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Sample records for bacteria regulated polymerization

  1. Molecularly Regulated Reversible DNA Polymerization.

    PubMed

    Chen, Niancao; Shi, Xuechen; Wang, Yong

    2016-06-01

    Natural polymers are synthesized and decomposed under physiological conditions. However, it is challenging to develop synthetic polymers whose formation and reversibility can be both controlled under physiological conditions. Here we show that both linear and branched DNA polymers can be synthesized via molecular hybridization in aqueous solutions, on the particle surface, and in the extracellular matrix (ECM) without the involvement of any harsh conditions. More importantly, these polymers can be effectively reversed to dissociate under the control of molecular triggers. Since nucleic acids can be conjugated with various molecules or materials, we anticipate that molecularly regulated reversible DNA polymerization holds potential for broad biological and biomedical applications. PMID:27100911

  2. Phylogenetic Analysis Identifies Many Uncharacterized Actin-like Proteins (Alps) in Bacteria: Regulated Polymerization, Dynamic Instability, and Treadmilling in Alp7A

    PubMed Central

    Derman, Alan I.; Becker, Eric C.; Truong, Bao D.; Fujioka, Akina; Tucey, Timothy M.; Erb, Marcella L.; Patterson, Paula C.; Pogliano, Joe

    2010-01-01

    Summary Actin, one of the most abundant proteins in the eukaryotic cell, also has an abundance of relatives in the eukaryotic proteome. To date though, only five families of actins have been characterized in bacteria. We have conducted a phylogenetic search and uncovered more than 35 highly divergent families of actin-like proteins (Alps) in bacteria. Their genes are found primarily on phage genomes, on plasmids, and on integrating conjugative elements, and are likely to be involved in a variety of functions. We characterize three Alps and find that all form filaments in the cell. The filaments of Alp7A, a plasmid partitioning protein and one of the most divergent of the Alps, display dynamic instability and also treadmill. Alp7A requires other elements from the plasmid to assemble into dynamic polymers in the cell. Our findings suggest that most if not all of the Alps are indeed actin relatives, and that actin is very well represented in bacteria. PMID:19602153

  3. Cell Size Regulation in Bacteria

    NASA Astrophysics Data System (ADS)

    Amir, Ariel

    2014-05-01

    Various bacteria such as the canonical gram negative Escherichia coli or the well-studied gram positive Bacillus subtilis divide symmetrically after they approximately double their volume. Their size at division is not constant, but is typically distributed over a narrow range. Here, we propose an analytically tractable model for cell size control, and calculate the cell size and interdivision time distributions, as well as the correlations between these variables. We suggest ways of extracting the model parameters from experimental data, and show that existing data for E. coli supports partial size control, and a particular explanation: a cell attempts to add a constant volume from the time of initiation of DNA replication to the next initiation event. This hypothesis accounts for the experimentally observed correlations between mother and daughter cells as well as the exponential dependence of size on growth rate.

  4. Ca2+-calmodulin regulates fesselin-induced actin polymerization.

    PubMed

    Schroeter, Mechthild; Chalovich, Joseph M

    2004-11-01

    Fesselin is a proline-rich actin-binding protein that was isolated from avian smooth muscle. Fesselin bundles actin and accelerates actin polymerization by facilitating nucleation. We now show that this polymerization of actin can be regulated by Ca(2+)-calmodulin. Fesselin was shown to bind to immobilized calmodulin in the presence of Ca(2+). The fesselin-calmodulin interaction was confirmed by a Ca(2+)-dependent increase in 2-(4-maleimidoanilino)naphthalene-6-sulfonic acid (MIANS) fluorescence upon addition of fesselin to MIANS-labeled wheat germ calmodulin. The affinity was estimated to be approximately 10(9) M(-1). The affinity of Ca(2+)-calmodulin to the fesselin F-actin complex was approximately 10(8) M(-1). Calmodulin binding to fesselin appeared to be functionally significant. In the presence of fesselin and calmodulin, the polymerization of actin was Ca(2+)-dependent. Ca(2+)-free calmodulin either had no effect or enhanced the ability of fesselin to accelerate actin polymerization. Ca(2+)-calmodulin not only reversed the stimulatory effect of fesselin but reduced the rate of polymerization below that observed in the absence of fesselin. While Ca(2+)-calmodulin had a large effect on the interaction of fesselin with G-actin, the effect on F-actin was small. Neither the binding of fesselin to F-actin nor the subsequent bundling of F-actin was greatly affected by Ca(2+)-calmodulin. Fesselin may function as an actin-polymerizing factor that is regulated by Ca(2+) levels. PMID:15504050

  5. Extracellular polymeric substances of bacteria and their potential environmental applications.

    PubMed

    More, T T; Yadav, J S S; Yan, S; Tyagi, R D; Surampalli, R Y

    2014-11-01

    Biopolymers are considered a potential alternative to conventional chemical polymers because of their ease of biodegradability, high efficiency, non-toxicity and non-secondary pollution. Recently, extracellular polymeric substances (EPS, biopolymers produced by the microorganisms) have been recognised by many researchers as a potential flocculent for their applications in various water, wastewater and sludge treatment processes. In this context, literature information on EPS is widely dispersed and is very scarce. Thus, this review marginalizes various studies conducted so far about EPS nature-production-recovery, properties, environmental applications and moreover, critically examines future research needs and advanced application prospective of the EPS. One of the most important aspect of chemical composition and structural details of different moieties of EPS in terms of carbohydrates, proteins, extracellular DNA, lipid and surfactants and humic substances are described. These chemical characteristics of EPS in relation to formation and properties of microbial aggregates as well as degradation of EPS in the matrix (biomass, flocs etc) are analyzed. The important engineering properties (based on structural characteristics) such as adsorption, biodegradability, hydrophilicity/hydrophobicity of EPS matrix are also discussed in details. Different aspects of EPS production process such as bacterial strain maintenance; inoculum and factors affecting EPS production were presented. The important factors affecting EPS production include growth phase, carbon and nitrogen sources and their ratio, role of other nutrients (phosphorus, micronutrients/trace elements, and vitamins), impact of pH, temperature, metals, aerobic versus anaerobic conditions and pure and mixed culture. The production of EPS in high concentration with high productivity is essential due to economic reasons. Therefore, the knowledge about all the aspects of EPS production (listed above) is highly

  6. Silver nanoparticles formation by extracellular polymeric substances (EPS) from electroactive bacteria.

    PubMed

    Li, Shan-Wei; Zhang, Xing; Sheng, Guo-Ping

    2016-05-01

    Microbial extracellular polymeric substances (EPS) excreted from microorganisms were a complex natural biological polymer mixture of proteins and polysaccharides, which played an important roles in the transport of metals, such as Ag(+). Electroactive bacteria, is an important class of environmental microorganisms, which can use iron or manganese mineral as terminal electron acceptors to generate energy for biosynthesis and cell maintenance. In this work, the EPS extracted of three electroactive bacteria (Shewanella oneidensis, Aeromonas hydrophila, and Pseudomonas putida) were used for reducing Ag(+) and forming silver nanoparticles (AgNPs). Results showed that all the three microbial EPS could reduce Ag(+) to AgNPs. The formed AgNPs were characterized in depth by the UV-visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The main components in the EPS from the three electroactive bacteria were analyzed. The presence of cytochrome c in these EPS was confirmed, and they were found to contribute to the reduction of Ag(+) to AgNPs. The results indicated that the EPS of electroactive bacteria could act as a reductant for AgNPs synthesis and could provide new information to understand the fate of metals and their metal nanoparticles in the natural environments. PMID:26797954

  7. Plasma nanotextured polymeric lab-on-a-chip for highly efficient bacteria capture and lysis.

    PubMed

    Tsougeni, K; Papadakis, G; Gianneli, M; Grammoustianou, A; Constantoudis, V; Dupuy, B; Petrou, P S; Kakabakos, S E; Tserepi, A; Gizeli, E; Gogolides, E

    2016-01-01

    We describe the design, fabrication, and successful demonstration of a sample preparation module comprising bacteria cell capture and thermal lysis on-chip with potential applications in food sample pathogen analysis. Plasma nanotexturing of the polymeric substrate allows increase of the surface area of the chip and the antibody binding capacity. Three different anti-Salmonella antibodies were directly and covalently linked to plasma treated chips without any additional linker chemistry or other treatment. Then, the Ab-modified chips were tested for their capacity to bind bacteria in the concentration range of 10(2)-10(8) cells per mL; the module exhibited 100% efficiency in Salmonella enterica serovar Typhimurium bacteria capture for cell suspensions below 10(5) cells per mL (10(4) cells injected with a 100 μL sample volume) and efficiency higher than 50% for 10(7) cells per mL. Moreover, thermal lysis achieved on-chip from as low as 10 captured cells was demonstrated and shown to compare well with off-chip lysis. Excellent selectivity (over 1 : 300) was obtained in a sample containing, in addition to S. Typhimurium and E. coli bacteria. PMID:26556673

  8. Extracellular polymeric substances mediate bioleaching/biocorrosion via interfacial processes involving iron(III) ions and acidophilic bacteria.

    PubMed

    Sand, Wolfgang; Gehrke, Tilman

    2006-01-01

    Extracellular polymeric substances seem to play a pivotal role in biocorrosion of metals and bioleaching, biocorrosion of metal sulfides for the winning of precious metals as well as acid rock drainage. For better control of both processes, the structure and function of extracellular polymeric substances of corrosion-causing or leaching bacteria are of crucial importance. Our research focused on the extremophilic bacteria Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans, because of the "simplicity" and knowledge about the interactions of these bacteria with their substrate/substratum and their environment. For this purpose, the composition of the corresponding extracellular polymeric substances and their functions were analyzed. The extracellular polymeric substances of both species consist mainly of neutral sugars and lipids. The functions of the exopolymers seem to be: (i) to mediate attachment to a (metal) sulfide surface, and (ii) to concentrate iron(III) ions by complexation through uronic acids or other residues at the mineral surface, thus, allowing an oxidative attack on the sulfide. Consequently, dissolution of the metal sulfide is enhanced, which may result in an acceleration of 20- to 100-fold of the bioleaching process over chemical leaching. Experiments were performed to elucidate the importance of the iron(III) ions complexed by extracellular polymeric substances for strain-specific differences in oxidative activity for pyrite. Strains of A. ferrooxidans with a high amount of iron(III) ions in their extracellular polymeric substances possess greater oxidation activity than those with fewer iron(III) ions. These data provide insight into the function of and consequently the advantages that extracellular polymeric substances provide to bacteria. The role of extracellular polymeric substances for attachment under the conditions of a space station and resulting effects like biofouling, biocorrosion, malodorous gases, etc. will be discussed

  9. The Interaction of Bacteria with Engineered Nanostructured Polymeric Materials: A Review

    PubMed Central

    Armentano, Ilaria; Arciola, Carla Renata; Fortunati, Elena; Ferrari, Davide; Mattioli, Samantha; Amoroso, Concetta Floriana; Rizzo, Jessica; Kenny, Jose M.; Imbriani, Marcello; Visai, Livia

    2014-01-01

    Bacterial infections are a leading cause of morbidity and mortality worldwide. In spite of great advances in biomaterials research and development, a significant proportion of medical devices undergo bacterial colonization and become the target of an implant-related infection. We present a review of the two major classes of antibacterial nanostructured materials: polymeric nanocomposites and surface-engineered materials. The paper describes antibacterial effects due to the induced material properties, along with the principles of bacterial adhesion and the biofilm formation process. Methods for antimicrobial modifications of polymers using a nanocomposite approach as well as surface modification procedures are surveyed and discussed, followed by a concise examination of techniques used in estimating bacteria/material interactions. Finally, we present an outline of future sceneries and perspectives on antibacterial applications of nanostructured materials to resist or counteract implant infections. PMID:25025086

  10. Stuttering Min oscillations within E. coli bacteria: a stochastic polymerization model

    NASA Astrophysics Data System (ADS)

    Sengupta, Supratim; Derr, Julien; Sain, Anirban; Rutenberg, Andrew D.

    2012-10-01

    We have developed a 3D off-lattice stochastic polymerization model to study the subcellular oscillation of Min proteins in the bacteria Escherichia coli, and used it to investigate the experimental phenomenon of Min oscillation stuttering. Stuttering was affected by the rate of immediate rebinding of MinE released from depolymerizing filament tips (processivity), protection of depolymerizing filament tips from MinD binding and fragmentation of MinD filaments due to MinE. Processivity, protection and fragmentation each reduce stuttering, speed oscillations and MinD filament lengths. Neither processivity nor tip protection were, on their own, sufficient to produce fast stutter-free oscillations. While filament fragmentation could, on its own, lead to fast oscillations with infrequent stuttering; high levels of fragmentation degraded oscillations. The infrequent stuttering observed in standard Min oscillations is consistent with short filaments of MinD, while we expect that mutants that exhibit higher stuttering frequencies will exhibit longer MinD filaments. Increased stuttering rate may be a useful diagnostic to find observable MinD polymerization under experimental conditions.

  11. Component analysis and heavy metal adsorption ability of extracellular polymeric substances (EPS) from sulfate reducing bacteria.

    PubMed

    Yue, Zheng-Bo; Li, Qing; Li, Chuan-chuan; Chen, Tian-hu; Wang, Jin

    2015-10-01

    Extracellular polymeric substances (EPS) play an important role in the treatment of acid mine drainage (AMD) by sulfate-reducing bacteria (SRB). In this paper, Desulfovibrio desulfuricans was used as the test strain to explore the effect of heavy metals on the components and adsorption ability of EPS. Fourier-transform infrared (FTIR) spectroscopy analysis results showed that heavy metals did not influence the type of functional groups of EPS. Potentiometric titration results indicated that the acidic constants (pKa) of the EPS fell into three ranges of 3.5-4.0, 5.9-6.7, and 8.9-9.8. The adsorption site concentrations of the surface functional groups also increased. Adsorption results suggested that EPS had a specific binding affinity for the dosed heavy metal, and that EPS extracted from the Zn(2+)-dosed system had a higher binding affinity for all heavy metals. Additionally, Zn(2+) decreased the inhibitory effects of Cd(2+) and Cu(2+) on the SRB. PMID:26210529

  12. Correlation among extracellular polymeric substances, tetracycline resistant bacteria and tetracycline resistance genes under trace tetracycline.

    PubMed

    Huang, Man-hong; Zhang, Wei; Zheng, Yu; Zhang, Wen

    2014-12-01

    Antibiotic resistance occurrences and proliferation in activated sludge have attracted more and more attention nowadays. However, the role which extracellular polymeric substance (EPS) plays on the antibiotic resistance is not clear. The changes and correlation among EPS, tetracycline (TC) resistant bacteria (TRB) and TC resistance genes (TRGs) of sequencing batch reactors (SBRs) were investigated. Performance of SBR without TC was compared with two other SBRs to which different amounts of TC were added. Total average EPS contents were found to increase significantly from 66 mg g−1 VSS to 181 mg g−1 VSS as the TC concentrations increased from 0 to 100 μg L−1. As the EPS content increased, TRB in sludge of the three SBRs increased significantly from 105 to 106 colony forming unit mL−1 after being exposed to TC. In addition, the concentrations of three groups of TRGs (copies mL−1) were determined by real-time fluorescence quantitative polymerase chain reaction and followed the order: efflux pump genes > ribosome protected genes > degradation enzyme genes. The numbers of TRGs in the idle stage were larger than those in the aeration sludge. Correlation coefficients (R2) between EPS and TRB in sludge were 0.823 (p < 0.01) while the correlation between EPS and total TRGs was poor (R2 = 0.463, p > 0.05). But it showed the same tendency that EPS and TRGs in sludge increased with the increasing of TC. PMID:25461932

  13. Regulation of kinesin-transport by microtubule age and polymerization conditions

    NASA Astrophysics Data System (ADS)

    Xu, Jing; Liang, Winnie; King, Stephen; Faysal, K.

    2015-03-01

    Microtubules are fundamental biopolymers in cells, formed via self-assembly (``polymerization'') of tubulin dimers. Microtubule polymerization conditions have been shown to alter the presence of defects in microtubule lattices, including point defects (missing tubulin dimers) and line defects (protofilament disruption). Potential impact of these lattice defects on molecular motor-based transport is not yet understood. Here we investigate the impact of microtubule polymerization conditions on multiple-kinesin transport, using single-molecule-type optical trapping experiments. We find that kinesin-based cargoes pause preferentially at specific locations along individual microtubules, and that the pause frequency and duration is strongly dependent on microtubule age and polymerization condition. Within each polymerization condition and for fresh microtubules, we also observe significant variations in multiple-kinesin travel distances, depending on which microtubules the motors travel along. Taken together, our study suggests an important role of microtubule lattice defect in regulating intracellular transport.

  14. Yersinia effector YopO uses actin as bait to phosphorylate proteins that regulate actin polymerization

    PubMed Central

    Lee, Wei Lin; Grimes, Jonathan M; Robinson, Robert C

    2016-01-01

    Pathogenic Yersinia species evade host immune systems through the injection of Yersinia outer proteins (Yops) into phagocytic cells. One Yop, YopO, also known as YpkA, induces actin-filament disruption, impairing phagocytosis. Here we describe the X-ray structure of Yersinia enterocolitica YopO in complex with actin, which reveals that YopO binds to an actin monomer in a manner that blocks polymerization yet allows the bound actin to interact with host actin-regulating proteins. SILAC-MS and biochemical analyses confirm that actin-polymerization regulators such as VASP, EVL, WASP, gelsolin and the formin diaphanous 1 are directly sequestered and phosphorylated by YopO through formation of ternary complexes with actin. This leads to a model in which YopO at the membrane sequesters actin from polymerization while using the bound actin as bait to recruit, phosphorylate and misregulate host actin-regulating proteins to disrupt phagocytosis. PMID:25664724

  15. Redox regulation by reversible protein S-thiolation in bacteria

    PubMed Central

    Loi, Vu Van; Rossius, Martina; Antelmann, Haike

    2015-01-01

    Low molecular weight (LMW) thiols function as thiol-redox buffers to maintain the reduced state of the cytoplasm. The best studied LMW thiol is the tripeptide glutathione (GSH) present in all eukaryotes and Gram-negative bacteria. Firmicutes bacteria, including Bacillus and Staphylococcus species utilize the redox buffer bacillithiol (BSH) while Actinomycetes produce the related redox buffer mycothiol (MSH). In eukaryotes, proteins are post-translationally modified to S-glutathionylated proteins under conditions of oxidative stress. S-glutathionylation has emerged as major redox-regulatory mechanism in eukaryotes and protects active site cysteine residues against overoxidation to sulfonic acids. First studies identified S-glutathionylated proteins also in Gram-negative bacteria. Advances in mass spectrometry have further facilitated the identification of protein S-bacillithiolations and S-mycothiolation as BSH- and MSH-mixed protein disulfides formed under oxidative stress in Firmicutes and Actinomycetes, respectively. In Bacillus subtilis, protein S-bacillithiolation controls the activities of the redox-sensing OhrR repressor and the methionine synthase MetE in vivo. In Corynebacterium glutamicum, protein S-mycothiolation was more widespread and affected the functions of the maltodextrin phosphorylase MalP and thiol peroxidase (Tpx). In addition, novel bacilliredoxins (Brx) and mycoredoxins (Mrx1) were shown to function similar to glutaredoxins in the reduction of BSH- and MSH-mixed protein disulfides. Here we review the current knowledge about the functions of the bacterial thiol-redox buffers glutathione, bacillithiol, and mycothiol and the role of protein S-thiolation in redox regulation and thiol protection in model and pathogenic bacteria. PMID:25852656

  16. Protein phosphorylation and regulation of adaptive responses in bacteria.

    PubMed Central

    Stock, J B; Ninfa, A J; Stock, A M

    1989-01-01

    Bacteria continuously adapt to changes in their environment. Responses are largely controlled by signal transduction systems that contain two central enzymatic components, a protein kinase that uses adenosine triphosphate to phosphorylate itself at a histidine residue and a response regulator that accepts phosphoryl groups from the kinase. This conserved phosphotransfer chemistry is found in a wide range of bacterial species and operates in diverse systems to provide different regulatory outputs. The histidine kinases are frequently membrane receptor proteins that respond to environmental signals and phosphorylate response regulators that control transcription. Four specific regulatory systems are discussed in detail: chemotaxis in response to attractant and repellent stimuli (Che), regulation of gene expression in response to nitrogen deprivation (Ntr), control of the expression of enzymes and transport systems that assimilate phosphorus (Pho), and regulation of outer membrane porin expression in response to osmolarity and other culture conditions (Omp). Several additional systems are also examined, including systems that control complex developmental processes such as sporulation and fruiting-body formation, systems required for virulent infections of plant or animal host tissues, and systems that regulate transport and metabolism. Finally, an attempt is made to understand how cross-talk between parallel phosphotransfer pathways can provide a global regulatory curcuitry. PMID:2556636

  17. Surfaces modified with nanometer-thick silver-impregnated polymeric films that kill bacteria but support growth of mammalian cells.

    PubMed

    Agarwal, Ankit; Weis, Tahlia L; Schurr, Michael J; Faith, Nancy G; Czuprynski, Charles J; McAnulty, Jonathan F; Murphy, Christopher J; Abbott, Nicholas L

    2010-02-01

    Silver is widely used as a biocidal agent in ointments and wound dressings. However, it has also been associated with tissue toxicity and impaired healing. In vitro characterization has also revealed that typical loadings of silver employed in ointments and dressings (approximately 100 microg/cm(2)) lead to cytotoxicity. In this paper, we report the results of an initial study that sought to determine if localization of carefully controlled loadings of silver nanoparticles within molecularly thin films immobilized on surfaces can lead to antimicrobial activity without inducing cytotoxicity. Polymeric thin films of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were prepared by layer-by-layer deposition and loaded with approximately 0.4 microg/cm(2) to approximately 23.6 microg/cm(2) of silver nanoparticles. Bacterial killing efficiencies of the silver-loaded films were investigated against Staphylococcus epidermidis, a gram-positive bacterium, and it was determined that as little as approximately 0.4 microg/cm(2) of silver in the polymeric films caused a reduction of 6log(10)CFU/mL (99.9999%) bacteria in suspensions incubated in contact with the films (water-borne assays). Significantly, whereas the antibacterial films containing high loadings of silver were found to be toxic to a murine fibroblast cell line (NIH-3T3), the polymeric films containing approximately 0.4 microg/cm(2) of silver were not toxic and allowed attachment, and growth of the mammalian cells. Thus, the results of this study go beyond prior reports by identifying silver-impregnated, polymeric thin films that are compatible with in vitro mammalian cell culture yet exhibit antibacterial activity. These results support the hypothesis that localization of carefully controlled loadings of silver nanoparticles within molecularly thin polymeric films can lead to antimicrobial activity without cytotoxicity. More broadly, this strategy of modifying surfaces with minimal loadings of

  18. The Role of the Cytoskeleton in the Life Cycle of Viruses and Intracellular Bacteria: Tracks, Motors, and Polymerization Machines

    PubMed Central

    Bearer, E.L.; Satpute-Krishnan, P.

    2013-01-01

    Recent advances in microbiology implicate the cytoskeleton in the life cycle of some pathogens, such as intracellular bacteria, Rickettsia and viruses. The cellular cytoskeleton provides the basis for intracellular movements such as those that transport the pathogen to and from the cell surface to the nuclear region, or those that produce cortical protrusions that project the pathogen outwards from the cell surface towards an adjacent cell. Transport in both directions within the neuron is required for pathogens such as the herpesviruses to travel to and from the nucleus and perinuclear region where replication takes place. This trafficking is likely to depend on cellular motors moving on a combination of microtubule and actin filament tracks. Recently, Bearer et al. reconstituted retrograde transport of herpes simplex virus (HSV) in the giant axon of the squid. These studies identified the tegument proteins as the viral proteins most likely to recruit retrograde motors for the transport of HSV to the neuronal nucleus. Similar microtubule-based intracellular movements are part of the biological behavior of vaccinia, a poxvirus, and of adenovirus. Pathogen-induced surface projections and motility within the cortical cytoplasm also play a role in the life cycle of intracellular pathogens. Such motility is driven by pathogen-mediated actin polymerization. Virulence depends on this actin-based motility, since virulence is reduced in Listeria ActA mutants that lack the ability to recruit Arp2/3 and polymerize actin and in vaccinia virus mutants that cannot stimulate actin polymerization. Inhibition of intracellular movements provides a potential strategy to limit pathogenicity. The host cell motors and tracks, as well as the pathogen factors that interact with them, are potential targets for novel antimicrobial therapy. PMID:12462128

  19. Isolation and characterization of polymeric galloyl-ester-degrading bacteria from a tannery discharge place.

    PubMed

    Franco, A R; Calheiros, C S C; Pacheco, C C; De Marco, P; Manaia, C M; Castro, P M L

    2005-11-01

    The culturable bacteria colonizing the rhizosphere of plants growing in the area of discharge of a tannery effluent were characterized. Relative proportions of aerobic, denitrifying, and sulfate-reducing bacteria were determined in the rhizosphere of Typha latifolia, Canna indica, and Phragmites australis. Aerobic bacteria were observed to be the most abundant group in the rhizosphere, and plant type did not seem to influence the abundance of the bacterial types analyzed. To isolate bacteria able to degrade polyphenols used in the tannery industry, enrichments were conducted under different conditions. Bacterial cultures were enriched with individual polyphenols (tannins Tara, Quebracho, or Mimosa) or with an undefined mixture of tannins present in the tannery effluent as carbon source. Cultures enriched with the effluent or Tara tannin were able to degrade tannic acid. Six bacterial isolates purified from these mixed cultures were able to use tannic acid as a sole carbon source in axenic culture. On the basis of 16S ribosomal DNA sequence analysis, these isolates were closely related to organisms belonging to the taxa Serratia, Stenotrophomonas maltophilia, Klebsiella oxytoca, Herbaspirillum chlorophenolicum, and Pseudomonas putida. PMID:16341641

  20. Polymerizing the fibre between bacteria and host cells: the biogenesis of functional amyloid fibres

    PubMed Central

    Epstein, Elisabeth Ashman; Chapman, Matthew R.

    2009-01-01

    Summary Amyloid fibres are proteinaceous aggregates associated with several human diseases, including Alzheimer’s, Huntington’s and Creutzfeldt Jakob’s. Disease-associated amyloid formation is the result of proteins that misfold and aggregate into β sheet-rich fibre polymers. Cellular toxicity is readily associated with amyloidogenesis, although the molecular mechanism of toxicity remains unknown. Recently, a new class of ‘functional’ amyloid fibres was discovered that demonstrates that amyloids can be utilized as a productive part of cellular biology. These functional amyloids will provide unique insights into how amyloid formation can be controlled and made less cytotoxic. Bacteria produce some of the best-characterized functional amyloids, including a surface amyloid fibre called curli. Assembled by enteric bacteria, curli fibres mediate attachment to surfaces and host tissues. Some bacterial amyloids, like harpins and microcinE492, have exploited amyloid toxicity in a directed and functional manner. Here, we review and discuss the functional amyloids assembled by bacteria. Special emphasis will be paid to the biology of functional amyloid synthesis and the connections between bacterial physiology and pathology. PMID:18373633

  1. Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis

    PubMed Central

    Yano, Jessica M.; Yu, Kristie; Donaldson, Gregory P.; Shastri, Gauri G.; Ann, Phoebe; Ma, Liang; Nagler, Cathryn R.; Ismagilov, Rustem F.; Mazmanian, Sarkis K.; Hsiao, Elaine Y.

    2015-01-01

    SUMMARY The gastrointestinal (GI) tract contains much of the body’s serotonin (5-hydroxytryptamine, 5-HT), but mechanisms controlling the metabolism of gut-derived 5-HT remain unclear. Here we demonstrate that the microbiota plays a critical role in regulating host 5-HT. Indigenous spore-forming bacteria (Sp) from the mouse and human microbiota promote 5-HT biosynthesis from colonic enterochromaffin cells (ECs), which supply 5-HT to the mucosa, lumen and circulating platelets. Importantly, microbiota-dependent effects on gut 5-HT significantly impact host physiology, modulating GI motility and platelet function. We identify select fecal metabolites that are increased by Sp and that elevate 5-HT in chromaffin cell cultures, suggesting direct metabolic signaling of gut microbes to ECs. Furthermore, elevating luminal concentrations of particular microbial metabolites increases colonic and blood 5-HT in germ-free mice. Altogether, these findings demonstrate that Sp are important modulators of host 5-HT, and further highlight a key role for host-microbiota interactions in regulating fundamental 5-HT-related biological processes. PMID:25860609

  2. Estrogen Regulates Protein Synthesis and Actin Polymerization in Hippocampal Neurons through Different Molecular Mechanisms

    PubMed Central

    Briz, Victor; Baudry, Michel

    2014-01-01

    Estrogen rapidly modulates hippocampal synaptic plasticity by activating selective membrane-associated receptors. Reorganization of the actin cytoskeleton and stimulation of mammalian target of rapamycin (mTOR)-mediated protein synthesis are two major events required for the consolidation of hippocampal long-term potentiation and memory. Estradiol regulates synaptic plasticity by interacting with both processes, but the underlying molecular mechanisms are not yet fully understood. Here, we used acute rat hippocampal slices to analyze the mechanisms underlying rapid changes in mTOR activity and actin polymerization elicited by estradiol. Estradiol-induced mTOR phosphorylation was preceded by rapid and transient activation of both extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) and by phosphatase and tensin homolog (PTEN) degradation. These effects were prevented by calpain and ERK inhibitors. Estradiol-induced mTOR stimulation did not require activation of classical estrogen receptors (ER), as specific ERα and ERβ agonists (PPT and DPN, respectively) failed to mimic this effect, and ER antagonists could not block it. Estradiol rapidly activated both RhoA and p21-activated kinase (PAK). Furthermore, a specific inhibitor of RhoA kinase (ROCK), H1152, and a potent and specific PAK inhibitor, PF-3758309, blocked estradiol-induced cofilin phosphorylation and actin polymerization. ER antagonists also blocked these effects of estrogen. Consistently, both PPT and DPN stimulated PAK and cofilin phosphorylation as well as actin polymerization. Finally, the effects of estradiol on actin polymerization were insensitive to protein synthesis inhibitors, but its stimulation of mTOR activity was impaired by latrunculin A, a drug that disrupts actin filaments. Taken together, our results indicate that estradiol regulates local protein synthesis and cytoskeletal reorganization via different molecular mechanisms and signaling pathways. PMID:24611062

  3. Airway bacteria drive a progressive COPD-like phenotype in mice with polymeric immunoglobulin receptor deficiency.

    PubMed

    Richmond, Bradley W; Brucker, Robert M; Han, Wei; Du, Rui-Hong; Zhang, Yongqin; Cheng, Dong-Sheng; Gleaves, Linda; Abdolrasulnia, Rasul; Polosukhina, Dina; Clark, Peter E; Bordenstein, Seth R; Blackwell, Timothy S; Polosukhin, Vasiliy V

    2016-01-01

    Mechanisms driving persistent airway inflammation in chronic obstructive pulmonary disease (COPD) are incompletely understood. As secretory immunoglobulin A (SIgA) deficiency in small airways has been reported in COPD patients, we hypothesized that immunobarrier dysfunction resulting from reduced SIgA contributes to chronic airway inflammation and disease progression. Here we show that polymeric immunoglobulin receptor-deficient (pIgR(-/-)) mice, which lack SIgA, spontaneously develop COPD-like pathology as they age. Progressive airway wall remodelling and emphysema in pIgR(-/-) mice are associated with an altered lung microbiome, bacterial invasion of the airway epithelium, NF-κB activation, leukocyte infiltration and increased expression of matrix metalloproteinase-12 and neutrophil elastase. Re-derivation of pIgR(-/-) mice in germ-free conditions or treatment with the anti-inflammatory phosphodiesterase-4 inhibitor roflumilast prevents COPD-like lung inflammation and remodelling. These findings show that pIgR/SIgA deficiency in the airways leads to persistent activation of innate immune responses to resident lung microbiota, driving progressive small airway remodelling and emphysema. PMID:27046438

  4. Airway bacteria drive a progressive COPD-like phenotype in mice with polymeric immunoglobulin receptor deficiency

    PubMed Central

    Richmond, Bradley W.; Brucker, Robert M.; Han, Wei; Du, Rui-Hong; Zhang, Yongqin; Cheng, Dong-Sheng; Gleaves, Linda; Abdolrasulnia, Rasul; Polosukhina, Dina; Clark, Peter E.; Bordenstein, Seth R.; Blackwell, Timothy S.; Polosukhin, Vasiliy V.

    2016-01-01

    Mechanisms driving persistent airway inflammation in chronic obstructive pulmonary disease (COPD) are incompletely understood. As secretory immunoglobulin A (SIgA) deficiency in small airways has been reported in COPD patients, we hypothesized that immunobarrier dysfunction resulting from reduced SIgA contributes to chronic airway inflammation and disease progression. Here we show that polymeric immunoglobulin receptor-deficient (pIgR−/−) mice, which lack SIgA, spontaneously develop COPD-like pathology as they age. Progressive airway wall remodelling and emphysema in pIgR−/− mice are associated with an altered lung microbiome, bacterial invasion of the airway epithelium, NF-κB activation, leukocyte infiltration and increased expression of matrix metalloproteinase-12 and neutrophil elastase. Re-derivation of pIgR−/− mice in germ-free conditions or treatment with the anti-inflammatory phosphodiesterase-4 inhibitor roflumilast prevents COPD-like lung inflammation and remodelling. These findings show that pIgR/SIgA deficiency in the airways leads to persistent activation of innate immune responses to resident lung microbiota, driving progressive small airway remodelling and emphysema. PMID:27046438

  5. Conserved-residue mutations in Wzy affect O-antigen polymerization and Wzz-mediated chain-length regulation in Pseudomonas aeruginosa PAO1

    NASA Astrophysics Data System (ADS)

    Islam, Salim T.; Huszczynski, Steven M.; Nugent, Timothy; Gold, Alexander C.; Lam, Joseph S.

    2013-12-01

    O antigen (O-Ag) in many bacteria is synthesized via the Wzx/Wzy-dependent pathway in which Wzy polymerizes lipid-linked O-Ag subunits to modal lengths regulated by Wzz. Characterization of 83 site-directed mutants of Wzy from Pseudomonas aeruginosa PAO1 (WzyPa) in topologically-mapped periplasmic (PL) and cytoplasmic loops (CL) verified the functional importance of PL3 and PL5, with the former shown to require overall cationic properties. Essential Arg residues in the RX10G motifs of PL3 and PL5 were found to be conserved in putative homologues of WzyPa, as was the overall sequence homology between these two periplasmic loops in each protein. Amino acid substitutions in CL6 were found to alter Wzz-mediated O-antigen modality, with evidence suggesting that these changes may perturb the C-terminal WzyPa tertiary structure. Together, these data suggest that the catch-and-release mechanism of O-Ag polymerization is widespread among bacteria and that regulation of polymer length is affected by interaction of Wzz with Wzy.

  6. The potential for hydrocarbon biodegradation and production of extracellular polymeric substances by aerobic bacteria isolated from a Brazilian petroleum reservoir.

    PubMed

    Vasconcellos, S P; Dellagnezze, B M; Wieland, A; Klock, J-H; Santos Neto, E V; Marsaioli, A J; Oliveira, V M; Michaelis, W

    2011-06-01

    Extracellular polymeric substances (EPS) can contribute to the cellular degradation of hydrocarbons and have a huge potential for application in biotechnological processes, such as bioremediation and microbial enhanced oil recovery (MEOR). Four bacterial strains from a Brazilian petroleum reservoir were investigated for EPS production, emulsification ability and biodegradation activity when hydrocarbons were supplied as substrates for microbial growth. Two strains of Bacillus species had the highest EPS production when phenanthrene and n-octadecane were offered as carbon sources, either individually or in a mixture. While Pseudomonas sp. and Dietzia sp., the other two evaluated strains, had the highest hydrocarbon biodegradation indices, EPS production was not detected. Low EPS production may not necessarily be indicative of an absence of emulsifier activity, as indicated by the results of a surface tension reduction assay and emulsification indices for the strain of Dietzia sp. The combined results gathered in this work suggest that a microbial consortium consisting of bacteria with interdependent metabolisms could thrive in petroleum reservoirs, thus overcoming the limitations imposed on each individual species by the harsh conditions found in such environments. PMID:25187151

  7. Regulating the Intersection of Metabolism and Pathogenesis in Gram-positive Bacteria

    PubMed Central

    RICHARDSON, ANTHONY R.; SOMERVILLE, GREG A.; SONENSHEIN, ABRAHAM L.

