies. Such projects highlight the need for methods to predict the molecular basis of transcriptional coregulation. A microarray project identified the 420 yeast transcripts whose synthesis displays cell cycle-dependent periodicity. We present here a statistical technique we developed to identify the sequence elements that may be responsible for this cell cycle regulation. Because most gene regulatory sites contain a short string of highly conserved nucleotides, any such strings that are involved in gene regulation will occur frequently in the upstream regions of the genes that they regulate, and rarely in the upstream regions of other genes. Our strategy therefore utilizes statistical procedures to identify short oligomers, five or six nucleotides in length, that are over-represented in upstream regions of genes whose expression peaks at the same phase of the cell cycle. We report, with a high level of confidence, that 9 hexamers and 12 pentamers are over-represented in the upstream regions of genes whose expression peaks at the early G(1), late G(1), S, G(2), or M phase of the cell cycle. Some of these sequence elements show a preference for a particular orientation, and others, through a separate statistical test, for a particular position upstream of the ATG start codon. The finding that the majority of the statistically significant sequence elements are located in late G(1) upstream regions correlates with other experiments that identified the late G(1)/early S boundary as a vital cell cycle control point. Our results highlight the importance of MCB, an element implicated previously in late G(1)/early S gene regulation, as most of the late G(1) oligomers contain the MCB sequence or variations thereof. It is striking that most MCB-like sequences localize to a specific region upstream of the ATG start codon. Additional sequences that we have

  5. Single cell and in vivo analyses elucidate the effect of xylC lactonase during production of D-xylonate in Saccharomyces cerevisiae.

    PubMed

    Nygård, Yvonne; Maaheimo, Hannu; Mojzita, Dominik; Toivari, Mervi; Wiebe, Marilyn; Resnekov, Orna; Gustavo Pesce, C; Ruohonen, Laura; Penttilä, Merja

    2014-09-01

    D-xylonate is a potential platform chemical which can be produced by engineered Saccharomyces cerevisiae strains. In order to address production constraints in more detail, we analysed the role of lactone ring opening in single cells and populations. Both D-xylono-γ-lactone and D-xylonate were produced when the Caulobacter crescentus xylB (D-xylose dehydrogenase) was expressed in S. cerevisiae, with or without co-expression of xylC (D-xylonolactonase), as seen by (1)H NMR. XylC facilitated rapid opening of the lactone and more D-xylonate was initially produced than in its absence. Using in vivo(1)H NMR analysis of cell extracts, culture media and intact cells we observed that the lactone and linear forms of D-xylonic acid were produced, accumulated intracellularly, and partially exported within 15-60min of D-xylose provision. During single-cell analysis of cells expressing the pH sensitive fluorescent probe pHluorin, pHluorin fluorescence was gradually lost from the cells during D-xylonate production, as expected for cells with decreasing intracellular pH. However, in the presence of D-xylose, only 9% of cells expressing xylB lost pHluorin fluorescence within 4.5h, whereas 99% of cells co-expressing xylB and xylC lost fluorescence, a large proportion of which also lost vitality, during this interval. Loss of vitality in the presence of D-xylose was correlated to the extracellular pH, but fluorescence was lost from xylB and xylC expressing cells regardless of the extracellular condition.

  6. Mitochondrial inheritance: cell cycle and actin cable dependence of polarized mitochondrial movements in Saccharomyces cerevisiae.

    PubMed

    Simon, V R; Karmon, S L; Pon, L A

    1997-01-01

    Asymmetric growth and division of budding yeast requires the vectorial transport of growth components and organelles from mother to daughter cells. Time lapse video microscopy and vital staining were used to study motility events which result in partitioning of mitochondria in dividing yeast. We identified four different stages in the mitochondrial inheritance cycle: (1) mitochondria align along the mother-bud axis prior to bud emergence in G1 phase, following polarization of the actin cytoskeleton; (2) during S phase, mitochondria undergo linear, continuous and polarized transfer from mother to bud; (3) during S and G2 phases, inherited mitochondria accumulate in the bud tip. This event occurs concomitant with accumulation of actin patches in this region; and (4) finally, during M phase prior to cytokinesis, mitochondria are released from the bud tip and redistribute throughout the bud. Previous studies showed that yeast mitochondria colocalize with actin cables and that isolated mitochondria contain actin binding and motor activities on their surface. We find that selective destabilization of actin cables in a strain lacking the tropomyosin 1 gene (TPM1) has no significant effect on the velocity of mitochondrial motor activity in vivo or in vitro. However, tpm1 delta mutants display abnormal mitochondrial distribution and morphology; loss of long distance, directional mitochondrial movement; and delayed transfer of mitochondria from the mother cell to the bud. Thus, cell cycle-linked mitochondrial motility patterns which lead to inheritance are strictly dependent on organized and properly oriented actin cables.

  7. Saccharomyces cerevisiae metabolism in ecological context.

    PubMed

    Jouhten, Paula; Ponomarova, Olga; Gonzalez, Ramon; Patil, Kiran R

    2016-11-01

    The architecture and regulation of Saccharomyces cerevisiae metabolic network are among the best studied owing to its widespread use in both basic research and industry. Yet, several recent studies have revealed notable limitations in explaining genotype-metabolic phenotype relations in this yeast, especially when concerning multiple genetic/environmental perturbations. Apparently unexpected genotype-phenotype relations may originate in the evolutionarily shaped cellular operating principles being hidden in common laboratory conditions. Predecessors of laboratory S. cerevisiae strains, the wild and the domesticated yeasts, have been evolutionarily shaped by highly variable environments, very distinct from laboratory conditions, and most interestingly by social life within microbial communities. Here we present a brief review of the genotypic and phenotypic peculiarities of S. cerevisiae in the context of its social lifestyle beyond laboratory environments. Accounting for this ecological context and the origin of the laboratory strains in experimental design and data analysis would be essential in improving the understanding of genotype-environment-phenotype relationships.

  8. Modular Spectral Imaging System for Discrimination of Pigments in Cells and Microbial Communities▿ †

    PubMed Central

    Polerecky, Lubos; Bissett, Andrew; Al-Najjar, Mohammad; Faerber, Paul; Osmers, Harald; Suci, Peter A.; Stoodley, Paul; de Beer, Dirk

    2009-01-01

    Here we describe a spectral imaging system for minimally invasive identification, localization, and relative quantification of pigments in cells and microbial communities. The modularity of the system allows pigment detection on spatial scales ranging from the single-cell level to regions whose areas are several tens of square centimeters. For pigment identification in vivo absorption and/or autofluorescence spectra are used as the analytical signals. Along with the hardware, which is easy to transport and simple to assemble and allows rapid measurement, we describe newly developed software that allows highly sensitive and pigment-specific analyses of the hyperspectral data. We also propose and describe a number of applications of the system for microbial ecology, including identification of pigments in living cells and high-spatial-resolution imaging of pigments and the associated phototrophic groups in complex microbial communities, such as photosynthetic endolithic biofilms, microbial mats, and intertidal sediments. This system provides new possibilities for studying the role of spatial organization of microorganisms in the ecological functioning of complex benthic microbial communities or for noninvasively monitoring changes in the spatial organization and/or composition of a microbial community in response to changing environmental factors. PMID:19074609

  9. Saccharomyces cerevisiae Live Cells Decreased In vitro Methane Production in Intestinal Content of Pigs

    PubMed Central

    Gong, Y. L.; Liao, X. D.; Liang, J. B.; Jahromi, M. F.; Wang, H.; Cao, Z.; Wu, Y. B.

    2013-01-01

    An in vitro gas production technique was used in this study to elucidate the effect of two strains of active live yeast on methane (CH4) production in the large intestinal content of pigs to provide an insight to whether active live yeast could suppress CH4 production in the hindgut of pigs. Treatments used in this study include blank (no substrate and no live yeast cells), control (no live yeast cells) and yeast (YST) supplementation groups (supplemented with live yeast cells, YST1 or YST2). The yeast cultures contained 1.8×1010 cells per g, which were added at the rates of 0.2 mg and 0.4 mg per ml of the fermented inoculum. Large intestinal contents were collected from 2 Duroc×Landrace×Yorkshire pigs, mixed with a phosphate buffer (1:2), and incubated anaerobically at 39°C for 24 h using 500 mg substrate (dry matter (DM) basis). Total gas and CH4 production decreased (p<0.05) with supplementation of yeast. The methane production reduction potential (MRP) was calculated by assuming net methane concentration for the control as 100%. The MRP of yeast 2 was more than 25%. Compared with the control group, in vitro DM digestibility (IVDMD) and total volatile fatty acids (VFA) concentration increased (p<0.05) in 0.4 mg/ml YST1 and 0.2 mg/ml YST2 supplementation groups. Proportion of propionate, butyrate and valerate increased (p<0.05), but that of acetate decreased (p<0.05), which led to a decreased (p<0.05) acetate: propionate (A: P) ratio in the both YST2 treatments and the 0.4 mg/ml YST 1 supplementation groups. Hydrogen recovery decreased (p<0.05) with yeast supplementation. Quantity of methanogenic archaea per milliliter of inoculum decreased (p<0.05) with yeast supplementation after 24 h of incubation. Our results suggest that live yeast cells suppressed in vitro CH4 production when inoculated into the large intestinal contents of pigs and shifted the fermentation pattern to favor propionate production together with an increased population of acetogenic

  10. Series assembly of microbial desalination cells containing stacked electrodialysis cells for partial or complete seawater desalination.

    PubMed

    Kim, Younggy; Logan, Bruce E

    2011-07-01

    A microbial desalination cell (MDC) is a new approach for desalinating water based on using the electrical current generated by exoelectrogenic bacteria. Previously developed MDCs have used only one or two desalination chambers with substantial internal resistance, and used low salinity catholytes containing a buffered or acid solution. Here we show that substantially improved MDC performance can be obtained even with a nonbuffered, saline catholyte, by using an electrodialysis stack consisting of 5 pairs of desalting and concentrating cells. When 4 stacked MDCs were used in series (20 total pairs of desalination chambers), the salinity of 0.06 L of synthetic seawater (35 g/L NaCl) was reduced by 44% using 0.12 L of anode solution (2:1). The resistive loss in the electrodialysis stack was negligible due to minimization of the intermembrane distances, and therefore the power densities produced by the MDC were similar to those produced by single chamber microbial fuel cells (MFCs) lacking desalination chambers. The observed current efficiency was 86%, indicating separation of 4.3 pairs of sodium and chloride ions for every electron transferred through the circuit. With two additional stages (total of 3.8 L of anolyte), desalination was increased to 98% salt removal, producing 0.3 L of fresh water (12.6:1). These results demonstrate that stacked MDCs can be used for efficient desalination of seawater while at the same time achieving power densities comparable to those obtained in MFCs.

  11. Riboflavin-shuttled extracellular electron transfer from Enterococcus faecalis to electrodes in microbial fuel cells.

    PubMed

    Zhang, Enren; Cai, Yamin; Luo, Yue; Piao, Zhe

    2014-11-01

    Great attention has been focused on Gram-negative bacteria in the application of microbial fuel cells. In this study, the Gram-positive bacterium Enterococcus faecalis was employed in microbial fuel cells. Bacterial biofilms formed by E. faecalis ZER6 were investigated with respect to electricity production through the riboflavin-shuttled extracellular electron transfer. Trace riboflavin was shown to be essential for transferring electrons derived from the oxidation of glucose outside the peptidoglycan layer in the cell wall of E. faecalis biofilms formed on the surface of electrodes, in the absence of other potential electron mediators (e.g., yeast extract).

  12. The Saccharomyces cerevisiae PRM1 homolog in Neurospora crassa is involved in vegetative and sexual cell fusion events but also has postfertilization functions.

    PubMed

    Fleissner, André; Diamond, Spencer; Glass, N Louise

    2009-02-01

    Cell-cell fusion is essential for a variety of developmental steps in many eukaryotic organisms, during both fertilization and vegetative cell growth. Although the molecular mechanisms associated with intracellular membrane fusion are well characterized, the molecular mechanisms of plasma membrane merger between cells are poorly understood. In the filamentous fungus Neurospora crassa, cell fusion events occur during both vegetative and sexual stages of its life cycle, thus making it an attractive model for studying the molecular basis of cell fusion during vegetative growth vs. sexual reproduction. In the unicellular yeast Saccharomyces cerevisiae, one of the few proteins implicated in plasma membrane merger during mating is Prm1p; prm1Delta mutants show an approximately 50% reduction in mating cell fusion. Here we report on the role of the PRM1 homolog in N. crassa. N. crassa strains with deletions of a Prm1-like gene (Prm1) showed an approximately 50% reduction in both vegetative and sexual cell fusion events, suggesting that PRM1 is part of the general cell fusion machinery. However, unlike S. cerevisiae, N. crassa strains carrying a Prm1 deletion exhibited complete sterility as either a male or female mating partner, a phenotype that was not complemented in a heterokaryon with wild type (WT). Crosses with DeltaPrm1 strains were blocked early in sexual development, well before development of ascogenous hyphae. The DeltaPrm1 sexual defect in N. crassa was not suppressed by mutations in Sad-1, which is required for meiotic silencing of unpaired DNA (MSUD). However, mutations in Sad-1 increased the number of progeny obtained in crosses with a DeltaPrm1 (Prm1-gfp) complemented strain. These data indicate multiple roles for PRM1 during sexual development.

  13. [Advance in the bioavailability monitoring of heavy metal based on microbial whole-cell sensor].

    PubMed

    Hou, Qi-Hui; Ma, An-Shou; Zhuang, Xiu-Liang; Zhuang, Guo-Qiang

    2013-01-01

    Microbial whole-cell biosensor is an excellent tool to assess the bioavailability of heavy metal in soil and water. However, the traditional physicochemical instruments are applied to detect the total metal. Furthermore, microbial whole-cell biosensor is simple, rapid and economical in manipulating, and is thus a highly qualified candidate for emergency detection of pollution incidents. The biological component of microbial whole-cell biosensor mostly consists of metalloregulatory proteins and reporter genes. In detail, metalloregulatory proteins mainly include the MerR family, ArsR family and RS family, and reporter genes mainly include gfp, lux and luc. Metalloregulatory protein and reporter gene are related to the sensitivity, specificity and properties in monitoring. The bioavailability of heavy metals is alterable under different conditions, influenced by pH, chelate and detection methods and so on. Increasing the accumulation of intracellular heavy metal, modifying the metalloregulatory proteins and optimizing the detecting conditions are important for improving the sensitivity, specificity and accuracy of the microbial whole-cell biosensor. The future direction of microbial whole-cell biosensor is to realize the monitoring of pollutions in situ and on line.

  14. Minimal RED cell pairs markedly improve electrode kinetics and power production in microbial reverse electrodialysis cells.

    PubMed

    Cusick, Roland D; Hatzell, Marta; Zhang, Fang; Logan, Bruce E

    2013-12-17

    Power production from microbial reverse electrodialysis cell (MRC) electrodes is substantially improved compared to microbial fuel cells (MFCs) by using ammonium bicarbonate (AmB) solutions in multiple RED cell pair stacks and the cathode chamber. Reducing the number of RED membranes pairs while maintaining enhanced electrode performance could help to reduce capital costs. We show here that using only a single RED cell pair (CP), created by operating the cathode in concentrated AmB, dramatically increased power production normalized to cathode area from both acetate (Acetate: from 0.9 to 3.1 W/m(2)-cat) and wastewater (WW: 0.3 to 1.7 W/m(2)), by reducing solution and charge transfer resistances at the cathode. A second RED cell pair increased RED stack potential and reduced anode charge transfer resistance, further increasing power production (Acetate: 4.2 W/m(2); WW: 1.9 W/m(2)). By maintaining near optimal electrode power production with fewer membranes, power densities normalized to total membrane area for the 1-CP (Acetate: 3.1 W/m(2)-mem; WW: 1.7 W/m(2)) and 2-CP (Acetate: 1.3 W/m(2)-mem; WW: 0.6 W/m(2)) reactors were much higher than previous MRCs (0.3-0.5 W/m(2)-mem with acetate). While operating at peak power, the rate of wastewater COD removal, normalized to reactor volume, was 30-50 times higher in 1-CP and 2-CP MRCs than that in a single chamber MFC. These findings show that even a single cell pair AmB RED stack can significantly enhance electrical power production and wastewater treatment.