    2015-01-01

    Pathogenic bacteria must contend with immune systems that actively restrict the availability of nutrients and cofactors, and create a hostile growth environment. To deal with these hostile environments, pathogenic bacteria have evolved or acquired virulence determinants that aid in the acquisition of nutrients. This connection between pathogenesis and nutrition may explain why regulators of metabolism in nonpathogenic bacteria are used by pathogenic bacteria to regulate both metabolism and virulence. Such coordinated regulation is presumably advantageous because it conserves carbon and energy by aligning synthesis of virulence determinants with the nutritional environment. In Gram-positive bacterial pathogens, at least three metabolite-responsive global regulators, CcpA, CodY, and Rex, have been shown to coordinate the expression of metabolism and virulence genes. In this chapter, we discuss how environmental challenges alter metabolism, the regulators that respond to this altered metabolism, and how these regulators influence the host-pathogen interaction. PMID:26185086

  8. Selectively bonded polymeric glaucoma drainage device for reliable regulation of intraocular pressure.

    PubMed

    Moon, Seunghwan; Im, Seongmin; An, Jaeyong; Park, Chang Ju; Kim, Hwang Gyun; Park, Sang Woo; Kim, Hyoung Ihl; Lee, Jong-Hyun

    2012-04-01

    A novel glaucoma drainage device (GDD) using a polymeric micro check valve with no reverse flow is presented for the effective regulation of intraocular pressure (IOP). A significant functional improvement was achieved by reducing the possible incidence of hypotony, as the proposed GDD only drains aqueous humor at a certain cracking pressure or higher. The device consists of three biocompatible polymer layers: a top layer (cover), an intermediate layer (membrane), and a bottom layer (base plate with a cannula). All three layers, made of soft polydimethylsiloxane (PDMS), were bonded together to realize the thin GDDs. The bottom layer was selectively coated with chromium (Cr)/gold (Au) to prevent stiction between the valve seat and the valve orifice so that the device could show enhanced reliability in operation and high yield in production. Two types of polymeric devices were fabricated; one was a glaucoma drainage device for humans (GDDH) and the other was a glaucoma drainage device for animals (GDDA). From subsequent in vitro tests, the cracking pressures were 18.33 ± 0.66 mmHg (mean ± standard deviation) for GDDH and 12.42 mmHg for GDDA, both of which were very close to the corresponding normal IOPs. From in vivo tests of GDDA, the IOP of all implanted devices was properly regulated within the target pressure (10-15 mmHg). The experimental results showed that the proposed polymeric GDD has high potential for use in the treatment of glaucoma disease in terms of its repeatability of the cracking pressure and patients' relief from post-operative discomfort. PMID:22094823

  9. Intersectin-2L Regulates Caveola Endocytosis Secondary to Cdc42-mediated Actin Polymerization*

    PubMed Central

    Klein, Irene K.; Predescu, Dan N.; Sharma, Tiffany; Knezevic, Ivana; Malik, Asrar B.; Predescu, Sanda

    2009-01-01

    Here we addressed the role of intersectin-2L (ITSN-2L), a guanine nucleotide exchange factor for the Rho GTPase Cdc42, in the mechanism of caveola endocytosis in endothelial cells (ECs). Immunoprecipitation and co-localization studies showed that ITSN-2L associates with members of the Cdc42-WASp-Arp2/3 actin polymerization pathway. Expression of Dbl homology-pleckstrin homology (DH-PH) region of ITSN-2L (DH-PHITSN-2L) induced specific activation of Cdc42, resulting in formation of extensive filopodia, enhanced cortical actin, as well as a shift from G-actin to F-actin. The “catalytically dead” DH-PH domain reversed these effects and induced significant stress fiber formation, without a detectable shift in actin pools. A biotin assay for caveola internalization indicated a significant decrease in the uptake of biotinylated proteins in DH-PHITSN-2L-transfected cells compared with control and 1 μm jasplakinolide-treated cells. ECs depleted of ITSN-2L by small interfering RNA, however, showed decreased Cdc42 activation and actin remodeling similar to the defective DH-PH, resulting in 62% increase in caveola-mediated uptake compared with controls. Thus, ITSN-2L, a guanine nucleotide exchange factor for Cdc42, regulates different steps of caveola endocytosis in ECs by controlling the temporal and spatial actin polymerization and remodeling sub-adjacent to the plasma membrane. PMID:19622753

  10. Intersectin-2L regulates caveola endocytosis secondary to Cdc42-mediated actin polymerization.

    PubMed

    Klein, Irene K; Predescu, Dan N; Sharma, Tiffany; Knezevic, Ivana; Malik, Asrar B; Predescu, Sanda

    2009-09-18

    Here we addressed the role of intersectin-2L (ITSN-2L), a guanine nucleotide exchange factor for the Rho GTPase Cdc42, in the mechanism of caveola endocytosis in endothelial cells (ECs). Immunoprecipitation and co-localization studies showed that ITSN-2L associates with members of the Cdc42-WASp-Arp2/3 actin polymerization pathway. Expression of Dbl homology-pleckstrin homology (DH-PH) region of ITSN-2L (DH-PH(ITSN-2L)) induced specific activation of Cdc42, resulting in formation of extensive filopodia, enhanced cortical actin, as well as a shift from G-actin to F-actin. The "catalytically dead" DH-PH domain reversed these effects and induced significant stress fiber formation, without a detectable shift in actin pools. A biotin assay for caveola internalization indicated a significant decrease in the uptake of biotinylated proteins in DH-PH(ITSN-2L)-transfected cells compared with control and 1 microM jasplakinolide-treated cells. ECs depleted of ITSN-2L by small interfering RNA, however, showed decreased Cdc42 activation and actin remodeling similar to the defective DH-PH, resulting in 62% increase in caveola-mediated uptake compared with controls. Thus, ITSN-2L, a guanine nucleotide exchange factor for Cdc42, regulates different steps of caveola endocytosis in ECs by controlling the temporal and spatial actin polymerization and remodeling sub-adjacent to the plasma membrane. PMID:19622753

  11. Inhibitory serpins. New insights into their folding, polymerization, regulation and clearance.

    PubMed

    Gettins, Peter G W; Olson, Steven T

    2016-08-01

    Serpins are a widely distributed family of high molecular mass protein proteinase inhibitors that can inhibit both serine and cysteine proteinases by a remarkable mechanism-based kinetic trapping of an acyl or thioacyl enzyme intermediate that involves massive conformational transformation. The trapping is based on distortion of the proteinase in the complex, with energy derived from the unique metastability of the active serpin. Serpins are the favoured inhibitors for regulation of proteinases in complex proteolytic cascades, such as are involved in blood coagulation, fibrinolysis and complement activation, by virtue of the ability to modulate their specificity and reactivity. Given their prominence as inhibitors, much work has been carried out to understand not only the mechanism of inhibition, but how it is fine-tuned, both spatially and temporally. The metastability of the active state raises the question of how serpins fold, whereas the misfolding of some serpin variants that leads to polymerization and pathologies of liver disease, emphysema and dementia makes it clinically important to understand how such polymerization might occur. Finally, since binding of serpins and their proteinase complexes, particularly plasminogen activator inhibitor-1 (PAI-1), to the clearance and signalling receptor LRP1 (low density lipoprotein receptor-related protein 1), may affect pathways linked to cell migration, angiogenesis, and tumour progression, it is important to understand the nature and specificity of binding. The current state of understanding of these areas is addressed here. PMID:27470592

  12. Regulation of actin polymerization by tropomodulin-3 controls megakaryocyte actin organization and platelet biogenesis.

    PubMed

    Sui, Zhenhua; Nowak, Roberta B; Sanada, Chad; Halene, Stephanie; Krause, Diane S; Fowler, Velia M

    2015-07-23

    The actin cytoskeleton is important for platelet biogenesis. Tropomodulin-3 (Tmod3), the only Tmod isoform detected in platelets and megakaryocytes (MKs), caps actin filament (F-actin) pointed ends and binds tropomyosins (TMs), regulating actin polymerization and stability. To determine the function of Tmod3 in platelet biogenesis, we studied Tmod3(-/-) embryos, which are embryonic lethal by E18.5. Tmod3(-/-) embryos often show hemorrhaging at E14.5 with fewer and larger platelets, indicating impaired platelet biogenesis. MK numbers are moderately increased in Tmod3(-/-) fetal livers, with only a slight increase in the 8N population, suggesting that MK differentiation is not significantly affected. However, Tmod3(-/-) MKs fail to develop a normal demarcation membrane system (DMS), and cytoplasmic organelle distribution is abnormal. Moreover, cultured Tmod3(-/-) MKs exhibit impaired proplatelet formation with a wide range of proplatelet bud sizes, including abnormally large proplatelet buds containing incorrect numbers of von Willebrand factor-positive granules. Tmod3(-/-) MKs exhibit F-actin disturbances, and Tmod3(-/-) MKs spreading on collagen fail to polymerize F-actin into actomyosin contractile bundles. Tmod3 associates with TM4 and the F-actin cytoskeleton in wild-type MKs, and confocal microscopy reveals that Tmod3, TM4, and F-actin partially colocalize near the membrane of proplatelet buds. In contrast, the abnormally large proplatelets from Tmod3(-/-) MKs show increased F-actin and redistribution of F-actin and TM4 from the cortex to the cytoplasm, but normal microtubule coil organization. We conclude that F-actin capping by Tmod3 regulates F-actin organization in mouse fetal liver-derived MKs, thereby controlling MK cytoplasmic morphogenesis, including DMS formation and organelle distribution, as well as proplatelet formation and sizing. PMID:25964668

  13. Thoracic Aortic Aneurysm (TAAD)-causing Mutation in Actin Affects Formin Regulation of Polymerization*

    PubMed Central

    Malloy, Lindsey E.; Wen, Kuo-Kuang; Pierick, Alyson R.; Wedemeyer, Elesa W.; Bergeron, Sarah E.; Vanderpool, Nicole D.; McKane, Melissa; Rubenstein, Peter A.; Bartlett, Heather L.

    2012-01-01

    More than 30 mutations in ACTA2, which encodes α-smooth muscle actin, have been identified to cause autosomal dominant thoracic aortic aneurysm and dissection. The mutation R256H is of particular interest because it also causes patent ductus arteriosus and moyamoya disease. R256H is one of the more prevalent mutations and, based on its molecular location near the strand-strand interface in the actin filament, may affect F-actin stability. To understand the molecular ramifications of the R256H mutation, we generated Saccharomyces cerevisiae yeast cells expressing only R256H yeast actin as a model system. These cells displayed abnormal cytoskeletal morphology and increased sensitivity to latrunculin A. After cable disassembly induced by transient exposure to latrunculin A, mutant cells were delayed in reestablishing the actin cytoskeleton. In vitro, mutant actin exhibited a higher than normal critical concentration and a delayed nucleation. Consequently, we investigated regulation of mutant actin by formin, a potent facilitator of nucleation and a protein needed for normal vascular smooth muscle cell development. Mutant actin polymerization was inhibited by the FH1-FH2 fragment of the yeast formin, Bni1. This fragment strongly capped the filament rather than facilitating polymerization. Interestingly, phalloidin or the presence of wild type actin reversed the strong capping behavior of Bni1. Together, the data suggest that the R256H actin mutation alters filament conformation resulting in filament instability and misregulation by formin. These biochemical effects may contribute to abnormal histology identified in diseased arterial samples from affected patients. PMID:22753406

  14. Thoracic aortic aneurysm (TAAD)-causing mutation in actin affects formin regulation of polymerization.

    PubMed

    Malloy, Lindsey E; Wen, Kuo-Kuang; Pierick, Alyson R; Wedemeyer, Elesa W; Bergeron, Sarah E; Vanderpool, Nicole D; McKane, Melissa; Rubenstein, Peter A; Bartlett, Heather L

    2012-08-17

    More than 30 mutations in ACTA2, which encodes α-smooth muscle actin, have been identified to cause autosomal dominant thoracic aortic aneurysm and dissection. The mutation R256H is of particular interest because it also causes patent ductus arteriosus and moyamoya disease. R256H is one of the more prevalent mutations and, based on its molecular location near the strand-strand interface in the actin filament, may affect F-actin stability. To understand the molecular ramifications of the R256H mutation, we generated Saccharomyces cerevisiae yeast cells expressing only R256H yeast actin as a model system. These cells displayed abnormal cytoskeletal morphology and increased sensitivity to latrunculin A. After cable disassembly induced by transient exposure to latrunculin A, mutant cells were delayed in reestablishing the actin cytoskeleton. In vitro, mutant actin exhibited a higher than normal critical concentration and a delayed nucleation. Consequently, we investigated regulation of mutant actin by formin, a potent facilitator of nucleation and a protein needed for normal vascular smooth muscle cell development. Mutant actin polymerization was inhibited by the FH1-FH2 fragment of the yeast formin, Bni1. This fragment strongly capped the filament rather than facilitating polymerization. Interestingly, phalloidin or the presence of wild type actin reversed the strong capping behavior of Bni1. Together, the data suggest that the R256H actin mutation alters filament conformation resulting in filament instability and misregulation by formin. These biochemical effects may contribute to abnormal histology identified in diseased arterial samples from affected patients. PMID:22753406

  15. Regulation by transcription factors in bacteria: beyond description.

    PubMed

    Balleza, Enrique; López-Bojorquez, Lucia N; Martínez-Antonio, Agustino; Resendis-Antonio, Osbaldo; Lozada-Chávez, Irma; Balderas-Martínez, Yalbi I; Encarnación, Sergio; Collado-Vides, Julio

    2009-01-01

    Transcription is an essential step in gene expression and its understanding has been one of the major interests in molecular and cellular biology. By precisely tuning gene expression, transcriptional regulation determines the molecular machinery for developmental plasticity, homeostasis and adaptation. In this review, we transmit the main ideas or concepts behind regulation by transcription factors and give just enough examples to sustain these main ideas, thus avoiding a classical ennumeration of facts. We review recent concepts and developments: cis elements and trans regulatory factors, chromosome organization and structure, transcriptional regulatory networks (TRNs) and transcriptomics. We also summarize new important discoveries that will probably affect the direction of research in gene regulation: epigenetics and stochasticity in transcriptional regulation, synthetic circuits and plasticity and evolution of TRNs. Many of the new discoveries in gene regulation are not extensively tested with wetlab approaches. Consequently, we review this broad area in Inference of TRNs and Dynamical Models of TRNs. Finally, we have stepped backwards to trace the origins of these modern concepts, synthesizing their history in a timeline schema. PMID:19076632

  16. Regulation by transcription factors in bacteria: beyond description

    PubMed Central

    Balleza, Enrique; López-Bojorquez, Lucia N; Martínez-Antonio, Agustino; Resendis-Antonio, Osbaldo; Lozada-Chávez, Irma; Balderas-Martínez, Yalbi I; Encarnación, Sergio; Collado-Vides, Julio

    2009-01-01

    Transcription is an essential step in gene expression and its understanding has been one of the major interests in molecular and cellular biology. By precisely tuning gene expression, transcriptional regulation determines the molecular machinery for developmental plasticity, homeostasis and adaptation. In this review, we transmit the main ideas or concepts behind regulation by transcription factors and give just enough examples to sustain these main ideas, thus avoiding a classical ennumeration of facts. We review recent concepts and developments: cis elements and trans regulatory factors, chromosome organization and structure, transcriptional regulatory networks (TRNs) and transcriptomics. We also summarize new important discoveries that will probably affect the direction of research in gene regulation: epigenetics and stochasticity in transcriptional regulation, synthetic circuits and plasticity and evolution of TRNs. Many of the new discoveries in gene regulation are not extensively tested with wetlab approaches. Consequently, we review this broad area in Inference of TRNs and Dynamical Models of TRNs. Finally, we have stepped backwards to trace the origins of these modern concepts, synthesizing their history in a timeline schema. PMID:19076632

  17. Theoretical studies on sRNA-mediated regulation in bacteria

    NASA Astrophysics Data System (ADS)

    Chang, Xiao-Xue; Xu, Liu-Fang; Shi, Hua-Lin

    2015-12-01

    Small RNA(sRNA)-mediated post-transcriptional regulation differs from protein-mediated regulation. Through base-pairing, sRNA can regulate the target mRNA in a catalytic or stoichiometric manner. Some theoretical models were built for comparison of the protein-mediated and sRNA-mediated modes in the steady-state behaviors and noise properties. Many experiments demonstrated that a single sRNA can regulate several mRNAs, which causes crosstalk between the targets. Here, we focus on some models in which two target mRNAs are silenced by the same sRNA to discuss their crosstalk features. Additionally, the sequence-function relationship of sRNA and its role in the kinetic process of base-pairing have been highlighted in model building. Project supported by the National Basic Research Program of China (Grant No. 2013CB834100), the National Natural Science Foundation of China (Grant Nos. 11121403 and 11274320), the Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Grant No. Y4KF171CJ1), the National Natural Science Foundation for Young Scholar of China (Grant No. 11304115), and the China Postdoctoral Science Foundation (Grant No. 2013M541282).

  18. Epigenetic Regulation of Enteric Neurotransmission by Gut Bacteria

    PubMed Central

    Savidge, Tor C.

    2016-01-01

    The Human Microbiome Project defined microbial community interactions with the human host, and provided important molecular insight into how epigenetic factors can influence intestinal ecosystems. Given physiological context, changes in gut microbial community structure are increasingly found to associate with alterations in enteric neurotransmission and disease. At present, it is not known whether shifts in microbial community dynamics represent cause or consequence of disease pathogenesis. The discovery of bacterial-derived neurotransmitters suggests further studies are needed to establish their role in enteric neuropathy. This mini-review highlights recent advances in bacterial communications to the autonomic nervous system and discusses emerging epigenetic data showing that diet, probiotic and antibiotic use may regulate enteric neurotransmission through modulation of microbial communities. A particular emphasis is placed on bacterial metabolite regulation of enteric nervous system function in the intestine. PMID:26778967

  19. Epigenetic Regulation of Enteric Neurotransmission by Gut Bacteria.

    PubMed

    Savidge, Tor C

    2015-01-01

    The Human Microbiome Project defined microbial community interactions with the human host, and provided important molecular insight into how epigenetic factors can influence intestinal ecosystems. Given physiological context, changes in gut microbial community structure are increasingly found to associate with alterations in enteric neurotransmission and disease. At present, it is not known whether shifts in microbial community dynamics represent cause or consequence of disease pathogenesis. The discovery of bacterial-derived neurotransmitters suggests further studies are needed to establish their role in enteric neuropathy. This mini-review highlights recent advances in bacterial communications to the autonomic nervous system and discusses emerging epigenetic data showing that diet, probiotic and antibiotic use may regulate enteric neurotransmission through modulation of microbial communities. A particular emphasis is placed on bacterial metabolite regulation of enteric nervous system function in the intestine. PMID:26778967

  20. Tubulin polymerization disrupts cardiac β-adrenergic regulation of late INa

    PubMed Central

    Dybkova, Nataliya; Wagner, Stefan; Backs, Johannes; Hund, Thomas J.; Mohler, Peter J.; Sowa, Thomas; Nikolaev, Viacheslav O.; Maier, Lars S.

    2014-01-01

    Aims The anticancer drug paclitaxel (TXL) that polymerizes microtubules is associated with arrhythmias and sinus node dysfunction. TXL can alter membrane expression of Na channels (NaV1.5) and Na current (INa), but the mechanisms are unknown. Calcium/calmodulin-dependent protein kinase II (CaMKII) can be activated by β-adrenergic stimulation and regulates INa gating. We tested whether TXL interferes with isoproterenol (ISO)-induced activation of CaMKII and consequent INa regulation. Methods and results In wild-type mouse myocytes, the addition of ISO (1 µmol/L) resulted in increased CaMKII auto-phosphorylation (western blotting). This increase was completely abolished after pre-treatment with TXL (100 µmol/L, 1.5 h). The mechanism was further investigated in human embryonic kidney cells. TXL inhibited the ISO-induced β-arrestin translocation. Interestingly, both knockdown of β-arrestin2 expression using small interfering RNA and inhibition of exchange protein directly activated by cAMP (Epac) blocked the ISO-induced CaMKII auto-phosphorylation similar to TXL. The generation of cAMP, however, was unaltered (Epac1-camps). CaMKII-dependent Na channel function was measured using patch-clamp technique in isolated cardiomyoctes. ISO stimulation failed to induce CaMKII-dependent enhancement of late INa and Na channel inactivation (negative voltage shift in steady-state activation and enhanced intermediate inactivation) after pre-incubation with TXL. Consistent with this, TXL also inhibited ISO-induced CaMKII-specific Na channel phosphorylation (at serine 571 of NaV1.5). Conclusion Pre-incubation with TXL disrupts the ISO-dependent CaMKII activation and consequent Na channel regulation. This may be important for patients receiving TXL treatments, but also relevant for conditions of increased CaMKII expression and enhanced β-adrenergic stimulation like in heart failure. PMID:24812278

  1. Structural Basis of Glycogen Biosynthesis Regulation in Bacteria.

    PubMed

    Cifuente, Javier O; Comino, Natalia; Madariaga-Marcos, Julene; López-Fernández, Sonia; García-Alija, Mikel; Agirre, Jon; Albesa-Jové, David; Guerin, Marcelo E

    2016-09-01

    ADP-glucose pyrophosphorylase (AGPase) catalyzes the rate-limiting step of bacterial glycogen and plant starch biosynthesis, the most common carbon storage polysaccharides in nature. A major challenge is to understand how AGPase activity is regulated by metabolites in the energetic flux within the cell. Here we report crystal structures of the homotetrameric AGPase from Escherichia coli in complex with its physiological positive and negative allosteric regulators, fructose-1,6-bisphosphate (FBP) and AMP, and sucrose in the active site. FBP and AMP bind to partially overlapping sites located in a deep cleft between glycosyltransferase A-like and left-handed β helix domains of neighboring protomers, accounting for the fact that sensitivity to inhibition by AMP is modulated by the concentration of the activator FBP. We propose a model in which the energy reporters regulate EcAGPase catalytic activity by intra-protomer interactions and inter-protomer crosstalk, with a sensory motif and two regulatory loops playing a prominent role. PMID:27545622

  2. New insights into regulation of the tryptophan biosynthetic operon in Gram-positive bacteria.

    PubMed

    Gutierrez-Preciado, A; Jensen, R A; Yanofsky, C; Merino, E

    2005-08-01

    The tryptophan operon of Bacillus subtilis serves as an excellent model for investigating transcription regulation in Gram-positive bacteria. In this article, we extend this knowledge by analyzing the predicted regulatory regions in the trp operons of other fully sequenced Gram-positive bacteria. Interestingly, it appears that in eight of the organisms examined, transcription of the trp operon appears to be regulated by tandem T-box elements. These regulatory elements have recently been described in the trp operons of two bacterial species. Single T-box elements are commonly found in Gram-positive bacteria in operons encoding aminoacyl tRNA synthetases and proteins performing other functions. Different regulatory mechanisms appear to be associated with variations of trp gene organization within the trp operon. PMID:15953653

  3. Control of magnetite nanocrystal morphology in magnetotactic bacteria by regulation of mms7 gene expression.

    PubMed

    Yamagishi, Ayana; Tanaka, Masayoshi; Lenders, Jos J M; Thiesbrummel, Jarla; Sommerdijk, Nico A J M; Matsunaga, Tadashi; Arakaki, Atsushi

    2016-01-01

    Living organisms can produce inorganic materials with unique structure and properties. The biomineralization process is of great interest as it forms a source of inspiration for the development of methods for production of diverse inorganic materials under mild conditions. Nonetheless, regulation of biomineralization is still a challenging task. Magnetotactic bacteria produce chains of a prokaryotic organelle comprising a membrane-enveloped single-crystal magnetite with species-specific morphology. Here, we describe regulation of magnetite biomineralization through controlled expression of the mms7 gene, which plays key roles in the control of crystal growth and morphology of magnetite crystals in magnetotactic bacteria. Regulation of the expression level of Mms7 in bacterial cells enables switching of the crystal shape from dumbbell-like to spherical. The successful regulation of magnetite biomineralization opens the door to production of magnetite nanocrystals of desired size and morphology. PMID:27417732

  4. Control of magnetite nanocrystal morphology in magnetotactic bacteria by regulation of mms7 gene expression

    PubMed Central

    Yamagishi, Ayana; Tanaka, Masayoshi; Lenders, Jos J. M.; Thiesbrummel, Jarla; Sommerdijk, Nico A. J. M.; Matsunaga, Tadashi; Arakaki, Atsushi

    2016-01-01

    Living organisms can produce inorganic materials with unique structure and properties. The biomineralization process is of great interest as it forms a source of inspiration for the development of methods for production of diverse inorganic materials under mild conditions. Nonetheless, regulation of biomineralization is still a challenging task. Magnetotactic bacteria produce chains of a prokaryotic organelle comprising a membrane-enveloped single-crystal magnetite with species-specific morphology. Here, we describe regulation of magnetite biomineralization through controlled expression of the mms7 gene, which plays key roles in the control of crystal growth and morphology of magnetite crystals in magnetotactic bacteria. Regulation of the expression level of Mms7 in bacterial cells enables switching of the crystal shape from dumbbell-like to spherical. The successful regulation of magnetite biomineralization opens the door to production of magnetite nanocrystals of desired size and morphology. PMID:27417732

  5. Group 3 innate lymphoid cells: regulating host-commensal bacteria interactions in inflammation and cancer.

    PubMed

    Goc, Jeremy; Hepworth, Matthew R; Sonnenberg, Gregory F

    2016-01-01

    A delicate balance exists between the mammalian immune system and normally beneficial commensal bacteria that colonize the gastrointestinal tract, which is necessary to maintain tissue homeostasis. Dysregulation of these interactions between the host and commensal bacteria is causally associated with chronic inflammation and the development of cancer. In contrast, recent reports have highlighted that commensal bacteria also play an essential role in promoting anti-tumor immune responses in several contexts, highlighting a paradox whereby interactions between the host and commensal bacteria can influence both pro- and anti-tumor immunity. Given the critical roles for group 3 innate lymphoid cells (ILC3s) in regulating inflammation, tissue repair and host-microbe interactions in the intestine, here we discuss new evidence that ILC3s may profoundly influence the development, progression and control of tumors. In this review, we provide an overview of recent advances in understanding the impact of commensal bacteria on tumorigenesis, discuss recent findings identifying ILC3s as critical regulators of host-microbe interactions and highlight the emerging role of this immune cell population in cancer and their potential implication as a therapeutic target. PMID:26451009

  6. Parvulin 17-catalyzed Tubulin Polymerization Is Regulated by Calmodulin in a Calcium-dependent Manner*

    PubMed Central

    Burgardt, Noelia Inés; Schmidt, Andreas; Manns, Annika; Schutkowski, Alexandra; Jahreis, Günther; Lin, Yi-Jan; Schulze, Bianca; Masch, Antonia; Lücke, Christian; Weiwad, Matthias

    2015-01-01

    Recently we have shown that the peptidyl-prolyl cis/trans isomerase parvulin 17 (Par17) interacts with tubulin in a GTP-dependent manner, thereby promoting the formation of microtubules. Microtubule assembly is regulated by Ca2+-loaded calmodulin (Ca2+/CaM) both in the intact cell and under in vitro conditions via direct interaction with microtubule-associated proteins. Here we provide the first evidence that Ca2+/CaM interacts also with Par17 in a physiologically relevant way, thus preventing Par17-promoted microtubule assembly. In contrast, parvulin 14 (Par14), which lacks only the first 25 N-terminal residues of the Par17 sequence, does not interact with Ca2+/CaM, indicating that this interaction is exclusive for Par17. Pulldown experiments and chemical shift perturbation analysis with 15N-labeled Par17 furthermore confirmed that calmodulin (CaM) interacts in a Ca2+-dependent manner with the Par17 N terminus. The reverse experiment with 15N-labeled Ca2+/CaM demonstrated that the N-terminal Par17 segment binds to both CaM lobes simultaneously, indicating that Ca2+/CaM undergoes a conformational change to form a binding channel between its two lobes, apparently similar to the structure of the CaM-smMLCK796–815 complex. In vitro tubulin polymerization assays furthermore showed that Ca2+/CaM completely suppresses Par17-promoted microtubule assembly. The results imply that Ca2+/CaM binding to the N-terminal segment of Par17 causes steric hindrance of the Par17 active site, thus interfering with the Par17/tubulin interaction. This Ca2+/CaM-mediated control of Par17-assisted microtubule assembly may provide a mechanism that couples Ca2+ signaling with microtubule function. PMID:25940090

  7. Regulation of coat protein polymerization by the scaffolding protein of bacteriophage P22

    SciTech Connect

    Fuller, M.T.; King, J.

    1980-10-01

    In the morphogenesis of double stranded DNA phages, a precursor protein shell empty of DNA is first assembled and then filled with DNA. The assembly of the correctly dimensioned precursor shell (procapsid) of Salmonella bacteriophage P22 requires the interaction of some 420 coat protein subunits with approx. 200 scaffolding protein subunits to form a double shelled particle with the scaffolding protein on the inside. In the course of DNA packaging, all of the scaffolding protein subunits exit from the procapsid and participate in further rounds of procapsid assembly. To study the mechanism of shell assembly we have purified the coat and scaffolding protein subunits by selective dissociation of isolated procapsids. Both proteins can be obtained as soluble sununits in Tris buffer at near neutral pH. The coat protein sedimented in sucrose gradients as a roughly spherical monomer, while the scaffolding protein sedimented as if it were an elongated monomer. When the two proteins were mixed together in 1.5 M guanidine hydrochloride and dialyzed back to buffer at room temperature, procapsids formed which were very similar in morphology, sedimentation behavior, and protein composition to procapsids formed in vivo. Incubation of either protein alone under the same conditions did not yield any large structures. We interpret these results to mean that the assembly of the shell involves a switching of both proteins from their nonaggregating to their aggregating forms through their mutual interaction. The results are discussed in terms of the general problem of self-regulated assembly and the control of protein polymerization in morphogenesis.

  8. Term-seq reveals abundant ribo-regulation of antibiotics resistance in bacteria.

    PubMed

    Dar, Daniel; Shamir, Maya; Mellin, J R; Koutero, Mikael; Stern-Ginossar, Noam; Cossart, Pascale; Sorek, Rotem

    2016-04-01

    Riboswitches and attenuators are cis-regulatory RNA elements, most of which control bacterial gene expression via metabolite-mediated, premature transcription termination. We developed an unbiased experimental approach for genome-wide discovery of such ribo-regulators in bacteria. We also devised an experimental platform that quantitatively measures the in vivo activity of all such regulators in parallel and enables rapid screening for ribo-regulators that respond to metabolites of choice. Using this approach, we detected numerous antibiotic-responsive ribo-regulators that control antibiotic resistance genes in pathogens and in the human microbiome. Studying one such regulator in Listeria monocytogenes revealed an attenuation mechanism mediated by antibiotic-stalled ribosomes. Our results expose broad roles for conditional termination in regulating antibiotic resistance and provide a tool for discovering riboswitches and attenuators that respond to previously unknown ligands. PMID:27120414

  9. Inactivation of bacteria by electric current in the presence of carbon nanotubes embedded within a polymeric membrane.

    PubMed

    Zhu, Anna; Liu, Harris K; Long, Feng; Su, Erzheng; Klibanov, Alexander M

    2015-01-01

    Uniform conductive composite membranes were prepared using a phase inversion method by blending carboxyl-functionalized multi-walled carbon nanotubes (CNTs) with a polysulfone polymer. At 6 % of the embedded CNTs, the membrane pore size measured by transmission electron microscopy (TEM) was approximately 50 nm. Electric current in the presence of the composite membranes markedly inactivated the model pathogenic bacteria Escherichia coli and Staphylococcus aureus, with the extent of bacterial inactivation rising when the current was increased. Over 99.999 % inactivation of both bacteria was observed in deionized water after 40 min at 5 mA direct current (DC); importantly, no appreciable inactivation occurred in the absence of either the electric field or the CNTs within the membranes under otherwise the same conditions. A much lower, although still pronounced, inactivation was seen with alternating current (AC) in a 25 mM NaCl aqueous solution. PMID:25342266

  10. Coupling Physiology and Gene Regulation in Bacteria: The Phosphotransferase Sugar Uptake System Delivers the Signals

    NASA Astrophysics Data System (ADS)

    Stülke, Jörg; Hillen, Wolfgang

    In many bacteria a crucial link between metabolism and regulation of catabolic genes is based on the phosphotransferase sugar uptake system (PTS). We summarize the mechanisms of the signaling pathways originating from PTS and leading to regulation of transcription. A protein domain, called PTS regulation domain (PRD), is linked to many antiterminators and transcriptional activators and regulates their activity depending on its state of phosphorylation. Two sites can be phosphorylated in most PRDs: HPr-dependent modification at one site leads to activation while enzyme II dependent phosphorylation of the other site renders it inactive. In addition, PTS components are used to generate cofactors for regulators of transcription. The paradigm is the enzyme II dependent activity of adenylate cyclase determining the cyclic AMP level in Escherichia coli and thereby the activity of the catabolite activator protein. In many gram-positive bacteria catabolite repression is mediated by the catabolite control protein CcpA, which requires HPr Ser-46 phosphate as a cofactor to regulate transcription of catabolic genes. HPr Ser-46 phosphate is produced by HPr kinase, the activity of which is under metabolic control via the concentrations of glycolytic intermediates. These recent results establish a multifaceted regulatory role for PTS in addition to its well-established function in active sugar uptake.

  11. YihE kinase is a central regulator of programmed cell death in bacteria

    PubMed Central

    Dorsey-Oresto, Angella; Lu, Tao; Mosel, Michael; Wang, Xiuhong; Salz, Tal; Drlica, Karl; Zhao, Xilin

    2013-01-01

    Stress-mediated programmed cell death (PCD) in bacteria has recently attracted attention, largely because it raises novel possibilities for controlling pathogens. How PCD in bacteria is regulated to avoid population extinction from transient, moderate stress remains a central question. We report that the YihE protein kinase is a key regulator that protects Escherichia coli from antimicrobial and environmental stressors by antagonizing the MazEF toxin-antitoxin module. YihE was linked to a reactive oxygen species (ROS) cascade, and a deficiency of yihE stimulated stress-induced PCD even after stress dissipated. YihE was partially regulated by the Cpx envelope stress-response system, which, along with MazF toxin and superoxide, has both protective and destructive roles that help bacteria make a live-or-die decision in response to stress. YihE probably acts early in the stress response to limit self-sustaining ROS production and PCD. Inhibition of YihE may provide a new way to enhance antimicrobial lethality and attenuate virulence. PMID:23416055

  12. YihE kinase is a central regulator of programmed cell death in bacteria.

    PubMed

    Dorsey-Oresto, Angella; Lu, Tao; Mosel, Michael; Wang, Xiuhong; Salz, Tal; Drlica, Karl; Zhao, Xilin

    2013-02-21

    Stress-mediated programmed cell death (PCD) in bacteria has recently attracted attention, largely because it raises novel possibilities for controlling pathogens. How PCD in bacteria is regulated to avoid population extinction due to transient, moderate stress remains a central question. Here, we report that the YihE protein kinase is a key regulator that protects Escherichia coli from antimicrobial and environmental stressors by antagonizing the MazEF toxin-antitoxin module. YihE was linked to a reactive oxygen species (ROS) cascade, and a deficiency of yihE stimulated stress-induced PCD even after stress dissipated. YihE was partially regulated by the Cpx envelope stress-response system, which, along with MazF toxin and superoxide, has both protective and destructive roles that help bacteria make a live-or-die decision in response to stress. YihE probably acts early in the stress response to limit self-sustaining ROS production and PCD. Inhibition of YihE may provide a way of enhancing antimicrobial lethality and attenuating virulence. PMID:23416055

  13. Polarized Exocytosis Induces Compensatory Endocytosis by Sec4p-Regulated Cortical Actin Polymerization.

    PubMed

    Johansen, Jesper; Alfaro, Gabriel; Beh, Christopher T

    2016-08-01

    Polarized growth is maintained by both polarized exocytosis, which transports membrane components to specific locations on the cell cortex, and endocytosis, which retrieves these components before they can diffuse away. Despite functional links between these two transport pathways, they are generally considered to be separate events. Using live cell imaging, in vivo and in vitro protein binding assays, and in vitro pyrene-actin polymerization assays, we show that the yeast Rab GTPase Sec4p couples polarized exocytosis with cortical actin polymerization, which induces endocytosis. After polarized exocytosis to the plasma membrane, Sec4p binds Las17/Bee1p (yeast Wiskott-Aldrich Syndrome protein [WASp]) in a complex with Sla1p and Sla2p during actin patch assembly. Mutations that inactivate Sec4p, or its guanine nucleotide exchange factor (GEF) Sec2p, inhibit actin patch formation, whereas the activating sec4-Q79L mutation accelerates patch assembly. In vitro assays of Arp2/3-dependent actin polymerization established that GTPγS-Sec4p overrides Sla1p inhibition of Las17p-dependent actin nucleation. These results support a model in which Sec4p relocates along the plasma membrane from polarized sites of exocytic vesicle fusion to nascent sites of endocytosis. Activated Sec4p then promotes actin polymerization and triggers compensatory endocytosis, which controls surface expansion and kinetically refines cell polarization. PMID:27526190

  14. Polarized Exocytosis Induces Compensatory Endocytosis by Sec4p-Regulated Cortical Actin Polymerization

    PubMed Central

    Johansen, Jesper; Alfaro, Gabriel; Beh, Christopher T.

    2016-01-01

    Polarized growth is maintained by both polarized exocytosis, which transports membrane components to specific locations on the cell cortex, and endocytosis, which retrieves these components before they can diffuse away. Despite functional links between these two transport pathways, they are generally considered to be separate events. Using live cell imaging, in vivo and in vitro protein binding assays, and in vitro pyrene-actin polymerization assays, we show that the yeast Rab GTPase Sec4p couples polarized exocytosis with cortical actin polymerization, which induces endocytosis. After polarized exocytosis to the plasma membrane, Sec4p binds Las17/Bee1p (yeast Wiskott—Aldrich Syndrome protein [WASp]) in a complex with Sla1p and Sla2p during actin patch assembly. Mutations that inactivate Sec4p, or its guanine nucleotide exchange factor (GEF) Sec2p, inhibit actin patch formation, whereas the activating sec4-Q79L mutation accelerates patch assembly. In vitro assays of Arp2/3-dependent actin polymerization established that GTPγS-Sec4p overrides Sla1p inhibition of Las17p-dependent actin nucleation. These results support a model in which Sec4p relocates along the plasma membrane from polarized sites of exocytic vesicle fusion to nascent sites of endocytosis. Activated Sec4p then promotes actin polymerization and triggers compensatory endocytosis, which controls surface expansion and kinetically refines cell polarization. PMID:27526190

  15. Bicc1 Polymerization Regulates the Localization and Silencing of Bound mRNA

    PubMed Central

    Rothé, Benjamin; Leal-Esteban, Lucia; Bernet, Florian; Urfer, Séverine; Doerr, Nicholas; Weimbs, Thomas; Iwaszkiewicz, Justyna

    2015-01-01

    Loss of the RNA-binding protein Bicaudal-C (Bicc1) provokes renal and pancreatic cysts as well as ectopic Wnt/β-catenin signaling during visceral left-right patterning. Renal cysts are linked to defective silencing of Bicc1 target mRNAs, including adenylate cyclase 6 (AC6). RNA binding of Bicc1 is mediated by N-terminal KH domains, whereas a C-terminal sterile alpha motif (SAM) self-polymerizes in vitro and localizes Bicc1 in cytoplasmic foci in vivo. To assess a role for multimerization in silencing, we conducted structure modeling and then mutated the SAM domain residues which in this model were predicted to polymerize Bicc1 in a left-handed helix. We show that a SAM-SAM interface concentrates Bicc1 in cytoplasmic clusters to specifically localize and silence bound mRNA. In addition, defective polymerization decreases Bicc1 stability and thus indirectly attenuates inhibition of Dishevelled 2 in the Wnt/β-catenin pathway. Importantly, aberrant C-terminal extension of the SAM domain in bpk mutant Bicc1 phenocopied these defects. We conclude that polymerization is a novel disease-relevant mechanism both to stabilize Bicc1 and to present associated mRNAs in specific silencing platforms. PMID:26217012

  16. Molecular Regulation of Photosynthetic Carbon Dioxide Fixation in Nonsulfur Purple Bacteria

    SciTech Connect

    Tabita, Fred Robert

    2015-12-01

    The overall objective of this project is to determine the mechanism by which a transcriptional activator protein affects CO2 fixation (cbb) gene expression in nonsulfur purple photosynthetic bacteria, with special emphasis to Rhodobacter sphaeroides and with comparison to Rhodopseudomonas palustris. These studies culminated in several publications which indicated that additional regulators interact with the master regulator CbbR in both R. sphaeroides and R. palustris. In addition, the interactive control of the carbon and nitrogen assimilatory pathways was studied and unique regulatory signals were discovered.

  17. Characterization of extracellular polymeric substances in the biofilms of typical bacteria by the sulfur K-edge XANES spectroscopy.

    PubMed

    Lin, Huirong; Ye, Chengsong; Lv, Lu; Zheng, Clark Renjun; Zhang, Shenghua; Zheng, Lei; Zhao, Yidong; Yu, Xin

    2014-08-01

    A combined approach of physicochemical extraction and sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy was applied to characterize the extracellular polymeric substances (EPS) of typical bacterial biofilms in this study. Physicochemical analysis showed variation of the contents of DNA, polysaccharide and protein in different fractions of EPS in different mediums. The sulfur K-edge XANES analysis yielded a variety of spectra. Spectral fitting of the XANES spectra utilizing a large set of model compounds showed that there was more reduced sulfur in both LB-EPS (loosely bound EPS) and TB-EPS (tightly bound EPS) of all the biofilms in LB medium than in R2A medium. More oxidized sulfur was identified in LB-EPS than that in TB-EPS, suggesting different niches and physiological heterogeneity in the biofilms. Our results suggested that the sulfur K-edge XANES can be a useful tool to analyze the sulfur speciation in EPS of biofilms. PMID:25108733

  18. Understanding How Commensal Obligate Anaerobic Bacteria Regulate Immune Functions in the Large Intestine

    PubMed Central

    Maier, Eva; Anderson, Rachel C.; Roy, Nicole C.