  15. Isolation of Candida glabrata Homologs of the Saccharomyces cerevisiae KRE9 and KNH1 Genes and Their Involvement in Cell Wall β-1,6-Glucan Synthesis

    PubMed Central

    Nagahashi, Shigehisa; Lussier, Marc; Bussey, Howard

    1998-01-01

    The Candida glabrata KRE9 (CgKRE9) and KNH1 (CgKNH1) genes have been isolated as multicopy suppressors of the tetracycline-sensitive growth of a Saccharomyces cerevisiae mutant with the disrupted KNH1 locus and the KRE9 gene placed under the control of a tetracycline-responsive promoter. Although a cgknh1Δ mutant showed no phenotype beyond slightly increased sensitivity to the K1 killer toxin, disruption of CgKRE9 resulted in several phenotypes similar to those of the S. cerevisiae kre9Δ null mutant: a severe growth defect on glucose medium, resistance to the K1 killer toxin, a 50% reduction of β-1,6-glucan, and the presence of aggregates of cells with abnormal morphology on glucose medium. Replacement in C. glabrata of the cognate CgKRE9 promoter with the tetracycline-responsive promoter in a cgknh1Δ background rendered cell growth tetracycline sensitive on media containing glucose or galactose. cgkre9Δ cells were shown to be sensitive to calcofluor white specifically on glucose medium. In cgkre9 mutants grown on glucose medium, cellular chitin levels were massively increased. PMID:9748432

  16. Size and Carbon Content of Sub-seafloor Microbial Cells at Landsort Deep, Baltic Sea

    PubMed Central

    Braun, Stefan; Morono, Yuki; Littmann, Sten; Kuypers, Marcel; Aslan, Hüsnü; Dong, Mingdong; Jørgensen, Bo B.; Lomstein, Bente Aa.

    2016-01-01

    The discovery of a microbial ecosystem in ocean sediments has evoked interest in life under extreme energy limitation and its role in global element cycling. However, fundamental parameters such as the size and the amount of biomass of sub-seafloor microbial cells are poorly constrained. Here we determined the volume and the carbon content of microbial cells from a marine sediment drill core retrieved by the Integrated Ocean Drilling Program (IODP), Expedition 347, at Landsort Deep, Baltic Sea. To determine their shape and volume, cells were separated from the sediment matrix by multi-layer density centrifugation and visualized via epifluorescence microscopy (FM) and scanning electron microscopy (SEM). Total cell-carbon was calculated from amino acid-carbon, which was analyzed by high-performance liquid chromatography (HPLC) after cells had been purified by fluorescence-activated cell sorting (FACS). The majority of microbial cells in the sediment have coccoid or slightly elongated morphology. From the sediment surface to the deepest investigated sample (~60 m below the seafloor), the cell volume of both coccoid and elongated cells decreased by an order of magnitude from ~0.05 to 0.005 μm3. The cell-specific carbon content was 19–31 fg C cell−1, which is at the lower end of previous estimates that were used for global estimates of microbial biomass. The cell-specific carbon density increased with sediment depth from about 200 to 1000 fg C μm−3, suggesting that cells decrease their water content and grow small cell sizes as adaptation to the long-term subsistence at very low energy availability in the deep biosphere. We present for the first time depth-related data on the cell volume and carbon content of sedimentary microbial cells buried down to 60 m below the seafloor. Our data enable estimates of volume- and biomass-specific cellular rates of energy metabolism in the deep biosphere and will improve global estimates of microbial biomass. PMID:27630628

  17. A simple microbial fuel cell model for improvement of biomedical device powering times.

    PubMed

    Roxby, Daniel N; Tran, Nham; Nguyen, Hung T

    2014-01-01

    This study describes a Matlab based Microbial Fuel Cell (MFC) model for a suspended microbial population, in the anode chamber for the use of the MFC in powering biomedical devices. The model contains three main sections including microbial growth, microbial chemical uptake and secretion and electrochemical modeling. The microbial growth portion is based on a Continuously Stirred Tank Reactor (CSTR) model for the microbial growth with substrate and electron acceptors. Microbial stoichiometry is used to determine chemical concentrations and their rates of change and transfer within the MFC. These parameters are then used in the electrochemical modeling for calculating current, voltage and power. The model was tested for typically exhibited MFC characteristics including increased electrode distances and surface areas, overpotentials and operating temperatures. Implantable biomedical devices require long term powering which is the main objective for MFCs. Towards this end, our model was tested with different initial substrate and electron acceptor concentrations, revealing a four-fold increase in concentrations decreased the power output time by 50%. Additionally, the model also predicts that for a 35.7% decrease in specific growth rate, a 50% increase in power longevity is possible.

  18. Trend of Mathematical Models in Microbial Fuel Cell for Environmental Energy Refinery from Waste/Water

    NASA Astrophysics Data System (ADS)

    Oh, Sung Taek

    A microbial fuel cell (MFC) is a device to use for bio electrochemical energy production. Electrophilic bacteria produce electrons in their metabolic pathway and the electrons can be extracted and concentrated on electrode by the electric potential difference (i.e. Galvanic cell). The bio-electrode may provide new opportunities for the renewable energy in waste water/swage treatment plants.

  19. Digestion of algal biomass for electricity generation in microbial fuel cells.

    PubMed

    Nishio, Koichi; Hashimoto, Kazuhito; Watanabe, Kazuya

    2013-01-01

    Algal biomass serves as a fuel for electricity generation in microbial fuel cells. This study constructed a model consortium comprised of an alga-digesting Lactobacillus and an iron-reducing Geobacter for electricity generation from photo-grown Clamydomonas cells. Total power-conversion efficiency (from Light to electricity) was estimated to be 0.47%.

  20. Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells

    EPA Science Inventory

    Cathode potential and O2 supply methods were investigated to improve H2O2 synthesis in an electrochemical cell, and optimal cathode conditions were applied for microbial electrochemical cells (MECs). Using aqueous O2 for the cathode significantly improved current density, but H2...

  1. [Clusters of nonsolvent water in partially destroyed Saccharomyces cerevisiae yeast cells].

    PubMed

    Turov, V V; Gun'ko, V M; Krupskaia, T V; Lipkovskaia, N A; Turova, A A

    2014-01-01

    The state of water in partially destroyed dry yeast cells has been studied using low-temperature 1H NMR spectroscopy. It has been shown that the residual water is in the form of clusters of strongly and weakly associated water (SAW and WAW, respectively). Three or more types of SAW different in the chemical shift values have been found. It has been established that the interfacial water poorly dissolves hydrochloric and trifluoroacetic acids as well as DMSO and CD3CN. Hydrochloric acid on a surface of biomaterials can be separated into HCl and water. This process is stabilized by polar co-solvents (DMSO and CD3CN) added to the CDCl3 dispersion medium.

  2. Graphite anode surface modification with controlled reduction of specific aryl diazonium salts for improved microbial fuel cells power output.