    2014-01-01

    The human gastrointestinal tract is colonised by trillions of commensal bacteria, most of which are obligate anaerobes residing in the large intestine. Appropriate bacterial colonisation is generally known to be critical for human health. In particular, the development and function of the immune system depends on microbial colonisation, and a regulated cross-talk between commensal bacteria, intestinal epithelial cells and immune cells is required to maintain mucosal immune homeostasis. This homeostasis is disturbed in various inflammatory disorders, such as inflammatory bowel diseases. Several in vitro and in vivo studies indicate a role for Faecalibacterium prausnitzii, Bacteroides thetaiotaomicron, Bacteroides fragilis, Akkermansia muciniphila and segmented filamentous bacteria in maintaining intestinal immune homeostasis. These obligate anaerobes are abundant in the healthy intestine but reduced in several inflammatory diseases, suggesting an association with protective effects on human health. However, knowledge of the mechanisms underlying the effects of obligate anaerobic intestinal bacteria remains limited, in part due to the difficulty of co-culturing obligate anaerobes together with oxygen-requiring human epithelial cells. By using novel dual-environment co-culture models, it will be possible to investigate the effects of the unstudied majority of intestinal microorganisms on the human epithelia. This knowledge will provide opportunities for improving human health and reducing the risk of inflammatory diseases. PMID:25545102

  19. New insights on molecular regulation of biofilm formation in plant-associated bacteria.

    PubMed

    Castiblanco, Luisa F; Sundin, George W

    2016-04-01

    Biofilms are complex bacterial assemblages with a defined three-dimensional architecture, attached to solid surfaces, and surrounded by a self-produced matrix generally composed of exopolysaccharides, proteins, lipids and extracellular DNA. Biofilm formation has evolved as an adaptive strategy of bacteria to cope with harsh environmental conditions as well as to establish antagonistic or beneficial interactions with their host. Plant-associated bacteria attach and form biofilms on different tissues including leaves, stems, vasculature, seeds and roots. In this review, we examine the formation of biofilms from the plant-associated bacterial perspective and detail the recently-described mechanisms of genetic regulation used by these organisms to orchestrate biofilm formation on plant surfaces. In addition, we describe plant host signals that bacterial pathogens recognize to activate the transition from a planktonic lifestyle to multicellular behavior. PMID:26377849

  20. [Regulation of sulfates, hydrogen sulfide and heavy metals in technogenic reservoirs by sulfate-reducing bacteria].

    PubMed

    Hudz', S P; Peretiatko, T B; Moroz, O M; Hnatush, S O; Klym, I R

    2011-01-01

    Sulfate-reducing bacteria Desulfovibrio desulfuricans Ya-11 in the presence of sulfates and organic compounds in the medium reduce sulfates to hydrogen sulfide (dissimilatory sulfate reduction). Heavy metals in concentration over 2 mM inhibit this process. Pb2+, Zn2+, Ni2+, Co2+, Fe2+ and Cd2+ ions in concentration 1-1.5 mM display insignificant inhibiting effect on sulfate reduction process, and metals precipitate in the form of sulfides. At concentrations of heavy metals 2-3 mM one can observe a decrease of sulfates reduction intensity, and a percent of metals binding does not exceed 72%. Obtained results give reason to confirm, that sulfate-reducing bacteria play an important role in regulation of the level of sulfates, hydrogen sulfide and heavy metals in reservoirs and they may be used for purification of water environment from these compounds. PMID:21598657

  1. Organism-Adapted Specificity of the Allosteric Regulation of Pyruvate Kinase in Lactic Acid Bacteria

    PubMed Central

    Veith, Nadine; Feldman-Salit, Anna; Cojocaru, Vlad; Henrich, Stefan; Kummer, Ursula; Wade, Rebecca C.

    2013-01-01

    Pyruvate kinase (PYK) is a critical allosterically regulated enzyme that links glycolysis, the primary energy metabolism, to cellular metabolism. Lactic acid bacteria rely almost exclusively on glycolysis for their energy production under anaerobic conditions, which reinforces the key role of PYK in their metabolism. These organisms are closely related, but have adapted to a huge variety of native environments. They include food-fermenting organisms, important symbionts in the human gut, and antibiotic-resistant pathogens. In contrast to the rather conserved inhibition of PYK by inorganic phosphate, the activation of PYK shows high variability in the type of activating compound between different lactic acid bacteria. System-wide comparative studies of the metabolism of lactic acid bacteria are required to understand the reasons for the diversity of these closely related microorganisms. These require knowledge of the identities of the enzyme modifiers. Here, we predict potential allosteric activators of PYKs from three lactic acid bacteria which are adapted to different native environments. We used protein structure-based molecular modeling and enzyme kinetic modeling to predict and validate potential activators of PYK. Specifically, we compared the electrostatic potential and the binding of phosphate moieties at the allosteric binding sites, and predicted potential allosteric activators by docking. We then made a kinetic model of Lactococcus lactis PYK to relate the activator predictions to the intracellular sugar-phosphate conditions in lactic acid bacteria. This strategy enabled us to predict fructose 1,6-bisphosphate as the sole activator of the Enterococcus faecalis PYK, and to predict that the PYKs from Streptococcus pyogenes and Lactobacillus plantarum show weaker specificity for their allosteric activators, while still having fructose 1,6-bisphosphate play the main activator role in vivo. These differences in the specificity of allosteric activation may

  2. Innate lymphoid cells regulate CD4+ T-cell responses to intestinal commensal bacteria.

    PubMed

    Hepworth, Matthew R; Monticelli, Laurel A; Fung, Thomas C; Ziegler, Carly G K; Grunberg, Stephanie; Sinha, Rohini; Mantegazza, Adriana R; Ma, Hak-Ling; Crawford, Alison; Angelosanto, Jill M; Wherry, E John; Koni, Pandelakis A; Bushman, Frederic D; Elson, Charles O; Eberl, Gérard; Artis, David; Sonnenberg, Gregory F

    2013-06-01

    Innate lymphoid cells (ILCs) are a recently characterized family of immune cells that have critical roles in cytokine-mediated regulation of intestinal epithelial cell barrier integrity. Alterations in ILC responses are associated with multiple chronic human diseases, including inflammatory bowel disease, implicating a role for ILCs in disease pathogenesis. Owing to an inability to target ILCs selectively, experimental studies assessing ILC function have predominantly used mice lacking adaptive immune cells. However, in lymphocyte-sufficient hosts ILCs are vastly outnumbered by CD4(+) T cells, which express similar profiles of effector cytokines. Therefore, the function of ILCs in the presence of adaptive immunity and their potential to influence adaptive immune cell responses remain unknown. To test this, we used genetic or antibody-mediated depletion strategies to target murine ILCs in the presence of an adaptive immune system. We show that loss of retinoic-acid-receptor-related orphan receptor-γt-positive (RORγt(+)) ILCs was associated with dysregulated adaptive immune cell responses against commensal bacteria and low-grade systemic inflammation. Remarkably, ILC-mediated regulation of adaptive immune cells occurred independently of interleukin (IL)-17A, IL-22 or IL-23. Genome-wide transcriptional profiling and functional analyses revealed that RORγt(+) ILCs express major histocompatibility complex class II (MHCII) and can process and present antigen. However, rather than inducing T-cell proliferation, ILCs acted to limit commensal bacteria-specific CD4(+) T-cell responses. Consistent with this, selective deletion of MHCII in murine RORγt(+) ILCs resulted in dysregulated commensal bacteria-dependent CD4(+) T-cell responses that promoted spontaneous intestinal inflammation. These data identify that ILCs maintain intestinal homeostasis through MHCII-dependent interactions with CD4(+) T cells that limit pathological adaptive immune cell responses to commensal

  3. Non-coding RNA regulation in pathogenic bacteria located inside eukaryotic cells

    PubMed Central

    Ortega, Álvaro D.; Quereda, Juan J.; Pucciarelli, M. Graciela; García-del Portillo, Francisco

    2014-01-01

    Intracellular bacterial pathogens have evolved distinct lifestyles inside eukaryotic cells. Some pathogens coexist with the infected cell in an obligate intracellular state, whereas others transit between the extracellular and intracellular environment. Adaptation to these intracellular lifestyles is regulated in both space and time. Non-coding small RNAs (sRNAs) are post-transcriptional regulatory molecules that fine-tune important processes in bacterial physiology including cell envelope architecture, intermediate metabolism, bacterial communication, biofilm formation, and virulence. Recent studies have shown production of defined sRNA species by intracellular bacteria located inside eukaryotic cells. The molecules targeted by these sRNAs and their expression dynamics along the intracellular infection cycle remain, however, poorly characterized. Technical difficulties linked to the isolation of “intact” intracellular bacteria from infected host cells might explain why sRNA regulation in these specialized pathogens is still a largely unexplored field. Transition from the extracellular to the intracellular lifestyle provides an ideal scenario in which regulatory sRNAs are intended to participate; so much work must be done in this direction. This review focuses on sRNAs expressed by intracellular bacterial pathogens during the infection of eukaryotic cells, strategies used with these pathogens to identify sRNAs required for virulence, and the experimental technical challenges associated to this type of studies. We also discuss varied techniques for their potential application to study RNA regulation in intracellular bacterial infections. PMID:25429360

  4. Orthologous transcription factors in bacteria have differentfunctions and regulate different genes

    SciTech Connect

    Price, Morgan N.; Dehal, Paramvir S.; Arkin, Adam P.

    2007-07-25

    Transcription factors (TFs) form large paralogous genefamilies and have complex evolutionary histories. Here, we ask whetherputative orthologs of TFs, from bidirectional best BLAST hits (BBHs), areevolutionary orthologs with conserved functions. We show that BBHs of TFsfrom distantly related bacteria are usually not evolutionary orthologs.Furthermore, the false orthologs usually respond to different signals andregulate distinct pathways, while the few BBHs that are evolutionaryorthologs do have conserved functions. To test the conservation ofregulatory interactions, we analyze expression patterns. We find thatregulatory relationships between TFs and their regulated genes areusually not conserved for BBHs in Escherichia coli K12 and Bacillussubtilis. Even in the much more closely related bacteria Vibrio choleraeand Shewanella oneidensis MR-1, predicting regulation from E. coli BBHshas high error rates. Using gene-regulon correlations, we identify geneswhose expression pattern differs between E. coli and S. oneidensis. Usingliterature searches and sequence analysis, we show that these changes inexpression patterns reflect changes ingene regulation, even forevolutionary orthologs. We conclude that the evolution of bacterialregulation should be analyzed with phylogenetic trees, rather than BBHs,and that bacterial regulatory networks evolve more rapidly thanpreviously thought.

  5. Fresh layers of RNA-mediated regulation in Gram-positive bacteria.

    PubMed

    Bouloc, Philippe; Repoila, Francis

    2016-04-01

    Bacterial regulatory RNAs have been defined as diverse classes of cis and trans elements that may intervene at each step of gene expression, from RNA and protein synthesis to degradation. Here, we report on a few examples from Gram-positive bacteria that extend the definition of regulatory RNAs to include 5' and 3' UTRs that also act as cis and trans regulators. New examples unveil the existence of cis and trans acting regulatory RNAs on a single molecule. Also, we highlight data showing that a key RNA chaperone in Enterobacteriaceae, Hfq, does not fulfill the same role in Gram-positive Firmicutes. PMID:26773797

  6. Antisense RNA regulation and application in the development of novel antibiotics to combat multidrug resistant bacteria.

    PubMed

    Ji, Yinduo; Lei, Ting

    2013-01-01

    Despite the availability of antibiotics and vaccines, infectious diseases remain one of most dangerous threats to humans and animals. The overuse and misuse of antibacterial agents have led to the emergence of multidrug resistant bacterial pathogens. Bacterial cells are often resilient enough to survive in even the most extreme environments. To do so, the organisms have evolved different mechanisms, including a variety of two-component signal transduction systems, which allow the bacteria to sense the surrounding environment and regulate gene expression in order to adapt and respond to environmental stimuli. In addition, some bacteria evolve resistance to antibacterial agents while many bacterial cells are able to acquire resistance genes from other bacterial species to enable them to survive in the presence of toxic antimicrobial agents. The crisis of antimicrobial resistance is an unremitting menace to human health and a burden on public health. The rapid increase in antimicrobial resistant organisms and limited options for development of new classes of antibiotics heighten the urgent need to develop novel potent antibacterial therapeutics in order to combat multidrug resistant infections. In this review, we introduce the regulatory mechanisms of antisense RNA and significant applications of regulated antisense RNA interference technology in early drug discovery. This includes the identification and evaluation of drug targets in vitro and in vivo, the determination of mode of action for antibiotics and new antibacterial agents, as well as the development of peptide-nucleic acid conjugates as novel antibacterials. PMID:23738437

  7. The Mannitol Operon Repressor MTIR belongs to a new class of transcription regulators in bacteria.

    SciTech Connect

    Tan, K.; Borovilos, M.; Zhou, M; Horer, S; Clancy, S; Moy, S; Volkart, LL; Sassoon, J; Baumann, U; Joachimiak, A

    2009-12-25

    Many bacteria express phosphoenolpyruvate-dependent phosphotransferase systems (PTS). The mannitol-specific PTS catalyze the uptake and phosphorylation of d-mannitol. The uptake system comprises several genes encoded in the single operon. The expression of the mannitol operon is regulated by a proposed transcriptional factor, mannitol operon repressor (MtlR) that was first studied in Escherichia coli. Here we report the first crystal structures of MtlR from Vibrio parahemeolyticus (Vp-MtlR) and its homolog YggD protein from Shigella flexneri (Sf-YggD). MtlR and YggD belong to the same protein family (Pfam05068). Although Vp-MtlR and Sf-YggD share low sequence identity (22%), their overall structures are very similar, representing a novel all {alpha}-helical fold, and indicate similar function. However, their lack of any known DNA-binding structural motifs and their unfavorable electrostatic properties imply that MtlR/YggD are unlikely to bind a specific DNA operator directly as proposed earlier. This structural observation is further corroborated by in vitro DNA-binding studies of E. coli MtlR (Ec-MtlR), which detected no interaction of Ec-MtlR with the well characterized mannitol operator/promoter region. Therefore, MtlR/YggD belongs to a new class of transcription factors in bacteria that may regulate gene expression indirectly as a part of a larger transcriptional complex.

  8. Identification of immune factors regulating anti-tumor immunity using polymeric vaccines with multiple adjuvants

    PubMed Central

    Ali, Omar A.; Verbeke, Catia; Johnson, Chris; Sands, Warren; Lewin, Sarah A.; White, Des; Doherty, Edward; Dranoff, Glenn; Mooney, David J.

    2014-01-01

    The innate cellular and molecular components required to mediate effective vaccination against weak tumor-associated antigens remain unclear. In this study we utilized polymeric cancer vaccines incorporating different classes of adjuvants to induce tumor protection, in order to identify dendritic cell subsets and cytokines critical to this efficacy. Three-dimensional, porous polymer matrices loaded with tumor lysates and presenting distinct combinations of GM-CSF and various TLR agonists effected 70–90% prophylactic tumor protection in B16-F10 melanoma models. In aggressive, therapeutic B16 models, the vaccine systems incorporating GM-CSF in combination with P(I:C) or CpG-ODN induced the complete regression of solid tumors (≤40mm2) resulting in 33% long-term survival. Regression analysis revealed that the numbers of vaccine-resident CD8(+) DCs and plasmacytoid DCs, along with local IL-12, and G-CSF concentrations correlated strongly to vaccine efficacy regardless of adjuvant type. Further, vaccine studies in Batf3−/− mice revealed that CD8(+) DCs are required to effect tumor protection, as vaccines in these mice were deficient in cytotoxic T cell priming, and IL-12 induction in comparison to wild-type. These studies broadly demonstrate that three-dimensional polymeric vaccines provide a potent platform for prophylactic and therapeutic protection, and can be used as a tool to identify critical components of a desired immune response. Specifically, these results suggest that CD8(+) DCs, plasmacytoid DCs, IL-12, and G-CSF play important roles in priming effective anti-tumor responses with these vaccines. PMID:24480625

  9. A prebiotic role of Ecklonia cava improves the mortality of Edwardsiella tarda-infected zebrafish models via regulating the growth of lactic acid bacteria and pathogen bacteria.

    PubMed

    Lee, WonWoo; Oh, Jae Young; Kim, Eun-A; Kang, Nalae; Kim, Kil-Nam; Ahn, Ginnae; Jeon, You-Jin

    2016-07-01

    In this study, the beneficial prebiotic roles of Ecklonia cava (E. cava, EC) were evaluated on the growth of lactic acid bacteria (LAB) and pathogen bacteria and the mortality of pathogen-bacteria infected zebrafish model. The result showed that the original E. cava (EC) led to the highest growth effects on three LABs (Lactobacillus brevis, L. brevis; Lactobacillus pentosus, L. pentosus; Lactobacillus plantarum; L. plantarum) and it was dose-dependent manners. Also, EC, its Celluclast enzymatic (ECC) and 100% ethanol extracts (ECE) showed the anti-bacterial activities on the fish pathogenic bacteria such as (Edwardsiella tarda; E. tarda, Streptococcus iniae; S. iniae, and Vibrio harveyi; V. harveyi). Interestingly, EC induced the higher production of the secondary metabolites from L. plantarum in MRS medium. The secondary metabolites produced by EC significantly inhibited the growth of pathogen bacteria. In further in vivo study, the co-treatment of EC and L. plantarum improved the growth and mortality of E. tarda-infected zebrafish as regulating the expression of inflammatory molecules such as iNOS and COX2. Taken together, our present study suggests that the EC plays an important role as a potential prebiotic and has a protective effect against the infection caused by E. tarda injection in zebrafish. Also, our conclusion from this evidence is that EC can be used and applied as a useful prebiotic. PMID:27192145

  10. Bacteria Regulate Intestinal Epithelial Cell Differentiation Factors Both In Vitro and In Vivo

    PubMed Central

    Becker, Svetlana; Oelschlaeger, Tobias A.; Wullaert, Andy; Pasparakis, Manolis; Wehkamp, Jan; Stange, Eduard F.; Gersemann, Michael

    2013-01-01

    Background The human colon harbours a plethora of bacteria known to broadly impact on mucosal metabolism and function and thought to be involved in inflammatory bowel disease pathogenesis and colon cancer development. In this report, we investigated the effect of colonic bacteria on epithelial cell differentiation factors in vitro and in vivo. As key transcription factors we focused on Hes1, known to direct towards an absorptive cell fate, Hath1 and KLF4, which govern goblet cell. Methods Expression of the transcription factors Hes1, Hath1 and KLF4, the mucins Muc1 and Muc2 and the defensin HBD2 were measured by real-time PCR in LS174T cells following incubation with several heat-inactivated E. coli strains, including the probiotic E. coli Nissle 1917+/− flagellin, Lactobacilli and Bifidobacteria. For protein detection Western blot experiments and chamber-slide immunostaining were performed. Finally, mRNA and protein expression of these factors was evaluated in the colon of germfree vs. specific pathogen free vs. conventionalized mice and colonic goblet cells were counted. Results Expression of Hes1 and Hath1, and to a minor degree also of KLF4, was reduced by E. coli K-12 and E. coli Nissle 1917. In contrast, Muc1 and HBD2 expression were significantly enhanced, independent of the Notch signalling pathway. Probiotic E. coli Nissle 1917 regulated Hes1, Hath1, Muc1 and HBD2 through flagellin. In vivo experiments confirmed the observed in vitro effects of bacteria by a diminished colonic expression of Hath1 and KLF4 in specific pathogen free and conventionalized mice as compared to germ free mice whereas the number of goblet cells was unchanged in these mice. Conclusions Intestinal bacteria influence the intestinal epithelial differentiation factors Hes1, Hath1 and KLF4, as well as Muc1 and HBD2, in vitro and in vivo. The induction of Muc1 and HBD2 seems to be triggered directly by bacteria and not by Notch. PMID:23418447

  11. One carbon metabolism in anaerobic bacteria: Regulation of carbon and electron flow during organic acid production

    SciTech Connect

    Zeikus, J.G.; Jain, M.

    1993-12-31

    The project deals with understanding the fundamental biochemical mechanisms that physiologically control and regulate carbon and electron flow in anaerobic chemosynthetic bacteria that couple metabolism of single carbon compounds and hydrogen to the production of organic acids (formic, acetic, butyric, and succinic) or methane. The authors compare the regulation of carbon dioxide and hydrogen metabolism by fermentation, enzyme, and electron carrier analysis using Butyribacterium methylotrophicum, Anaeroblospirillum succiniciproducens, Methanosarcina barkeri, and a newly isolated tri-culture composed of a syntrophic butyrate degrader strain IB, Methanosarcina mazei and Methanobacterium formicicum as model systems. To understand the regulation of hydrogen metabolism during butyrate production or acetate degradation, hydrogenase activity in B. methylotrophicum or M. barkeri is measured in relation to growth substrate and pH; hydrogenase is purified and characterized to investigate number of hydrogenases; their localization and functions; and, their sequences are determined. To understand the mechanism for catabolic CO{sub 2} fixation to succinate the PEP carboxykinase enzyme and gene of A. succiniciproducens are purified and characterized. Genetically engineered strains of Escherichia coli containing the phosphoenolpyruvate (PEP) carboxykinase gene are examined for their ability to produce succinate in high yield. To understand the mechanism of fatty acid degradation by syntrophic acetogens during mixed culture methanogenesis formate and hydrogen production are characterized by radio tracer studies. It is intended that these studies provide strategies to improve anaerobic fermentations used for the production of organic acids or methane and, new basic understanding on catabolic CO{sub 2} fixation mechanisms and on the function of hydrogenase in anaerobic bacteria.

  12. Elk-3 is a KLF4-regulated gene that modulates the phagocytosis of bacteria by macrophages.

    PubMed

    Tsoyi, Konstantin; Geldart, Adriana M; Christou, Helen; Liu, Xiaoli; Chung, Su Wol; Perrella, Mark A

    2015-01-01

    ETS family proteins play a role in immune responses. A unique member of this family, Elk-3, is a transcriptional repressor that regulates the expression of HO-1. Elk-3 is very sensitive to the effects of inflammatory mediators and is down-regulated by bacterial endotoxin (LPS). In the present study, exposure of mouse macrophages to Escherichia coli LPS resulted in decreased, full-length, and splice-variant isoforms of Elk-3. We isolated the Elk-3 promoter and demonstrated that LPS also decreased promoter activity. The Elk-3 promoter contains GC-rich regions that are putative binding sites for zinc-finger transcription factors, such as Sp1 and KLFs. Mutation of the GC-rich region from bp -613 to -603 blunted LPS-induced down-regulation of the Elk-3 promoter. Similar to the LPS response, coexpression of KLF4 led to repression of Elk-3 promoter activity, whereas coexpression of Sp1 increased activity. ChIP assays revealed that KLF4 binding to the Elk-3 promoter was increased by LPS exposure, and Sp1 binding was decreased. Thus, down-regulation of Elk-3 by bacterial LPS is regulated, in part, by the transcriptional repressor KLF4. Overexpression of Elk-3, in the presence of E. coli bacteria, resulted in decreased macrophage phagocytosis. To determine whether limited expression of HO-1 may contribute to this response, we exposed HO-1-deficient bone marrow-derived macrophages to E. coli and found a comparable reduction in bacterial phagocytosis. These data suggest that down-regulation of Elk-3 and the subsequent induction of HO-1 are important for macrophage function during the inflammatory response to infection. PMID:25351511

  13. Elk-3 is a KLF4-regulated gene that modulates the phagocytosis of bacteria by macrophages

    PubMed Central

    Tsoyi, Konstantin; Geldart, Adriana M.; Christou, Helen; Liu, Xiaoli; Chung, Su Wol; Perrella, Mark A.

    2015-01-01

    ETS family proteins play a role in immune responses. A unique member of this family, Elk-3, is a transcriptional repressor that regulates the expression of HO-1. Elk-3 is very sensitive to the effects of inflammatory mediators and is down-regulated by bacterial endotoxin (LPS). In the present study, exposure of mouse macrophages to Escherichia coli LPS resulted in decreased, full-length, and splice-variant isoforms of Elk-3. We isolated the Elk-3 promoter and demonstrated that LPS also decreased promoter activity. The Elk-3 promoter contains GC-rich regions that are putative binding sites for zinc-finger transcription factors, such as Sp1 and KLFs. Mutation of the GC-rich region from bp –613 to –603 blunted LPS-induced down-regulation of the Elk-3 promoter. Similar to the LPS response, coexpression of KLF4 led to repression of Elk-3 promoter activity, whereas coexpression of Sp1 increased activity. ChIP assays revealed that KLF4 binding to the Elk-3 promoter was increased by LPS exposure, and Sp1 binding was decreased. Thus, down-regulation of Elk-3 by bacterial LPS is regulated, in part, by the transcriptional repressor KLF4. Overexpression of Elk-3, in the presence of E. coli bacteria, resulted in decreased macrophage phagocytosis. To determine whether limited expression of HO-1 may contribute to this response, we exposed HO-1-deficient bone marrow-derived macrophages to E. coli and found a comparable reduction in bacterial phagocytosis. These data suggest that down-regulation of Elk-3 and the subsequent induction of HO-1 are important for macrophage function during the inflammatory response to infection. PMID:25351511

  14. Stimulation of growth by proteorhodopsin phototrophy involves regulation of central metabolic pathways in marine planktonic bacteria

    PubMed Central

    Palovaara, Joakim; Akram, Neelam; Baltar, Federico; Bunse, Carina; Forsberg, Jeremy; Pedrós-Alió, Carlos; González, José M.; Pinhassi, Jarone

    2014-01-01

    Proteorhodopsin (PR) is present in half of surface ocean bacterioplankton, where its light-driven proton pumping provides energy to cells. Indeed, PR promotes growth or survival in different bacteria. However, the metabolic pathways mediating the light responses remain unknown. We analyzed growth of the PR-containing Dokdonia sp. MED134 (where light-stimulated growth had been found) in seawater with low concentrations of mixed [yeast extract and peptone (YEP)] or single (alanine, Ala) carbon compounds as models for rich and poor environments. We discovered changes in gene expression revealing a tightly regulated shift in central metabolic pathways between light and dark conditions. Bacteria showed relatively stronger light responses in Ala compared with YEP. Notably, carbon acquisition pathways shifted toward anaplerotic CO2 fixation in the light, contributing 31 ± 8% and 24 ± 6% of the carbon incorporated into biomass in Ala and YEP, respectively. Thus, MED134 was a facultative double mixotroph, i.e., photo- and chemotrophic for its energy source and using both bicarbonate and organic matter as carbon sources. Unexpectedly, relative expression of the glyoxylate shunt genes (isocitrate lyase and malate synthase) was >300-fold higher in the light—but only in Ala—contributing a more efficient use of carbon from organic compounds. We explored these findings in metagenomes and metatranscriptomes and observed similar prevalence of the glyoxylate shunt compared with PR genes and highest expression of the isocitrate lyase gene coinciding with highest solar irradiance. Thus, regulatory interactions between dissolved organic carbon quality and central metabolic pathways critically determine the fitness of surface ocean bacteria engaging in PR phototrophy. PMID:25136122

  15. New family of tungstate-responsive transcriptional regulators in sulfate-reducing bacteria.

    PubMed

    Kazakov, Alexey E; Rajeev, Lara; Luning, Eric G; Zane, Grant M; Siddartha, Kavya; Rodionov, Dmitry A; Dubchak, Inna; Arkin, Adam P; Wall, Judy D; Mukhopadhyay, Aindrila; Novichkov, Pavel S

    2013-10-01

    The trace elements molybdenum and tungsten are essential components of cofactors of many metalloenzymes. However, in sulfate-reducing bacteria, high concentrations of molybdate and tungstate oxyanions inhibit growth, thus requiring the tight regulation of their homeostasis. By a combination of bioinformatic and experimental techniques, we identified a novel regulator family, tungstate-responsive regulator (TunR), controlling the homeostasis of tungstate and molybdate in sulfate-reducing deltaproteobacteria. The effector-sensing domains of these regulators are similar to those of the known molybdate-responsive regulator ModE, while their DNA-binding domains are homologous to XerC/XerD site-specific recombinases. Using a comparative genomics approach, we identified DNA motifs and reconstructed regulons for 40 TunR family members. Positional analysis of TunR sites and putative promoters allowed us to classify most TunR proteins into two groups: (i) activators of modABC genes encoding a high-affinity molybdenum and tungsten transporting system and (ii) repressors of genes for toluene sulfonate uptake (TSUP) family transporters. The activation of modA and modBC genes by TunR in Desulfovibrio vulgaris Hildenborough was confirmed in vivo, and we discovered that the activation was diminished in the presence of tungstate. A predicted 30-bp TunR-binding motif was confirmed by in vitro binding assays. A novel TunR family of bacterial transcriptional factors controls tungstate and molybdate homeostasis in sulfate-reducing deltaproteobacteria. We proposed that TunR proteins participate in protection of the cells from the inhibition by these oxyanions. To our knowledge, this is a unique case of a family of bacterial transcriptional factors evolved from site-specific recombinases. PMID:23913324

  16. Redox regulation of energy transfer efficiency in antennas of green photosynthetic bacteria

    NASA Technical Reports Server (NTRS)

    Blankenship, R. E.; Cheng, P.; Causgrove, T. P.; Brune, D. C.; Wang, J.

    1993-01-01

    The efficiency of energy transfer from the peripheral chlorosome antenna structure to the membrane-bound antenna in green sulfur bacteria depends strongly on the redox potential of the medium. The fluorescence spectra and lifetimes indicate that efficient quenching pathways are induced in the chlorosome at high redox potential. The midpoint redox potential for the induction of this effect in isolated chlorosomes from Chlorobium vibrioforme is -146 mV at pH 7 (vs the normal hydrogen electrode), and the observed midpoint potential (n = 1) decreases by 60 mV per pH unit over the pH range 7-10. Extraction of isolated chlorosomes with hexane has little effect on the redox-induced quenching, indicating that the component(s) responsible for this effect are bound and not readily extractable. We have purified and partially characterized the trimeric water-soluble bacteriochlorophyll a-containing protein from the thermophilic green sulfur bacterium Chlorobium tepidum. This protein is located between the chlorosome and the membrane. Fluorescence spectra of the purified protein indicate that it also contains groups that quench excitations at high redox potential. The results indicate that the energy transfer pathway in green sulfur bacteria is regulated by redox potential. This regulation appears to operate in at least two distinct places in the energy transfer pathway, the oligomeric pigments in the interior of the chlorosome and in the bacteriochlorophyll a protein. The regulatory effect may serve to protect the cell against superoxide-induced damage when oxygen is present. By quenching excitations before they reach the reaction center, reduction and subsequent autooxidation of the low potential electron acceptors found in these organisms is avoided.

  17. Signal transduction and transcriptional and posttranscriptional control of iron-regulated genes in bacteria.

    PubMed

    Crosa, J H

    1997-09-01

    Iron is an essential element for nearly all living cells. Thus, the ability of bacteria to utilize iron is a crucial survival mechanism independent of the ecological niche in which the microorganism lives, because iron is scarce both in potential biological hosts, where it is bound by high-affinity iron-binding proteins, and in the environment, where it is present as part of insoluble complex hydroxides. Therefore, pathogens attempting to establish an infection and environmental microorganisms must all be able to utilize the otherwise unavailable iron. One of the strategies to perform this task is the possession of siderophore-mediated iron uptake systems that are capable of scavenging the hoarded iron. This metal is, however, a double-edged sword for the cell because it can catalyze the production of deadly free hydroxyl radicals, which are harmful to the cells. It is therefore imperative for the cell to control the concentration of iron at levels that permit key metabolic steps to occur without becoming a messenger of cell death. Early work identified a repressor, Fur, which as a complex with iron repressed the expression of most iron uptake systems as well as other iron-regulated genes when the iron concentration reached a certain level. However, later work demonstrated that this regulation by Fur was not the only answer under low-iron conditions, there was a need for activation of iron uptake genes as well as siderophore biosynthetic genes. Furthermore, it was also realized that in some instances the actual ferric iron-siderophore complex induced the transcription of the cognate receptor and transport genes. It became evident that control of the expression of iron-regulated genes was more complex than originally envisioned. In this review, I analyze the processes of signal transduction, transcriptional control, and posttranscriptional control of iron-regulated genes as reported for the ferric dicitrate system in Escherichia coli; the pyochelin, pyoverdin, and

  18. Silencing of Anopheles stephensi Heme Peroxidase HPX15 Activates Diverse Immune Pathways to Regulate the Growth of Midgut Bacteria

    PubMed Central

    Kajla, Mithilesh; Choudhury, Tania P.; Kakani, Parik; Gupta, Kuldeep; Dhawan, Rini; Gupta, Lalita; Kumar, Sanjeev

    2016-01-01

    Anopheles mosquito midgut harbors a diverse group of endogenous bacteria that grow extensively after the blood feeding and help in food digestion and nutrition in many ways. Although, the growth of endogenous bacteria is regulated by various factors, however, the robust antibacterial immune reactions are generally suppressed in this body compartment by a heme peroxidase HPX15 crosslinked mucins barrier. This barrier is formed on the luminal side of the midgut and blocks the direct interactions and recognition of bacteria or their elicitors by the immune reactive midgut epithelium. We hypothesized that in the absence of HPX15, an increased load of exogenous bacteria will enormously induce the mosquito midgut immunity and this situation in turn, can easily regulate mosquito-pathogen interactions. In this study, we found that the blood feeding induced AsHPX15 gene in Anopheles stephensi midgut and promoted the growth of endogenous as well as exogenous fed bacteria. In addition, the mosquito midgut also efficiently regulated the number of these bacteria through the induction of classical Toll and Imd immune pathways. In case of AsHPX15 silenced midguts, the growth of midgut bacteria was largely reduced through the induction of nitric oxide synthase (NOS) gene, a downstream effector molecule of the JAK/STAT pathway. Interestingly, no significant induction of the classical immune pathways was observed in these midguts. Importantly, the NOS is a well known negative regulator of Plasmodium development, thus, we proposed that the induction of diverged immune pathways in the absence of HPX15 mediated midgut barrier might be one of the strategies to manipulate the vectorial capacity of Anopheles mosquito.

  19. Temperature and Carbon Assimilation Regulate the Chlorosome Biogenesis in Green Sulfur Bacteria

    PubMed Central

    Tang, Joseph Kuo-Hsiang; Saikin, Semion K.; Pingali, Sai Venkatesh; Enriquez, Miriam M.; Huh, Joonsuk; Frank, Harry A.; Urban, Volker S.; Aspuru-Guzik, Alán

    2013-01-01

    Green photosynthetic bacteria adjust the structure and functionality of the chlorosome—the light-absorbing antenna complex—in response to environmental stress factors. The chlorosome is a natural self-assembled aggregate of bacteriochlorophyll (BChl) molecules. In this study, we report the regulation of the biogenesis of the Chlorobaculum tepidum chlorosome by carbon assimilation in conjunction with temperature changes. Our studies indicate that the carbon source and thermal stress culture of C. tepidum grows slower and incorporates fewer BChl c in the chlorosome. Compared with the chlorosome from other cultural conditions we investigated, the chlorosome from the carbon source and thermal stress culture displays (a) smaller cross-sectional radius and overall size, (b) simplified BChl c homologs with smaller side chains, (c) blue-shifted Qy absorption maxima, and (d) a sigmoid-shaped circular dichroism spectra. Using a theoretical model, we analyze how the observed spectral modifications can be associated with structural changes of BChl aggregates inside the chlorosome. Our report suggests a mechanism of metabolic regulation for chlorosome biogenesis. PMID:24047985

  20. MAP1S Protein Regulates the Phagocytosis of Bacteria and Toll-like Receptor (TLR) Signaling.

    PubMed

    Shi, Ming; Zhang, Yifan; Liu, Leyuan; Zhang, Tingting; Han, Fang; Cleveland, Joseph; Wang, Fen; McKeehan, Wallace L; Li, Yu; Zhang, Dekai

    2016-01-15

    Phagocytosis is a critical cellular process for innate immune defense against microbial infection. The regulation of phagocytosis process is complex and has not been well defined. An intracellular molecule might regulate cell surface-initiated phagocytosis, but the underlying molecular mechanism is poorly understood (1). In this study, we found that microtubule-associated protein 1S (MAP1S), a protein identified recently that is involved in autophagy (2), is expressed primarily in macrophages. MAP1S-deficient macrophages are impaired in the phagocytosis of bacteria. Furthermore, we demonstrate that MAP1S interacts directly with MyD88, a key adaptor of Toll-like receptors (TLRs), upon TLR activation and affects the TLR signaling pathway. Intriguingly, we also observe that, upon TLR activation, MyD88 participates in autophagy processing in a MAP1S-dependent manner by co-localizing with MAP1 light chain 3 (MAP1-LC3 or LC3). Therefore, we reveal that an intracellular autophagy-related molecule of MAP1S controls bacterial phagocytosis through TLR signaling. PMID:26565030

  1. A novel transcriptional regulator of L-arabinose utilization in human gut bacteria

    PubMed Central

    Chang, Changsoo; Tesar, Christine; Li, Xiaoqing; Kim, Youngchang; Rodionov, Dmitry A.; Joachimiak, Andrzej

    2015-01-01

    Carbohydrate metabolism plays a crucial role in the ecophysiology of human gut microbiota. Mechanisms of transcriptional regulation of sugar catabolism in commensal and prevalent human gut bacteria such as Bacteroides thetaiotaomicron remain mostly unknown. By a combination of bioinformatics and experimental approaches, we have identified an NrtR family transcription factor (BT0354 in B. thetaiotaomicron, BtAraR) as a novel regulator controlling the arabinose utilization genes. L-arabinose was confirmed to be a negative effector of BtAraR. We have solved the crystal structures of the apo and L-arabinose-bound BtAraR proteins, as well as the complex of apo-protein with a specific DNA operator. BtAraR forms a homodimer with each subunit comprised of the ligand-binding Nudix hydrolase-like domain and the DNA-binding winged-helix-turn-helix (wHTH) domain. We have identified the residues involved in binding of L-arabinose and recognition of DNA. The majority of these residues are well conserved in the AraR orthologs in Bacteroidetes. In the structure of the BtAraR–DNA complex, we found the unique interaction of arginine intercalating its guanidinum moiety into the base pair stacking of B-DNA. L-arabinose binding induces movement of wHTH domains, resulting in a conformation unsuitable for DNA binding. Our analysis facilitates reconstruction of the metabolic and regulatory networks involved in carbohydrate utilization in human gut Bacteroides. PMID:26438537

  2. Prediction of CsrA-regulating small RNAs in bacteria and their experimental verification in Vibrio fischeri

    PubMed Central

    Kulkarni, Prajna R.; Cui, Xiaohui; Williams, Joshua W.; Stevens, Ann M.; Kulkarni, Rahul V.

    2006-01-01

    The role of small RNAs as critical components of global regulatory networks has been highlighted by several recent studies. An important class of such small RNAs is represented by CsrB and CsrC of Escherichia coli, which control the activity of the global regulator CsrA. Given the critical role played by CsrA in several bacterial species, an important problem is the identification of CsrA-regulating small RNAs. In this paper, we develop a computer program (CSRNA_FIND) designed to locate potential CsrA-regulating small RNAs in bacteria. Using CSRNA_FIND to search the genomes of bacteria having homologs of CsrA, we identify all the experimentally known CsrA-regulating small RNAs and also make predictions for several novel small RNAs. We have verified experimentally our predictions for two CsrA-regulating small RNAs in Vibrio fischeri. As more genomes are sequenced, CSRNA_FIND can be used to locate the corresponding small RNAs that regulate CsrA homologs. This work thus opens up several avenues of research in understanding the mode of CsrA regulation through small RNAs in bacteria. PMID:16822857

  3. Ribosome Inactivation Leads to Attenuation of Intestinal Polymeric Ig Receptor Expression via Differential Regulation of Human Antigen R.

    PubMed

    Do, Kee Hun; Park, Seong-Hwan; Kim, Juil; Yu, Mira; Moon, Yuseok

    2016-08-01

    The polymeric IgR (pIgR) is a central component in the transport of IgA across enterocytes and thereby plays a crucial role in the defense against enteropathogens and in the regulation of circulating IgA levels. The present study was performed to address the novel regulation of pIgR expression in intestinal epithelia undergoing ribosome inactivation. Insults to mucosa that led to ribosome inactivation attenuated pIgR expression in enterocytes. However, IFN regulatory factor-1 (IRF-1) as a central transcription factor of pIgR induction was superinduced by ribosome inactivation in the presence of IFN-γ as a result of mRNA stabilization by the RNA-binding protein HuR. Another important transcription factor for pIgR expression, NF-κB, was marginally involved in suppression of pIgR by ribosome inactivation. In contrast to a positive contribution of HuR in early induction of IRF-1 expression, extended exposure to ribosome inactivation caused nuclear entrapment of HuR, resulting in destabilization of late-phase-induced pIgR mRNA. These HuR-linked differential regulations of pIgR and of IRF-1 led to a reduced mucosal secretion of IgA and, paradoxically, an induction of IRF-1-activated target genes, including colitis-associated IL-7. Therefore, these events can account for ribosome inactivation-related mucosal disorders and provide new insight into interventions for HuR-linked pathogenesis in diverse mucosa-associated diseases, including inflammatory bowel disease and IgA nephritis. PMID:27307561

  4. A novel transcriptional regulator of L-arabinose utilization in human gut bacteria

    DOE PAGESBeta

    Chang, Changsoo; Tesar, Christine; Li, Xiaoqing; Kim, Youngchang; Rodionov, Dmitry A.; Joachimiak, Andrzej

    2015-10-04

    We report that carbohydrate metabolism plays a crucial role in the ecophysiology of human gut microbiota. Mechanisms of transcriptional regulation of sugar catabolism in commensal and prevalent human gut bacteria such as Bacteroides thetaiotaomicron remain mostly unknown. By a combination of bioinformatics and experimental approaches, we have identified an NrtR family transcription factor (BT0354 in B. thetaiotaomicron, BtAraR) as a novel regulator controlling the arabinose utilization genes. L-arabinose was confirmed to be a negative effector of BtAraR. We have solved the crystal structures of the apo and L-arabinose-bound BtAraR proteins, as well as the complex of apo-protein with a specificmore » DNA operator. BtAraR forms a homodimer with each subunit comprised of the ligand-binding Nudix hydrolase-like domain and the DNA-binding winged-helix-turn-helix (wHTH) domain. We have identified the residues involved in binding of L-arabinose and recognition of DNA. The majority of these residues are well conserved in the AraR orthologs in Bacteroidetes. In the structure of the BtAraR–DNA complex, we found the unique interaction of arginine intercalating its guanidinum moiety into the base pair stacking of B-DNA. L-arabinose binding induces movement of wHTH domains, resulting in a conformation unsuitable for DNA binding. Furthermore, our analysis facilitates reconstruction of the metabolic and regulatory networks involved in carbohydrate utilization in human gut Bacteroides.« less

  5. A novel transcriptional regulator of L-arabinose utilization in human gut bacteria

    SciTech Connect

    Chang, Changsoo; Tesar, Christine; Li, Xiaoqing; Kim, Youngchang; Rodionov, Dmitry A.; Joachimiak, Andrzej

    2015-10-04

    We report that carbohydrate metabolism plays a crucial role in the ecophysiology of human gut microbiota. Mechanisms of transcriptional regulation of sugar catabolism in commensal and prevalent human gut bacteria such as Bacteroides thetaiotaomicron remain mostly unknown. By a combination of bioinformatics and experimental approaches, we have identified an NrtR family transcription factor (BT0354 in B. thetaiotaomicron, BtAraR) as a novel regulator controlling the arabinose utilization genes. L-arabinose was confirmed to be a negative effector of BtAraR. We have solved the crystal structures of the apo and L-arabinose-bound BtAraR proteins, as well as the complex of apo-protein with a specific DNA operator. BtAraR forms a homodimer with each subunit comprised of the ligand-binding Nudix hydrolase-like domain and the DNA-binding winged-helix-turn-helix (wHTH) domain. We have identified the residues involved in binding of L-arabinose and recognition of DNA. The majority of these residues are well conserved in the AraR orthologs in Bacteroidetes. In the structure of the BtAraR–DNA complex, we found the unique interaction of arginine intercalating its guanidinum moiety into the base pair stacking of B-DNA. L-arabinose binding induces movement of wHTH domains, resulting in a conformation unsuitable for DNA binding. Furthermore, our analysis facilitates reconstruction of the metabolic and regulatory networks involved in carbohydrate utilization in human gut Bacteroides.

  6. Regulation of the Activity of Lactate Dehydrogenases from Four Lactic Acid Bacteria*

    PubMed Central

    Feldman-Salit, Anna; Hering, Silvio; Messiha, Hanan L.; Veith, Nadine; Cojocaru, Vlad; Sieg, Antje; Westerhoff, Hans V.; Kreikemeyer, Bernd; Wade, Rebecca C.; Fiedler, Tomas

    2013-01-01

    Despite high similarity in sequence and catalytic properties, the l-lactate dehydrogenases (LDHs) in lactic acid bacteria (LAB) display differences in their regulation that may arise from their adaptation to different habitats. We combined experimental and computational approaches to investigate the effects of fructose 1,6-bisphosphate (FBP), phosphate (Pi), and ionic strength (NaCl concentration) on six LDHs from four LABs studied at pH 6 and pH 7. We found that 1) the extent of activation by FBP (Kact) differs. Lactobacillus plantarum LDH is not regulated by FBP, but the other LDHs are activated with increasing sensitivity in the following order: Enterococcus faecalis LDH2 ≤ Lactococcus lactis LDH2 < E. faecalis LDH1 < L. lactis LDH1 ≤ Streptococcus pyogenes LDH. This trend reflects the electrostatic properties in the allosteric binding site of the LDH enzymes. 2) For L. plantarum, S. pyogenes, and E. faecalis, the effects of Pi are distinguishable from the effect of changing ionic strength by adding NaCl. 3) Addition of Pi inhibits E. faecalis LDH2, whereas in the absence of FBP, Pi is an activator of S. pyogenes LDH, E. faecalis LDH1, and L. lactis LDH1 and LDH2 at pH 6. These effects can be interpreted by considering the computed binding affinities of Pi to the catalytic and allosteric binding sites of the enzymes modeled in protonation states corresponding to pH 6 and pH 7. Overall, the results show a subtle interplay among the effects of Pi, FBP, and pH that results in different regulatory effects on the LDHs of different LABs. PMID:23720742

  7. The role of commensal bacteria in the regulation of sensitization to food allergens

    PubMed Central

    Cao, Severine; Feehley, Taylor J.; Nagler, Cathryn R.

    2014-01-01

    The prevalence of life-threatening anaphylactic responses to food is rising at an alarming rate. The emerging role of the gut microbiota in regulating food allergen sensitization may help explain this trend. The mechanisms by which commensal bacteria influence sensitization to dietary antigens are only beginning to be explored. We have found that a population of mucosa-associated commensal anaerobes prevents food allergen sensitization by promoting an IL-22-dependent barrier protective immune response that limits the access of food allergens to the systemic circulation. This early response is followed by an adaptive immune response mediated in part by an expansion of Foxp3+ Tregs that fortifies the tolerogenic milieu needed to maintain non-responsiveness to food. Bacterial metabolites, such as short-chain fatty acids, may contribute to the process through their ability to promote Foxp3+ Treg differentiation. This work suggests that environmentally induced alterations of the gut microbiota offset the regulatory signals conferred by protective bacterial species to promote aberrant responses to food. Our research presents exciting new possibilities for preventing and treating food allergies based on interventions that modulate the composition of the gut microbiota. PMID:24791655

  8. The role of commensal bacteria in the regulation of sensitization to food allergens.

    PubMed

    Cao, Severine; Feehley, Taylor J; Nagler, Cathryn R

    2014-11-17

    The prevalence of life-threatening anaphylactic responses to food is rising at an alarming rate. The emerging role of the gut microbiota in regulating food allergen sensitization may help explain this trend. The mechanisms by which commensal bacteria influence sensitization to dietary antigens are only beginning to be explored. We have found that a population of mucosa-associated commensal anaerobes prevents food allergen sensitization by promoting an IL-22-dependent barrier protective immune response that limits the access of food allergens to the systemic circulation. This early response is followed by an adaptive immune response mediated in part by an expansion of Foxp3(+) Tregs that fortifies the tolerogenic milieu needed to maintain non-responsiveness to food. Bacterial metabolites, such as short-chain fatty acids, may contribute to the process through their ability to promote Foxp3(+) Treg differentiation. This work suggests that environmentally induced alterations of the gut microbiota offset the regulatory signals conferred by protective bacterial species to promote aberrant responses to food. Our research presents exciting new possibilities for preventing and treating food allergies based on interventions that modulate the composition of the gut microbiota. PMID:24791655

  9. Role of Protein Phosphorylation in the Regulation of Cell Cycle and DNA-Related Processes in Bacteria

    PubMed Central

    Garcia-Garcia, Transito; Poncet, Sandrine; Derouiche, Abderahmane; Shi, Lei; Mijakovic, Ivan; Noirot-Gros, Marie-Françoise

    2016-01-01

    In all living organisms, the phosphorylation of proteins modulates various aspects of their functionalities. In eukaryotes, protein phosphorylation plays a key role in cell signaling, gene expression, and differentiation. Protein phosphorylation is also involved in the global control of DNA replication during the cell cycle, as well as in the mechanisms that cope with stress-induced replication blocks. Similar to eukaryotes, bacteria use Hanks-type kinases and phosphatases for signal transduction, and protein phosphorylation is involved in numerous cellular processes. However, it remains unclear whether protein phosphorylation in bacteria can also regulate the activity of proteins involved in DNA-mediated processes such as DNA replication or repair. Accumulating evidence supported by functional and biochemical studies suggests that phospho-regulatory mechanisms also take place during the bacterial cell cycle. Recent phosphoproteomics and interactomics studies identified numerous phosphoproteins involved in various aspect of DNA metabolism strongly supporting the existence of such level of regulation in bacteria. Similar to eukaryotes, bacterial scaffolding-like proteins emerged as platforms for kinase activation and signaling. This review reports the current knowledge on the phosphorylation of proteins involved in the maintenance of genome integrity and the regulation of cell cycle in bacteria that reveals surprising similarities to eukaryotes. PMID:26909079

  10. Overview of the gene regulation network and the bacteria biotope tasks in BioNLP'13 shared task

    PubMed Central

    2015-01-01

    Background We present the two Bacteria Track tasks of BioNLP 2013 Shared Task (ST): Gene Regulation Network (GRN) and Bacteria Biotope (BB). These tasks were previously introduced in the 2011 BioNLP-ST Bacteria Track as Bacteria Gene Interaction (BI) and Bacteria Biotope (BB). The Bacteria Track was motivated by a need to develop specific BioNLP tools for fine-grained event extraction in bacteria biology. The 2013 tasks expand on the 2011 version by better addressing the biological knowledge modeling needs. New evaluation metrics were designed for the new goals. Moving beyond a list of gene interactions, the goal of the GRN task is to build a gene regulation network from the extracted gene interactions. BB'13 is dedicated to the extraction of bacteria biotopes, i.e. bacterial environmental information, as was BB'11. BB'13 extends the typology of BB'11 to a large diversity of biotopes, as defined by the OntoBiotope ontology. The detection of entities and events is tackled by distinct subtasks in order to measure the progress achieved by the participant systems since 2011. Results This paper details the corpus preparations and the evaluation metrics, as well as summarizing and discussing the participant results. Five groups participated in each of the two tasks. The high diversity of the participant methods reflects the dynamism of the BioNLP research community. The highest scores for the GRN and BB'13 tasks are similar to those obtained by the participants in 2011, despite of the increase in difficulty. The high density of events in short text segments (multi-event extraction) was a difficult issue for the participating systems for both tasks. The analysis of the BB'13 results also shows that co-reference resolution and entity boundary detection remain major hindrances. Conclusion The evaluation results suggest new research directions for the improvement and development of Information Extraction for molecular and environmental biology. The Bacteria Track tasks

  11. Polymeric microspheres

    DOEpatents

    Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

    2004-04-13

    The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

  12. Activated sludge filterability improvement by nitrifying bacteria abundance regulation in an adsorption membrane bioreactor (Ad-MBR).

    PubMed

    Sun, Fei-yun; Lv, Xiao-mei; Li, Ji; Peng, Zhong-yi; Li, Pu; Shao, Ming-fei

    2014-10-01

    Autotrophic nitrifying bacteria have its intrinsic properties including low EPS production, dense colonial structure and slow-growth rate, favoring the sludge filterability improvement. An adsorption-MBR (Ad-MBR) was developed to enrich nitrifier abundance in the MBR chamber by inlet C/N regulation, and its possible positive effect on sludge filterability and underlying mechanisms were investigated. By DNA extraction, PCR amplification and Illumina high-throughput pyrosequencing, the abundance of nitrifying bacteria was accurately quantified. More than 8.29% nitrifier abundance was achieved in Ad-MBR sludge, which was above three times of that in conventional MBR. Regulated C/N ratio and thereafter nitrifier abundance enrichment improved sludge filterability by altering sludge mixture and its supernatant properties, reflected by a good sludge settleability, a low supernatant viscosity and turbidity, a low supernatant organic substances concentration, and a small amount of strong hydrophobic fractional components, thus to profoundly improve sludge filterability and decelerate membrane fouling. PMID:25146315

  13. Development and Use of a Selectable, Broad-Host-Range Reporter Transposon for Identifying Environmentally Regulated Promoters in Bacteria

    PubMed Central

    Spinler, Jennifer K.; Zajdowicz, Sheryl L. W.; Haller, Jon C.; Oram, Diana Marra; Gill, Ronald E.; Holmes, Randall K.

    2009-01-01

    This report describes the development and use of TnKnXSp, a selectable broad-host-range reporter transposon with a promoterless aphA gene. Insertion of TnKnXSp into the chromosome of a kanamycin-susceptible bacterium confers resistance to kanamycin only if aphA is transcribed from an active promoter adjacent to the insertion site. We designed TnKnXSp as a tool for identifying environmentally regulated promoters in bacteria and developed general methods for initial characterization of any TnKnXSp integrant. To identify putative iron-regulated promoters in Corynebacterium diphtheriae, we constructed TnKnXSp integrants and identified a subgroup that expressed kanamycin resistance under low-iron, but not high-iron, conditions. We characterized representative integrants with this phenotype, located the TnKnXSp insertion in each, and demonstrated that transcription of aphA was repressed under high-iron vs. low-iron growth conditions. We also demonstrated that TnKnXSp can be used in bacteria other than C. diphtheriae, including Escherichia coli and Bacillus subtilus. Our findings validate TnKnXSp as a useful tool for identifying environmentally regulated promoters in bacteria. PMID:19146571

  14. Coral-associated bacteria, quorum sensing disrupters, and the regulation of biofouling.

    PubMed

    Golberg, Karina; Pavlov, Valentina; Marks, Robert S; Kushmaro, Ariel

    2013-01-01

    Marine biofouling, the settlement of microorganisms and macroorganisms on structures submerged in seawater, although economically detrimental, is a successful strategy for survival in hostile environments, where coordinated bacterial communities establish biofilms via the regulation of quorum sensing (QS) communication systems. The inhibition of QS activity among bacteria isolated from different coral species was investigated to gain further insight into its potency in the attenuation, or even the prevention, of undesirable biofouling on marine organisms. It is hypothesized that coral mucus/microorganism interactions are competitive, suggesting that the dominant communities secrete QS disruptive compounds. One hundred and twenty bacterial isolates were collected from healthy coral species and screened for their ability to inhibit QS using three bioreporter strains. Approximately 12, 11, and 24% of the isolates exhibited anti-QS activity against Escherichia coli pSB1075, Chromobacterium violaceum CV026, and Agrobacterium tumefaciens KYC55 indicator strains, respectively. Isolates with positive activity against the bioluminescent monitor strains were scanned via a cytotoxic/genotoxic, E. coli TV1061 and DPD2794 antimicrobial panel. Isolates detected by C. violaceum CV026 and A. tumefaciens KYC55 reporter strains were tested for their ability to inhibit the growth of these reporter strains, which were found to be unaffected. Tests of the Favia sp. coral isolate Fav 2-50-7 (>98% similarity to Vibrio harveyi) for its ability to attenuate the formation of biofilm showed extensive inhibitory activity against biofilms of Pseudomonas aeruginosa and Acinetobacter baumannii. To ascertain the stability and general structure of the active compound, cell-free culture supernatants exposed to an increasing temperature gradient or to digestion by proteinase K, were shown to maintain potent QS attenuation and the ability to inhibit the growth of biofilms. Mass spectrometry confirmed

  15. Zonulin Regulates Intestinal Permeability and Facilitates Enteric Bacteria Permeation in Coronary Artery Disease

    PubMed Central

    Li, Chuanwei; Gao, Min; Zhang, Wen; Chen, Caiyu; Zhou, Faying; Hu, Zhangxu; Zeng, Chunyu

    2016-01-01

    Several studies have reported an association between enteric bacteria and atherosclerosis. Bacterial 16S ribosomal RNA (rRNA) gene belong to Enterobacteriaceae have been detected in atherosclerotic plaques. How intestinal bacteria go into blood is not known. Zonulin reversibly modulate intestinal permeability (IP), the circulating zonulin levels were increased in diabetes, obesity, all of which are risk factors for atherosclerosis. It is unclear whether the circulating zonulin levels were changed in coronary artery disease (CAD) patients and modulate IP. The 16S rRNA gene of bacteria in blood sample was checked by 454 pyrosequencing. The zonulin levels were determined by enzyme-linked immunosorbent assay (ELISA) methods. The distribution of zonulin was detected by confocal immunofluorescence microscopy. Bacteria and Caco-2 cell surface micro-structure were checked by transmission electron microscopy. A high diversity of bacterial 16S rRNA gene can be detected in samples from CAD patients, most of them (99.4%) belong to Enterobacteriaceaes, eg. Rahnella. The plasma zonulin levels were significantly higher in CAD patients. Pseudomonas fluorescens exposure significantly increased zonulin expression and decreased IP in a time dependent manner. The elevated zonulin increase IP and may facilitate enteric translocation by disassembling the tight junctions, which might explain the observed high diversity of bacterial 16S rRNA genes in blood samples. PMID:27353603

  16. Zonulin Regulates Intestinal Permeability and Facilitates Enteric Bacteria Permeation in Coronary Artery Disease.

    PubMed

    Li, Chuanwei; Gao, Min; Zhang, Wen; Chen, Caiyu; Zhou, Faying; Hu, Zhangxu; Zeng, Chunyu

    2016-01-01

    Several studies have reported an association between enteric bacteria and atherosclerosis. Bacterial 16S ribosomal RNA (rRNA) gene belong to Enterobacteriaceae have been detected in atherosclerotic plaques. How intestinal bacteria go into blood is not known. Zonulin reversibly modulate intestinal permeability (IP), the circulating zonulin levels were increased in diabetes, obesity, all of which are risk factors for atherosclerosis. It is unclear whether the circulating zonulin levels were changed in coronary artery disease (CAD) patients and modulate IP. The 16S rRNA gene of bacteria in blood sample was checked by 454 pyrosequencing. The zonulin levels were determined by enzyme-linked immunosorbent assay (ELISA) methods. The distribution of zonulin was detected by confocal immunofluorescence microscopy. Bacteria and Caco-2 cell surface micro-structure were checked by transmission electron microscopy. A high diversity of bacterial 16S rRNA gene can be detected in samples from CAD patients, most of them (99.4%) belong to Enterobacteriaceaes, eg. Rahnella. The plasma zonulin levels were significantly higher in CAD patients. Pseudomonas fluorescens exposure significantly increased zonulin expression and decreased IP in a time dependent manner. The elevated zonulin increase IP and may facilitate enteric translocation by disassembling the tight junctions, which might explain the observed high diversity of bacterial 16S rRNA genes in blood samples. PMID:27353603

  17. Why do bacteria regulate public goods by quorum sensing?—How the shapes of cost and benefit functions determine the form of optimal regulation

    PubMed Central

    Heilmann, Silja; Krishna, Sandeep; Kerr, Benjamin

    2015-01-01

    Many bacteria secrete compounds which act as public goods. Such compounds are often under quorum sensing (QS) regulation, yet it is not understood exactly when bacteria may gain from having a public good under QS regulation. Here, we show that the optimal public good production rate per cell as a function of population size (the optimal production curve, OPC) depends crucially on the cost and benefit functions of the public good and that the OPC will fall into one of two categories: Either it is continuous or it jumps from zero discontinuously at a critical population size. If, e.g., the public good has accelerating returns and linear cost, then the OPC is discontinuous and the best strategy thus to ramp up production sharply at a precise population size. By using the example of public goods with accelerating and diminishing returns (and linear cost) we are able to determine how the two different categories of OPSs can best be matched by production regulated through a QS signal feeding back on its own production. We find that the optimal QS parameters are different for the two categories and specifically that public goods which provide accelerating returns, call for stronger positive signal feedback. PMID:26284049

  18. Ubiquitination of Innate Immune Regulator TRAF3 Orchestrates Expulsion of Intracellular Bacteria by Exocyst Complex.

    PubMed

    Miao, Yuxuan; Wu, Jianxuan; Abraham, Soman N

    2016-07-19

    Although the intracellular trafficking system is integral to most physiologic activities, its role in mediating immune responses to infection has remained elusive. Here, we report that infected bladder epithelial cells (BECs) mobilized the exocyst complex, a powerful exporter of subcellular vesicles, to rapidly expel intracellular bacteria back for clearance. Toll-like receptor (TLR) 4 signals emanating from bacteria-containing vesicles (BCVs) were found to trigger K33-linked polyubiquitination of TRAF3 at Lys168, which was then detected by RalGDS, a guanine nucleotide exchange factor (GEF) that precipitated the assembly of the exocyst complex. Although this distinct modification of TRAF3 served to connect innate immune signaling to the cellular trafficking apparatus, it crucially ensured temporal and spatial accuracy in determining which among the many subcellular vesicles was recognized and selected for expulsion in response to innate immune signaling. PMID:27438768

  19. Formulations of polymeric biodegradable low-cost foam by melt extrusion to deliver plant growth-promoting bacteria in agricultural systems.

    PubMed

    Marcelino, Paulo Ricardo Franco; Milani, Karina Maria Lima; Mali, Suzana; Santos, Odair José Andrade Pais Dos; de Oliveira, André Luiz Martinez

    2016-08-01

    The extrusion technology of blends formed by compounds with different physicochemical properties often results in new materials that present properties distinctive from its original individual constituents. Here, we report the use of melt extrusion of blends made from low-cost materials to produce a biodegradable foam suitable for use as an inoculant carrier of plant growth-promoting bacteria (PGPB). Six formulations were prepared with variable proportions of the raw materials; the resulting physicochemical and structural properties are described, as well as formulation performance in the maintenance of bacterial viability during 120 days of storage. Differences in blend composition influenced foam density, porosity, expansion index, and water absorption. Additionally, differences in the capability of sustaining bacterial viability for long periods of time were more related to the foam composition than to the resulting physicochemical characteristics. Microscopic analyses showed that the inoculant bacteria had firmly attached to the extruded material by forming biofilms. Inoculation assays using maize plants demonstrated that the bacteria attached to the extruded foams could survive in the soil for up to 10 days before maize sowing, without diminishing its ability to promote plant growth. The results presented demonstrate the viability of the new matrix as a biotechnological material for bacterial delivery not only in agriculture but also in other biotechnological applications, according to the selected bacterial strains. PMID:27147530

  20. [Experiences with the detection of E. coli and coliform bacteria with reference to the drinking water regulation of 1986].

    PubMed

    Hübner, I; Knoll, C; Obst, U

    1989-02-01

    After the introduction of a limiting value for coliform bacteria in the German Drinking Water Regulation from May 22, 1986 the detection of coliform bacteria has become as important as that of E. coli to indicate pathogenic Enterobacteriaceae and fecal contamination. 130 water samples from different steps of drinking water treatment and distribution have been investigated for Enterobacteriaceae, even when typical indicating marks for such as acid- and gas-formation in the enrichment media were absent. We found the total of 46 isolates of Enterobacteriaceae, among which E. coli was the most frequent one. Whereas in 7 samples with acid- and gas-formation in the enrichment media Enterobacteriaceae could not be isolated, coliform bacteria and other enterobacteriaceae were found in 6 samples without these characteristics. As our experiences have show, those 'false positive' results can be avoided by a careful identification procedure of isolated microorganisms. The hygienically much more important 'false negative' results would not be recognized in routine control of drinking water following the prescribed methods. PMID:2494815

  1. A super-family of transcriptional activators regulates bacteriophage packaging and lysis in Gram-positive bacteria.

    PubMed

    Quiles-Puchalt, Nuria; Tormo-Más, María Ángeles; Campoy, Susana; Toledo-Arana, Alejandro; Monedero, Vicente; Lasa, Iñigo; Novick, Richard P; Christie, Gail E; Penadés, José R

    2013-08-01

    The propagation of bacteriophages and other mobile genetic elements requires exploitation of the phage mechanisms involved in virion assembly and DNA packaging. Here, we identified and characterized four different families of phage-encoded proteins that function as activators required for transcription of the late operons (morphogenetic and lysis genes) in a large group of phages infecting Gram-positive bacteria. These regulators constitute a super-family of proteins, here named late transcriptional regulators (Ltr), which share common structural, biochemical and functional characteristics and are unique to this group of phages. They are all small basic proteins, encoded by genes present at the end of the early gene cluster in their respective phage genomes and expressed under cI repressor control. To control expression of the late operon, the Ltr proteins bind to a DNA repeat region situated upstream of the terS gene, activating its transcription. This involves the C-terminal part of the Ltr proteins, which control specificity for the DNA repeat region. Finally, we show that the Ltr proteins are the only phage-encoded proteins required for the activation of the packaging and lysis modules. In summary, we provide evidence that phage packaging and lysis is a conserved mechanism in Siphoviridae infecting a wide variety of Gram-positive bacteria. PMID:23771138

  2. A super-family of transcriptional activators regulates bacteriophage packaging and lysis in Gram-positive bacteria

    PubMed Central

    Quiles-Puchalt, Nuria; Tormo-Más, María Ángeles; Campoy, Susana; Toledo-Arana, Alejandro; Monedero, Vicente; Lasa, Íñigo; Novick, Richard P.; Christie, Gail E.; Penadés, José R.

    2013-01-01

    The propagation of bacteriophages and other mobile genetic elements requires exploitation of the phage mechanisms involved in virion assembly and DNA packaging. Here, we identified and characterized four different families of phage-encoded proteins that function as activators required for transcription of the late operons (morphogenetic and lysis genes) in a large group of phages infecting Gram-positive bacteria. These regulators constitute a super-family of proteins, here named late transcriptional regulators (Ltr), which share common structural, biochemical and functional characteristics and are unique to this group of phages. They are all small basic proteins, encoded by genes present at the end of the early gene cluster in their respective phage genomes and expressed under cI repressor control. To control expression of the late operon, the Ltr proteins bind to a DNA repeat region situated upstream of the terS gene, activating its transcription. This involves the C-terminal part of the Ltr proteins, which control specificity for the DNA repeat region. Finally, we show that the Ltr proteins are the only phage-encoded proteins required for the activation of the packaging and lysis modules. In summary, we provide evidence that phage packaging and lysis is a conserved mechanism in Siphoviridae infecting a wide variety of Gram-positive bacteria. PMID:23771138

  3. Regulation Systems of Bacteria such as Escherichia coli in Response to Nutrient Limitation and Environmental Stresses

    PubMed Central

    Shimizu, Kazuyuki

    2013-01-01

    An overview was made to understand the regulation system of a bacterial cell such as Escherichia coli in response to nutrient limitation such as carbon, nitrogen, phosphate, sulfur, ion sources, and environmental stresses such as oxidative stress, acid shock, heat shock, and solvent stresses. It is quite important to understand how the cell detects environmental signals, integrate such information, and how the cell system is regulated. As for catabolite regulation, F1,6B P (FDP), PEP, and PYR play important roles in enzyme level regulation together with transcriptional regulation by such transcription factors as Cra, Fis, CsrA, and cAMP-Crp. αKG plays an important role in the coordinated control between carbon (C)- and nitrogen (N)-limitations, where αKG inhibits enzyme I (EI) of phosphotransferase system (PTS), thus regulating the glucose uptake rate in accordance with N level. As such, multiple regulation systems are co-ordinated for the cell synthesis and energy generation against nutrient limitations and environmental stresses. As for oxidative stress, the TCA cycle both generates and scavenges the reactive oxygen species (ROSs), where NADPH produced at ICDH and the oxidative pentose phosphate pathways play an important role in coping with oxidative stress. Solvent resistant mechanism was also considered for the stresses caused by biofuels and biochemicals production in the cell. PMID:24958385

  4. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1987-05-12

    A process is described for polymerizing at least one alpha olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst system which comprises: a supported catalyst prepared under anhydrous conditions by the sequential steps of: preparing a slurry of inert particulate support material; adding to the slurry a solution of an organomagnesium compound; adding to the slurry and reacting a solution of a zirconium halide compound, hafnium compound or mixtures thereof; adding to the slurry and reacting a halogenator; adding to the slurry and reacting a tetravalent titanium halide compound; and recovering solid catalyst.

  5. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1986-10-21

    A process is described for polymerizing at least one alpha-olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst comprising: a supported catalyst prepared under anhydrous conditions by the steps of: (1) sequentially; (a) preparing a slurry of inert particulate support material; (b) adding to the slurry a solution of an organomagnesium compound; (c) adding to the slurry and reacting a solution of zirconium compound; and (2) thereafter; (d) adding to the slurry and reacting a halogenator; (e) adding to the slurry and reacting a tetravalent titanium compound; (f) recovering solid catalyst; and an organoaluminum compound.

  6. Regulation of genetic flux between bacteria by restriction–modification systems

    PubMed Central

    Touchon, Marie

    2016-01-01

    Restriction–modification (R-M) systems are often regarded as bacteria's innate immune systems, protecting cells from infection by mobile genetic elements (MGEs). Their diversification has been recently associated with the emergence of particularly virulent lineages. However, we have previously found more R-M systems in genomes carrying more MGEs. Furthermore, it has been suggested that R-M systems might favor genetic transfer by producing recombinogenic double-stranded DNA ends. To test whether R-M systems favor or disfavor genetic exchanges, we analyzed their frequency with respect to the inferred events of homologous recombination and horizontal gene transfer within 79 bacterial species. Genetic exchanges were more frequent in bacteria with larger genomes and in those encoding more R-M systems. We created a recognition target motif predictor for Type II R-M systems that identifies genomes encoding systems with similar restriction sites. We found more genetic exchanges between these genomes, independently of their evolutionary distance. Our results reconcile previous studies by showing that R-M systems are more abundant in promiscuous species, wherein they establish preferential paths of genetic exchange within and between lineages with cognate R-M systems. Because the repertoire and/or specificity of R-M systems in bacterial lineages vary quickly, the preferential fluxes of genetic transfer within species are expected to constantly change, producing time-dependent networks of gene transfer. PMID:27140615

  7. Structure, Function, and Regulation of Antenna Complexes of Green Photosynthetic Bacteria

    SciTech Connect

    Robert E. Blankenship

    2001-04-27

    This project is concerned with the structure and function of the chlorosome antennas found in green photosynthetic bacteria. Chlorosomes are ellipsoidal structures attached to the cytoplasmic side of the inner cell membrane. These antenna complexes provide a very large absorption cross section for light capture. Evidence is overwhelming that the chlorosome represents a very different type of antenna from that found in any other photosynthetic system yet studied. It is now clear that chlorosomes do not contain traditional pigment-proteins, in which the pigments bind to specific sites on proteins. Instead, the chlorosome pigments are organized in vivo into pigment oligomers in which direct pigment-pigment interactions are of dominant importance. Our group has used a multidisciplinary approach to investigate this unique system, including model systems, ultrafast spectroscopy, molecular biology, protein chemistry and X-ray crystallography.

  8. Regulating the surface poly(ethylene glycol) density of polymeric nanoparticles and evaluating its role in drug delivery in vivo.

    PubMed

    Du, Xiao-Jiao; Wang, Ji-Long; Liu, Wei-Wei; Yang, Jin-Xian; Sun, Chun-Yang; Sun, Rong; Li, Hong-Jun; Shen, Song; Luo, Ying-Li; Ye, Xiao-Dong; Zhu, Yan-Hua; Yang, Xian-Zhu; Wang, Jun

    2015-11-01

    Poly(ethylene glycol) (PEG) is usually used to protect nanoparticles from rapid clearance in blood. The effects are highly dependent on the surface PEG density of nanoparticles. However, there lacks a detailed and informative study in PEG density and in vivo drug delivery due to the critical techniques to precisely control the surface PEG density when maintaining other nano-properties. Here, we regulated the polymeric nanoparticles' size and surface PEG density by incorporating poly(ε-caprolactone) (PCL) homopolymer into poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL) and adjusting the mass ratio of PCL to PEG-PCL during the nanoparticles preparation. We further developed a library of polymeric nanoparticles with different but controllable sizes and surface PEG densities by changing the molecular weight of the PCL block in PEG-PCL and tuning the molar ratio of repeating units of PCL (CL) to that of PEG (EG). We thus obtained a group of nanoparticles with variable surface PEG densities but with other nano-properties identical, and investigated the effects of surface PEG densities on the biological behaviors of nanoparticles in mice. We found that, high surface PEG density made the nanoparticles resistant to absorption of serum protein and uptake by macrophages, leading to a greater accumulation of nanoparticles in tumor tissue, which recuperated the defects of decreased internalization by tumor cells, resulting in superior antitumor efficacy when carrying docetaxel. PMID:26275857

  9. Intestinal commensal bacteria promote T cell hyporesponsiveness and down-regulate the serum antibody responses induced by dietary antigen.

    PubMed

    Tsuda, Masato; Hosono, Akira; Yanagibashi, Tsutomu; Kihara-Fujioka, Miran; Hachimura, Satoshi; Itoh, Kikuji; Hirayama, Kazuhiro; Takahashi, Kyoko; Kaminogawa, Shuichi

    2010-08-16

    Colonization of the gut by commensal bacteria modulates the induction of oral tolerance and allergy. However, how these intestinal bacteria modulate antigen-specific T cell responses induced by oral antigens remains unclear. In order to investigate this, we used germ-free (GF) ovalbumin (OVA)-specific T cell receptor transgenic (OVA23-3) mice. Conventional (CV) or GF mice were administered an OVA-containing diet. Cytokine production by CD4(+) cells from spleen (SP), mesenteric lymph nodes (MLN) and Peyer's patches (PP) was evaluated by ELISA, as was the peripheral antibody titer. T cell phenotype was assessed by flow cytometry. CD4(+) cells from the SP and MLN of CV and GF mice fed an OVA diet for 3 weeks produced significantly less IL-2 than the corresponding cells from mice receiving a control diet, suggesting that oral tolerance could be induced at the T cell level in the systemic and intestinal immune systems of both bacterial condition of mice. However, we also observed that the T cell hyporesponsiveness induced by dietary antigen was delayed in the systemic immune tissues and was weaker in the intestinal immune tissues of the GF mice. Intestinal MLN and PP CD4(+) T cells from these animals also produced lower levels of IL-10, had less activated/memory type CD45RB(low) cells, and expressed lower levels of CTLA-4 but not Foxp3 compared to their CV counterparts. Furthermore, GF mice produced higher serum levels of OVA-specific antibodies than CV animals. CD40L expression by SP CD4(+) cells from GF mice fed OVA was higher than that of CV mice. These results suggest that intestinal commensal bacteria promote T cell hyporesponsiveness and down-regulate serum antibody responses induced by dietary antigens through modulation of the intestinal and systemic T cell phenotype. PMID:20621647

  10. The mutual co-regulation of extracellular polymeric substances and iron ions in biocorrosion of cast iron pipes.

    PubMed

    Jin, Juntao; Guan, Yuntao

    2014-10-01

    New insights into the biocorrosion process may be gained through understanding of the interaction between extracellular polymeric substances (EPS) and iron. Herein, the effect of iron ions on the formation of biofilms and production of EPS was investigated. Additionally, the impact of EPS on the corrosion of cast iron coupons was explored. The results showed that a moderate concentration of iron ions (0.06 mg/L) promoted both biofilm formation and EPS production. The presence of EPS accelerated corrosion during the initial stage, while inhibited corrosion at the later stage. The functional groups of EPS acted as electron shuttles to enable the binding of iron ions. Binding of iron ions with EPS led to anodic dissolution and promoted corrosion, while corrosion was later inhibited through oxygen reduction and availability of phosphorus from EPS. The presence of EPS also led to changes in crystalline phases of corrosion products. PMID:25069092

  11. RNA-binding proteins involved in post-transcriptional regulation in bacteria

    PubMed Central

    Van Assche, Elke; Van Puyvelde, Sandra; Vanderleyden, Jos; Steenackers, Hans P.

    2015-01-01

    Post-transcriptional regulation is a very important mechanism to control gene expression in changing environments. In the past decade, a lot of interest has been directed toward the role of small RNAs (sRNAs) in bacterial post-transcriptional regulation. However, sRNAs are not the only molecules controlling gene expression at this level, RNA-binding proteins (RBPs) play an important role as well. CsrA and Hfq are the two best studied bacterial proteins of this type, but recently, additional proteins involved in post-transcriptional control have been identified. This review focuses on the general working mechanisms of post-transcriptionally active RBPs, which include (i) adaptation of the susceptibility of mRNAs and sRNAs to RNases, (ii) modulating the accessibility of the ribosome binding site of mRNAs, (iii) recruiting and assisting in the interaction of mRNAs with other molecules and (iv) regulating transcription terminator/antiterminator formation, and gives an overview of both the well-studied and the newly identified proteins that are involved in post-transcriptional regulatory processes. Additionally, the post-transcriptional mechanisms by which the expression or the activity of these proteins is regulated, are described. For many of the newly identified proteins, however, mechanistic questions remain. Most likely, more post-transcriptionally active proteins will be identified in the future. PMID:25784899

  12. RNA synthetic biology inspired from bacteria: construction of transcription attenuators under antisense regulation

    NASA Astrophysics Data System (ADS)

    Dawid, Alexandre; Cayrol, Bastien; Isambert, Hervé

    2009-06-01

    Among all biopolymers, ribonucleic acids or RNA have unique functional versatility, which led to the early suggestion that RNA alone (or a closely related biopolymer) might have once sustained a primitive form of life based on a single type of biopolymer. This has been supported by the demonstration of processive RNA-based replication and the discovery of 'riboswitches' or RNA switches, which directly sense their metabolic environment. In this paper, we further explore the plausibility of this 'RNA world' scenario and show, through synthetic molecular design guided by advanced RNA simulations, that RNA can also perform elementary regulation tasks on its own. We demonstrate that RNA synthetic regulatory modules directly inspired from bacterial transcription attenuators can efficiently activate or repress the expression of other RNA by merely controlling their folding paths 'on the fly' during transcription through simple RNA-RNA antisense interaction. Factors, such as NTP concentration and RNA synthesis rate, affecting the efficiency of this kinetic regulation mechanism are also studied and discussed in the light of evolutionary constraints. Overall, this suggests that direct coupling among synthesis, folding and regulation of RNAs may have enabled the early emergence of autonomous RNA-based regulation networks in absence of both DNA and protein partners.