    PubMed

    Picot, Matthieu; Lapinsonnière, Laure; Rothballer, Michael; Barrière, Frédéric

    2011-10-15

    Graphite electrodes were modified with reduction of aryl diazonium salts and implemented as anodes in microbial fuel cells. First, reduction of 4-aminophenyl diazonium is considered using increased coulombic charge density from 16.5 to 200 mC/cm(2). This procedure introduced aryl amine functionalities at the surface which are neutral at neutral pH. These electrodes were implemented as anodes in "H" type microbial fuel cells inoculated with waste water, acetate as the substrate and using ferricyanide reduction at the cathode and a 1000 Ω external resistance. When the microbial anode had developed, the performances of the microbial fuel cells were measured under acetate saturation conditions and compared with those of control microbial fuel cells having an unmodified graphite anode. We found that the maximum power density of microbial fuel cell first increased as a function of the extent of modification, reaching an optimum after which it decreased for higher degree of surface modification, becoming even less performing than the control microbial fuel cell. Then, the effect of the introduction of charged groups at the surface was investigated at a low degree of surface modification. It was found that negatively charged groups at the surface (carboxylate) decreased microbial fuel cell power output while the introduction of positively charged groups doubled the power output. Scanning electron microscopy revealed that the microbial anode modified with positively charged groups was covered by a dense and homogeneous biofilm. Fluorescence in situ hybridization analyses showed that this biofilm consisted to a large extent of bacteria from the known electroactive Geobacter genus. In summary, the extent of modification of the anode was found to be critical for the microbial fuel cell performance. The nature of the chemical group introduced at the electrode surface was also found to significantly affect the performance of the microbial fuel cells. The method used for

  3. Wiring microbial biofilms to the electrode by osmium redox polymer for the performance enhancement of microbial fuel cells.

    PubMed

    Yuan, Yong; Shin, Hyosul; Kang, Chan; Kim, Sunghyun

    2016-04-01

    An osmium redox polymer, PAA-PVI-[Os(4,4'-dimethyl-2,2'-bipyridine)2Cl]+/2+ that has been used in enzymatic fuel cells and microbial sensors, was applied for the first time to the anode of single-chamber microbial fuel cells with the mixed culture inoculum aiming at enhancing performance. Functioning as a molecular wire connecting the biofilm to the anode, power density increased from 1479 mW m(-2) without modification to 2355 mW m(-2) after modification of the anode. Evidence from cyclic voltammetry showed that the catalytic activity of an anodic biofilm was greatly enhanced in the presence of an osmium redox polymer, indicating that electrons were more efficiently transferred to the anode via co-immobilized osmium complex tethered to wiring polymer chains at the potential range of -0.3 V-+0.1 V (vs. SCE). The optimum amount of the redox polymer was determined to be 0.163 mg cm(-2).

  4. Immobilization of microbial cell and yeast cell and its application to biomass conversion using radiation techniques

    NASA Astrophysics Data System (ADS)

    Kaetsu, Isao; Kumakura, Minoru; Fujimura, Takashi; Kasai, Noboru; Tamada, Masao

    The recent results of immobilization of cellulase-producing cells and ethanol-fermentation yeast by radiation were reported. The enzyme of cellulase produced by immobilized cells was used for saccharification of lignocellulosic wastes and immobilized yeast cells were used for fermentation reaction from glucose to ethanol. The wastes such as chaff and bagasse were treated by γ-ray or electron-beam irradiation in the presence of alkali and subsequent mechanical crushing, to form a fine powder less than 50 μm in diameter. On the other hand, Trichoderma reesei as a cellulase-producing microbial cell was immobilized on a fibrous carrier having a specific porous structure and cultured to produce cellulase. The enzymatic saccharification of the pretreated waste was carried out using the produced cellulase. The enhanced fermentation process to produce ethanol from glucose with the immobilized yeast by radiation was also studied. The ethanol productivity of immobilized growing yeast cells thus obtained was thirteen times that of free yeast cells in a 1:1 volume of liquid medium to immobilized yeast cells.

  5. Application of a weak magnetic field to improve microbial fuel cell performance.

    PubMed

    Tong, Zhong-Hua; Yu, Han-Qing; Li, Wen-Wei; Wang, Yun-Kun; Sun, Min; Liu, Xian-Wei; Sheng, Guo-Ping

    2015-12-01

    Microbial fuel cells (MFCs) have emerged as a promising technology for wastewater treatment with concomitant energy production but the performance is usually limited by low microbial activities. This has spurred intensive research interest for microbial enhancement. This study demonstrated an interesting stimulation effect of a static magnetic field (MF) on sludge-inoculated MFCs and explored into the mechanisms. The implementation of a 100-mT MF accelerated the reactor startup and led to increased electricity generation. Under the MF exposure, the activation loss of the MFC was decreased, but there was no increased secretion of redox mediators. Thus, the MF effect was mainly due to enhanced bioelectrochemical activities of anodic microorganisms, which are likely attributed to the oxidative stress and magnetohydrodynamic effects under an MF exposure. This work implies that weak MF may be applied as a simple and effective approach to stimulate microbial activities for various bioelectrochemical energy production and decontamination applications.

  6. Enhanced biofilm distribution and cell performance of microfluidic microbial fuel cells with multiple anolyte inlets.

    PubMed

    Yang, Yang; Ye, Dingding; Liao, Qiang; Zhang, Pengqing; Zhu, Xun; Li, Jun; Fu, Qian

    2016-05-15

    A laminar-flow controlled microfluidic microbial fuel cell (MMFC) is considered as a promising approach to be a bio-electrochemical system (BES). But poor bacterial colonization and low power generation are two severe bottlenecks to restrict its development. In this study, we reported a MMFC with multiple anolyte inlets (MMFC-MI) to enhance the biofilm formation and promote the power density of MMFCs. Voltage profiles during the inoculation process demonstrated MMFC-MI had a faster start-up process than the conventional microfluidic microbial fuel cell with one inlet (MMFC-OI). Meanwhile, benefited from the periodical replenishment of boundary layer near the electrode, a more densely-packed bacterial aggregation was observed along the flow direction and also the substantially low internal resistance for MMFC-MI. Most importantly, the output power density of MMFC-MI was the highest value among the reported µl-scale MFCs to our best knowledge. The presented MMFC-MI appears promising for bio-chip technology and extends the scope of microfluidic energy.

  7. Variable cell morphology approach for individual-based modeling of microbial communities.

    PubMed

    Storck, Tomas; Picioreanu, Cristian; Virdis, Bernardino; Batstone, Damien J

    2014-05-06

    An individual-based, mass-spring modeling framework has been developed to investigate the effect of cell properties on the structure of biofilms and microbial aggregates through Lagrangian modeling. Key features that distinguish this model are variable cell morphology described by a collection of particles connected by springs and a mechanical representation of deformable intracellular, intercellular, and cell-substratum links. A first case study describes the colony formation of a rod-shaped species on a planar substratum. This case shows the importance of mechanical interactions in a community of growing and dividing rod-shaped cells (i.e., bacilli). Cell-substratum links promote formation of mounds as opposed to single-layer biofilms, whereas filial links affect the roundness of the biofilm. A second case study describes the formation of flocs and development of external filaments in a mixed-culture activated sludge community. It is shown by modeling that distinct cell-cell links, microbial morphology, and growth kinetics can lead to excessive filamentous proliferation and interfloc bridging, possible causes for detrimental sludge bulking. This methodology has been extended to more advanced microbial morphologies such as filament branching and proves to be a very powerful tool in determining how fundamental controlling mechanisms determine diverse microbial colony architectures.

  8. Variable Cell Morphology Approach for Individual-Based Modeling of Microbial Communities

    PubMed Central

    Storck, Tomas; Picioreanu, Cristian; Virdis, Bernardino; Batstone, Damien J.