  13. Gene regulation of plasmid- and chromosome-determined inorganic ion transport in bacteria.

    PubMed Central

    Silver, S; Walderhaug, M

    1992-01-01

    Regulation of chromosomally determined nutrient cation and anion uptake systems shows important similarities to regulation of plasmid-determined toxic ion resistance systems that mediate the outward transport of deleterious ions. Chromosomally determined transport systems result in accumulation of K+, Mg2+, Fe3+, Mn2+, PO4(3-), SO4(2-), and additional trace nutrients, while bacterial plasmids harbor highly specific resistance systems for AsO2-, AsO4(3-), CrO4(2-), Cd2+, Co2+, Cu2+, Hg2+, Ni2+, SbO2-, TeO3(2-), Zn2+, and other toxic ions. To study the regulation of these systems, we need to define both the trans-acting regulatory proteins and the cis-acting target operator DNA regions for the proteins. The regulation of gene expression for K+ and PO4(3-) transport systems involves two-component sensor-effector pairs of proteins. The first protein responds to an extracellular ionic (or related) signal and then transmits the signal to an intracellular DNA-binding protein. Regulation of Fe3+ transport utilizes the single iron-binding and DNA-binding protein Fur. The MerR regulatory protein for mercury resistance both represses and activates transcription. The ArsR regulatory protein functions as a repressor for the arsenic and antimony(III) efflux system. Although the predicted cadR regulatory gene has not been identified, cadmium, lead, bismuth, zinc, and cobalt induce this system in a carefully regulated manner from a single mRNA start site. The cadA Cd2+ resistance determinant encodes an E1(1)-1E2-class efflux ATPase (consisting of two polypeptides, rather than the one earlier identified). Cadmium resistance is also conferred by the czc system (which confers resistances to zinc and cobalt in Alcaligenes species) via a complex efflux pump consisting of four polypeptides. These two cadmium efflux systems are not otherwise related. For chromate resistance, reduced cellular accumulation is again the resistance mechanism, but the regulatory components are not identified

  14. An Ancient Riboswitch Class in Bacteria Regulates Purine Biosynthesis and One-carbon Metabolism

    PubMed Central

    Kim, Peter B.; Nelson, James W.; Breaker, Ronald R.

    2015-01-01

    SUMMARY Over thirty years ago, ZTP (5-amino-4-imidazole carboxamide riboside 5'-triphosphate), a modified purine biosynthetic intermediate, was proposed to signal 10-formyl-tetrahydrofolate (10f-THF) deficiency in bacteria. However, the mechanisms by which this putative alarmone or its precursor ZMP (5-aminoimidazole-4-carboxamide ribonucleotide, also known as AICAR) brings about any metabolic changes remain unexplained. Herein we report the existence of a widespread riboswitch class that is most commonly associated with genes related to de novo purine biosynthesis and one carbon metabolism. Biochemical data confirms that members of this riboswitch class selectively bind ZMP and ZTP with nanomolar affinity, while strongly rejecting numerous natural analogs. Indeed, increases in the ZMP/ZTP pool, caused by folate stress in bacterial cells, trigger changes in the expression of a reporter gene fused to representative ZTP riboswitches in vivo. The wide distribution of this riboswitch class suggests that ZMP/ZTP signaling is important for species in numerous bacterial lineages. PMID:25616067

  15. Potential of lactic acid bacteria at regulating Escherichia coli infection and inflammation of bovine endometrium.

    PubMed

    Genís, Sandra; Bach, Àlex; Fàbregas, Francesc; Arís, Anna

    2016-03-01

    About 40% of dairy cattle develop uterine disease during postpartum period, causing infertility. Some studies indicate that uterine infection, predominantly by Escherichia coli in the first week postpartum, is associated with metritis, an uterus inflammation in which the cow fails to completely clear bacterial contaminants. The aim of this study was to evaluate the potential of four lactic acid bacteria (LAB) (Lactobacillus rhamnosus, Pediococcus acidilactici, Lactobacillus reuteri, and Lactobacillus sakei) to modulate the E coli infection and inflammation in endometrial cells. Primary endometrial epithelial cells were isolated from fresh endometrium of a healthy cow and cultured in vitro to evaluate the effects of LAB at three different doses. Cell extracts were obtained to analyze the expression of proinflammatory cytokines and to quantify E coli infection on MacConkey agar plates. L sakei and L reuteri showed a positive effect preventing E coli infection (87% and 78%, respectively, P < 0.001); however, they were also associated to a dose-variable effect on tissular inflammation that could further exacerbate the proinflammatory status. Infection of E coli was clearly reduced (P < 0.001) up to an 83% with P acidilactici, whereas, the expression of proinflammatory cytokines IL-8 and IL-1β dropped significantly (P < 0.001) up to 85.11 and 5.24 folds, respectively, in the presence of L rhamnosus. In conclusion, these results demonstrate a clear potential of some LAB in the modulation of endometrial infection and inflammation in cattle. PMID:26549120

  16. A bioinformatic survey of distribution, conservation, and probable functions of LuxR solo regulators in bacteria

    PubMed Central

    Subramoni, Sujatha; Florez Salcedo, Diana Vanessa; Suarez-Moreno, Zulma R.

    2015-01-01

    LuxR solo transcriptional regulators contain both an autoinducer binding domain (ABD; N-terminal) and a DNA binding Helix-Turn-Helix domain (HTH; C-terminal), but are not associated with a cognate N-acyl homoserine lactone (AHL) synthase coding gene in the same genome. Although a few LuxR solos have been characterized, their distributions as well as their role in bacterial signal perception and other processes are poorly understood. In this study we have carried out a systematic survey of distribution of all ABD containing LuxR transcriptional regulators (QS domain LuxRs) available in the InterPro database (IPR005143), and identified those lacking a cognate AHL synthase. These LuxR solos were then analyzed regarding their taxonomical distribution, predicted functions of neighboring genes and the presence of complete AHL-QS systems in the genomes that carry them. Our analyses reveal the presence of one or multiple predicted LuxR solos in many proteobacterial genomes carrying QS domain LuxRs, some of them harboring genes for one or more AHL-QS circuits. The presence of LuxR solos in bacteria occupying diverse environments suggests potential ecological functions for these proteins beyond AHL and interkingdom signaling. Based on gene context and the conservation levels of invariant amino acids of ABD, we have classified LuxR solos into functionally meaningful groups or putative orthologs. Surprisingly, putative LuxR solos were also found in a few non-proteobacterial genomes which are not known to carry AHL-QS systems. Multiple predicted LuxR solos in the same genome appeared to have different levels of conservation of invariant amino acid residues of ABD questioning their binding to AHLs. In summary, this study provides a detailed overview of distribution of LuxR solos and their probable roles in bacteria with genome sequence information. PMID:25759807

  17. Horizontal Gene Transfer Regulation in Bacteria as a “Spandrel” of DNA Repair Mechanisms

    PubMed Central

    Fall, Saliou; Mercier, Anne; Bertolla, Franck; Calteau, Alexandra; Gueguen, Laurent; Perrière, Guy; Vogel, Timothy M.; Simonet, Pascal

    2007-01-01

    the bacteria to hijack DNA repair mechanisms in order to generate genetic diversity without losing too much genomic stability. PMID:17957239

  18. pH regulates ammonia-oxidizing bacteria and archaea in paddy soils in Southern China.

    PubMed

    Li, Hu; Weng, Bo-Sen; Huang, Fu-Yi; Su, Jian-Qiang; Yang, Xiao-Ru

    2015-07-01

    Ammonia-oxidizing archaea (AOA) and bacteria (AOB) play important roles in nitrogen cycling. However, the effects of environmental factors on the activity, abundance, and diversity of AOA and AOB and the relative contributions of these two groups to nitrification in paddy soils are not well explained. In this study, potential nitrification activity (PNA), abundance, and diversity of amoA genes from 12 paddy soils in Southern China were determined by potential nitrification assay, quantitative PCR, and cloning. The results showed that PNA was highly variable between paddy soils, ranging from 4.05 ± 0.21 to 9.81 ± 1.09 mg NOx-N kg(-1) dry soil day(-1), and no significant correlation with soil parameters was found. The abundance of AOA was predominant over AOB, indicating that AOA may be the major members in aerobic ammonia oxidation in these paddy soils. Community compositions of AOA and AOB were highly variable among samples, but the variations were best explained by pH. AOA sequences were affiliated to the Nitrosopumilus cluster and Nitrososphaera cluster, and AOB were classified into the lineages of Nitrosospira and Nitrosomonas, with Nitrosospira being predominant over Nitrosomonas, accounting for 83.6 % of the AOB community. Moreover, the majority of Nitrosomonas was determined in neutral soils. Canonical correspondence analysis (CCA) analysis further demonstrated that AOA and AOB community structures were significantly affected by pH, soil total organic carbon, total nitrogen, and C/N ratio, suggesting that these factors exert strong effects on the distribution of AOB and AOA in paddy soils in Southern China. In conclusion, our results imply that soil pH was a key explanatory variable for both AOA and AOB community structure and nitrification activity. PMID:25744648

  19. Polymeric nanoparticles

    PubMed Central

    Bolhassani, Azam; Javanzad, Shabnam; Saleh, Tayebeh; Hashemi, Mehrdad; Aghasadeghi, Mohammad Reza; Sadat, Seyed Mehdi

    2014-01-01

    Nanocarriers with various compositions and biological properties have been extensively applied for in vitro/in vivo drug and gene delivery. The family of nanocarriers includes polymeric nanoparticles, lipid-based carriers (liposomes/micelles), dendrimers, carbon nanotubes, and gold nanoparticles (nanoshells/nanocages). Among different delivery systems, polymeric carriers have several properties such as: easy to synthesize, inexpensive, biocompatible, biodegradable, non-immunogenic, non-toxic, and water soluble. In addition, cationic polymers seem to produce more stable complexes led to a more protection during cellular trafficking than cationic lipids. Nanoparticles often show significant adjuvant effects in vaccine delivery since they may be easily taken up by antigen presenting cells (APCs). Natural polymers such as polysaccharides and synthetic polymers have demonstrated great potential to form vaccine nanoparticles. The development of new adjuvants or delivery systems for DNA and protein immunization is an expanding research field. This review describes polymeric carriers especially PLGA, chitosan, and PEI as vaccine delivery systems. PMID:24128651

  20. Regulated pH-Responsive Polymeric Micelles for Doxorubicin Delivery to the Nucleus of Liver Cancer Cells.

    PubMed

    Li, Hao; Li, Xian; Zhang, Chao; Sun, Qiquan; Yi, Wei; Wang, Xuan; Cheng, Du; Chen, Shupeng; Liang, Biling; Shuai, Xintao

    2016-06-01

    A diblock copolymer of poly(ethylene glycol) (PEG) and poly(γ-benzyl L-glutamate) (PBLG), PEG-PBLG, was synthesized via the ring-opening polymerization of γ-benzyl L-glutamate N-carboxyanhydride (BLG-NCA) using allyl-PEG-NH2 as a macroinitiator. After deprotection of the benzyl groups, N,N-diisopropyl ethylenediamine (DIP) was conjugated to poly(L-glutamic acid) (PGA) blocks as side groups. The pendant DIP groups on the PGA blocks greatly enhance the pH-sensitivity of poly(ethylene glycol)-block-poly[N-(N',N'-diisopropylaminoethyl) glutamide] [PEG-PGA(DIP)] micelles, and a higher grafting percentage of DIP favors a faster acid-response. In neutral aqueous solution, the PEG-PGA(DIP) can self-assemble into stable micelles featuring an acid-responsive PGA(DIP) core with the encapsulated anticancer drug doxorubicin (DOX). In an acidic environment, the hydrophobic-hydrophilic transition of the PGA block leads to the gradual expansion and disassembly of these micelles and, consequently, an accelerated release of DOX. Thus, DOX transported by PEG-PGA(DIP) micelles can be entrapped more efficiently into the nuclei of hepatoma Bel 7402 cells. PMID:27319219

  1. Theoretical models for the regulation of DNA replication in fast-growing bacteria

    NASA Astrophysics Data System (ADS)

    Creutziger, Martin; Schmidt, Mischa; Lenz, Peter

    2012-09-01

    Growing in always changing environments, Escherichia coli cells are challenged by the task to coordinate growth and division. In particular, adaption of their growth program to the surrounding medium has to guarantee that the daughter cells obtain fully replicated chromosomes. Replication is therefore to be initiated at the right time, which is particularly challenging in media that support fast growth. Here, the mother cell initiates replication not only for the daughter but also for the granddaughter cells. This is possible only if replication occurs from several replication forks that all need to be correctly initiated. Despite considerable efforts during the last 40 years, regulation of this process is still unknown. Part of the difficulty arises from the fact that many details of the relevant molecular processes are not known. Here, we develop a novel theoretical strategy for dealing with this general problem: instead of analyzing a single model, we introduce a wide variety of 128 different models that make different assumptions about the unknown processes. By comparing the predictions of these models we are able to identify the key quantities that allow the experimental discrimination of the different models. Analysis of these quantities yields that out of the 128 models 94 are not consistent with available experimental data. From the remaining 34 models we are able to conclude that mass growth and DNA replication need either to be truly coupled, by coupling DNA replication initiation to the event of cell division, or to the amount of accumulated mass. Finally, we make suggestions for experiments to further reduce the number of possible regulation scenarios.

  2. A conserved structural module regulates transcriptional responses to diverse stress signals in bacteria

    SciTech Connect

    Campbell, Elizabeth A.; Greenwell, Roger S.; Anthony, Jennifer R.; Wang, Sheng; Lim, Lee; Das, Kakoli; Sofia, Heidi J.; Donohue, Timothy J.; Darst, Seth A.

    2007-09-07

    In Rhodbacter sphaeroides, transcriptional response to singlet oxygen is controlled by the ECF (extracytoplasmic function) transcription factor, σΕ. ECF σ’s comprise the largest and most divergent group of the σ70-family members and are negatively regulated by their cognate anti-σ factor. Here, we determine the crystal structure of the Rhodobacter sphaeroides ECF σ factor, σE, in an inhibitory complex with its anti-σ, ChrR. The structure reveals that ChrR is composed of two structural domains separated by a flexible linker. The N-terminal domain sterically occludes the two primary binding determinants on σE for core RNA polymerase and is thus referred to as the ASD (anti-σ domain). Genetic and biochemical characterization of the two domains show that the ASD is sufficient to inhibit σE dependant transcription and the C-terminal domain is required for response to singlet oxygen and the release of σE from the ASD. In addition, structural and sequence analyses of the ASD of ChrR and other ECF anti-σ’s, reveal that the N-terminal domain of different groups of ECF anti-σ’s share a common structural fold with some sequence similarity. Bioinformatics studies show that the ASD occurs in as many as one third of ECF anti-σ’s, many of which have diverse C-terminal domains. The conserved ASD are sometimes fused to diverse C-terminal domains. These studies reveal that the ASD class of anti-σ’s are extraordinarily diverse, based on the type of σΕ factors they are associated with and the C-terminal domains to which they are linked.

  3. Immunobiotic lactic acid bacteria beneficially regulate immune response triggered by poly(I:C) in porcine intestinal epithelial cells

    PubMed Central

    2011-01-01

    This study analyzed the functional expression of TLR3 in various gastrointestinal tissues from adult swine and shows that TLR3 is expressed preferentially in intestinal epithelial cells (IEC), CD172a+CD11R1high and CD4+ cells from ileal Peyer's patches. We characterized the inflammatory immune response triggered by TLR3 activation in a clonal porcine intestinal epitheliocyte cell line (PIE cells) and in PIE-immune cell co-cultures, and demonstrated that these systems are valuable tools to study in vitro the immune response triggered by TLR3 on IEC and the interaction between IEC and immune cells. In addition, we selected an immunobiotic lactic acid bacteria strain, Lactobacillus casei MEP221106, able to beneficially regulate the anti-viral immune response triggered by poly(I:C) stimulation in PIE cells. Moreover, we deepened our understanding of the possible mechanisms of immunobiotic action by demonstrating that L. casei MEP221106 modulates the interaction between IEC and immune cells during the generation of a TLR3-mediated immune response. PMID:22046952

  4. Defining a role for Hfq in Gram-positive bacteria: evidence for Hfq-dependent antisense regulation in Listeria monocytogenes

    PubMed Central

    Nielsen, Jesper Sejrup; Lei, Lisbeth Kristensen; Ebersbach, Tine; Olsen, Anders Steno; Klitgaard, Janne Kudsk; Valentin-Hansen, Poul; Kallipolitis, Birgitte Haahr

    2010-01-01

    Small trans-encoded RNAs (sRNAs) modulate the translation and decay of mRNAs in bacteria. In Gram-negative species, antisense regulation by trans-encoded sRNAs relies on the Sm-like protein Hfq. In contrast to this, Hfq is dispensable for sRNA-mediated riboregulation in the Gram-positive species studied thus far. Here, we provide evidence for Hfq-dependent translational repression in the Gram-positive human pathogen Listeria monocytogenes, which is known to encode at least 50 sRNAs. We show that the Hfq-binding sRNA LhrA controls the translation and degradation of its target mRNA by an antisense mechanism, and that Hfq facilitates the binding of LhrA to its target. The work presented here provides the first experimental evidence for Hfq-dependent riboregulation in a Gram-positive bacterium. Our findings indicate that modulation of translation by trans-encoded sRNAs may occur by both Hfq-dependent and -independent mechanisms, thus adding another layer of complexity to sRNA-mediated riboregulation in Gram-positive species. PMID:19942685

  5. Genome-wide study predicts promoter-G4 DNA motifs regulate selective functions in bacteria: radioresistance of D. radiodurans involves G4 DNA-mediated regulation

    PubMed Central

    Beaume, Nicolas; Pathak, Rajiv; Yadav, Vinod Kumar; Kota, Swathi; Misra, Hari S.; Gautam, Hemant K.; Chowdhury, Shantanu

    2013-01-01

    A remarkable number of guanine-rich sequences with potential to adopt non-canonical secondary structures called G-quadruplexes (or G4 DNA) are found within gene promoters. Despite growing interest, regulatory role of quadruplex DNA motifs in intrinsic cellular function remains poorly understood. Herein, we asked whether occurrence of potential G4 (PG4) DNA in promoters is associated with specific function(s) in bacteria. Using a normalized promoter-PG4-content (PG4P) index we analysed >60 000 promoters in 19 well-annotated species for (a) function class(es) and (b) gene(s) with enriched PG4P. Unexpectedly, PG4-associated functional classes were organism specific, suggesting that PG4 motifs may impart specific function to organisms. As a case study, we analysed radioresistance. Interestingly, unsupervised clustering using PG4P of 21 genes, crucial for radioresistance, grouped three radioresistant microorganisms including Deinococcus radiodurans. Based on these predictions we tested and found that in presence of nanomolar amounts of the intracellular quadruplex-binding ligand N-methyl mesoporphyrin (NMM), radioresistance of D. radiodurans was attenuated by ∼60%. In addition, important components of the RecF recombinational repair pathway recA, recF, recO, recR and recQ genes were found to harbour promoter-PG4 motifs and were also down-regulated in presence of NMM. Together these results provide first evidence that radioresistance may involve G4 DNA-mediated regulation and support the rationale that promoter-PG4s influence selective functions. PMID:23161683

  6. Fructose Utilization in Lactococcus lactis as a Model for Low-GC Gram-Positive Bacteria: Its Regulator, Signal, and DNA-Binding Site

    PubMed Central

    Barrière, Charlotte; Veiga-da-Cunha, Maria; Pons, Nicolas; Guédon, Eric; van Hijum, Sacha A. F. T.; Kok, Jan; Kuipers, Oscar P.; Ehrlich, Dusko S.; Renault, Pierre

    2005-01-01

    In addition to its role as carbon and energy source, fructose metabolism was reported to affect other cellular processes, such as biofilm formation by streptococci and bacterial pathogenicity in plants. Fructose genes encoding a 1-phosphofructokinase and a phosphotransferase system (PTS) fructose-specific enzyme IIABC component reside commonly in a gene cluster with a DeoR family regulator in various gram-positive bacteria. We present a comprehensive study of fructose metabolism in Lactococcus lactis, including a systematic study of fru mutants, global messenger analysis, and a molecular characterization of its regulation. The fru operon is regulated at the transcriptional level by both FruR and CcpA and at the metabolic level by inducer exclusion. The FruR effector is fructose-1-phosphate (F1P), as shown by combined analysis of transcription and measurements of the intracellular F1P pools in mutants either unable to produce this metabolite or accumulating it. The regulation of the fru operon by FruR requires four adjacent 10-bp direct repeats. The well-conserved organization of the fru promoter region in various low-GC gram-positive bacteria, including CRE boxes as well as the newly defined FruR motif, suggests that the regulation scheme defined in L. lactis could be applied to these bacteria. Transcriptome profiling of fruR and fruC mutants revealed that the effect of F1P and FruR regulation is limited to the fru operon in L. lactis. This result is enforced by the fact that no other targets for FruR were found in the available low-GC gram-positive bacteria genomes, suggesting that additional phenotypical effects due to fructose metabolism do not rely directly on FruR control, but rather on metabolism. PMID:15901699

  7. Papaverine Prevents Vasospasm by Regulation of Myosin Light Chain Phosphorylation and Actin Polymerization in Human Saphenous Vein

    PubMed Central

    Hocking, Kyle M.; Putumbaka, Gowthami; Wise, Eric S.; Cheung-Flynn, Joyce; Brophy, Colleen M.; Komalavilas, Padmini

    2016-01-01

    Objective Papaverine is used to prevent vasospasm in human saphenous veins (HSV) during vein graft preparation prior to implantation as a bypass conduit. Papaverine is a nonspecific inhibitor of phosphodiesterases, leading to increases in both intracellular cGMP and cAMP. We hypothesized that papaverine reduces force by decreasing intracellular calcium concentrations ([Ca2+]i) and myosin light chain phosphorylation, and increasing actin depolymerization via regulation of actin regulatory protein phosphorylation. Approach and Results HSV was equilibrated in a muscle bath, pre-treated with 1 mM papaverine followed by 5 μM norepinephrine, and force along with [Ca2+]i levels were concurrently measured. Filamentous actin (F-actin) level was measured by an in vitro actin assay. Tissue was snap frozen to measure myosin light chain and actin regulatory protein phosphorylation. Pre-treatment with papaverine completely inhibited norepinephrine-induced force generation, blocked increases in [Ca2+]i and led to a decrease in the phosphorylation of myosin light chain. Papaverine pre-treatment also led to increased phosphorylation of the heat shock-related protein 20 (HSPB6) and the vasodilator stimulated phosphoprotein (VASP), as well as decreased filamentous actin (F-actin) levels suggesting depolymerization of actin. Conclusions These results suggest that papaverine-induced force inhibition of HSV involves [Ca2+]i-mediated inhibition of myosin light chain phosphorylation and actin regulatory protein phosphorylation-mediated actin depolymerization. Thus, papaverine induces sustained inhibition of contraction of HSV by the modulation of both myosin cross-bridge formation and actin cytoskeletal dynamics and is a pharmacological alternative to high pressure distention to prevent vasospasm. PMID:27136356

  8. Retinoic acid-loaded polymeric nanoparticles enhance vascular regulation of neural stem cell survival and differentiation after ischaemia

    NASA Astrophysics Data System (ADS)

    Ferreira, R.; Fonseca, M. C.; Santos, T.; Sargento-Freitas, J.; Tjeng, R.; Paiva, F.; Castelo-Branco, M.; Ferreira, L. S.; Bernardino, L.

    2016-04-01

    Stroke is one of the leading causes of death and disability worldwide. However, current therapies only reach a small percentage of patients and may cause serious side effects. We propose the therapeutic use of retinoic acid-loaded nanoparticles (RA-NP) to safely and efficiently repair the ischaemic brain by creating a favourable pro-angiogenic environment that enhances neurogenesis and neuronal restitution. Our data showed that RA-NP enhanced endothelial cell proliferation and tubule network formation and protected against ischaemia-induced death. To evaluate the effect of RA-NP on vascular regulation of neural stem cell (NSC) survival and differentiation, endothelial cell-conditioned media (EC-CM) were collected. EC-CM from healthy RA-NP-treated cells reduced NSC death and promoted proliferation while EC-CM from ischaemic RA-NP-treated cells decreased cell death, increased proliferation and neuronal differentiation. In parallel, human endothelial progenitor cells (hEPC), which are part of the endogenous repair response to vascular injury, were collected from ischaemic stroke patients. hEPC treated with RA-NP had significantly higher proliferation, which further highlights the therapeutic potential of this formulation. To conclude, RA-NP protected endothelial cells from ischaemic death and stimulated the release of pro-survival, proliferation-stimulating factors and differentiation cues for NSC. RA-NP were shown to be up to 83-fold more efficient than free RA and to enhance hEPC proliferation. These data serve as a stepping stone to use RA-NP as vasculotrophic and neurogenic agents for vascular disorders and neurodegenerative diseases with compromised vasculature.

  9. Chain Reaction Polymerization.

    ERIC Educational Resources Information Center

    McGrath, James E.

    1981-01-01

    The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

  10. Bacteria clustering by polymers induces the expression of quorum sense controlled phenotypes

    PubMed Central

    Lui, Leong T.; Xue, Xuan; Sui, Cheng; Brown, Alan; Pritchard, David I.; Halliday, Nigel; Winzer, Klaus; Howdle, Steven M.; Fernandez-Trillo, Francisco; Krasnogor, Natalio; Alexander, Cameron

    2014-01-01

    Bacteria deploy a range of chemistries to regulate their behaviour and respond to their environment. Quorum sensing is one mean by which bacteria use chemical reactions to modulate pre-infection behaviour such as surface attachment. Polymers that can interfere with bacterial adhesion or the chemical reactions used for quorum sensing are thus a potential means to control bacterial population responses. Here we report how polymericbacteria sequestrants”, designed to bind to bacteria through electrostatic interactions and thus inhibit bacterial adhesion to surfaces, induce the expression of quorum sensing controlled phenotypes as a consequence of cell clustering. A combination of polymer and analytical chemistry, biological assays and computational modelling has been used to characterise the feedback between bacteria clustering and quorum sensing signaling. We have also derived design principles and chemical strategies for controlling bacterial behaviour at the population level. PMID:24256871

  11. Bacteria clustering by polymers induces the expression of quorum-sensing-controlled phenotypes

    NASA Astrophysics Data System (ADS)

    Lui, Leong T.; Xue, Xuan; Sui, Cheng; Brown, Alan; Pritchard, David I.; Halliday, Nigel; Winzer, Klaus; Howdle, Steven M.; Fernandez-Trillo, Francisco; Krasnogor, Natalio; Alexander, Cameron

    2013-12-01

    Bacteria deploy a range of chemistries to regulate their behaviour and respond to their environment. Quorum sensing is one method by which bacteria use chemical reactions to modulate pre-infection behaviour such as surface attachment. Polymers that can interfere with bacterial adhesion or the chemical reactions used for quorum sensing are therefore a potential means to control bacterial population responses. Here, we report how polymericbacteria sequestrants’, designed to bind to bacteria through electrostatic interactions and therefore inhibit bacterial adhesion to surfaces, induce the expression of quorum-sensing-controlled phenotypes as a consequence of cell clustering. A combination of polymer and analytical chemistry, biological assays and computational modelling has been used to characterize the feedback between bacteria clustering and quorum sensing signalling. We have also derived design principles and chemical strategies for controlling bacterial behaviour at the population level.

  12. Regulation of Bacterial Peptidoglycan Polymerization.

    PubMed

    Arthur, Michel

    2016-07-01

    How bacterial cells control the activity of peptidoglycan polymerases has remained mysterious. Biochemical characterization of derivatives of penicillin-binding protein PBP1b that are functional in the absence of lipoprotein LpoB provides evidence for allosteric control of PBP1b glycosyltransferase activity via binding of LpoB to the PBP1b UBH1 domain. PMID:27236859

  13. Effects of interactions of auxin-producing bacteria and bacterial-feeding nematodes on regulation of peanut growths.

    PubMed

    Xu, Li; Xu, Wensi; Jiang, Ying; Hu, Feng; Li, Huixin

    2015-01-01

    The influences of an IAA (indole-3-acetic acid)-producing bacterium (Bacillus megaterium) and two bacterial-feeding nematodes (Cephalobus sp. or Mesorhabditis sp.) on the growth of peanut (Arachis hypogaea L. cv. Haihua 1) after various durations of time were investigated in natural soils. The addition of bacteria and nematodes and incubation time all significantly affected plant growth, plant root growth, plant nutrient concentrations, soil nutrient concentrations, soil microorganisms and soil auxin concentration. The addition of nematodes caused greater increases in these indices than those of bacteria, while the addition of the combination of bacteria and nematodes caused further increases. After 42-day growth, the increases in soil respiration differed between the additions of two kinds of nematodes because of differences in their life strategies. The effects of the bacteria and nematodes on the nutrient and hormone concentrations were responsible for the increases in plant growth. These results indicate the potential for promoting plant growth via the addition of nematodes and bacteria to soil. PMID:25867954

  14. Effects of Interactions of Auxin-Producing Bacteria and Bacterial-Feeding Nematodes on Regulation of Peanut Growths

    PubMed Central

    Xu, Li; Xu, Wensi; Jiang, Ying; Hu, Feng; Li, Huixin

    2015-01-01

    The influences of an IAA (indole-3-acetic acid)-producing bacterium (Bacillus megaterium) and two bacterial-feeding nematodes (Cephalobus sp. or Mesorhabditis sp.) on the growth of peanut (Arachis hypogaea L. cv. Haihua 1) after various durations of time were investigated in natural soils. The addition of bacteria and nematodes and incubation time all significantly affected plant growth, plant root growth, plant nutrient concentrations, soil nutrient concentrations, soil microorganisms and soil auxin concentration. The addition of nematodes caused greater increases in these indices than those of bacteria, while the addition of the combination of bacteria and nematodes caused further increases. After 42-day growth, the increases in soil respiration differed between the additions of two kinds of nematodes because of differences in their life strategies. The effects of the bacteria and nematodes on the nutrient and hormone concentrations were responsible for the increases in plant growth. These results indicate the potential for promoting plant growth via the addition of nematodes and bacteria to soil. PMID:25867954

  15. Epigenetic regulation of human β-defensin 2 and CC chemokine ligand 20 expression in gingival epithelial cells in response to oral bacteria

    PubMed Central

    Yin, L; Chung, W O

    2011-01-01

    Gingival epithelia utilize multiple signaling pathways to regulate innate immune responses to various oral bacteria, but little is understood about how these bacteria alter epithelial epigenetic status. In this study we report that DNA methyltransferase (DNMT1) and histone deacetylase expression were decreased in gingival epithelial cells treated with oral pathogen Porphyromonas gingivalis and nonpathogen Fusobacterium nucleatum. Pretreatment with trichostatin A and sodium butyrate, which increase acetylation of chromatin histones, significantly enhanced the gene expression of antimicrobial proteins human β-defensin 2 (hBD2) and CC chemokine ligand 20 (CCL20) in response to both bacterial challenges. Pretreatment with DNMT inhibitor 5′-azacytidine increased hBD2 and CCL20 expression in response to F. nucleatum, but not to P. gingivalis. Furthermore, we observed a differential pattern of protein levels of H3K4me3, which has been associated with chromatin remodeling and activation of gene transcription, in response to P. gingivalis vs. F. nucleatum. This study provides a new insight into the bacteria-specific innate immune responses via epigenetic regulation. PMID:21248725

  16. Photoacid-mediated ring opening polymerization driven by visible light.

    PubMed

    Fu, Changkui; Xu, Jiangtao; Boyer, Cyrille

    2016-06-01

    A novel methodology of visible light regulated ring opening polymerization in the presence of reversible merocyanine-based photoacid was reported for the first time. In combination with a photoinduced radical polymerization technique, a dual wavelength light controlled orthogonal polymerization system was investigated to switch the polymerization between two different monomers and for the preparation of block and graft copolymers in one pot. PMID:27167862

  17. Cellulose biosynthesis and function in bacteria.

    PubMed Central

    Ross, P; Mayer, R; Benziman, M

    1991-01-01

    The current model of cellulose biogenesis in plants, as well as bacteria, holds that the membranous cellulose synthase complex polymerizes glucose moieties from UDP-Glc into beta-1,4-glucan chains which give rise to rigid crystalline fibrils upon extrusion at the outer surface of the cell. The distinct arrangement and degree of association of the polymerizing enzyme units presumably govern extracellular chain assembly in addition to the pattern and width of cellulose fibril deposition. Most evident for Acetobacter xylinum, polymerization and assembly appear to be tightly coupled. To date, only bacteria have been effectively studied at the biochemical and genetic levels. In A. xylinum, the cellulose synthase, composed of at least two structurally similar but functionally distinct subunits, is subject to a multicomponent regulatory system. Regulation is based on the novel nucleotide cyclic diguanylic acid, a positive allosteric effector, and the regulatory enzymes maintaining its intracellular turnover: diguanylate cyclase and Ca2(+)-sensitive bis-(3',5')-cyclic diguanylic acid (c-di-GMP) phosphodiesterase. Four genes have been isolated from A. xylinum which constitute the operon for cellulose synthesis. The second gene encodes the catalytic subunit of cellulose synthase; the functions of the other three gene products are still unknown. Exclusively an extracellular product, bacterial cellulose appears to fulfill diverse biological roles within the natural habitat, conferring mechanical, chemical, and physiological protection in A. xylinum and Sarcina ventriculi or facilitating cell adhesion during symbiotic or infectious interactions in Rhizobium and Agrobacterium species. A. xylinum is proving to be most amenable for industrial purposes, allowing the unique features of bacterial cellulose to be exploited for novel product applications. Images PMID:2030672

  18. Metabolic Regulation and Coordination of the Metabolism in Bacteria in Response to a Variety of Growth Conditions.

    PubMed

    Shimizu, Kazuyuki

    2016-01-01

    Living organisms have sophisticated but well-organized regulation system. It is important to understand the metabolic regulation mechanisms in relation to growth environment for the efficient design of cell factories for biofuels and biochemicals production. Here, an overview is given for carbon catabolite regulation, nitrogen regulation, ion, sulfur, and phosphate regulations, stringent response under nutrient starvation as well as oxidative stress regulation, redox state regulation, acid-shock, heat- and cold-shock regulations, solvent stress regulation, osmoregulation, and biofilm formation, and quorum sensing focusing on Escherichia coli metabolism and others. The coordinated regulation mechanisms are of particular interest in getting insight into the principle which governs the cell metabolism. The metabolism is controlled by both enzyme-level regulation and transcriptional regulation via transcription factors such as cAMP-Crp, Cra, Csr, Fis, P(II)(GlnB), NtrBC, CysB, PhoR/B, SoxR/S, Fur, MarR, ArcA/B, Fnr, NarX/L, RpoS, and (p)ppGpp for stringent response, where the timescales for enzyme-level and gene-level regulations are different. Moreover, multiple regulations are coordinated by the intracellular metabolites, where fructose 1,6-bisphosphate (FBP), phosphoenolpyruvate (PEP), and acetyl-CoA (AcCoA) play important roles for enzyme-level regulation as well as transcriptional control, while α-ketoacids such as α-ketoglutaric acid (αKG), pyruvate (PYR), and oxaloacetate (OAA) play important roles for the coordinated regulation between carbon source uptake rate and other nutrient uptake rate such as nitrogen or sulfur uptake rate by modulation of cAMP via Cya. PMID:25712586

  19. Anaerobic bacteria

    MedlinePlus

    Anaerobic bacteria are bacteria that do not live or grow when oxygen is present. In humans, these ... Goldstein EJ. Diseases caused by non-spore forming anaerobic bacteria. In: Goldman L, Schafer AI, eds. Goldman's ...

  20. Regulation by gut commensal bacteria of carcinoembryonic antigen-related cell adhesion molecule expression in the intestinal epithelium.

    PubMed

    Kitamura, Yasuaki; Murata, Yoji; Park, Jung-Ha; Kotani, Takenori; Imada, Shinya; Saito, Yasuyuki; Okazawa, Hideki; Azuma, Takeshi; Matozaki, Takashi

    2015-07-01

    Carcinoembryonic antigen-related cell adhesion molecule (CEACAM) 1 and CEACAM20, immunoglobulin superfamily members, are predominantly expressed in intestinal epithelial cells (IECs) and co-localized at the apical surface of these cells. We here showed that the expression of mouse CEACAM1 and CEACAM20 at both mRNA and protein levels was markedly reduced in IECs of the small intestine by the treatment of mice with antibiotics against Gram-positive bacteria. The expression of both proteins was also decreased in IECs of the small intestine from germ-free mice, compared with that from control specific-pathogen-free mice. Exposure of intestinal organoids to IFN-γ markedly increased the expression of either CEACAM1 or CEACAM20, whereas the exposure to TNF-α increased the expression of the former protein, but not that of the latter. In contrast, the expression of CEACAM20, but not of CEACAM1, in intestinal organoids was markedly increased by exposure to butyrate, a short-chain fatty acid produced by bacterial fermentation in the intestine. Collectively, our results suggest that Gram-positive bacteria promote the mRNA expression of CEACAM1 or CEACAM20 in the small intestine. Inflammatory cytokines or butyrate likely participates in such effects of commensal bacteria. PMID:25908210

  1. Isolation and characterization of endophytic plant growth-promoting (PGPB) or stress homeostasis-regulating (PSHB) bacteria associated to the halophyte Prosopis strombulifera.

    PubMed

    Sgroy, Verónica; Cassán, Fabricio; Masciarelli, Oscar; Del Papa, María Florencia; Lagares, Antonio; Luna, Virginia

    2009-11-01

    This study was designed to isolate and characterize endophytic bacteria from halophyte Prosopis strombulifera grown under extreme salinity and to evaluate in vitro the bacterial mechanisms related to plant growth promotion or stress homeostasis regulation. Isolates obtained from P. strombulifera were compared genotypically by BOX-polymerase chain reaction, grouped according to similarity, and identified by amplification and partial sequences of 16S DNAr. Isolates were grown until exponential growth phase to evaluate the atmospheric nitrogen fixation, phosphate solubilization, siderophores, and phytohormones, such as indole-3-acetic acid, zeatin, gibberellic acid and abscisic acid production, as well as antifungal, protease, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. A total of 29 endophytic strains were grouped into seven according to similarity. All bacteria were able to grow and to produce some phytohormone in chemically defined medium with or without addition of a nitrogen source. Only one was able to produce siderophores, and none of them solubilized phosphate. ACC deaminase activity was positive for six strains. Antifungal and protease activity were confirmed for two of them. In this work, we discuss the possible implications of these bacterial mechanisms on the plant growth promotion or homeostasis regulation in natural conditions. PMID:19655138

  2. Contrasting regulation of macrophage iron homeostasis in response to infection with Listeria monocytogenes depending on localization of bacteria.