    2014-01-01

    An individual-based, mass-spring modeling framework has been developed to investigate the effect of cell properties on the structure of biofilms and microbial aggregates through Lagrangian modeling. Key features that distinguish this model are variable cell morphology described by a collection of particles connected by springs and a mechanical representation of deformable intracellular, intercellular, and cell-substratum links. A first case study describes the colony formation of a rod-shaped species on a planar substratum. This case shows the importance of mechanical interactions in a community of growing and dividing rod-shaped cells (i.e., bacilli). Cell-substratum links promote formation of mounds as opposed to single-layer biofilms, whereas filial links affect the roundness of the biofilm. A second case study describes the formation of flocs and development of external filaments in a mixed-culture activated sludge community. It is shown by modeling that distinct cell-cell links, microbial morphology, and growth kinetics can lead to excessive filamentous proliferation and interfloc bridging, possible causes for detrimental sludge bulking. This methodology has been extended to more advanced microbial morphologies such as filament branching and proves to be a very powerful tool in determining how fundamental controlling mechanisms determine diverse microbial colony architectures. PMID:24806936

  9. A new cultivation method for microbial oil production: cell pelletization and lipid accumulation by Mucor circinelloides.

    PubMed

    Xia, Chunjie; Zhang, Jianguo; Zhang, Weidong; Hu, Bo

    2011-06-02

    The recent energy crisis has triggered significant attention on the microbial synthesis of lipids, which comprise the raw material for biodiesel production. Microbial oil accumulation with filamentous fungi has great potential because filamentous fungi can form pellets during cell growth, and these pellets are much easier to harvest from cell broth. This paper focuses on the cell pelletization process of the oleaginous Mucor circinelloides. We have studied the effect of various cultural conditions on pelletized cell growth and lipid accumulation. This study is the first to report that pH adjustment during cell growth plays a key role in pellet formation of M. circinelloides and describes a handy method by which to induce cell pelletization in submerged fungal cultivation. Our study reveals that cell growth and lipid production are not significantly affected by pelletization and that lipid accumulation is triggered at stressed conditions, such as a high carbon-to-nitrogen ratio and high temperature.

  10. Electrochemical communication between microbial cells and electrodes via osmium redox systems.

    PubMed

    Hasan, Kamrul; Patil, Sunil A; Leech, Dónal; Hägerhäll, Cecilia; Gorton, Lo

    2012-12-01

    Electrochemical communication between micro-organisms and electrodes is the integral and fundamental part of BESs (bioelectrochemical systems). The immobilization of bacterial cells on the electrode and ensuring efficient electron transfer to the electrode via a mediator are decisive features of mediated electrochemical biosensors. Notably, mediator-based systems are essential to extract electrons from the non-exoelectrogens, a major group of microbes in Nature. The advantage of using polymeric mediators over diffusible mediators led to the design of osmium redox polymers. Their successful use in enzyme-based biosensors and BFCs (biofuel cells) paved the way for exploring their use in microbial BESs. The present mini-review focuses on osmium-bound redox systems used to date in microbial BESs and their role in shuttling electrons from viable microbial cells to electrodes.

  11. Substrates and pathway of electricity generation in a nitrification-based microbial fuel cell.

    PubMed

    Chen, Hui; Zheng, Ping; Zhang, Jiqiang; Xie, Zuofu; Ji, Junyuan; Ghulam, Abbas

    2014-06-01

    Nitrification-based microbial fuel cell (N-MFC) is a novel inorganic microbial fuel cell based on nitrification in the anode compartment. So far, little information is available on the substrates and pathway of N-MFC. The results of this study indicated that apart from the primary nitrification substrate (ammonium), the intermediates (hydroxylamine and nitrite) could also serve as anodic fuel to generate current, and the end product nitrate showed an inhibitory effect on electricity generation. Based on the research, a pathway of electricity generation was proposed for N-MFC: ammonium was oxidized first to nitrite by ammonia-oxidizing bacteria (AOB), then the nitrite in anolyte and the potassium permanganate in catholyte constituted a chemical cell to generate current. In other words, the electricity generation in N-MFC was not only supported by microbial reaction as we expected, but both biological and electrochemical reactions contributed.

  12. Cell cycle regulators interact with pathways that modulate microtubule stability in Saccharomyces cerevisiae.

    PubMed

    Shohat-Tal, Aya; Eshel, Dan

    2011-12-01

    The integrity of mitosis is dependent upon strict regulation of microtubule stability and dynamics. Although much information has been accumulated on regulators of the microtubule cytoskeleton, our knowledge of the specific pathways involved is still limited. Here we designed genetic screens to identify regulators of microtubule stability that are dispensable in the wild type yet become essential under microtubule-disrupting conditions. We found that the transcriptional cofactor Swi6p and activator Swi4p, as well as the G(2)/M-specific cyclin Clb2p, are required in a microtubule-destabilizing environment. Swi6p and Swi4p can combine as a transcriptional complex, called the SBF complex (SBF for Swi4/6 cell cycle box [SCB]-binding factor) that is functionally homologous to the metazoan DP1/2-E2F complex and that controls the G(1)/S transition through the genes it regulates. We show that Swi6p's contribution to microtubule stability can be either dependent or independent of the SBF complex. The SBF-dependent pathway requires downregulation of SBF complex levels and may thereby reroute the transcriptional program in favor of greater microtubule stability. This pathway can be triggered by overexpression of Fcp1p, a phosphatase in the general transcription machinery, or by expression of an allele of SWI6 that is associated with reduced transcription from SBF-controlled promoters. The SBF-independent pathway is activated by a constitutively nuclear allele of Swi6p. Our results introduce novel roles in microtubule stability for genes whose participation in the process may be masked under normal conditions yet nonetheless acquire a dominant role when microtubule stability is compromised.

  13. Differential effects of Cdc68 on cell cycle-regulated promoters in Saccharomyces cerevisiae.

    PubMed Central

    Lycan, D; Mikesell, G; Bunger, M; Breeden, L

    1994-01-01

    Swi4 and Swi6 form a complex which is required for Start-dependent activation of HO and for high-level expression of G1 cyclin genes CLN1 and CLN2. To identify other regulators of this pathway, we screened for dominant, recessive, conditional, and allele-specific suppressors of swi4 mutants. We isolated 16 recessive suppressors that define three genes, SSF1, SSF5, and SSF9 (suppressor of swi four). Mutations in all three genes bypass the requirement for both Swi4 and Swi6 for HO transcription and activate transcription from reporter genes lacking upstream activating sequences (UASs). SSF5 is allelic with SIN4 (TSF3), a gene implicated in global repression of transcription and chromatin structure, and SSF9 is likely to be a new global repressor of transcription. SSF1 is allelic with CDC68 (SPT16). cdc68 mutations have been shown to increase expression from defective promoters, while preventing transcription from other intact promoters, including CLN1 and CLN2. We find that CDC68 is a required activator of both SWI4 and SWI6, suggesting that CDC68's role at the CLN promoters may be indirect. The target of CDC68 within the SWI4 promoter is complex in that known activating elements (MluI cell cycle boxes) in the SWI4 promoter are required for CDC68 dependence but only within the context of the full-length promoter. This result suggests that there may be both a chromatin structure and a UAS-specific component to Cdc68 function at SWI4. We suggest that Cdc68 functions both in the assembly of repressive complexes that form on many intact promoters in vivo and in the relief of this repression during gene activation. Images PMID:7935460

  14. Effect of pH, aeration and sucrose feeding on the invertase activity of intact S. cerevisiae cells grown in sugarcane blackstrap molasses.

    PubMed

    Vitolo, M; Duranti, M A; Pellegrim, M B

    1995-08-01

    S. cerevisiae was grown in a blackstrap molasses containing medium in batch and fed-batch cultures. The following parameters were varied: pH (from 4.0 to 6.5), dissolved oxygen (DO) (from 0 to 5.0 mg O2 L-1) and sucrose feeding rate. When glucose concentration (S) was higher than 0.5 g L-1 a reduction in the specific invertase activity of intact cells (v) and an oscillatory behavior of v values during fermentation were observed. Both the invertase reduction and the oscillatory behavior of v values could be related to the glucose inhibitory effect on invertase biosynthesis. The best culture conditions for attaining S. cerevisiae cells suitable for invertase production were: temperature = 30 degrees C; pH = 5.0; DO = 3.3 mg O2 L-1; (S) = 0.5 g L-1 and sucrose added into the fermenter according to the equations: (V-Vo) = t2/16 or (V - Vo) = (Vf - Vo).(e0.6t-1)/10.

  15. Comparison of Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, Spodoptera frugiperda, and COS7 cells for recombinant gene expression. Application to a rabbit liver carboxylesterase.

    PubMed

    Morton, C L; Potter, P M

    2000-11-01

    Expression of a rabbit liver carboxylesterase has been achieved in several different model systems including Escherichia coli, Pichia pastoris, Saccharomyces cerevisiae, Spodoptera frugiperda, and COS7 cells. Although, recombinant protein was observed in E. coli sonicates, little or no enzymatic activity was detected. Similarly, no activity was observed following expression in S. cerevisiae. In contrast, active protein was produced in P. pastoris, from S. frugiperda following baculoviral infection and in COS7 cells following transient transfection of plasmid DNA. For the preparation of small amounts of protein for kinetic and biochemical studies, enzyme expressed in P. pastoris has proved sufficient. However, to produce large amounts of carboxylesterase for structural studies, baculoviral-mediated expression of a secreted form of the protein in S. frugiperda was the most efficient. Using this system, we have generated and purified milligram quantities of essentially pure protein. These results demonstrate that the choice of in vitro system for the generation of large amounts of active carboxylesterase, and probably most endoplasmic reticulum processed proteins, is crucial for high level expression and subsequent purification.

  16. Plant cell walls: Protecting the barrier from degradation by microbial enzymes.

    PubMed

    Lagaert, Stijn; Beliën, Tim; Volckaert, Guido

    2009-12-01

    Plant cell walls are predominantly composed of polysaccharides, which are connected in a strong, yet resilient network. They determine the size and shape of plant cells and form the interface between the cell and its often hostile environment. To penetrate the cell wall and thus infect plants, most phytopathogens secrete numerous cell wall degrading enzymes. Conversely, as a first line of defense, plant cell walls contain an array of inhibitors of these enzymes. Scientific knowledge on these inhibitors significantly progressed in the past years and this review is meant to give a comprehensive overview of plant inhibitors against microbial cell wall degrading enzymes and their role in plant protection.

  17. The phylogenetically invariant ACAGAGA and AGC sequences of U6 small nuclear RNA are more tolerant of mutation in human cells than in Saccharomyces cerevisiae.

    PubMed Central

    Datta, B; Weiner, A M

    1993-01-01

    U6 small nuclear RNA (snRNA) is the most highly conserved of the five spliceosomal snRNAs that participate in nuclear mRNA splicing. The proposal that U6 snRNA plays a key catalytic role in splicing [D. Brow and C. Guthrie, Nature (London) 337:14-15, 1989] is supported by the phylogenetic conservation of U6, the sensitivity of U6 to mutation, cross-linking of U6 to the vicinity of the 5' splice site, and genetic evidence for extensive base pairing between U2 and U6 snRNAs. We chose to mutate the phylogenetically invariant 41-ACAGAGA-47 and 53-AGC-55 sequences of human U6 because certain point mutations within the homologous regions of Saccharomyces cerevisiae U6 selectively block the first or second step of mRNA splicing. We found that both sequences are more tolerant to mutation in human cells (assayed by transient expression in vivo) than in S. cerevisiae (assayed by effects on growth or in vitro splicing). These differences may reflect different rate-limiting steps in the particular assays used or differential reliance on redundant RNA-RNA or RNA-protein interactions. The ability of mutations in U6 nucleotides A-45 and A-53 to selectively block step 2 of splicing in S. cerevisiae had previously been construed as evidence that these residues might participate directly in the second chemical step of splicing; an indirect, structural role seems more likely because the equivalent mutations have no obvious phenotype in the human transient expression assay. Images PMID:8355689

  18. Analytical applications of microbial fuel cells. Part II: Toxicity, microbial activity and quantification, single analyte detection and other uses.

    PubMed

    Abrevaya, Ximena C; Sacco, Natalia J; Bonetto, Maria C; Hilding-Ohlsson, Astrid; Cortón, Eduardo

    2015-01-15

    Microbial fuel cells were rediscovered twenty years ago and now are a very active research area. The reasons behind this new activity are the relatively recent discovery of electrogenic or electroactive bacteria and the vision of two important practical applications, as wastewater treatment coupled with clean energy production and power supply systems for isolated low-power sensor devices. Although some analytical applications of MFCs were proposed earlier (as biochemical oxygen demand sensing) only lately a myriad of new uses of this technology are being presented by research groups around the world, which combine both biological-microbiological and electroanalytical expertises. This is the second part of a review of MFC applications in the area of analytical sciences. In Part I a general introduction to biological-based analytical methods including bioassays, biosensors, MFCs design, operating principles, as well as, perhaps the main and earlier presented application, the use as a BOD sensor was reviewed. In Part II, other proposed uses are presented and discussed. As other microbially based analytical systems, MFCs are satisfactory systems to measure and integrate complex parameters that are difficult or impossible to measure otherwise, such as water toxicity (where the toxic effect to aquatic organisms needed to be integrated). We explore here the methods proposed to measure toxicity, microbial metabolism, and, being of special interest to space exploration, life sensors. Also, some methods with higher specificity, proposed to detect a single analyte, are presented. Different possibilities to increase selectivity and sensitivity, by using molecular biology or other modern techniques are also discussed here.

  19. Variations of electron flux and microbial community in air-cathode microbial fuel cells fed with different substrates.

    PubMed

    Yu, Jaecheul; Park, Younghyun; Cho, Haein; Chun, Jieun; Seon, Jiyun; Cho, Sunja; Lee, Taeho

    2012-01-01

    Microbial fuel cells (MFCs) can convert chemical energy to electricity using microbes as catalysts and a variety of organic wastewaters as substrates. However, electron loss occurs when fermentable substrates are used because fermentation bacteria and methanogens are involved in electron flow from the substrates to electricity. In this study, MFCs using glucose (G-MFC), propionate (P-MFC), butyrate (B-MFC), acetate (A-MFC), and a mix (M-MFC, glucose:propionate:butyrate:acetate = 1:1:1:1) were operated in batch mode. The metabolites and microbial communities were analyzed. The current was the largest electron sink in M-, G-, B-, and A-MFCs; the initial chemical oxygen demands (COD(ini)) involved in current production were 60.1% for M-MFC, 52.7% for G-MFC, 56.1% for B-MFC, and 68.3% for A-MFC. Most of the glucose was converted to propionate (40.6% of COD(ini)) and acetate (21.4% of COD(ini)) through lactate (80.3% of COD(ini)) and butyrate (6.1% of COD(ini)). However, an unknown source (62.0% of COD(ini)) and the current (34.5% of COD(ini)) were the largest and second-largest electron sinks in P-MFC. Methane gas was only detected at levels of more than 10% in G- and M-MFCs, meaning that electrochemically active bacteria (EAB) could out-compete acetoclastic methanogens. The microbial communities were different for fermentable and non-fermentable substrate-fed MFCs. Probably, bacteria related to Lactococcus spp. found in G-MFCs with fermentable substrates would be involved in both fermentation and electricity generation. Acinetobacter-like species, and Rhodobacter-like species detected in all the MFCs would be involved in oxidation of organic compounds and electricity generation.

  20. Electricity generation from wastewaters with starch as carbon source using a mediatorless microbial fuel cell.

    PubMed

    Herrero-Hernandez, E; Smith, T J; Akid, R

    2013-01-15

    Microbial fuel cells represent a new method for producing electricity from the oxidation of organic matter. A mediatorless microbial fuel cell was developed using Escherichia coli as the active bacterial component with synthetic wastewater of potato extract as the energy source. The two-chamber fuel cell, with a relation of volume between anode and cathode chamber of 8:1, was operated in batch mode. The response was similar to that obtained when glucose was used as the carbon source. The performance characteristics of the fuel cell were evaluated with two different anode and cathode shapes, platinised titanium strip or mesh; the highest maximum power density (502mWm(-2)) was achieved in the microbial fuel cell with mesh electrodes. In addition to electricity generation, the MFC exhibited efficient treatment of wastewater so that significant reduction of initial oxygen demand of wastewater by 61% was observed. These results demonstrate that potato starch can be used for power generation in a mediatorless microbial fuel cell with high removal efficiency of chemical oxygen demand.