    PubMed

    Haschka, David; Nairz, Manfred; Demetz, Egon; Wienerroither, Sebastian; Decker, Thomas; Weiss, Günter

    2015-06-01

    Due to its multiple roles for the proliferation and pathogenicity of many microbes on the one hand and via modulation of immune effector functions on the other hand the control over iron homeostasis is thought to play a decisive role in the course of infections. Diversion of cellular iron traffic is considered as an important defense mechanism of macrophages to reduce metal availability for intracellular bacteria residing in the phagosome. However, evidence is lacking whether such alterations of iron homeostasis also become evident upon infection with bacteria gaining access to the cytosol like Listeria monocytogenes. Here we show that infection of macrophages with L. monocytogenes triggers the expression of the major cellular iron exporter ferroportin1 and induces cellular iron egress. As the growth of Listeria within macrophages is promoted by iron, stimulation of ferroportin1 functionality limits the availability of the metal for Listeria residing in the cytoplasm, whereas ferroportin1 degradation upon hepcidin treatment increases intracellular bacterial growth. In parallel to an increase of ferroportin1 expression, infected macrophages induce anti-microbial immune effector mechanisms such as TNFα formation or NO expression which are aggravated upon iron deficiency. These adaptive changes of iron homeostasis and immune response pathways are only found in macrophages infected with Listeria which express listeriolysin O and are therefore able to escape from the phagosome to the cytoplasm. Listeriolysin O deficient Listeria which are restricted to the phagosome are even killed by excess iron which may be based on "iron intoxification" via macrophage radical formation, because iron supplementation in that setting is paralleled by increased ROS formation. Our results indicate that ferroportin1 mediated iron export is a nutritional immune effector pathway to control infection with Listeria residing in the cytoplasm, whereas a different strategy is observed in mutant

  3. Polymerization of perfluorobutadiene

    NASA Technical Reports Server (NTRS)

    Newman, J.; Toy, M. S.

    1970-01-01

    Diisopropyl peroxydicarbonate dissolved in liquid perfluorobutadiene is conducted in a sealed vessel at the autogenous pressure of polymerization. Reaction temperature, ratio of catalyst to monomer, and amount of agitation determine degree of polymerization and product yield.

  4. Composition, Reactivity and Regulation of Extracellular Metal-Reducing Structures (Bacterial Nanowires) Produced by Dissimilatory Metal - Reducing Bacteria.

    SciTech Connect

    Beveridge, Terrance J; Whitfield, Christopher

    2013-03-06

    This is the final technical report for the project. There were two objectives in the proposal. The first was to describe the composition and function of electrically conductive appendages, known as bacterial nanowires, which resemble pili but are longer and are electrically conductive. They were first identified on the dissimilatory metal-reducing bacteria (DMRB), Shewanella and Geobacter. Specifically, this project investigated the role of these structures in: (i) the reductive transformation of iron oxides as solid phase electron acceptors; (ii) the use of as uranium as a dissolved electron acceptor to form nanocrystalline particles of uraninite upon reduction. The Beveridge group investigated these processes using advanced cryo-transmission electron microscopy (cryoTEM) to visualize the points of connection between the distal ends of nanowires and the effect they have on solid phase Fe minerals. At the same time, immuno-electron microscopy was applied in an attempt to identify where metal reductases and cytochromes are located on the cell surface, or in the nanowires. The second objective was to define the surface physicochemistry of Shewanella spp. in an attempt to decipher how weak bonding (electrostatics and hydrophobicity) affects the adherence of the bacteria to Fe oxides. This bonding could be dictated by the chemistry of lipopolysaccharide (LPS), or the presence/absence of capsular polysaccharide.

  5. Single-Cell Analysis of Growth in Budding Yeast and Bacteria Reveals a Common Size Regulation Strategy.

    PubMed

    Soifer, Ilya; Robert, Lydia; Amir, Ariel

    2016-02-01

    To maintain a constant cell size, dividing cells have to coordinate cell-cycle events with cell growth. This coordination has long been supposed to rely on the existence of size thresholds determining cell-cycle progression [1]. In budding yeast, size is controlled at the G1/S transition [2]. In agreement with this hypothesis, the size at birth influences the time spent in G1: smaller cells have a longer G1 period [3]. Nevertheless, even though cells born smaller have a longer G1, the compensation is imperfect and they still bud at smaller cell sizes. In bacteria, several recent studies have shown that the incremental model of size control, in which size is controlled by addition of a constant volume (in contrast to a size threshold), is able to quantitatively explain the experimental data on four different bacterial species [4-7]. Here, we report on experimental results for the budding yeast Saccharomyces cerevisiae, finding, surprisingly, that cell size control in this organism is very well described by the incremental model, suggesting a common strategy for cell size control with bacteria. Additionally, we argue that for S. cerevisiae the "volume increment" is not added from birth to division, but rather between two budding events. PMID:26776734

  6. Polymerization Reactor Engineering.

    ERIC Educational Resources Information Center

    Skaates, J. Michael

    1987-01-01

    Describes a polymerization reactor engineering course offered at Michigan Technological University which focuses on the design and operation of industrial polymerization reactors to achieve a desired degree of polymerization and molecular weight distribution. Provides a list of the course topics and assigned readings. (TW)

  7. pH-regulated activation and release of a bacteria-associated phospholipase C during intracellular infection by Listeria monocytogenes.

    PubMed

    Marquis, H; Hager, E J

    2000-01-01

    Listeria monocytogenes grows in the cytosol of mammalian cells and spreads from cell to cell without exiting the intracellular milieu. During cell-cell spread, bacteria become transiently entrapped in double-membrane vacuoles. Escape from these vacuoles is mediated in part by a bacterial phospholipase C (PC-PLC), whose activation requires cleavage of an N-terminal peptide. PC-PLC activation occurs in the acidified vacuolar environment. In this study, the pH-dependent mechanism of PC-PLC activation was investigated by manipulating the intracellular pH of the host. PC-PLC secreted into infected cells was immunoprecipitated, and both forms of the protein were identified by SDS-PAGE fluorography. PC-PLC activation occurred at pH 7.0 and lower, but not at pH 7.3. Total amounts of PC-PLC secreted into infected cells increased several-fold over controls within 5 min of a decrease in intracellular pH, and the active form of PC-PLC was the most abundant species detected. Bacterial release of active PC-PLC was dependent on Mpl, a bacterial metalloprotease that processes the proform (proPC-PLC), and did not require de novo protein synthesis. The amount of proPC-PLC released in response to a decrease in pH was the same in wild-type and Mpl-minus-infected cells. Immunofluorescence detection of PC-PLC in infected cells was performed. When fixed and permeabilized infected cells were treated with a bacterial cell wall hydrolase, over 97% of wild-type and Mpl-minus bacteria stained positively for PC-PLC, in contrast to less than 5% in untreated cells. These results indicate that intracellular bacteria carry pools of proPC-PLC. Upon cell-cell spread, a decrease in vacuolar pH triggers Mpl activation of proPC-PLC, resulting in bacterial release of active PC-PLC. PMID:10652090

  8. [Ability of representatives of Pantoea agglomerans, as well as Bacillus subtilis and some Pseudomonas species to suppress the development of phytopathgenic bacteria and micromycetes in regulating plant growth].

    PubMed

    Romanenko, V M; Alimov, D M

    2000-01-01

    The ability of representatives of Pantoea agglomerans (Erwinia herbicola (Lohnis) Dye [21]), Bacillus subtilis and some species of Pseudomonas genus to inhibit the growth of phytopathogenic bacteria and micromycetes and to regulate the growth of plants has been comparatively studied. The ability to inhibit the growth of mycellium of phytopathogenic Fusarium avenaceum, F. gibbosum, F. oxysporum was found out in all of 13 investigated strains of P. agglomerans, while the growth of F. culmorum is inhibited by 2 strains and Bipolaris sorokiniana is inhibited by 7 strains. The strains of P. agglomerans and Bacillus subtilis inhibit the growth of mycellium of these mycromycetes to the greater extent than the representatives of Pseudomonas genus. The mycellium growth of B. sorokiniana is better inhibited by B. subtilis and representatives of Pseudomonas genus. Besides the antifungal action 8 strains of P. agglomerans manifested the antagonistic activity in respect to phytopathogenic Agrobacterium tumefaciens and representatives of genera Clavibacter, Erwinia, Pseudomonas, Xanthomonas and also in respect to the microflora which is present in the cabbage and wheat seeds. The strains have been revealed which, parallel with high antagonistic activity in respect to phytopathogenic micromycetes and bacteria, stimulate the seed germination and increase the weight of the cabbage and wheat sprouts. PMID:11421000

  9. A large family of antivirulence regulators modulates the effects of transcriptional activators in Gram-negative pathogenic bacteria.

    PubMed

    Santiago, Araceli E; Ruiz-Perez, Fernando; Jo, Noah Y; Vijayakumar, Vidhya; Gong, Mei Q; Nataro, James P

    2014-05-01

    We have reported that transcription of a hypothetical small open reading frame (orf60) in enteroaggregative E. coli (EAEC) strain 042 is impaired after mutation of aggR, which encodes a global virulence activator. We have also reported that the cryptic orf60 locus was linked to protection against EAEC diarrhea in two epidemiologic studies. Here, we report that the orf60 product acts as a negative regulator of aggR itself. The orf60 protein product lacks homology to known repressors, but displays 44-100% similarity to at least fifty previously undescribed small (<10 kDa) hypothetical proteins found in many gram negative pathogen genomes. Expression of orf60 homologs from enterotoxigenic E. coli (ETEC) repressed the expression of the AraC-transcriptional ETEC regulator CfaD/Rns and its regulon in ETEC strain H10407. Complementation in trans of EAEC 042orf60 by orf60 homologs from ETEC and the mouse pathogen Citrobacter rodentium resulted in dramatic suppression of aggR. A C. rodentium orf60 homolog mutant showed increased levels of activator RegA and increased colonization of the adult mouse. We propose the name Aar (AggR-activated regulator) for the clinically and epidemiologically important orf60 product in EAEC, and postulate the existence of a large family of homologs among pathogenic Enterobacteriaceae and Pasteurellaceae. We propose the name ANR (AraC Negative Regulators) for this family. PMID:24875828

  10. A Large Family of Antivirulence Regulators Modulates the Effects of Transcriptional Activators in Gram-negative Pathogenic Bacteria

    PubMed Central

    Santiago, Araceli E.; Ruiz-Perez, Fernando; Jo, Noah Y.; Vijayakumar, Vidhya; Gong, Mei Q.; Nataro, James P.

    2014-01-01

    We have reported that transcription of a hypothetical small open reading frame (orf60) in enteroaggregative E. coli (EAEC) strain 042 is impaired after mutation of aggR, which encodes a global virulence activator. We have also reported that the cryptic orf60 locus was linked to protection against EAEC diarrhea in two epidemiologic studies. Here, we report that the orf60 product acts as a negative regulator of aggR itself. The orf60 protein product lacks homology to known repressors, but displays 44–100% similarity to at least fifty previously undescribed small (<10 kDa) hypothetical proteins found in many gram negative pathogen genomes. Expression of orf60 homologs from enterotoxigenic E. coli (ETEC) repressed the expression of the AraC-transcriptional ETEC regulator CfaD/Rns and its regulon in ETEC strain H10407. Complementation in trans of EAEC 042orf60 by orf60 homologs from ETEC and the mouse pathogen Citrobacter rodentium resulted in dramatic suppression of aggR. A C. rodentium orf60 homolog mutant showed increased levels of activator RegA and increased colonization of the adult mouse. We propose the name Aar (AggR-activated regulator) for the clinically and epidemiologically important orf60 product in EAEC, and postulate the existence of a large family of homologs among pathogenic Enterobacteriaceae and Pasteurellaceae. We propose the name ANR (AraC Negative Regulators) for this family. PMID:24875828

  11. Soil bacteria confer plant salt tolerance by tissue-specific regulation of the sodium transporter HKT1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Elevated sodium (Na+) decreases plant growth and thereby agricultural productivity. The ion transporter HKT1 controls Na+ import in roots, yet dysfunction or over-expression of HKT1 fails to increase salt tolerance, raising questions as to HKT1’s role in regulating Na+ homeostasis. Here, we report t...

  12. Use of the lactococcal nisA promoter to regulate gene expression in gram-positive bacteria: comparison of induction level and promoter strength.

    PubMed

    Eichenbaum, Z; Federle, M J; Marra, D; de Vos, W M; Kuipers, O P; Kleerebezem, M; Scott, J R

    1998-08-01

    We characterized the regulated activity of the lactococcal nisA promoter in strains of the gram-positive species Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, Enterococcus faecalis, and Bacillus subtilis. nisA promoter activity was dependent on the proteins NisR and NisK, which constitute a two-component signal transduction system that responds to the extracellular inducer nisin. The nisin sensitivity and inducer concentration required for maximal induction varied among the strains. Significant induction of the nisA promoter (10- to 60-fold induction) was obtained in all of the species studied at a nisin concentration just below the concentration at which growth is inhibited. The efficiency of the nisA promoter was compared to the efficiencies of the Spac, xylA, and lacA promoters in B. subtilis and in S. pyogenes. Because nisA promoter-driven expression is regulated in many gram-positive bacteria, we expect it to be useful for genetic studies, especially studies with pathogenic streptococci in which no other regulated promoters have been described. PMID:9687428

  13. Inhibition of MAP kinases and down regulation of TNF-alpha, IL-beta and COX-2 genes by the crude extracts from marine bacteria.

    PubMed

    Krishnaveni, M; Jayachandran, S

    2009-08-01

    Crude ethyl acetate extracts from marine bacterial isolates Staphylococcus arlettae KP2 (GenBank accession No. EU594442) and Planococcus maritimus KP8 (GenBank accession No. EU594443) isolated from Andaman seas were studied for their anti-inflammatory effect by lymphocyte proliferation assay (LPA) employing peripheral blood mononuclear cells (PBMCs). The crude extracts from both the bacteria down regulated the synthesis of inflammatory mediators such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and cyclooxygenase-2 (COX-2), besides markedly inhibiting p38 mitogen activated protein (MAP) kinase. These results suggest that the crude ethyl acetate extracts from both the isolates do contain compounds capable of inhibiting inflammation in mitogen induced PBMC and efforts to score potential bioactive molecules from these extracts may prove to be a promising preposition. PMID:18996678

  14. A regulating method for the distribution of phosphorus fractions based on environmental parameters related to the key phosphate-solubilizing bacteria during composting.

    PubMed

    Wei, Yuquan; Wei, Zimin; Cao, Zhenyu; Zhao, Yue; Zhao, Xinyu; Lu, Qian; Wang, Xueqin; Zhang, Xu

    2016-07-01

    This study was conducted to assess the abundance, incidence and diversity of the culturable phosphate-solubilizing bacteria (PSB) community during different organic wastes composting. The key PSB affecting different phosphorus (P) fractions and their relationship with environmental variables were analyzed by redundancy analysis (RDA). The results showed that there were distinct differences in amounts, incidence and community composition of PSB for the composts from different sources. Regression analysis demonstrated significant corrections between the density and incidence of PSB and pH, temperature, OM and DOC/DON. Most of culturable PSB showed high percentages of identity with the phyla of Firmicutes and Proteobacteria. There were thirteen key PSB correlated closely (p<0.05) with different P fractions variation. Conclusively, we suggested a process control method to regulate the distribution of P fractions during composting based on the relationship between the key PSB and P fractions as well as environmental parameters. PMID:27043056

  15. Novel sigmaB regulation modules of Gram-positive bacteria involve the use of complex hybrid histidine kinases.

    PubMed

    de Been, Mark; Francke, Christof; Siezen, Roland J; Abee, Tjakko

    2011-01-01

    A common bacterial strategy to cope with stressful conditions is the activation of alternative sigma factors that control specific regulons enabling targeted responses. In the human pathogen Bacillus cereus, activation of the major stress-responsive sigma factor σ(B) is controlled by a signalling route that involves the multi-sensor hybrid histidine kinase RsbK. RsbK-type kinases are not restricted to the B. cereus group, but occur in a wide variety of other bacterial species, including members of the the low-GC Gram-positive genera Geobacillus and Paenibacillus as well as the high-GC actinobacteria. Genome context and protein sequence analyses of 118 RsbK homologues revealed extreme variability in N-terminal sensory as well as C-terminal regulatory domains and suggested that RsbK-type kinases are subject to complex fine-tuning systems, including sensitization and desensitization via methylation and demethylation within the helical domain preceding the H-box. The RsbK-mediated stress-responsive sigma factor activation mechanism that has evolved in B. cereus and the other species differs markedly from the extensively studied and highly conserved RsbRST-mediated σ(B) activation route found in Bacillus subtilis and other low-GC Gram-positive bacteria. Implications for future research on sigma factor control mechanisms are presented and current knowledge gaps are briefly discussed. PMID:21051490

  16. Cu(II)-mediated atom transfer radical polymerization of methyl methacrylate via a strategy of thermo-regulated phase-separable catalysis in a liquid/liquid biphasic system: homogeneous catalysis, facile heterogeneous separation, and recycling.

    PubMed

    Pan, Jinlong; Zhang, Bingjie; Jiang, Xiaowu; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

    2014-09-01

    A strategy of thermo-regulated phase-separable catalysis (TPSC) is applied to the Cu(II)-mediated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in a p-xylene/PEG-200 biphasic system. Initiators for continuous activator regeneration ATRP (ICAR ATRP) are used to establish the TPSC-based ICAR ATRP system using water-soluble TPMA as a ligand, EBPA as an initiator, CuBr2 as a catalyst, and AIBN as a reducing agent. By heating to 70 °C, unlimited miscibility of both solvents is achieved and the polymerization can be carried out under homogeneous conditions; then on cooling to 25 °C, the mixture separates into two phases again. As a result, the catalyst complex remains in the PEG-200 phase while the obtained polymers stay in the p-xylene phase. The catalyst can therefore be removed from the resultant polymers by easily separating the two different layers and can be reused again. It is important that well-defined PMMA with a controlled molecular weight and narrow molecular weight distribution could be obtained using this TPSC-based ICAR ATRP system. PMID:25155655

  17. The regulation of actin polymerization in differentiating U937 cells correlates with increased membrane levels of the pertussis-toxin-sensitive G-protein Gi2.

    PubMed Central

    Sheth, B; Banks, P; Burton, D R; Monk, P N

    1991-01-01

    Undifferentiated U937 cells appear to lack a capacity of increase cellular F-actin. However, electropermeabilized cells gain the ability to respond in this way to a guanine nucleotide analogue, guanosine 5'-[gamma-thio]trisphosphate (GTP[S]) after 1 h of treatment with dibutyryl cyclic AMP (db-cAMP). The results reported here show that the levels of membrane association of the G-protein Gi2 alpha increase with a time course identical with that of the GTP[S]-sensitivity of electropermeabilized cells. These results suggest that Gi2 alpha may be involved in the signal-transduction pathway leading to actin polymerization in db-cAMP-differentiated U937 cells. PMID:1645523

  18. Regulated dielectric loss of polymer composites from coating carbon nanotubes with a cross-linked silsesquioxane shell through free-radical polymerization.

    PubMed

    Sun, Da; Zhou, Zheng; Chen, Guang-Xin; Li, Qifang

    2014-11-12

    We report a synthetic strategy for coating multiwalled carbon nanotubes (MWCNTs) with cross-linked octa-methacrylate-polyhedral oligomeric silsesquioxane (MA-POSS) by direct, in situ free-radical polymerization in a controlled manner. This strategy resulted in a core-shell structure with an MWCNT center. The shell thickness could be varied from ∼ 7 nm to 40 nm by choosing different initiators, solvents, and weight ratios of MWCNT and octa-MA-POSS. Coated MWCNT hybrids had controlled electrical performance depending on the coating layer thickness and were well-dispersed in the polymer matrix. POSS-coated MWCNTs were compounded with poly(vinylidene fluoride) to obtain a composite with high dielectric permittivity and low dielectric loss. PMID:25337905

  19. RFX Transcription Factor DAF-19 Regulates 5-HT and Innate Immune Responses to Pathogenic Bacteria in Caenorhabditis elegans

    PubMed Central

    Choi, Sunju; Xu, Lu; Sze, Ji Ying

    2013-01-01

    In Caenorhabditis elegans the Toll-interleukin receptor domain adaptor protein TIR-1 via a conserved mitogen-activated protein kinase (MAPK) signaling cascade induces innate immunity and upregulates serotonin (5-HT) biosynthesis gene tph-1 in a pair of ADF chemosensory neurons in response to infection. Here, we identify transcription factors downstream of the TIR-1 signaling pathway. We show that common transcription factors control the innate immunity and 5-HT biosynthesis. We demonstrate that a cysteine to tyrosine substitution in an ARM motif of the HEAT/Arm repeat region of the TIR-1 protein confers TIR-1 hyperactivation, leading to constitutive tph-1 upregulation in the ADF neurons, increased expression of intestinal antimicrobial genes, and enhanced resistance to killing by the human opportunistic pathogen Pseudomonas aeruginosa PA14. A forward genetic screen for suppressors of the hyperactive TIR-1 led to the identification of DAF-19, an ortholog of regulatory factor X (RFX) transcription factors that are required for human adaptive immunity. We show that DAF-19 concerts with ATF-7, a member of the activating transcription factor (ATF)/cAMP response element-binding B (CREB) family of transcription factors, to regulate tph-1 and antimicrobial genes, reminiscent of RFX-CREB interaction in human immune cells. daf-19 mutants display heightened susceptibility to killing by PA14. Remarkably, whereas the TIR-1-MAPK-DAF-19/ATF-7 pathway in the intestinal immunity is regulated by DKF-2/protein kinase D, we found that the regulation of tph-1 expression is independent of DKF-2 but requires UNC-43/Ca2+/calmodulin-dependent protein kinase (CaMK) II. Our results suggest that pathogenic cues trigger a common core-signaling pathway via tissue-specific mechanisms and demonstrate a novel role for RFX factors in neuronal and innate immune responses to infection. PMID:23505381

  20. CD4(+) T-cell activation is differentially modulated by bacteria-primed dendritic cells, but is generally down-regulated by n-3 polyunsaturated fatty acids.

    PubMed

    Brix, Susanne; Lund, Pia; Kjaer, Tanja M R; Straarup, Ellen M; Hellgren, Lars I; Frøkiaer, Hanne

    2010-03-01

    Appropriate activation of CD4(+) T cells is fundamental for efficient initiation and progression of acquired immune responses. Here, we showed that CD4(+) T-cell activation is dependent on changes in membrane n-3 polyunsaturated fatty acids (PUFAs) and is dynamically regulated by the type of signals provided by dendritic cells (DCs). Upon interaction with DCs primed by different concentrations and species of gut bacteria, CD4(+) T cells were activated according to the type of DC stimulus. The levels of CD80 were found to correlate to the levels of expression of CD28 and to the proliferation of CD4(+) T cells, while the presence of CD40 and CD86 on DCs inversely affected inducible costimulator (ICOS) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) levels in CD4(+) T cells. For all DC stimuli, cells high in n-3 PUFAs showed reduced ability to respond to CD28 stimulation, to proliferate, and to express ICOS and CTLA-4. Diminished T-cell receptor (TCR) and CD28 signalling was found to be responsible for n-3 PUFA effects. Thus, the dietary fatty acid composition influences the overall level of CD4(+) T-cell activation induced by DCs, while the priming effect of the DC stimuli modulates CD80, CD86 and CD40 levels, thereby affecting and shaping activation of acquired immunity by differential regulation of proliferation and costimulatory molecule expression in CD4(+) T cells. PMID:19909377

  1. CD4+ T-cell activation is differentially modulated by bacteria-primed dendritic cells, but is generally down-regulated by n-3 polyunsaturated fatty acids

    PubMed Central

    Brix, Susanne; Lund, Pia; Kjaer, Tanja M R; Straarup, Ellen M; Hellgren, Lars I; Frøkiær, Hanne

    2010-01-01

    Appropriate activation of CD4+ T cells is fundamental for efficient initiation and progression of acquired immune responses. Here, we showed that CD4+ T-cell activation is dependent on changes in membrane n-3 polyunsaturated fatty acids (PUFAs) and is dynamically regulated by the type of signals provided by dendritic cells (DCs). Upon interaction with DCs primed by different concentrations and species of gut bacteria, CD4+ T cells were activated according to the type of DC stimulus. The levels of CD80 were found to correlate to the levels of expression of CD28 and to the proliferation of CD4+ T cells, while the presence of CD40 and CD86 on DCs inversely affected inducible costimulator (ICOS) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) levels in CD4+ T cells. For all DC stimuli, cells high in n-3 PUFAs showed reduced ability to respond to CD28 stimulation, to proliferate, and to express ICOS and CTLA-4. Diminished T-cell receptor (TCR) and CD28 signalling was found to be responsible for n-3 PUFA effects. Thus, the dietary fatty acid composition influences the overall level of CD4+ T-cell activation induced by DCs, while the priming effect of the DC stimuli modulates CD80, CD86 and CD40 levels, thereby affecting and shaping activation of acquired immunity by differential regulation of proliferation and costimulatory molecule expression in CD4+ T cells. PMID:19909377

  2. Polymerized nano-curcumin attenuates neurological symptoms in EAE model of multiple sclerosis through down regulation of inflammatory and oxidative processes and enhancing neuroprotection and myelin repair.

    PubMed

    Mohajeri, Maryam; Sadeghizadeh, Majid; Najafi, Farhood; Javan, Mohammad

    2015-12-01

    Multiple Sclerosis (MS) is an inflammatory demyelinating disorder of central nervous system (CNS). Polyphenol curcumin has been used in traditional medicine as an effective drug for a variety of diseases. Different formulations of curcumin are introduced to increase its stability and effectiveness. Here we have examined the effect of polymerized form of nano-curcumin (PNC) on experimental autoimmune encephalomyelitis (EAE) as an animal model of MS. EAE was induced in female Lewis rats and PNC or curcumin was daily administrated intraperitonealy from day 12-29 post immunization. When the prophylactic effect of PNC was under investigation, rats received PNC from the first day of immunization. Treatment with PNC resulted in decreased scores of disease in therapeutic and prophylactic administration when compared with control group. Staining by luxol fast blue and H&E and immuno-staining of lumbar spinal cord cross sections, confirmed a significant decrease in the amounts of demyelination, inflammation and BBB breaking down. Gene expression studies in lumbar spinal cord showed a corrected balance of pro-inflammatory and anti-inflammatory genes expression, decreased oxidative stress, improved remyelination and increased progenitor cell markers after treatment with PNC. Our results demonstrated an efficient therapeutic effect of PNC as an anti-inflammatory and anti-oxidative stress agent, with significant effects on the EAE scores and myelin repair mechanisms. PMID:26211978

  3. Transient activation of mucosal effector immune responses by resident intestinal bacteria in normal hosts is regulated by interleukin-10 signalling.

    PubMed

    Wu, Cong; Sartor, R Balfour; Huang, Kehe; Tonkonogy, Susan L

    2016-07-01

    Interleukin-10 (IL-10) is a key regulator of mucosal homeostasis. In the current study we investigated the early events after monoassociating germ-free (GF) wild-type (WT) mice with an Escherichia coli strain that we isolated previously from the caecal contents of a normal mouse housed under specific pathogen-free conditions. Our results show that interferon-γ (IFN-γ) secreted by mesenteric lymph node (MLN) cells from both IL-10 deficient mice and WT mice, stimulated ex vivo with E. coli lysate, was dramatically higher at day 4 after monoassociation compared with IFN-γ secreted by cells from GF mice without E. coli colonization. Production of IFN-γ rapidly and progressively declined after colonization of WT but not IL-10-deficient mice. The E. coli lysate-stimulated WT MLN cells also produced IL-10 that peaked at day 4 and subsequently declined, but not as precipitously as IFN-γ. WT cells that express CD4, CD8 and NKp46 produced IFN-γ; WT CD4-positive cells and B cells produced IL-10. Recombinant IL-10 added to E. coli-stimulated MLN cell cultures inhibited IFN-γ secretion in a dose-dependent fashion. MLN cells from WT mice treated in vivo with neutralizing anti-IL-10 receptor antibody produced more IFN-γ compared with MLN cells from isotype control antibody-treated mice. These findings show that a resident E. coli that induces chronic colitis in monoassociated IL-10-deficient mice rapidly but transiently activates the effector immune system in normal hosts, in parallel with induction of protective IL-10 produced by B cells and CD4(+) cells that subsequently suppresses this response to mediate mucosal homeostasis. PMID:27147411

  4. Polymeric Carbon Dioxide

    SciTech Connect

    Yoo, C-S.

    1999-11-02

    Synthesis of polymeric carbon dioxide has long been of interest to many chemists and materials scientists. Very recently we discovered the polymeric phase of carbon dioxide (called CO{sub 2}-V) at high pressures and temperatures. Our optical and x-ray results indicate that CO{sub 2}-V is optically non-linear, generating the second harmonic of Nd: YLF laser at 527 nm and is also likely superhard similar to cubic-boron nitride or diamond. CO{sub 2}-V is made of CO{sub 4} tetrahedra, analogous to SiO{sub 2} polymorphs, and is quenchable at ambient temperature at pressures above 1 GPa. In this paper, we describe the pressure-induced polymerization of carbon dioxide together with the stability, structure, and mechanical and optical properties of polymeric CO{sub 2}-V. We also present some implications of polymeric CO{sub 2} for high-pressure chemistry and new materials synthesis.

  5. Spatial control of actin polymerization during neutrophil chemotaxis

    PubMed Central

    Weiner, Orion D.; Servant, Guy; Welch, Matthew D.; Mitchison, Timothy J.; Sedat, John W.; Bourne, Henry R.

    2010-01-01

    Neutrophils respond to chemotactic stimuli by increasing the nucleation and polymerization of actin filaments, but the location and regulation of these processes are not well understood. Here, using a permeabilized-cell assay, we show that chemotactic stimuli cause neutrophils to organize many discrete sites of actin polymerization, the distribution of which is biased by external chemotactic gradients. Furthermore, the Arp2/3 complex, which can nucleate actin polymerization, dynamically redistributes to the region of living neutrophils that receives maximal chemotactic stimulation, and the least-extractable pool of the Arp2/3 complex co-localizes with sites of actin polymerization. Our observations indicate that chemoattractant-stimulated neutrophils may establish discrete foci of actin polymerization that are similar to those generated at the posterior surface of the intracellular bacterium Listeria monocytogenes. We propose that asymmetrical establishment and/or maintenance of sites of actin polymerization produces directional migration of neutrophils in response to chemotactic gradients. PMID:10559877

  6. Antimicrobial selenium nanoparticle coatings on polymeric medical devices

    NASA Astrophysics Data System (ADS)

    Tran, Phong A.; Webster, Thomas J.

    2013-04-01

    Bacteria colonization on medical devices remains one of the most serious complications following implantation. Traditional antibiotic treatment has proven ineffective, creating an increasingly high number of drug-resistant bacteria. Polymeric medical devices represent a significant portion of the total medical devices used today due to their excellent mechanical properties (such as durability, flexibility, etc). However, many polymers (such as polyvinyl chloride (PVC), polyurethane (PU) and silicone) become readily colonized and infected by bacteria immediately after use. Therefore, in this study, a novel antimicrobial coating was developed to inhibit bacterial growth on PVC, PU and silicone. Specifically, here, the aforementioned polymeric substrates were coated with selenium (Se) nanoparticles in situ. The Se-coated substrates were characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy and bacteria assays. Most importantly, bacterial growth was significantly inhibited on the Se-coated substrates compared to their uncoated counterparts. The reduction of bacteria growth directly correlated with the density of Se nanoparticles on the coated substrate surfaces. In summary, these results demonstrate that Se should be further studied as a novel anti-bacterial polymeric coating material which can decrease bacteria functions without the use of antibiotics.

  7. Antimicrobial selenium nanoparticle coatings on polymeric medical devices.

    PubMed

    Tran, Phong A; Webster, Thomas J

    2013-04-19

    Bacteria colonization on medical devices remains one of the most serious complications following implantation. Traditional antibiotic treatment has proven ineffective, creating an increasingly high number of drug-resistant bacteria. Polymeric medical devices represent a significant portion of the total medical devices used today due to their excellent mechanical properties (such as durability, flexibility, etc). However, many polymers (such as polyvinyl chloride (PVC), polyurethane (PU) and silicone) become readily colonized and infected by bacteria immediately after use. Therefore, in this study, a novel antimicrobial coating was developed to inhibit bacterial growth on PVC, PU and silicone. Specifically, here, the aforementioned polymeric substrates were coated with selenium (Se) nanoparticles in situ. The Se-coated substrates were characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy and bacteria assays. Most importantly, bacterial growth was significantly inhibited on the Se-coated substrates compared to their uncoated counterparts. The reduction of bacteria growth directly correlated with the density of Se nanoparticles on the coated substrate surfaces. In summary, these results demonstrate that Se should be further studied as a novel anti-bacterial polymeric coating material which can decrease bacteria functions without the use of antibiotics. PMID:23519147

  8. Polymerization catalyst system

    SciTech Connect

    Graves, V.

    1986-03-25

    This patent describes a catalyst system for polymerizing at least one alpha-olefin under conditions characteristic of Ziegler polymerization. This system consists of: 1. a supported polymerization catalyst or mixture of polymerization catalysts prepared under anhydrous conditions by the sequential steps of: (a) preparing a slurry of inert particulate porous support material; (b) adding to the slurry a solution of an organomagnesium compound; (c) adding to the slurry and reacting a solution of a zirconium halide compound, hafnium compound or mixtures thereof; (d) adding to the slurry and reacting a halogenator; (e) adding to the slurry and reacting a tetravalent titanium halide compound; and (f) recovering solid catalyst component; 2. an organoaluminum compound; and 3. a promotor of chlorinated hydrocarbons having one to 20 carbon atoms.

  9. Magnetic Bacteria.

    ERIC Educational Resources Information Center

    Nelson, Jane Bray; Nelson, Jim

    1992-01-01

    Describes the history of Richard Blakemore's discovery of magnetotaxic organisms. Discusses possible reasons why the magnetic response in bacteria developed. Proposes research experiments integrating biology and physics in which students investigate problems using cultures of magnetotaxic organisms. (MDH)

  10. Anaerobic bacteria

    MedlinePlus

    Brook I, Goldstein EJ. Diseases caused by non-spore forming anaerobic bacteria. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 297. Stedman's Online ...

  11. Radical-Mediated Enzymatic Polymerizations

    PubMed Central

    Zavada, Scott R.; Battsengel, Tsatsral; Scott, Timothy F.

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes―catalytic proteins―owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol–ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  12. Radical-Mediated Enzymatic Polymerizations.

    PubMed

    Zavada, Scott R; Battsengel, Tsatsral; Scott, Timothy F

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes--catalytic proteins--owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol-ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  13. Quorum quenching activity in cell-free lysate of endophytic bacteria isolated from Pterocarpus santalinus Linn., and its effect on quorum sensing regulated biofilm in Pseudomonas aeruginosa PAO1.

    PubMed

    Rajesh, P S; Ravishankar Rai, V

    2014-01-01

    Quorum sensing mechanism allows the microorganisms to resist the antibiotic treatment by forming biofilms. Quorum quenching is one of the mechanisms to control the development of drug resistance in microbes. Endophyte bacteria are beneficial to plant growth as they support the immune system against the pathogen attack. The endophytic bacteria present in Pterocarpus santalinus were screened for the presence of N-acyl homoserine lactones (AHLs) degrading bacteria using biosensor strains and further confirmed by quantifying the violacein production. Cell-free lysate of endophytic bacteria, Bacillus firmus PT18 and Enterobacter asburiae PT39 exhibited potent AHL degrading ability by inhibiting about 80% violacein production in biosensor strain. Furthermore, when the cell-free lysate was applied to Pseudomonas aeruginosa PAO1 and PAO1-JP2 biofilm it resulted in significant (p<0.01) inhibition of biofilm formation. The biofilm inhibition was confirmed by visualization of biofilm slides under fluorescence microscopy, which showed decrease in total biomass formation in treated slides. Isolation and amplification of the gene (aiiA) indicated that the presence of AHL lactonase in cell-free lysate and sequence alignment indicated that AiiA contains a "HXHXDH" zinc-binding motif that is being conserved in several groups of metallohydrolases. Therefore, the study shows the potential of AHLs degradation by AHL lactonase present in cell-free lysate of isolated endophytic bacteria and inhibition of quorum sensing regulated biofilm formation in P. aeruginosa PAO1. PMID:24268182

  14. Heat-killed probiotic bacteria differentially regulate colonic epithelial cell production of human β-defensin-2: dependence on inflammatory cytokines.

    PubMed

    Habil, N; Abate, W; Beal, J; Foey, A D

    2014-12-01

    The inducible antimicrobial peptide human β-defensin-2 (hBD-2) stimulated by pro-inflammatory cytokines and bacterial products is essential to antipathogen responses of gut epithelial cells. Commensal and probiotic bacteria can augment such mucosal defences. Probiotic use in the treatment of inflammatory bowel disease, however, may have adverse effects, boosting inflammatory responses. The aim of this investigation was to determine the effect of selected probiotic strains on hBD-2 production by epithelial cells induced by pathologically relevant pro-inflammatory cytokines and the role of cytokine modulators in controlling hBD-2. Caco-2 colonic intestinal epithelial cells were pre-incubated with heat-killed probiotics, i.e. Lactobacillus casei strain Shirota (LcS) or Lactobacillus fermentum strain MS15 (LF), followed by stimulation of hBD-2 by interleukin (IL)-1β and tumour necrosis factor alpha (TNF-α) in the absence or presence of exogenous IL-10 or anti-IL-10 neutralising antibody. Cytokines and hBD-2 mRNA and protein were analysed by real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. LcS augmented IL-1β-induced hBD-2, whereas LF enhanced TNF-α- and suppressed IL-1β-induced hBD-2. LF enhanced TNF-α-induced TNF-α and suppressed IL-10, whereas augmented IL-1β-induced IL-10. LcS upregulated IL-1β-induced TNF-α mRNA and suppressed IL-10. Endogenous IL-10 differentially regulated hBD-2; neutralisation of IL-10 augmented TNF-α- and suppressed IL-1β-induced hBD-2. Exogenous IL-10, however, suppressed both TNF-α- and IL-1β-induced hBD-2; LcS partially rescued suppression in TNF-α- and IL-1β-stimulation, whereas LF further suppressed IL-1β-induced hBD-2. It can be concluded that probiotic strains differentially regulate hBD-2 mRNA expression and protein secretion, modulation being dictated by inflammatory stimulus and resulting cytokine environment. PMID:25116382

  15. Colchicine activates actin polymerization by microtubule depolymerization.

    PubMed

    Jung, H I; Shin, I; Park, Y M; Kang, K W; Ha, K S

    1997-06-30

    Swiss 3T3 fibroblasts were treated with the microtubule-disrupting agent colchicine to study any interaction between microtubule dynamics and actin polymerization. Colchicine increased the amount of filamentous actin (F-actin), in a dose- and time-dependent manner with a significant increase at 1 h by about 130% over control level. Confocal microscopic observation showed that colchicine increased F-actin contents by stress fiber formation without inducing membrane ruffling. Colchicine did not activate phospholipase C and phospholipase D, whereas lysophosphatidic acid did, indicating that colchicine may have a different mechanism of actin polymerization regulation from LPA. A variety of microtubule-disrupting agents stimulated actin polymerization in Swiss 3T3 and Rat-2 fibroblasts as did colchicine, but the microtubule-stabilizing agent taxol inhibited actin polymerization induced by the above microtubule-disrupting agents. In addition, colchicine-induced actin polymerization was blocked by two protein phosphatase inhibitors, okadaic acid and calyculin A. These results suggest that microtubule depolymerization activates stress fiber formation by serine/threonine dephosphorylation in fibroblasts. PMID:9264034

  16. Methanotrophic bacteria.

    PubMed Central

    Hanson, R S; Hanson, T E

    1996-01-01

    Methane-utilizing bacteria (methanotrophs) are a diverse group of gram-negative bacteria that are related to other members of the Proteobacteria. These bacteria are classified into three groups based on the pathways used for assimilation of formaldehyde, the major source of cell carbon, and other physiological and morphological features. The type I and type X methanotrophs are found within the gamma subdivision of the Proteobacteria and employ the ribulose monophosphate pathway for formaldehyde assimilation, whereas type II methanotrophs, which employ the serine pathway for formaldehyde assimilation, form a coherent cluster within the beta subdivision of the Proteobacteria. Methanotrophic bacteria are ubiquitous. The growth of type II bacteria appears to be favored in environments that contain relatively high levels of methane, low levels of dissolved oxygen, and limiting concentrations of combined nitrogen and/or copper. Type I methanotrophs appear to be dominant in environments in which methane is limiting and combined nitrogen and copper levels are relatively high. These bacteria serve as biofilters for the oxidation of methane produced in anaerobic environments, and when oxygen is present in soils, atmospheric methane is oxidized. Their activities in nature are greatly influenced by agricultural practices and other human activities. Recent evidence indicates that naturally occurring, uncultured methanotrophs represent new genera. Methanotrophs that are capable of oxidizing methane at atmospheric levels exhibit methane oxidation kinetics different from those of methanotrophs available in pure cultures. A limited number of methanotrophs have the genetic capacity to synthesize a soluble methane monooxygenase which catalyzes the rapid oxidation of environmental pollutants including trichloroethylene. PMID:8801441

  17. The fecal bacteria

    USGS Publications Warehouse

    Sadowsky, Michael J., (Edited By); Whitman, Richard L.