  1. Recent progress and continuing challenges in bio-fuel cells. Part II: Microbial.

    PubMed

    Osman, M H; Shah, A A; Walsh, F C

    2010-11-15

    Recent key developments in microbial fuel cell technology are reviewed. Fuel sources, electron transfer mechanisms, anode materials and enhanced O(2) reduction are discussed in detail. A summary of recently developed microbial fuel cell systems, including performance measurements, is conveniently provided in tabular form. The current challenges involved in developing practical bio-fuel cell systems are described, with particular emphasis on a fundamental understanding of the reaction environment, the performance and stability requirements, modularity and scalability. This review is the second part of a review of bio-fuel cells. In Part 1 a general introduction to bio-fuel cells, including their operating principles and applications, was provided and enzymatic fuel cell technology was reviewed.

  2. Effect of separator and inoculum type on electricity generation and microbial community in single-chamber microbial fuel cells.

    PubMed

    Yu, Jaecheul; Park, Younghyun; Lee, Taeho

    2014-04-01

    Single-chamber microbial fuel cell (SMFC)-I consisted of 4 separator-electrode assemblies (SEAs) with two types of cation exchange membrane (CEM: Nafion and CMI 7000) and an anion exchange membrane (AEM: AMI 7001). SMFC-II consisted of 4 SEAs with Nafion and three types of nonwoven fabric. SMFC-I and -II were inoculated with anaerobic digested and activated sludge, respectively, and operated under fed-batch mode. In SMFC I, AEM-SEA showed a maximum power density (PDmax). Nafion-SEA showed a PDmax in SMFC II, which was similar to that of Nafion-SEA of SMFC I. Although different bacteria were developed in SMFC-I (Deltaproteobacteria and Firmicutes) and SMFC-II (Gammaproteobacteria, Betaproteobacteria and Bacteroidetes), the inoculum type little affects electricity generation. Variations of pH and oxygen in biofilm have influenced microbial community structure and electricity generation according to the electrode and separator material. Although the electricity generation of non-woven fabric-SEA was less than that of Nafion-SEA, the use of non-woven fabrics is expected to reduce the construction and operating costs of MFCs.

  3. Performance and microbial community of carbon nanotube fixed-bed microbial fuel cell continuously fed with hydrothermal liquefied cornstalk biomass.

    PubMed

    Liu, Zhidan; He, Yanhong; Shen, Ruixia; Zhu, Zhangbing; Xing, Xin-Hui; Li, Baoming; Zhang, Yuanhui

    2015-06-01

    Hydrothermal liquefaction (HTL) is a green technology for biomass pretreatment with the omission of hazardous chemicals. This study reports a novel integration of HTL and carbon nanotubes (CNTs) fixed-bed microbial fuel cell (FBMFC) for continuous electricity generation from cornstalk biomass. Two FBMFCs in parallel achieved similar performance fed with cornstalk hydrolysate at different organic loading rates (OLRs) (0.82-8.16g/L/d). About 80% of Chemical oxygen demand (COD) and Total organic carbon (TOC) was removed from low-Biochemical oxygen demand (BOD)/COD (0.16) cornstalk hydrolysate at 8.16g/L/d, whereas a maximum power density (680mW/m(3)) was obtained at 2.41g/L/d, and a smallest internal resistance (Rin) (28Ω) at 3.01g/L/d. Illumina MiSeq sequencing reveals the diverse microbial structure induced by the complex composition of cornstalk hydrolysate. Distinguished from Proteobacteria, which a number of exoelectrogens belong to, the identified dominant genus Rhizobium in FBMFC was closely related to degradation of cellulosic biomass.

  4. Membrane engineering of S. cerevisiae targeting sphingolipid metabolism

    PubMed Central

    Lindahl, Lina; Santos, Aline X. S.; Olsson, Helén; Olsson, Lisbeth; Bettiga, Maurizio

    2017-01-01

    The sustainable production of fuels and chemicals using microbial cell factories is now well established. However, many microbial production processes are still limited in scale due to inhibition from compounds that are present in the feedstock or are produced during fermentation. Some of these inhibitors interfere with cellular membranes and change the physicochemical properties of the membranes. Another group of molecules is dependent on their permeation rate through the membrane for their inhibition. We have investigated the use of membrane engineering to counteract the negative effects of inhibitors on the microorganism with focus on modulating the abundance of complex sphingolipids in the cell membrane of Saccharomyces cerevisiae. Overexpression of ELO3, involved in fatty acid elongation, and AUR1, which catalyses the formation of complex sphingolipids, had no effect on the membrane lipid profile or on cellular physiology. Deletion of the genes ORM1 and ORM2, encoding negative regulators of sphingolipid biosynthesis, decreased cell viability and considerably reduced phosphatidylinositol and complex sphingolipids. Additionally, combining ELO3 and AUR1 overexpression with orm1/2Δ improved cell viability and increased fatty acyl chain length compared with only orm1/2Δ. These findings can be used to further study the sphingolipid metabolism, as well as giving guidance in membrane engineering. PMID:28145511

  5. Biosynthesis of silver nanoparticles using Saccharomyces cerevisiae.

    PubMed

    Korbekandi, Hassan; Mohseni, Soudabeh; Mardani Jouneghani, Rasoul; Pourhossein, Meraj; Iravani, Siavash

    2016-01-01

    The objectives of this study were the biosynthesis of silver nanoparticles (NPs) by biotransformations using Saccharomyces cerevisiae and analysis of the sizes and shapes of the NPs produced. Dried and freshly cultured S. cerevisiae were used as the biocatalyst. Dried yeast synthesized few NPs, but freshly cultured yeast produced a large amount of them. Silver NPs were spherical, 2-20 nm in diameter, and the NPs with the size of 5.4 nm were the most frequent ones. NPs were seen inside the cells, within the cell membrane, attached to the cell membrane during the exocytosis, and outside of the cells.

  6. Effect of initial carbon sources on the performance of microbial fuel cells containing Proteus vulgaris.

    PubMed

    Kim, N; Choi, Y; Jung, S; Kim, S

    2000-10-05

    Mediator-coupled microbial fuel cells containing Proteus vulgaris were constructed and the cell performance was tested. Fuel cell efficiency depended on the carbon source in the initial medium of the microorganism. Maltose and trehalose were not utilized substantially by P. vulgaris; however, their presence in the initial medium resulted in enhanced cell performance. In particular, galactose showed 63% coulombic efficiency in a biofuel cell after P. vulgaris was cultured in a trehalose-containing medium. This work demonstrates that optimum utilization of carbon sources by microorganisms, which leads to the maximization of fuel cell performance, is possible simply by adjusting initial carbon sources.

  7. Identification of candidate microbial sequences from inflammatory lesion of giant cell arteritis.

    PubMed

    Gordon, Lynn K; Goldman, Melissa; Sandusky, Hallie; Ziv, Nurit; Hoffman, Gary S; Goodglick, Todd; Goodglick, Lee

    2004-06-01

    Giant cell arteritis (GCA) is a granulomatous inflammatory disease of medium and large arteries which is prevalent in the elderly population. The etiology of GCA is unknown, although the immunologic features suggest the possible presence of a microorganism. Our group has examined whether microbial DNA fragments were present at GCA lesions and whether such microbial fragments could be associated with disease pathogenesis. Initial identification of microbial sequences was performed using genomic representational difference analysis (RDA). Laser dissecting microscopy was used to isolate cells from GCA lesions and adjacent uninvolved temporal artery. Using genomic RDA, we isolated 10 gene fragments; three of these sequences had high homology with prokaryotic genes and were considered high-priority candidates for further study. An examination of serum from GCA(+) individuals (in contrast to healthy age-matched controls) showed the presence of IgG which recognized in vitro translated proteins from these clones.