    2011-01-01

    The Fecal Bacteria offers a balanced, integrated discussion of fecal bacteria and their presence and ecology in the intestinal tract of mammals, in the environment, and in the food supply. This volume covers their use in examining and assessing water quality in order to offer protection from illnesses related to swimming in or ingesting contaminated water, in addition to discussing their use in engineering considerations of water quality, modeling, monitoring, and regulations. Fecal bacteria are additionally used as indicators of contamination of ready-to-eat foods and fresh produce. The intestinal environment, the microbial community structure of the gut microbiota, and the physiology and genomics of this broad group of microorganisms are explored in the book. With contributions from an internationally recognized group of experts, the book integrates medicine, public health, environmental, and microbiological topics in order to provide a unique, holistic understanding of fecal bacteria. Moreover, it shows how the latest basic science and applied research findings are helping to solve problems and develop effective management strategies. For example, readers will discover how the latest tools and molecular approaches have led to our current understanding of fecal bacteria and enabled us to improve human health and water quality. The Fecal Bacteria is recommended for microbiologists, clinicians, animal scientists, engineers, environmental scientists, food safety experts, water quality managers, and students. It will help them better understand fecal bacteria and use their knowledge to protect human and environmental health. They can also apply many of the techniques and molecular tools discussed in this book to the study of a broad range of microorganisms in a variety of habitats.

  18. Organocatalyzed Group Transfer Polymerization.

    PubMed

    Chen, Yougen; Kakuchi, Toyoji

    2016-08-01

    In contrast to the conventional group transfer polymerization (GTP) using a catalyst of either an anionic nucleophile or a transition-metal compound, the organocatalyzed GTP has to a great extent improved the living characteristics of the polymerization from the viewpoints of synthesizing structurally well-defined acrylic polymers and constructing defect-free polymer architectures. In this article, we describe the organocatalyzed GTP from a relatively personal perspective to provide our colleagues with a perspicuous and systematic overview on its recent progress as well as a reply to the curiosity of how excellently the organocatalysts have performed in this field. The stated perspectives of this review mainly cover five aspects, in terms of the assessment of the livingness of the polymerization, limit and scope of applicable monomers, mechanistic studies, control of the polymer structure, and a new GTP methodology involving the use of tris(pentafluorophenyl)borane and hydrosilane. PMID:27427399

  19. Controlled polymerization by incarceration of monomers in nanochannels.

    PubMed

    Uemura, Takashi; Kitagawa, Susumu

    2010-01-01

    Porous Coordination Polymers (PCPs) composed of transition metal ions and bridging organic ligands have been extensively studied. The characteristic features of PCPs are highly regular channel structures, controllable channel sizes approximating molecular dimensions, designable surface potentials and functionality, and flexible frameworks responsive to guest molecules. Owing to these advantages, successful applications of PCPs range from molecular storage and separation to heterogeneous catalysts. In particular, use of their regulated and tunable nanochannels in the field of polymerization has allowed multi-level control of polymerization via control of stereoregularlity, molecular weight, etc. In this chapter, we focus on recent progress in polymerization utilizing the nanochannels of PCPs, and demonstrate why this polymerization system is attractive and promising from the viewpoint of precision control of polymeric structures. PMID:21618745

  20. Variable Effect during Polymerization

    ERIC Educational Resources Information Center

    Lunsford, S. K.

    2005-01-01

    An experiment performing the polymerization of 3-methylthiophene(P-3MT) onto the conditions for the selective electrode to determine the catechol by using cyclic voltammetry was performed. The P-3MT formed under optimized conditions improved electrochemical reversibility, selectivity and reproducibility for the detection of the catechol.

  1. Polymerized and functionalized triglycerides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant oils are useful sustainable raw materials for the development of new chemical products. As part of our research emphasis in sustainability and green polymer chemistry, we have explored a new method for polymerizing epoxidized triglycerides with the use of fluorosulfonic acid. Depending on the ...

  2. Programmable Supramolecular Polymerizations.

    PubMed

    van der Zwaag, Daan; de Greef, Tom F A; Meijer, E W

    2015-07-13

    Living large: Rational design of self-assembly pathways has been demonstrated in supramolecular polymers. By controlling the concentration of an aggregation-competent monomer through intramolecular interactions, living supramolecular polymerization conditions were achieved. This universal approach can be used to obtain aggregates of well-defined length and narrow dispersity, and allows access to new supramolecular polymer architectures. PMID:26095705

  3. Effective integrative supramolecular polymerization.

    PubMed

    Zhang, Qiwei; Tian, He

    2014-09-26

    Exercise control: By taking advantage of self-sorting processes among host-guest components, a controlled supramolecular polymerization can be realized, as demonstrated recently with the preparation of a cucurbit[n]uril-based supramolecular polymer. This method may be used for the design of more ordered supramolecular polymers from complex and discrete components. PMID:25080388

  4. Protein specific polymeric immunomicrospheres

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Dreyer, William J. (Inventor)

    1980-01-01

    Small, round, bio-compatible microspheres capable of covalently bonding proteins and having a uniform diameter below about 3500 A are prepared by substantially instantaneously initiating polymerization of an aqueous emulsion containing no more than 35% total monomer including an acrylic monomer substituted with a covalently bondable group such as hydroxyl, amino or carboxyl and a minor amount of a cross-linking agent.

  5. Mechanisms of post-transcriptional gene regulation in bacterial biofilms

    PubMed Central

    Martínez, Luary C.; Vadyvaloo, Viveka

    2014-01-01

    Biofilms are characterized by a dense multicellular community of microorganisms that can be formed by the attachment of bacteria to an inert surface and to each other. The development of biofilm involves the initial attachment of planktonic bacteria to a surface, followed by replication, cell-to-cell adhesion to form microcolonies, maturation, and detachment. Mature biofilms are embedded in a self-produced extracellular polymeric matrix composed primarily of bacterial-derived exopolysaccharides, specialized proteins, adhesins, and occasionally DNA. Because the synthesis and assembly of biofilm matrix components is an exceptionally complex process, the transition between its different phases requires the coordinate expression and simultaneous regulation of many genes by complex genetic networks involving all levels of gene regulation. The finely controlled intracellular level of the chemical second messenger molecule, cyclic-di-GMP is central to the post-transcriptional mechanisms governing the switch between the motile planktonic lifestyle and the sessile biofilm forming state in many bacteria. Several other post-transcriptional regulatory mechanisms are known to dictate biofilm development and assembly and these include RNA-binding proteins, small non-coding RNAs, toxin-antitoxin systems, riboswitches, and RNases. Post-transcriptional regulation is therefore a powerful molecular mechanism employed by bacteria to rapidly adjust to the changing environment and to fine tune gene expression to the developmental needs of the cell. In this review, we discuss post-transcriptional mechanisms that influence the biofilm developmental cycle in a variety of pathogenic bacteria. PMID:24724055

  6. Polyurethane biocidal polymeric surface modifiers.

    PubMed

    Makal, Umit; Wood, Lynn; Ohman, Dennis E; Wynne, Kenneth J

    2006-03-01

    Polyurethanes (PUs) with soft blocks containing semifluorinated (-CH2OCH2CF3) and 5,5-dimethylhydantoin pendant groups were prepared and employed (2 wt%) as biocidal polymeric surface modifiers (PSMs) for a conventional PU coating comprised of an isophorone diisocyanate/1,4-butanediol-derived hard block (50%) and poly(tetramethylene oxide) soft block. Surface enrichment of the PSM was verified by dynamic contact angle measurements. The PSM modified PU was activated by converting near-surface amide groups to chloramide with 3wt% hypochlorite. The conversion of near-surface amide to chloramide is reflected in somewhat increased hydrophobic character for the antimicrobial chloramide functionalized surfaces. Biocidal activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa, and Escherichia coli) bacteria was demonstrated by using a modified version of American Association of Textile Chemists and Colorists (AATCC-100) test. By changing the PSM concentration it was found that only 1.6 wt% PSM (0.66 wt% biocide, 5,5-dimethylhydantoin) in a conventional PU affected complete kill of P. aeruginosa in 15 min by using this biocidal testing protocol. PMID:16181672

  7. Bacteria Counter

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Science Applications, Inc.'s ATP Photometer makes a rapid and accurate count of the bacteria in a body fluid sample. Instrument provides information on the presence and quantity of bacteria by measuring the amount of light emitted by the reaction between two substances. Substances are ATP adenosine triphosphate and luciferase. The reactants are applied to a human body sample and the ATP Photometer observes the intensity of the light emitted displaying its findings in a numerical output. Total time lapse is usually less than 10 minutes, which represents a significant time savings in comparison of other techniques. Other applications are measuring organisms in fresh and ocean waters, determining bacterial contamination of foodstuffs, biological process control in the beverage industry, and in assay of activated sewage sludge.

  8. Actin Polymerization is Stimulated by Actin Crosslinking Protein Palladin

    PubMed Central

    Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G.; Orlova, Albina; Egelman, Edward H.; Beck, Moriah R.

    2016-01-01

    The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the coordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. Here we show that the actin binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro crosslinking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of G-actin, akin to metal ions, either through charge neutralization or conformational changes. PMID:26607837

  9. 78 FR 46265 - Complex Polymeric Polyhydroxy Acids; Exemption From the Requirement of a Tolerance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-31

    ...This regulation establishes an exemption from the requirement of a tolerance for residues of Complex Polymeric Polyhydroxy Acids in or on all food commodities. This regulation eliminates the need to establish a maximum permissible level for residues of Complex Polymeric Polyhydroxy Acids (CPPA) under...

  10. Frontal Polymerization in Microgravity

    NASA Technical Reports Server (NTRS)

    Pojman, John A.

    1999-01-01

    Frontal polymerization systems, with their inherent large thermal and compositional gradients, are greatly affected by buoyancy-driven convection. Sounding rocket experiments allowed the preparation of benchmark materials and demonstrated that methods to suppress the Rayleigh-Taylor instability in ground-based research did not significantly affect the molecular weight of the polymer. Experiments under weightlessness show clearly that bubbles produced during the reaction interact very differently than under 1 g.

  11. Polymeric Bicontinuous Microemulsions

    NASA Astrophysics Data System (ADS)

    Bates, Frank S.; Maurer, Wayne W.; Lipic, Paul M.; Hillmyer, Marc A.; Almdal, Kristoffer; Mortensen, Kell; Fredrickson, Glenn H.; Lodge, Timothy P.

    1997-08-01

    High molecular weight block copolymers can be viewed as macromolecular surfactants when blended with thermodynamically incompatible homopolymers. This Letter describes the formation of polymeric bicontinuous microemulsions in mixtures containing a model diblock copolymer and two homopolymers. Although we attribute development of this equilibrium morphology to the effects of fluctuations, mean-field theory provides a quantitative strategy for preparing the bicontinuous state at blend compositions near an isotropic Lifshitz point.

  12. Surface polymerization agents

    SciTech Connect

    Taylor, C.; Wilkerson, C.

    1996-12-01

    This is the final report of a 1-year, Laboratory-Directed R&D project at LANL. A joint technical demonstration was proposed between US Army Missile Command (Redstone Arsenal) and LANL. Objective was to demonstrate that an unmanned vehicle or missile could be used as a platform to deliver a surface polymerization agent in such a manner as to obstruct the filters of an air-breathing mechanism, resulting in operational failure.

  13. Regulatory RNAs in Bacteria

    PubMed Central

    Waters, Lauren S.; Storz, Gisela

    2011-01-01

    RNA regulators in bacteria are a heterogenous group of molecules that act by various mechanisms to modulate a wide range of physiological responses. One class comprises riboswitches, which are parts of the mRNAs they regulate. These leader sequences fold into structures amenable to conformational changes upon the binding of small molecules. Riboswitches thus sense and respond to the availability of various nutrients in the cell. Other small transcripts bind to proteins, among them global regulators, and antagonize their functions. The largest and most extensively studied set of small RNA regulators act through base pairing with RNAs, usually modulating the translation and stability of mRNAs. The majority of these small RNAs regulate responses to changes in environmental conditions. Finally, a recently discovered group of RNA regulators, known as the CRISPR RNAs, contain short regions of homology to bacteriophage and plasmid sequences. CRISPR RNAs interfere with bacteriophage infection and plasmid conjugation by targeting the homologous foreign DNA through an unknown mechanism. Here we discuss what is known about these RNA regulators, as well as the many intriguing questions that remain to be addressed. PMID:19239884

  14. Extracellular signaling cues for nuclear actin polymerization.

    PubMed

    Plessner, Matthias; Grosse, Robert

    2015-01-01

    Contrary to cytoplasmic actin structures, the biological functions of nuclear actin filaments remain largely enigmatic. Recent progress in the field, however, has determined nuclear actin structures in somatic cells either under steady state conditions or in response to extracellular signaling cues. These actin structures differ in size and shape as well as in their temporal appearance and dynamics. Thus, a picture emerges that suggests that mammalian cells may have different pathways and mechanisms to assemble nuclear actin filaments. Apart from serum- or LPA-triggered nuclear actin polymerization, integrin activation by extracellular matrix interaction was recently implicated in nuclear actin polymerization through the linker of nucleoskeleton and cytoskeleton (LINC) complex. Some of these extracellular cues known so far appear to converge at the level of nuclear formin activity and subsequent regulation of myocardin-related transcription factors. Nevertheless, as the precise signaling events are as yet unknown, the regulation of nuclear actin polymerization may be of significant importance for different cellular functions as well as disease conditions caused by altered nuclear dynamics and architecture. PMID:26059398

  15. Importance of Extracellular Polymeric Substances from Thiobacillus ferrooxidans for Bioleaching

    PubMed Central

    Gehrke, Tilman; Telegdi, Judit; Thierry, Dominique; Sand, Wolfgang

    1998-01-01

    Leaching bacteria such as Thiobacillus ferrooxidans attach to pyrite or sulfur by means of extracellular polymeric substances (EPS) (lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrochemical interaction with the negatively charged pyrite surface. EPS from sulfur cells possess increased hydrophobic properties and do not attach to pyrite, indicating adaptability to the substrate or substratum. PMID:9647862

  16. Acrylic esters in radiation polymerization

    SciTech Connect

    Fomina, N.V.; Khoromskaya, V.A.; Shiryaeva, G.V.

    1988-03-01

    The radiation behavior of (meth)acrylic esters of varying structure was studied. It was shown that in radiation polymerization, in contrast to thermal polymerization, the structure of the ester part can significantly affect the reaction rate and capacity for polymerization in the presence of oxygen. The experimental data are explained from the point of view of consideration of nonvalence effects of the substitutent on the reactivity of the double bond.

  17. Polymerization Evaluation by Spectrophotometric Measurements.

    ERIC Educational Resources Information Center

    Dunach, Jaume

    1985-01-01

    Discusses polymerization evaluation by spectrophotometric measurements by considering: (1) association degrees and molar absorptivities; (2) association degrees and equilibrium constants; and (3) absorbance and equilibrium constants. (JN)

  18. Sustainable polymerizations in recoverable microemulsions.

    PubMed

    Chen, Zhenzhen; Yan, Feng; Qiu, Lihua; Lu, Jianmei; Zhou, Yinxia; Chen, Jiaxin; Tang, Yishan; Texter, John

    2010-03-16

    Free radical and atom-transfer radical polymerizations were conducted in monomer/ionic liquid microemulsions. After the polymerization and isolation of the resultant polymers, the mixture of the catalyst and ionic liquids (surfactant and continuous phase) can be recovered and reused, thereby dramatically improving the environmental sustainability of such chemical processing. The addition of monomer to recovered ionic liquid mixtures regenerates transparent, stable microemulsions that are ready for the next polymerization cycle upon addition of initiator. The method combines the advantages of IL recycling and microemulsion polymerization and minimizes environmental disposable effects from surfactants and heavy metal ions. PMID:20170175

  19. Continuous polymerization reactor

    SciTech Connect

    Wilt, M.S.

    1986-05-06

    A method is described for contacting olefinic monomer and initiator in a continuous polymerization process comprising of the steps of: creating three turbulent zones in a vessel; introducing the olefinic monomer into a first part of the periphery of each one of the three turbulent zones; introducing the initiator into a second part of the periphery of each one of the three turbulent zones, wherein the first part of the periphery of each one of the three turbulent zones is substantially diametrically opposed to the second part of the periphery of each one of the three turbulent zones respectively.

  20. Bimorphic polymeric photomechanical actuator

    NASA Technical Reports Server (NTRS)

    Sarkisov, Sergey S. (Inventor); Curley, Michael J. (Inventor); Adamovsky, Grigory (Inventor); Sarkisov, Jr., Sergey S. (Inventor); Fields, Aisha B. (Inventor)

    2006-01-01

    A bimorphic polymeric photomechanical actuator, in one embodiment using polyvinylidene fluoride (PVDF) as a photosensitive body, transmitting light over fiber optic cables, and controlling the shape and pulse duration of the light pulse to control movement of the actuator. Multiple light beams are utilized to generate different ranges of motion for the actuator from a single photomechanical body and alternative designs use multiple light beams and multiple photomechanical bodies to provide controlled movement. Actuator movement using one or more ranges of motion is utilized to control motion to position an actuating element in three dimensional space.

  1. Living olefin polymerization processes

    DOEpatents

    Schrock, Richard R.; Bauman, Robert

    2006-11-14

    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  2. Living olefin polymerization processes

    DOEpatents

    Schrock, Richard R.; Baumann, Robert

    2003-08-26

    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  3. Living olefin polymerization processes

    DOEpatents

    Schrock, R.R.; Baumann, R.

    1999-03-30

    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  4. Living olefin polymerization processes

    DOEpatents

    Schrock, Richard R.; Baumann, Robert

    1999-01-01

    Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

  5. Acetoin metabolism in bacteria.

    PubMed

    Xiao, Zijun; Xu, Ping

    2007-01-01

    Acetoin is an important physiological metabolite excreted by many microorganisms. The excretion of acetoin, which can be diagnosed by the Voges Proskauer test and serves as a microbial classification marker, has its vital physiological meanings to these microbes mainly including avoiding acification, participating in the regulation of NAD/NADH ratio, and storaging carbon. The well-known anabolism of acetoin involves alpha-acetolactat synthase and alpha-acetolactate decarboxylase; yet its catabolism still contains some differing views, although much attention has been focused on it and great advances have been achieved. Current findings in catabolite control protein A (CcpA) mediated carbon catabolite repression may provide a fuller understanding of the control mechanism in bacteria. In this review, we first examine the acetoin synthesis pathways and its physiological meanings and relevancies; then we discuss the relationship between the two conflicting acetoin cleavage pathways, the enzymes of the acetoin dehydrogenase enzyme system, major genes involved in acetoin degradation, and the CcpA mediated acetoin catabolite repression pathway; in the end we discuss the genetic engineering progresses concerning applications. To date, this is the first integrated review on acetoin metabolism in bacteria, especially with regard to catabolic aspects. The apperception of the generation and dissimilation of acetoin in bacteria will help provide a better understanding of microbial strategies in the struggle for resources, which will consequently better serve the utilization of these microbes. PMID:17558661

  6. Organometallic Polymeric Conductors

    NASA Technical Reports Server (NTRS)

    1997-01-01

    For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. The highest conductivities reported (approximately 4/Scm) were achieved with polythiophene in a polystyrene host polymer. The best films using a polyamide as base polymer were four orders of magnitude less conductive than the polystyrene films. The authors suggested that this was because polyimides were unable to swell sufficiently for infiltration of monomer as in the polystyrene. It was not clear, however, if the different conductivities obtained were merely the result of differing oxidation conditions. Oxidation time, temperature and oxidant concentration varied widely among the studies.

  7. Coating of plasma polymerized film

    NASA Technical Reports Server (NTRS)

    Morita, S.; Ishibashi, S.

    1980-01-01

    Plasma polymerized thin film coating and the use of other coatings is suggested for passivation film, thin film used for conducting light, and solid body lubrication film of dielectrics of ultra insulators for electrical conduction, electron accessories, etc. The special features of flow discharge development and the polymerized film growth mechanism are discussed.

  8. Beneficial bacteria inhibit cachexia

    PubMed Central

    Varian, Bernard J.; Goureshetti, Sravya; Poutahidis, Theofilos; Lakritz, Jessica R.; Levkovich, Tatiana; Kwok, Caitlin; Teliousis, Konstantinos; Ibrahim, Yassin M.; Mirabal, Sheyla; Erdman, Susan E.

    2016-01-01

    Muscle wasting, known as cachexia, is a debilitating condition associated with chronic inflammation such as during cancer. Beneficial microbes have been shown to optimize systemic inflammatory tone during good health; however, interactions between microbes and host immunity in the context of cachexia are incompletely understood. Here we use mouse models to test roles for bacteria in muscle wasting syndromes. We find that feeding of a human commensal microbe, Lactobacillus reuteri, to mice is sufficient to lower systemic indices of inflammation and inhibit cachexia. Further, the microbial muscle-building phenomenon extends to normal aging as wild type animals exhibited increased growth hormone levels and up-regulation of transcription factor Forkhead Box N1 [FoxN1] associated with thymus gland retention and longevity. Interestingly, mice with a defective FoxN1 gene (athymic nude) fail to inhibit sarcopenia after L. reuteri therapy, indicating a FoxN1-mediated mechanism. In conclusion, symbiotic bacteria may serve to stimulate FoxN1 and thymic functions that regulate inflammation, offering possible alternatives for cachexia prevention and novel insights into roles for microbiota in mammalian ontogeny and phylogeny. PMID:26933816

  9. Beneficial bacteria inhibit cachexia.

    PubMed

    Varian, Bernard J; Goureshetti, Sravya; Poutahidis, Theofilos; Lakritz, Jessica R; Levkovich, Tatiana; Kwok, Caitlin; Teliousis, Konstantinos; Ibrahim, Yassin M; Mirabal, Sheyla; Erdman, Susan E

    2016-03-15

    Muscle wasting, known as cachexia, is a debilitating condition associated with chronic inflammation such as during cancer. Beneficial microbes have been shown to optimize systemic inflammatory tone during good health; however, interactions between microbes and host immunity in the context of cachexia are incompletely understood. Here we use mouse models to test roles for bacteria in muscle wasting syndromes. We find that feeding of a human commensal microbe, Lactobacillus reuteri, to mice is sufficient to lower systemic indices of inflammation and inhibit cachexia. Further, the microbial muscle-building phenomenon extends to normal aging as wild type animals exhibited increased growth hormone levels and up-regulation of transcription factor Forkhead Box N1 [FoxN1] associated with thymus gland retention and longevity. Interestingly, mice with a defective FoxN1 gene (athymic nude) fail to inhibit sarcopenia after L. reuteri therapy, indicating a FoxN1-mediated mechanism. In conclusion, symbiotic bacteria may serve to stimulate FoxN1 and thymic functions that regulate inflammation, offering possible alternatives for cachexia prevention and novel insights into roles for microbiota in mammalian ontogeny and phylogeny. PMID:26933816

  10. Nitrogen control in bacteria.

    PubMed Central

    Merrick, M J; Edwards, R A

    1995-01-01

    Nitrogen metabolism in prokaryotes involves the coordinated expression of a large number of enzymes concerned with both utilization of extracellular nitrogen sources and intracellular biosynthesis of nitrogen-containing compounds. The control of this expression is determined by the availability of fixed nitrogen to the cell and is effected by complex regulatory networks involving regulation at both the transcriptional and posttranslational levels. While the most detailed studies to date have been carried out with enteric bacteria, there is a considerable body of evidence to show that the nitrogen regulation (ntr) systems described in the enterics extend to many other genera. Furthermore, as the range of bacteria in which the phenomenon of nitrogen control is examined is being extended, new regulatory mechanisms are also being discovered. In this review, we have attempted to summarize recent research in prokaryotic nitrogen control; to show the ubiquity of the ntr system, at least in gram-negative organisms; and to identify those areas and groups of organisms about which there is much still to learn. PMID:8531888

  11. Bacteria-tight sealing of exposed dog pulps.

    PubMed

    Wijnbergen-Buijen van Weelderen, M; van Mullem, P J

    1984-05-01

    Penetration of bacteria past filling materials can interfere with the vitality of exposed pulps. In the present study, seventy-three dog's teeth were filled--after exposure--with Cavit -W and then sealed either with a chemically or a UV polymerizing bonding. After 14 days a failure rate of 28% was demonstrated using the chemically polymerizing Concise and of 4.5% using the UV polymerizing Uvio -Bond. After 42 days the latter bonding revealed a success rate of 100%. To achieve a bacteria-tight seal of deep cavities for middle long term animal experimentation, Uvio -Bond can be used--after etching--to cover the filling material and the surrounding enamel. PMID:6234386

  12. 49 CFR 176.907 - Polymeric Beads and Plastic Molding Compounds.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Polymeric Beads and Plastic Molding Compounds. 176.907 Section 176.907 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS..., and Plastic Molding Compounds § 176.907 Polymeric Beads and Plastic Molding Compounds. (a)...

  13. 49 CFR 176.907 - Polymeric Beads and Plastic Molding Compounds.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Polymeric Beads and Plastic Molding Compounds. 176.907 Section 176.907 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS..., and Plastic Molding Compounds § 176.907 Polymeric Beads and Plastic Molding Compounds. (a)...

  14. Back To Bacteria.

    ERIC Educational Resources Information Center

    Flannery, Maura C.

    1997-01-01

    Explores new research about bacteria. Discusses bacterial genomes, archaea, unusual environments, evolution, pathogens, bacterial movement, biofilms, bacteria in the body, and a bacterial obsession. Contains 29 references. (JRH)

  15. Magnetic bacteria against MIC

    SciTech Connect

    Javaherdashti, R.

    1997-12-01

    In this article, it is suggested to use the sensitivity of magnetotactic bacteria to changes of magnetic field direction and the natural ability of this bacteria in rapid growth during relatively short time intervals against corrosion-enhancing bacteria and especially sulfate-reducing bacteria. If colonies of sulfate-reducing bacteria could be packed among magnetotactic bacteria, then, by applying sufficiently powerful magnetic field (about 0.5 gauss), all of these bacteria (magnetic and non-magnetic) will be oriented towards an Anti-bacteria agent (oxygen or biocide). So, Microbiologically-Influenced Corrosion in the system would be controlled to a large extent.

  16. Dynamic bioactive stimuli-responsive polymeric surfaces

    NASA Astrophysics Data System (ADS)

    Pearson, Heather Marie

    This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH < 2.3, the P2VP segments are protonated and extend, but for pH > 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and Φ11 bacteriophages (phages) on PE and PTFE surface

  17. Distribution of tetracycline resistance genes in anaerobic treatment of waste sludge: The role of pH in regulating tetracycline resistant bacteria and horizontal gene transfer.

    PubMed

    Huang, Haining; Chen, Yinguang; Zheng, Xiong; Su, Yinglong; Wan, Rui; Yang, Shouye

    2016-10-01

    Although pH value has been widely regarded as an important factor that affects resource recovery of waste sludge, the potential influence of diverse pHs on the distribution of tetracycline resistance genes (TRGs) during sludge anaerobic treatment is largely unknown. Here we reported that in the range of pH 4-10, 0.58-1.18 log unit increase of target TRGs was observed at pH 4, compared with that at pH 7, while 0.70-1.31 log unit further removal were obtained at pH 10. Mechanism study revealed that varied pHs not only altered the community structures of tetracycline resistant bacteria (TRB), but also changed their relative abundances, benefitting the propagation (acidic pHs) or attenuation (alkaline pHs) of TRB. Further investigation indicated that the amount and gene-possessing abilities of key genetic vectors for horizontal TRGs transfer were greatly promoted at acidic pHs but restricted under alkaline conditions. PMID:27485281

  18. clpP of Streptococcus salivarius Is a Novel Member of the Dually Regulated Class of Stress Response Genes in Gram-Positive Bacteria

    PubMed Central

    Chastanet, Arnaud; Msadek, Tarek

    2003-01-01

    Nucleotide sequence analysis of the Streptococcus salivarius clpP locus revealed potential binding sites for both the CtsR and HrcA repressors. Dual regulation by HrcA and CtsR was demonstrated by using Bacillus subtilis as a heterologous host, and CtsR was shown to bind directly to the clpP promoter sequence. This is the first example of a clpP gene under the control of HrcA. PMID:12511518

  19. Production of monodisperse, polymeric microspheres

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Rhim, Won-Kyu (Inventor); Hyson, Michael T. (Inventor); Chang, Manchium (Inventor)

    1990-01-01

    Very small, individual polymeric microspheres with very precise size and a wide variation in monomer type and properties are produced by deploying a precisely formed liquid monomer droplet, suitably an acrylic compound such as hydroxyethyl methacrylate into a containerless environment. The droplet which assumes a spheroid shape is subjected to polymerizing radiation such as ultraviolet or gamma radiation as it travels through the environment. Polymeric microspheres having precise diameters varying no more than plus or minus 5 percent from an average size are recovered. Many types of fillers including magnetic fillers may be dispersed in the liquid droplet.

  20. Melting line of polymeric nitrogen

    NASA Astrophysics Data System (ADS)

    Yakub, L. N.

    2013-05-01

    We made an attempt to predict location of the melting line of polymeric nitrogen using two equations for Helmholtz free energy: proposed earlier for cubic gauche-structure and developed recently for liquid polymerized nitrogen. The P-T relation, orthobaric densities and latent heat of melting were determined using a standard double tangent construction. The estimated melting temperature decreases with increasing pressure, alike the temperature of molecular-nonmolecular transition in solid. We discuss the possibility of a triple point (solid-molecular fluid-polymeric fluid) at ˜80 GPa and observed maximum of melting temperature of nitrogen.

  1. High temperature structural, polymeric foams from high internal emulsion polymerization

    SciTech Connect

    Hoisington, M.A.; Duke, J.R.; Apen, P.G.

    1996-02-01

    In 1982, a high internal phase emulsion (HIPE) polymerization process to manufacture microcellular, polymeric foam systems was patented by Unilever. This patent discloses a polymerization process that occurs in a water-in-oil emulsion in which the water represents at least 76% of the emulsion by volume. The oil phase consists of vinyl monomers such as styrene and acrylates that are crosslinked by divinyl monomers during polymerization. After polymerization and drying to remove the water phase, the result is a crosslinked polymer foam with an open cell microstructure that is homogeneous throughout in terms of morphology, density, and mechanical properties. Since 1982, numerous patents have examined various HIPE polymerized foam processing techniques and applications that include absorbents for body fluids, cleaning materials, and ion exchange systems. All the published HIPE polymerized foams have concentrated on materials for low temperature applications. Copolymerization of styrene with maleic anhydride and N-substituted maleimides to produce heat resistant thermoplastics has been studied extensively. These investigations have shown that styrene will free radically copolymerize with N-substituted maleimides to create an alternating thermoplastic copolymer with a Tg of approximately 200{degrees}C. However, there are many difficulties in attempting the maleimide styrene copolymerization in a HIPE such as lower polymerization temperatures, maleimide solubility difficulties in both styrene and water, and difficulty obtaining a stable HIPE with a styrene/maleimide oil phase. This work describes the preparation of copolymer foams from N-ethylmaleimide and Bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane with styrene based monomers and crosslinking agents.

  2. Organometallic Polymeric Conductors

    NASA Technical Reports Server (NTRS)

    Youngs, Wiley J.

    1997-01-01

    For aerospace applications, the use of polymers can result in tremendous weight savings over metals. Suitable polymeric materials for some applications like EMI shielding, spacecraft grounding, and charge dissipation must combine high electrical conductivity with long-term environmental stability, good processability, and good mechanical properties. Recently, other investigators have reported hybrid films made from an electrically conductive polymer combined with insulating polymers. In all of these instances, the films were prepared by infiltrating an insulating polymer with a precursor for a conductive polymer (either polypyrrole or polythiophene), and oxidatively polymerizing the precursor in situ. The resulting composite films have good electrical conductivity, while overcoming the brittleness inherent in most conductive polymers. Many aerospace applications require a combination of properties. Thus, hybrid films made from polyimides or other engineering resins are of primary interest, but only if conductivities on the same order as those obtained with a polystyrene base could be obtained. Hence, a series of experiments was performed to optimize the conductivity of polyimide-based composite films. The polyimide base chosen for this study was Kapton. 3-MethylThiophene (3MT) was used for the conductive phase. Three processing variables were identified for producing these composite films, namely time, temperature, and oxidant concentration for the in situ oxidation. Statistically designed experiments were used to examine the effects of these variables and synergistic/interactive effects among variables on the electrical conductivity and mechanical strength of the films. Multiple linear regression analysis of the tensile data revealed that temperature and time have the greatest effect on maximum stress. The response surface of maximum stress vs. temperature and time (for oxidant concentration at 1.2 M) is shown. Conductivity of the composite films was measured for

  3. 75 FR 1773 - Notice of Receipt of a Pesticide Petition Filed for Residues of Polymeric Polyhydroxy Acid in or...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-13

    ...This notice announces the Agency's receipt of an initial filing of a pesticide petition proposing the establishment of a regulation for residues of the plant growth regulator, polymeric polyhydroxy acid, in or on all food...

  4. Versatile and Rapid Postfunctionalization from Cyclodextrin Modified Host Polymeric Membrane Substrate.

    PubMed

    Deng, Jie; Liu, Xinyue; Zhang, Shuqing; Cheng, Chong; Nie, Chuanxiong; Zhao, Changsheng

    2015-09-01

    Surface modification has long been of great interest to impart desired functionalities to the bioimplants. However, due to the limitations of recent technologies in surface modification, it is highly desirable to explore novel protocols, which can advantageously and efficiently endow the inert material surfaces with versatile biofunctionalities. Herein, to achieve versatile and rapid postfunctionalization of polymeric membrane, we demonstrate a new strategy for the fabrication of β-cyclodextrin (β-CD) modified host membrane substrate that can recognize a series of well-designed guest macromolecules. The surface assembly procedure was driven by the host-guest interaction between adamantane (Ad) and β-CD. β-CD immobilized host membrane was fabricated via two steps: (1) epoxy groups enriched poly(ether sulfone) (PES) membrane was first prepared via in situ cross-linking polymerization and subsequently phase separation; (2) mono-6-deoxy-6-ethylenediamine-β-CD (EDA-β-CD) was then anchored onto the surface of the epoxy functionalized PES membrane to obtain PES-CD. Subsequently, three types of Ad-terminated polymers, including Ad-poly(styrenesulfonate-co-sodium acrylate) (Ad-PSA), Ad-methoxypoly(ethylene glycol) (Ad-PEG), and Ad-poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate (Ad-PMT), were separately assembled onto the β-CD immobilized surfaces to endow the membranes with anticoagulant, antifouling, and antibacterial capability, respectively. Activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) measurements were carried out to explore the anticoagulant activity. The antifouling capability was evaluated via protein adsorption and platelet adhesion measurements. Moreover, Staphyllococcous aureus (S. aureus) was selected as model bacteria to evaluate the antibacterial ability of the functionalized membranes. The results indicated that well-regulated blood compatibility, antifouling capability, and

  5. Admicellar polymerization of precipated silica

    SciTech Connect

    Reynolds, J.L.; Grady, B.P.; Harwell, J.H.

    1996-10-01

    The tendency of a surfactant molecule to adsorb at a solid-liquid interface is the basis for an in situ surface modification process, termed admicellar polymerization. The four-step admicellar polymerization process includes: (1) adsorption of surfactant at the solid-liquid interface, (2) adsolubilization of monomer into the surfactant bilayer, (3) polymerization using free-radical initiators and heat, (4) removal of excess surfactant to expose the polymer modified surface. The process is used to apply polymer to precipitated silica to enhance the compatibility of the silica when added to filled rubber. The adsorption isotherms were first determined for particular surfactant/silica combinations to find the surfactant concentration that would sufficiently adsolubilize the monomer, while remaining below the critical micelle concentration. A series of experiments were then devised for the polymerization reactions in which the surfactant and monomer amounts were varied over three levels to establish the optimal combination.

  6. Polymerization of anionic wormlike micelles.

    PubMed

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

  7. Kinetics of silica polymerization

    SciTech Connect

    Weres, O.; Yee, A.; Tsao, L.

    1980-05-01

    The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

  8. Chemical communication in bacteria

    NASA Astrophysics Data System (ADS)

    Suravajhala, Srinivasa Sandeep; Saini, Deepak; Nott, Prabhu

    Luminescence in Vibrio fischeri is a model for quorum-sensing-gene-regulation in bacteria. We study luminescence response of V. fischeri to both internal and external cues at the single cell and population level. Experiments with ES114, a wild-type strain, and ainS mutant show that luminescence induction in cultures is not always proportional to cell-density and there is always a basal level of luminescence. At any given concentration of the exogenously added signals, C6-HSL and C8-HSL, luminescence per cell reaches a maximum during the exponential phase and decreases thereafter. We hypothesize that (1) C6-HSL production and LuxR activity are not proportional to cell-density, and (2) there is a shift in equilibrium from C6-HSL to C8-HSL during the later stages of growth of the culture. RT-PCR analysis of luxI and luxR shows that the expression of these genes is maximum corresponding to the highest level of luminescence. The shift in equilibrium is shown by studying competitive binding of C6-HSL and C8-HSL to LuxR. We argue that luminescence is a unicellular behaviour, and an intensive property like per cell luminescence is more important than gross luminescence of the population in understanding response of bacteria to chemical signalling. Funding from the Department of Science and Technology, India is acknowledged.