  8. Microbial electrolysis cells for high yield hydrogen gas production from organic matter.

    PubMed

    Logan, Bruce E; Call, Douglas; Cheng, Shaoan; Hamelers, Hubertus V M; Sleutels, Tom H J A; Jeremiasse, Adriaan W; Rozendal, René A

    2008-12-01

    The use of electrochemically active bacteria to break down organic matter, combined with the addition of a small voltage (> 0.2 V in practice) in specially designed microbial electrolysis cells (MECs), can result in a high yield of hydrogen gas. While microbial electrolysis was invented only a few years ago, rapid developments have led to hydrogen yields approaching 100%, energy yields based on electrical energy input many times greater than that possible by water electrolysis, and increased gas production rates. MECs used to make hydrogen gas are similar in design to microbial fuel cells (MFCs) that produce electricity, but there are important differences in architecture and analytical methods used to evaluate performance. We review here the materials, architectures, performance, and energy efficiencies of these MEC systems that show promise as a method for renewable and sustainable energy production, and wastewater treatment.

  9. Sustainable Hypersaline Microbial Fuel Cells: Inexpensive Recyclable Polymer Supports for Carbon Nanotube Conductive Paint Anodes.

    PubMed

    Grattieri, Matteo; Shivel, Nelson D; Sifat, Iram; Bestetti, Massimiliano; Minteer, Shelley D

    2017-02-28

    Microbial fuel cells are an emerging technology for wastewater treatment, but to be commercially viable and sustainable, the electrode materials must be inexpensive, recyclable, and reliable. In this study, recyclable polymeric supports were explored for the development of anode electrodes to be applied in single-chamber microbial fuel cells operated in field under hypersaline conditions. The support was covered with a carbon nanotube (CNT) based conductive paint, and biofilms were able to colonize the electrodes. The single-chamber microbial fuel cells with Pt-free cathodes delivered a reproducible power output after 15 days of operation to achieve 12±1 mW m(-2) at a current density of 69±7 mA m(-2) . The decrease of the performance in long-term experiments was mostly related to inorganic precipitates on the cathode electrode and did not affect the performance of the anode, as shown by experiments in which the cathode was replaced and the fuel cell performance was regenerated. The results of these studies show the feasibility of polymeric supports coated with CNT-based paint for microbial fuel cell applications.

  10. Identification of a potent microbial lipid antigen for diverse Natural Killer T cells1

    PubMed Central

    Wolf, Benjamin J.; Tatituri, Raju V. V.; Almeida, Catarina F.; Le Nours, Jérôme; Bhowruth, Veemal; Johnson, Darryl; Uldrich, Adam P.; Hsu, Fong-Fu; Brigl, Manfred; Besra, Gurdyal S.; Rossjohn, Jamie; Godfrey, Dale I.; Brenner, Michael B.

    2016-01-01

    Invariant Natural Killer T (iNKT) cells are a well-characterized CD1d-restricted T cell subset. The availability of potent antigens and tetramers for iNKT cells has allowed this population to be extensively studied and has revealed their central roles in infection, autoimmunity, and tumor immunity. In contrast, diverse Natural Killer T (dNKT) cells are poorly understood because the lipid antigens they recognize are largely unknown. We sought to identify dNKT cell lipid antigen(s) by interrogating a panel of dNKT mouse cell hybridomas with lipid extracts from the pathogen Listeria monocytogenes. We identified Listeria phosphatidylglycerol (PG) as a microbial antigen that was significantly more potent than a previously characterized dNKT cell antigen, mammalian PG. Further, while mammalian PG loaded CD1d tetramers did not stain dNKT cells, the Listeria-derived PG loaded tetramers did. The structure of Listeria PG was distinct from mammalian PG since it contained shorter, fully-saturated anteiso fatty acid lipid tails. CD1d binding lipid displacement studies revealed that the microbial PG antigen binds significantly better to CD1d than counterparts with the same headgroup. These data reveal a highly-potent microbial lipid antigen for a subset of dNKT cells and provide an explanation for its increased antigen potency compared to the mammalian counterpart. PMID:26254340

  11. Hydrophobic substances induce water stress in microbial cells

    PubMed Central

    Bhaganna, Prashanth; Volkers, Rita J. M.; Bell, Andrew N. W.; Kluge, Kathrin; Timson, David J.; McGrath, John W.; Ruijssenaars, Harald J.; Hallsworth, John E.

    2010-01-01

    Summary Ubiquitous noxious hydrophobic substances, such as hydrocarbons, pesticides and diverse industrial chemicals, stress biological systems and thereby affect their ability to mediate biosphere functions like element and energy cycling vital to biosphere health. Such chemically diverse compounds may have distinct toxic activities for cellular systems; they may also share a common mechanism of stress induction mediated by their hydrophobicity. We hypothesized that the stressful effects of, and cellular adaptations to, hydrophobic stressors operate at the level of water : macromolecule interactions. Here, we present evidence that: (i) hydrocarbons reduce structural interactions within and between cellular macromolecules, (ii) organic compatible solutes – metabolites that protect against osmotic and chaotrope‐induced stresses – ameliorate this effect, (iii) toxic hydrophobic substances induce a potent form of water stress in macromolecular and cellular systems, and (iv) the stress mechanism of, and cellular responses to, hydrophobic substances are remarkably similar to those associated with chaotrope‐induced water stress. These findings suggest that it may be possible to devise new interventions for microbial processes in both natural environments and industrial reactors to expand microbial tolerance of hydrophobic substances, and hence the biotic windows for such processes. PMID:21255365

  12. Single cell visualization of sulfur cycling in intertidal microbial mats

    NASA Astrophysics Data System (ADS)

    Dawson, K.; Green, A.; Orphan, V. J.

    2014-12-01

    Chemoautrophic microbial mats form in shallow intertidal pools adjacent to sulfidic hydrothermal vents in San Pedro, CA. Sulfide is primarily geologically derived. However, microscopy revealed deltaproteobacteria closely associated with Beggiatoa -like filaments, indicating an additional biogenic sulfide source, derived from sulfate reduction or sulfur disproportionation. At small scales the intercellular interaction of sulfide producing and sulfide consuming bacteria may play a important role in biogeochemical sulfur cycling. We explored the intracellular transfer of biologically derived sulfide in this system with triple and quadruple stable isotope labeling experiments: 13C, 15N, 33S, and 34S. Silicon wafers colonized by microbial mats in situ, were then incubated with 34SO42- or 34SO42- and 33S0 as well as 13C-acetate and 15NH4+and analyzed by fluorescent in situ hybridization (FISH) coupled to nanometer-scale secondary ion mass spectrometry (NanoSIMS). We observed enrichment of 34S and 33S in both deltaproteobacteria and sulfide oxidizing gammaproteobacteria. Greater enrichment relative to killed controls occurred in deltaproteobacteria than the sulfide oxidizers during both sulfate reducing (Δ34Sdelta-killed = 240‰, Δ34Sgamma-killed = 40‰) and sulfur disproportionating incubations (Δ33Sdelta-killed = 1730‰, Δ33Sgamma-killed = 1050‰). These results provide a direct visualization of interspecies sulfur transfer and indicate that biogenic sulfide derived from either sulfate or intermediate oxidation state sulfur species plays a role in sulfur cycling in this system.

  13. Engineering cellular redox balance in Saccharomyces cerevisiae for improved production of L-lactic acid.

    PubMed

    Lee, Ju Young; Kang, Chang Duk; Lee, Seung Hyun; Park, Young Kyoung; Cho, Kwang Myung

    2015-04-01

    Owing to the growing market for the biodegradable and renewable polymer, polylactic acid, world demand for lactic acid is rapidly increasi