  9. Impact of Carbon Nanomaterials on Actin Polymerization.

    PubMed

    Dong, Ying; Sun, Haiyan; Li, Xu; Li, Xin; Zhao, Lina

    2016-03-01

    Many nanomaterials have entered people's daily lives and impact the normal process of biological entities consequently. As one kind of the important nanomaterials, carbon based nanomaterials have invoked a lot of concerns from scientific researches because of their unique physicochemical properties. In eukaryotes, actin is the most abundantly distributed protein in both cytoplasm and cell nucleus, and closely controls the cell proliferation and mobility. Recently, many investigations have found some carbon based nanomaterials can affect actin cytoskeleton remarkably, including fullerenes derivatives, carbon nanotubes, graphene and its derivatives. However, these interaction processes are complicated and the underlying mechanism is far from being understood clearly. In this review, we discussed the different mechanisms of carbon nanomaterials impact on actin polymerization into three pathways, as triggering the signaling pathways from carbon nanomaterials outside of cells, increasing the production of reactive oxygen species from carbon nanomaterials inside of cells and direct interaction from carbon nanomaterials inside of cells. As a result, the dimension and size of carbon nanomaterials play a key role in regulation of actin cytoskeleton. Furthermore, we forecasted the possible investigation strategy for meeting the challenges of the future study on this topic. We hope the findings are helpful in understanding the molecular mechanism in carbon nanomaterials regulating actin polymerization, and provide new insight in novel nanomedicine development for inhibition tumor cell migration. PMID:27455649

  10. Stochastic model of profilin-actin polymerization

    NASA Astrophysics Data System (ADS)

    Horan, Brandon; Vavylonis, Dimitrios

    A driving factor in cell motility and other processes that involve changes of cell shape is the rapid polymerization of actin subunits into long filaments. This process is regulated by profilin, a protein which binds to actin subunits and regulates elongation of actin filaments. Whether profilin stimulates polymerization by coupling to hydrolysis of ATP-bound actin is debated. Previous studies have proposed indirect coupling to ATP hydrolysis using rate equations, but did not include the effects of fluctuations that are important near the critical concentration. We developed stochastic simulations using the Gillespie algorithm to study single filament elongation at the barbed end in the presence of profilin. We used recently measured rate constants and estimated the rate of profilin binding to the barbed end such that detailed balance is satisfied. Fast phosphate release at the tip of the filament was accounted for. The elongation rate and length diffusivity as functions of profilin and actin concentration were calculated and used to extract the critical concentrations of free actin and of total actin. We show under what conditions profilin leads to an increase in the critical concentration of total actin but a decrease in the critical concentration of free actin.

  11. Polymeric materials in Space

    NASA Astrophysics Data System (ADS)

    Skurat, Vladimir

    Paper of short review type. It is the continuation of and addition to previous review papers "V. E. Skurat. Polymers in Space. In: Encyclopedia of aerospace engineering, vol. 4, Wiley and sons, 2010; Ibid., 2012 (on line)". Following topics are considered: (1) Destruction of polymers by solar radiation with various wavelengths in different spectral regions (visible-UV, vacuum UV (VUV), deep UV, soft and hard X-rays) are discussed. In difference with common polymer photochemistry induced by UV radiation, directions of various routs of polymer phototransformations and their relative yields are greatly dependent on wavelength of light (photon energy) during illuminations in VUV, deep UV and X-ray regions. During last twenty years, intensive spacecraft investigations of solar spectrum show great periodic and spontaneous variations of radiation intensities in short-wavelengths regions - up to one - two decimal orders of magnitude for X-rays. As a result, during solar flares the absorbed dose on the polymer surfaces from X-rays can be compared with absorbed dose from VUV radiation. (2) Some new approaches to predictions of reaction efficiencies of fast orbital atomic oxygen in their interaction with polymeric materials are considered. (3) Some aspects of photocatalitic destruction of polymers in vacuum conditions by full-spectrum solar radiation are discussed. This process can take place in enamels containing semiconducting particles (TiO2, ZnO) as pigments. (4) Contamination of spacecraft surfaces from intrinsic outer atmosphere play important role not only from the point of view of deterioration of optical and thermophysical properties. Layers of SiO2 contaminations with nanometer thicknesses can greatly diminish mass losses from perfluorinated polymers under VUV irradiation.

  12. Polymeric materials for neovascularization

    NASA Astrophysics Data System (ADS)

    DeVolder, Ross John

    Revascularization therapies have emerged as a promising strategy to treat various acute and chronic wounds, cardiovascular diseases, and tissue defects. It is common to either administer proangiogenic growth factors, such as vascular endothelial growth factor (VEGF), or transplant cells that endogenously express multiple proangiogenic factors. Additionally, these strategies utilize a wide variety of polymeric systems, including hydrogels and biodegradable plastics, to deliver proangiogenic factors in a sophisticated manner to maintain a sustained proangiogenic environment. Despite some impressive results in rebuilding vascular networks, it is still a challenging task to engineer mature and functional neovessels in target tissues, because of the increasing complexities involved with neovascularization applications. To resolve these challenges, this work aims to design a wide variety of proangiogenic biomaterial systems with tunable properties used for neovascularization therapies. This thesis describes the design of several biomaterial systems used for the delivery of proangiogenic factors in neovascularization therapies, including: an electrospun/electrosprayed biodegradable plastic patch used for directional blood vessel growth (Chapter 2), an alginate-g-pyrrole hydrogel system that biochemically stimulates cellular endogenous proangiogenic factor expression (Chapter 3), an enzyme-catalyzed alginate-g-pyrrole hydrogel system for VEGF delivery (Chapter 4), an enzyme-activated alginate-g-pyrrole hydrogel system with systematically controllable electrical and mechanical properties (Chapter 5), and an alginate-g-pyrrole hydrogel that enables the decoupled control of electrical conductivity and mechanical rigidity and is use to electrically stimulate cellular endogenous proangiogenic factor expression (Chapter 6). Overall, the biomaterial systems developed in this thesis will be broadly useful for improving the quality of a wide array of molecular and cellular based

  13. Augmented IFN-γ and TNF-α Induced by Probiotic Bacteria in NK Cells Mediate Differentiation of Stem-Like Tumors Leading to Inhibition of Tumor Growth and Reduction in Inflammatory Cytokine Release; Regulation by IL-10

    PubMed Central

    Bui, Vickie T.; Tseng, Han-Ching; Kozlowska, Anna; Maung, Phyu Ou; Kaur, Kawaljit; Topchyan, Paytsar; Jewett, Anahid

    2015-01-01

    Our previous reports demonstrated that the magnitude of natural killer (NK) cell-mediated cytotoxicity correlate directly with the stage and level of differentiation of tumor cells. In addition, we have shown previously that activated NK cells inhibit growth of cancer cells through induction of differentiation, resulting in the resistance of tumor cells to NK cell-mediated cytotoxicity through secreted cytokines, as well as direct NK-tumor cell contact. In this report, we show that in comparison to IL-2 + anti-CD16mAb-treated NK cells, activation of NK cells by probiotic bacteria (sAJ2) in combination with IL-2 and anti-CD16mAb substantially decreases tumor growth and induces maturation, differentiation, and resistance of oral squamous cancer stem cells, MIA PaCa-2 stem-like/poorly differentiated pancreatic tumors, and healthy stem cells of apical papillae through increased secretion of IFN-γ and TNF-α, as well as direct NK-tumor cell contact. Tumor resistance to NK cell-mediated killing induced by IL-2 + anti-CD16mAb + sAJ2-treated NK cells is induced by combination of IFN-γ and TNF-α since antibodies to both, and not each cytokine alone, were able to restore tumor sensitivity to NK cells. Increased surface expression of CD54, B7H1, and MHC-I on NK-differentiated tumors was mediated by IFN-γ since the addition of anti-IFN-γ abolished their increase and restored the ability of NK cells to trigger cytokine and chemokine release; whereas differentiated tumors inhibited cytokine release by the NK cells. Monocytes synergize with NK cells in the presence of probiotic bacteria to induce regulated differentiation of stem cells through secretion of IL-10 resulting in resistance to NK cell-mediated cytotoxicity and inhibition of cytokine release. Therefore, probiotic bacteria condition activated NK cells to provide augmented differentiation of cancer stem cells resulting in inhibition of tumor growth, and decreased inflammatory cytokine release. PMID

  14. FtsZ Polymerization Assays: Simple Protocols and Considerations

    PubMed Central

    Król, Ewa; Scheffers, Dirk-Jan

    2013-01-01

    During bacterial cell division, the essential protein FtsZ assembles in the middle of the cell to form the so-called Z-ring. FtsZ polymerizes into long filaments in the presence of GTP in vitro, and polymerization is regulated by several accessory proteins. FtsZ polymerization has been extensively studied in vitro using basic methods including light scattering, sedimentation, GTP hydrolysis assays and electron microscopy. Buffer conditions influence both the polymerization properties of FtsZ, and the ability of FtsZ to interact with regulatory proteins. Here, we describe protocols for FtsZ polymerization studies and validate conditions and controls using Escherichia coli and Bacillus subtilis FtsZ as model proteins. A low speed sedimentation assay is introduced that allows the study of the interaction of FtsZ with proteins that bundle or tubulate FtsZ polymers. An improved GTPase assay protocol is described that allows testing of GTP hydrolysis over time using various conditions in a 96-well plate setup, with standardized incubation times that abolish variation in color development in the phosphate detection reaction. The preparation of samples for light scattering studies and electron microscopy is described. Several buffers are used to establish suitable buffer pH and salt concentration for FtsZ polymerization studies. A high concentration of KCl is the best for most of the experiments. Our methods provide a starting point for the in vitro characterization of FtsZ, not only from E. coli and B. subtilis but from any other bacterium. As such, the methods can be used for studies of the interaction of FtsZ with regulatory proteins or the testing of antibacterial drugs which may affect FtsZ polymerization. PMID:24300445

  15. Evidence for NH/sub 4//sup +/ switch-off regulation of nitrogenase activity by bacteria in salt marsh sediments and roots of the grass Spartina alterniflora

    SciTech Connect

    Yoch, D.C.; Whiting, G.J.

    1986-01-01

    The regulatory effect of NH/sub 4//sup +/ on nitrogen fixation in a Spartina alterniflora salt marsh was examined. Acetylene reduction activity (ARA) measured in situ was only partially inhibited by NH/sub 4//sup +/ in both the light and dark after 2 h. In vitro analysis of bulk sediment divided into sediment particles, live and dead roots, and rhizomes showed that microbes associated with sediment and dead roots have a great potential for anaerobic C/sub 2/H/sub 2/ reduction, but only if amended with a carbon source such as mannose. Only live roots had significant rates of ARA without an added carbon source. In sediment, N/sub 2/-fixing mannose enrichment cultures could be distinguished from those enriched by lactate in that only the latter were rapidly inhibited by NH/sub 4//sup +/. Ammonia also inhibited ARA in dead and live roots and in surface-sterilized roots. The rate of this inhibition appeared to be too rapid to be attributed to the repression and subsequent dilution of nitrogenase. The kinetic characteristics of this inhibition and its prevention in root-associated microbes by methionine sulfoximine are consistent with the NH/sub 4//sup +/ switch-off-switch-on mechanism of nitrogenase regulation.

  16. Bacteria isolated from amoebae/bacteria consortium

    DOEpatents

    Tyndall, Richard L.

    1995-01-01

    New protozoan derived microbial consortia and method for their isolation are provided. Consortia and bacteria isolated therefrom are useful for treating wastes such as trichloroethylene and trinitrotoluene. Consortia, bacteria isolated therefrom, and dispersants isolated therefrom are useful for dispersing hydrocarbons such as oil, creosote, wax, and grease.

  17. Bacteria isolated from amoebae/bacteria consortium

    DOEpatents

    Tyndall, R.L.

    1995-05-30

    New protozoan derived microbial consortia and method for their isolation are provided. Consortia and bacteria isolated therefrom are useful for treating wastes such as trichloroethylene and trinitrotoluene. Consortia, bacteria isolated therefrom, and dispersants isolated therefrom are useful for dispersing hydrocarbons such as oil, creosote, wax, and grease.

  18. Polymeric bicontinuous microemulsions

    NASA Astrophysics Data System (ADS)

    Krishnan, Kasiraman

    Rheology of complex fluids has been a topic of considerable interest recently. Bicontinuous microemulsions (BmuE), made by mixing appropriate amounts of oil, water and a surfactant, form a unique class of complex fluids. They possess a characteristic nanostructure consisting of undulating surfaces with vanishingly small interfacial curvature. BmuEs can also be generated in polymers by mixing appropriate amounts of two homopolymers and their corresponding diblock copolymer. The main objective of the present research is to study effects of shear on a model polymeric BmuE. Scattering is used as a predominant tool with in situ flow devices, along with optical microscopy and rheology. The model BmuE consists of a ternary blend of poly(ethyl ethylene) (PEE), poly(dimethyl siloxane) (PDMS) and a PEE-PDMS diblock copolymer. Steady shear experiments reveal four regimes as a function of shear rate. At low shear rates (regime I), Newtonian behavior is observed; there is onset of shear thinning at higher rates (regime II). In regime III, the stress is independent of shear rate, whereas it increases with shear rate once again in regime IV. Morphological characterization was carried out for each of these four regimes using scattering and microscopy, the key result being the evidence for flow-induced phase separation in regime III. Transient rheological measurements were conducted for startup and step changes in shear rate, and the BmuE exhibits features similar to worm-like micellar colloidal systems. Time-resolved light scattering and microscopy also reveal interesting characteristics. Dynamic mechanical spectroscopy indicates similarities with neat block copolymers near the order-disorder transition. The equilibrium rheological behavior is intriguing and detailed comparisons are made with Landau-Ginzburg theoretical models. Other areas of research as a part of this thesis include study of structural dynamics of BmuEs with dynamic light scattering, and the rheological

  19. Stereospecific olefin polymerization catalysts

    DOEpatents

    Bercaw, John E.; Herzog, Timothy A.

    1998-01-01

    A metallocene catalyst system for the polymerization of .alpha.-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula ##STR1## wherein: R.sup.1, R.sup.2, and R.sup.3 are independently selected from the group consisting of hydrogen, C.sub.1 to C.sub.10 alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C.sub.1 to C.sub.10 alkyls as a substituent, C.sub.6 to C.sub.15 aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R.sup.8).sub.3 where R.sup.8 is selected from the group consisting of C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; R.sup.4 and R.sup.6 are substituents both having van der Waals radii larger than the van der Waals radii of groups R.sup.1 and R.sup.3 ; R.sup.5 is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E.sup.1, E.sup.2 are independently selected from the group consisting of Si(R.sup.9).sub.2, Si(R.sup.9).sub.2 --Si(R.sup.9).sub.2, Ge(R.sup.9).sub.2, Sn(R.sup.9).sub.2, C(R.sup.9).sub.2, C(R.sup.9).sub.2 --C(R.sup.9).sub.2, where R.sup.9 is C.sub.1 to C.sub.10 alkyl, C.sub.6 to C.sub.15 aryl or C.sub.3 to C.sub.10 cycloalkyl; and the ligand may have C.sub.S or C.sub.1 -symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from .alpha.-olefin monomers.

  20. Stereospecific olefin polymerization catalysts

    DOEpatents

    Bercaw, J.E.; Herzog, T.A.

    1998-01-13

    A metallocene catalyst system is described for the polymerization of {alpha}-olefins to yield stereospecific polymers including syndiotactic, and isotactic polymers. The catalyst system includes a metal and a ligand of the formula shown wherein: R{sup 1}, R{sup 2}, and R{sup 3} are independently selected from the group consisting of hydrogen, C{sub 1} to C{sub 10} alkyl, 5 to 7 membered cycloalkyl, which in turn may have from 1 to 3 C{sub 1} to C{sub 10} alkyls as a substituent, C{sub 6} to C{sub 15} aryl or arylalkyl in which two adjacent radicals may together stand for cyclic groups having 4 to 15 carbon atoms which in turn may be substituted, or Si(R{sup 8}){sub 3} where R{sup 8} is selected from the group consisting of C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; R{sup 4} and R{sup 6} are substituents both having van der Waals radii larger than the van der Waals radii of groups R{sup 1} and R{sup 3}; R{sup 5} is a substituent having a van der Waals radius less than about the van der Waals radius of a methyl group; E{sup 1}, E{sup 2} are independently selected from the group consisting of Si(R{sup 9}){sub 2}, Si(R{sup 9}){sub 2}--Si(R{sup 9}){sub 2}, Ge(R{sup 9}){sub 2}, Sn(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}, C(R{sup 9}){sub 2}--C(R{sup 9}){sub 2}, where R{sup 9} is C{sub 1} to C{sub 10} alkyl, C{sub 6} to C{sub 15} aryl or C{sub 3} to C{sub 10} cycloalkyl; and the ligand may have C{sub S} or C{sub 1}-symmetry. Preferred metals are selected from the group consisting of group III, group IV, group V or lanthanide group elements. The catalysts are used to prepare stereoregular polymers including polypropylene from {alpha}-olefin monomers.

  1. Bacteria Inactivation During Lithotripsy

    NASA Astrophysics Data System (ADS)

    del Sol Quintero, María; Mora, Ulises; Gutiérrez, Jorge; Mues, Enrique; Castaño, Eduardo; Fernández, Francisco; Loske, Achim M.

    2006-09-01

    The influence of extracorporeal and intracorporeal lithotripsy on the viability of bacteria contained inside artificial kidney stones was investigated in vitro. Two different bacteria were exposed to the action of one extracorporeal shock wave generator and four intracorporeal lithotripters.

  2. CHAPTER IV-2 BACTERIA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Entomopathogenic bacteria provide an alternative to chemical pesticides used in insect control programs. Today, the principal microbial insecticides utilize spore forming bacteria or toxins produced by these bacteria as their active ingredients, either in formulations or by incorporation of toxin g...

  3. Bacteria-Targeting Nanoparticles for Managing Infections

    NASA Astrophysics Data System (ADS)

    Radovic-Moreno, Aleksandar Filip

    Bacterial infections continue to be a significant concern particularly in healthcare settings and in the developing world. Current challenges include the increasing spread of drug resistant (DR) organisms, the side effects of antibiotic therapy, the negative consequences of clearing the commensal bacterial flora, and difficulties in developing prophylactic vaccines. This thesis was an investigation of the potential of a class of polymeric nanoparticles (NP) to contribute to the management of bacterial infections. More specifically, steps were taken towards using these NPs (1) to achieve greater spatiotemporal control over drug therapy by more targeted antibiotic delivery to bacteria, and (2) to develop a prophylactic vaccine formulation against the common bacterial sexually transmitted disease (STD) caused by Chlamydia trachomatis. In the first part, we synthesized polymeric NPs containing poly(lactic-co-glycolic acid)-block-poly(L-histidine)-block-poly(ethylene glycol) (PLGA-PLH-PEG). We show that these NPs are able to bind to bacteria under model acidic infection conditions and are able to encapsulate and deliver vancomycin to inhibit the growth of Staphylococcus aureus bacteria in vitro. Further work showed that the PLGA-PLH-PEG-based NPs demonstrated the potential for competition for binding bacteria at a site of infection from soluble protein and model phagocytic and tissue-resident cells in a NP composition dependent manner. The NPs demonstrated low toxicity in vitro, were well tolerated by mice in vivo, and circulated in the blood on timescales comparable to control PLGA-PEG NPs. In the second part, we used PLGA-PLH-PEG-based NPs to design a prophylactic vaccine against the obligate intracellular bacterium Chlamydia trachomatis, the most common cause of bacterial STD in the world. Currently, no vaccines against this pathogen are approved for use in humans. We first formulated NPs encapsulating the TLR7 agonist R848 conjugated to poly(lactic acid) (R848-PLA

  4. Group transfer polymerization. Mechanism revisted

    SciTech Connect

    Sogah, D.Y.

    1993-12-31

    Group Transfer Polymerization (GTP) is a living polymerization technique that allows control of characteristics of vinyl polymers, especially those derived from methacrylate monomers. Several mechanistic pathways have been proposed by different research groups. This presentation will examine the most plausible mechanisms and the evidence supporting each one. The dependence of the reaction on the type, nature and concentrations of catalysts, other additives, initiators and monomers will be discussed. The crucial role that chiral organosilicon reagents may play will be examined using a novel cyclic initiator containing 2,2`-dialkylsilyl-1,1`-binaphthyl.

  5. Deactivator for olefin polymerization catalyst

    SciTech Connect

    Rekers, L.J.; Speca, A.N.; Mayhew, H.W.

    1987-03-10

    A method is described comprising deactivating an olefin polymerization catalyst selected from the group consisting of Ziegler-Natta transition element catalysts and catalysts based on transition metal oxides by contacting the catalyst with a copolymer. The copolymer consists of an alpha-olefin having from 2 to about 12 carbon atoms and an unsaturated ester of a carboxylic acid. The deactivating copolymer is present in an amount such that the molar ratio of the unsaturated ester thereof to the sum of the transition element component of the polymerization catalyst and a cocatalyst for the transition element catalyst is in the range of between about 0.1 and about 6.

  6. On-demand photoinitiated polymerization

    DOEpatents

    Boydston, Andrew J; Grubbs, Robert H; Daeffler, Chris; Momcilovic, Nebojsa

    2013-12-10

    Compositions and methods for adjustable lenses are provided. In some embodiments, the lenses contain a lens matrix material, a masking compound, and a prepolymer. The lens matrix material provides structure to the lens. The masking compound is capable of blocking polymerization or crosslinking of the prepolymer, until photoisomerization of the compound is triggered, and the compound is converted from a first isomer to a second isomer having a different absorption profile. The prepolymer is a composition that can undergo a polymerization or crosslinking reaction upon photoinitiation to alter one or more of the properties of the lenses.

  7. On-demand photoinitiated polymerization

    DOEpatents

    Boydston, Andrew J; Grubbs, Robert H; Daeffler, Chris; Momcilovic, Nebojsa

    2015-01-13

    Compositions and methods for adjustable lenses are provided. In some embodiments, the lenses contain a lens matrix material, a masking compound, and a prepolymer. The lens matrix material provides structure to the lens. The masking compound is capable of blocking polymerization or crosslinking of the prepolymer, until photoisomerization of the compound is triggered, and the compound is converted from a first isomer to a second isomer having a different absorption profile. The prepolymer is a composition that can undergo a polymerization or crosslinking reaction upon photoinitiation to alter one or more of the properties of the lenses.

  8. Thermal control of virulence factors in bacteria: A hot topic

    PubMed Central

    Lam, Oliver; Wheeler, Jun; Tang, Christoph M

    2014-01-01

    Pathogenic bacteria sense environmental cues, including the local temperature, to control the production of key virulence factors. Thermal regulation can be achieved at the level of DNA, RNA or protein and although many virulence factors are subject to thermal regulation, the exact mechanisms of control are yet to be elucidated in many instances. Understanding how virulence factors are regulated by temperature presents a significant challenge, as gene expression and protein production are often influenced by complex regulatory networks involving multiple transcription factors in bacteria. Here we highlight some recent insights into thermal regulation of virulence in pathogenic bacteria. We focus on bacteria which cause disease in mammalian hosts, which are at a significantly higher temperature than the outside environment. We outline the mechanisms of thermal regulation and how understanding this fundamental aspect of the biology of bacteria has implications for pathogenesis and human health. PMID:25494856

  9. Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates

    NASA Technical Reports Server (NTRS)

    Simpson, Joycely O. (Inventor); St.Clair, Terry L. (Inventor)

    1999-01-01

    A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers. acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors, in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors. weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 1000 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium; applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

  10. Adhesion controls bacterial actin polymerization-based movement.

    PubMed

    Soo, Frederick S; Theriot, Julie A

    2005-11-01

    As part of its infectious life cycle, the bacterial pathogen Listeria monocytogenes propels itself through the host-cell cytoplasm by triggering the polymerization of host-cell actin near the bacterial surface, harnessing the activity of several cytoskeletal proteins used during actin-based cell crawling. To distinguish among several classes of biophysical models of actin-based bacterial movement, we used a high-throughput tracking technique to record the movement of many individual bacteria during temperature shifts. The speed of each bacterium varied strongly with temperature, closely following the Arrhenius rate law. Among bacteria, the prefactor A of the Arrhenius dependence unexpectedly varied exponentially with apparent activation energy, E(a), over a wide range (8-21 kcal/mol), reminiscent of the "rate compensation effect" of classical catalytic reactions. Average E(a) were increased for mutant bacteria deficient in binding Ena/VASP proteins and bacteria moving in diluted extract. These two effects were additive. The observed temperature and rate compensation effects are consistent with a class of simple kinetic models in which the bacterium advances through the thermally driven, cooperative breakage of groups of adhesive bonds on its surface. The estimated number of coupled adhesive bonds N on the bacterial surface varies between 10 and 40 bonds. In contrast to other models, this model correctly predicts an experimentally observed negative correlation between bacterial speed and actin gel density. The idea that speed depends on adhesion, rather than polymerization, suggests several alternative mechanisms by which known cytoskeletal regulatory proteins could control cellular movement. PMID:16251274

  11. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

    1993-10-19

    A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

  12. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

    1992-05-19

    A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6]/hv.

  13. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, T.J.; Ijadi-Maghsooodi, S; Yi Pang.

    1993-10-19

    A polymeric material is described which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6].

  14. Nonlinear optical and conductive polymeric material

    DOEpatents

    Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

    1992-05-19

    A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

  15. Low vibration polymeric composite engine

    NASA Astrophysics Data System (ADS)

    Guimond, David P.; Muench, Rolf K.

    1994-12-01

    An internal combustion engine is constructed with metallic parts in its regions which are subjected to high stress (temperature, pressure) during combustion and polymeric materials in its regions which are subjected to relatively lower stresses. The integrated construction helps realize increased power densities and reductions on engine noise without compromising engine performance. V-configuration Diesel engines particularly benefit from this construction.

  16. Novel polymeric materials from triglycerides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Triglycerides are good platforms for new polymeric products that can substitute for petroleum-based materials. As part of our research emphasis in sustainability and green polymer chemistry, we have explored a number of reactions in efforts to produce a wide range of value-added products. In this ...

  17. Supramolecular polymerization: Living it up

    NASA Astrophysics Data System (ADS)

    Würthner, Frank

    2014-03-01

    Protein fibril formation is involved in many human diseases and thus has been mechanistically elucidated in the context of understanding -- and in turn treating -- them. This biological phenomenon has now also inspired the design of a supramolecular system that undergoes living polymerization.

  18. The Viscosity of Polymeric Fluids.

    ERIC Educational Resources Information Center

    Perrin, J. E.; Martin, G. C.

    1983-01-01

    To illustrate the behavior of polymeric fluids and in what respects they differ from Newtonian liquids, an experiment was developed to account for the shear-rate dependence of non-Newtonian fluids. Background information, procedures, and results are provided for the experiment. Useful in transport processes, fluid mechanics, or physical chemistry…

  19. The absorption of polymeric composites

    NASA Astrophysics Data System (ADS)

    Řídký, R.; Popovič, M.; Rolc, S.; Drdlová, M.; Krátký, J.

    2016-06-01

    An absorption capacity of soft, viscoelastic materials at high strain rates is important for wide range of practical applications. Nowadays there are many variants of numerical models suitable for this kind of analysis. The main difficulty is in selection of the most realistic numerical model and a correct setup of many unknown material constants. Cooperation between theoretical simulations and real testing is next crucial point in the investigation process. Standard open source material database offer material properties valid for strain rates less than 250 s-1. There are experiments suitable for analysis of material properties with strain rates close to 2000 s-1. The high strain-rate characteristics of a specific porous blast energy absorbing material measured by modified Split Hopkinson Pressure Bar apparatus is presented in this study. Testing these low impedance materials using a metallic split Hopkinson pressure bar setup results in poor signal to noise ratios due to impedance mismatching. These difficulties are overcome by using polymeric Hopkinson bars. Conventional Hopkinson bar analysis cannot be used on the polymeric bars due to the viscoelastic nature of the bar material. One of the possible solution leads to complex and frequency depended Young modulus of testing bars material. This testing technique was applied to materials composed of porous glass/ceramic filler and polymeric binder, with density of 125 - 300 kg/m3 and particle size in range of 50 µm - 2 mm. The achieved material model was verified in practical application of sandwich structure includes polymeric composites under a blast test.

  20. POLYMERIC INTERFACES FOR STACK MONITORING

    EPA Science Inventory

    Research has been performed on the use of polymeric interfaces for in situ continuous stack monitoring of gaseous pollutants. Permeabilities of candidate interface materials to SO2 were measured at temperatures from ambient to 200C, and the results were used to design interfaces ...

  1. Glycine Polymerization on Oxide Minerals

    NASA Astrophysics Data System (ADS)

    Kitadai, Norio; Oonishi, Hiroyuki; Umemoto, Koichiro; Usui, Tomohiro; Fukushi, Keisuke; Nakashima, Satoru

    2016-07-01

    It has long been suggested that mineral surfaces played an important role in peptide bond formation on the primitive Earth. However, it remains unclear which mineral species was key to the prebiotic processes. This is because great discrepancies exist among the reported catalytic efficiencies of minerals for amino acid polymerizations, owing to mutually different experimental conditions. This study examined polymerization of glycine (Gly) on nine oxide minerals (amorphous silica, quartz, α-alumina and γ-alumina, anatase, rutile, hematite, magnetite, and forsterite) using identical preparation, heating, and analytical procedures. Results showed that a rutile surface is the most effective site for Gly polymerization in terms of both amounts and lengths of Gly polymers synthesized. The catalytic efficiency decreased as rutile > anatase > γ-alumina > forsterite > α- alumina > magnetite > hematite > quartz > amorphous silica. Based on reported molecular-level information for adsorption of Gly on these minerals, polymerization activation was inferred to have arisen from deprotonation of the NH3 + group of adsorbed Gly to the nucleophilic NH2 group, and from withdrawal of electron density from the carboxyl carbon to the surface metal ions. The orientation of adsorbed Gly on minerals is also a factor influencing the Gly reactivity. The examination of Gly-mineral interactions under identical experimental conditions has enabled the direct comparison of various minerals' catalytic efficiencies and has made discussion of polymerization mechanisms and their relative influences possible Further systematic investigations using the approach reported herein (which are expected to be fruitful) combined with future microscopic surface analyses will elucidate the role of minerals in the process of abiotic peptide bond formation.

  2. Plasma polymerized carvone as an antibacterial and biocompatible coating.

    PubMed

    Chan, Yuen Wah; Siow, Kim Shyong; Ng, Pei Yuen; Gires, Usup; Yeop Majlis, Burhanuddin

    2016-11-01

    Antibacterial coating is important to prevent the colonization of medical devices by biofilm forming bacteria that would cause infection and sepsis in patients. Current coating techniques such as immobilization of antimicrobial compounds, time-releasing antibiotic agents and silver nanoparticles, require multiple processing steps, and they have low efficacy and low stability. We proposed a single-step plasma polymerization of an essential oil known as carvone to produce a moderately hydrophobic antibacterial coating (ppCar) with an average roughness of <1nm. ppCar had a static water contact angle of 78°, even after 10days of air aging and it maintained its stability throughout 24h of LB broth immersion. ppCar showed promising results in the live-dead fluorescence assay and crystal violet assay. The biofilm assay showed an effective reduction of E. coli and S. aureus bacteria by 86% and 84% respectively. ppCar is also shown to rupture the bacteria membrane for its bactericidal effects. The cytotoxicity test indicated that the coating is not cytotoxic to the human cell line. This study would be of interest to researcher keen on producing a bacteria-resistance and biocompatible coating on different substrates in a cost-effective manner. PMID:27524089

  3. Actin polymerization is stimulated by actin cross-linking protein palladin.

    PubMed

    Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G; Orlova, Albina; Egelman, Edward H; Beck, Moriah R

    2016-02-15

    The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the co-ordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. In the present study, we show that the actin-binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro cross-linking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of globular or monomeric actin (G-actin), akin to metal ions, either through charge neutralization or through conformational changes. PMID:26607837

  4. Polymeric N-halamine latex emulsions for use in antimicrobial paints.

    PubMed

    Cao, Zhengbing; Sun, Yuyu

    2009-02-01

    A new N-halamine monomer, N-chloro-2,2,6,6-tetramethyl-4-piperidinyl methacrylate (Cl-TMPM), was synthesized and used to prepare water-based polymeric N-halamines by emulsion polymerization. The chemical structures of the samples were characterized with Fourier transform IR, (13)C NMR, UV/vis, and differential scanning calorimetry analyses. Upon the addition of a small amount of the polymeric N-halamine latex emulsions into commercial water-based latex paints as antimicrobial additives, the new paints provided potent antimicrobial activities against Staphylococcus aureus (S. aureus; Gram-positive bacteria), methicillin-resistant S. aureus (MRSA; drug-resistant Gram-positive bacteria), vancomycin-resistant enterococcus (VRE; drug-resistant Gram-positive bacteria), Escherichia coli (E. coli; Gram-negative bacteria), Candida tropicalis (C. tropicalis; fungi), MS2 virus (15597-B; virus), and Stachybotrys chartarum spore (S. chartarum; mold), and they successfully prevented biofilm formation and development. The antimicrobial functions of the new paints were long-lasting for more than 1 year under normal in-use conditions, easily monitorable by a simple potassium iodine/starch test, and readily rechargeable if the functions were accidentally lost as a result of challenging conditions such as heavy soil, flooding, etc. PMID:20353242

  5. SUMO chains: polymeric signals.

    PubMed

    Vertegaal, Alfred C O

    2010-02-01

    Ubiquitin and ubiquitin-like proteins are conjugated to a wide variety of target proteins that play roles in all biological processes. Target proteins are conjugated to ubiquitin monomers or to ubiquitin polymers that form via all seven internal lysine residues of ubiquitin. The fate of these target proteins is controlled in a chain architecture-dependent manner. SUMO (small ubiquitin-related modifier) shares the ability of ubiquitin to form chains via internal SUMOylation sites. Interestingly, a SUMO-binding site in Ubc9 is important for SUMO chain synthesis. Similar to ubiquitin-polymer cleavage by USPs (ubiquitin-specific proteases), SUMO chain formation is reversible. SUMO polymers are cleaved by the SUMO proteases SENP6 [SUMO/sentrin/SMT3 (suppressor of mif two 3)-specific peptidase 6], SENP7 and Ulp2 (ubiquitin-like protease 2). SUMO chain-binding proteins including ZIP1, SLX5/8 (synthetic lethal of unknown function 5/8), RNF4 (RING finger protein 4) and CENP-E (centromere-associated protein E) have been identified that interact non-covalently with SUMO chains, thereby regulating target proteins that are conjugated to SUMO multimers. SUMO chains play roles in replication, in the turnover of SUMO targets by the proteasome and during mitosis and meiosis. Thus signalling via polymers is an exciting feature of the SUMO family. PMID:20074033

  6. A structured interdomain linker directs self-polymerization of human uromodulin

    PubMed Central

    Bokhove, Marcel; Nishimura, Kaoru; Brunati, Martina; Han, Ling; de Sanctis, Daniele; Rampoldi, Luca

    2016-01-01

    Uromodulin (UMOD)/Tamm–Horsfall protein, the most abundant human urinary protein, plays a key role in chronic kidney diseases and is a promising therapeutic target for hypertension. Via its bipartite zona pellucida module (ZP-N/ZP-C), UMOD forms extracellular filaments that regulate kidney electrolyte balance and innate immunity, as well as protect against renal stones. Moreover, salt-dependent aggregation of UMOD filaments in the urine generates a soluble molecular net that captures uropathogenic bacteria and facilitates their clearance. Despite the functional importance of its homopolymers, no structural information is available on UMOD and how it self-assembles into filaments. Here, we report the crystal structures of polymerization regions of human UMOD and mouse ZP2, an essential sperm receptor protein that is structurally related to UMOD but forms heteropolymers. The structure of UMOD reveals that an extensive hydrophobic interface mediates ZP-N domain homodimerization. This arrangement is required for filament formation and is directed by an ordered ZP-N/ZP-C linker that is not observed in ZP2 but is conserved in the sequence of deafness/Crohn’s disease-associated homopolymeric glycoproteins α-tectorin (TECTA) and glycoprotein 2 (GP2). Our data provide an example of how interdomain linker plasticity can modulate the function of structurally similar multidomain proteins. Moreover, the architecture of UMOD rationalizes numerous pathogenic mutations in both UMOD and TECTA genes. PMID:26811476

  7. Genomics of Probiotic Bacteria

    NASA Astrophysics Data System (ADS)

    O'Flaherty, Sarah; Goh, Yong Jun; Klaenhammer, Todd R.

    Probiotic bacteria from the Lactobacillus and Bifidobacterium species belong to the Firmicutes and the Actinobacteria phylum, respectively. Lactobacilli are members of the lactic acid bacteria (LAB) group, a broadly defined family of microorganisms that ferment various hexoses into primarily lactic acid. Lactobacilli are typically low G + C gram-positive species which are phylogenetically diverse, with over 100 species documented to date. Bifidobacteria are heterofermentative, high G + C content bacteria with about 30 species of bifidobacteria described to date.

  8. Peptide conversations in Gram-positive bacteria.

    PubMed

    Monnet, Véronique; Juillard, Vincent; Gardan, Rozenn

    2016-05-01

    Within Gram-positive bacteria, the expression of target genes is controlled at the population level via signaling peptides, also known as pheromones. Pheromones control a wide range of functions, including competence, virulence, and others that remain unknown. Until now, their role in bacterial gene regulation has probably been underestimated; indeed, bacteria are able to produce, by ribosomal synthesis or surface protein degradation, an extraordinary variety of peptides which are released outside bacteria and among which, some are pheromones that mediate cell-to-cell communication. The review aims at giving an updated overview of these peptide-dependant communication pathways. More specifically, it follows the whole peptide circuit from the peptide production and secretion in the extracellular medium to its interaction with sensors at bacterial surface or re-import into the bacteria where it plays its regulation role. In recent years, as we have accumulated more knowledge about these systems, it has become apparent that they are more complex than they first appeared. For this reason, more research on peptide-dependant pathways is needed to develop new strategies for controlling functions of interest in Gram-positive bacteria. In particular, such research could lead to alternatives to the use of antibiotics against pathogenic bacteria. In perspective, the review identifies new research questions that emerge in this field and that have to be addressed. PMID:25198780

  9. Polymeric Nanofibers in Tissue Engineering

    PubMed Central

    Dahlin, Rebecca L.; Kasper, F. Kurtis

    2011-01-01

    Polymeric nanofibers can be produced using methods such as electrospinning, phase separation, and self-assembly, and the fiber composition, diameter, alignment, degradation, and mechanical properties can be tailored to the intended application. Nanofibers possess unique advantages for tissue engineering. The small diameter closely matches that of extracellular matrix fibers, and the relatively large surface area is beneficial for cell attachment and bioactive factor loading. This review will update the reader on the aspects of nanofiber fabrication and characterization important to tissue engineering, including control of porous structure, cell infiltration, and fiber degradation. Bioactive factor loading will be discussed with specific relevance to tissue engineering. Finally, applications of polymeric nanofibers in the fields of bone, cartilage, ligament and tendon, cardiovascular, and neural tissue engineering will be reviewed. PMID:21699434

  10. Metal containing polymeric functional microspheres

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Rembaum, Alan (Inventor); Molday, Robert S. (Inventor)

    1979-01-01

    Polymeric functional microspheres containing metal or metal compounds are formed by addition polymerization of a covalently bondable olefinic monomer such as hydroxyethylmethacrylate in the presence of finely divided metal or metal oxide particles, such as iron, gold, platinum or magnetite, which are embedded in the resulting microspheres. The microspheres can be covalently bonded to chemotherapeutic agents, antibodies, or other proteins providing a means for labeling or separating labeled cells. Labeled cells or microspheres can be concentrated at a specific body location such as in the vicinity of a malignant tumor by applying a magnetic field to the location and then introducing the magnetically attractable microspheres or cells into the circulatory system of the subject. Labeled cells can be separated from a cell mixture by applying a predetermined magnetic field to a tube in which the mixture is flowing. After collection of the labeled cells, the magnetic field is discontinued and the labeled sub-cell population recovered.

  11. Polymeric cationic substituted acrylamide surfactants

    SciTech Connect

    Nieh, E.C.Y.

    1983-11-15

    A new composition of matter comprises a copolymer of a surface active quaternary ammonium monomer salt and from 50 to 97% by wt of acrylamide. The new copolymers can have molecular weights substantially greater than 10,000 and still remain water soluble and surface active. Copolymers are prepared by polymerization techniques known in the art. The quaternary ammonium monomer is dispersed under inert atmosphere in aqueous solution which may additionally contain dissolved therein a low molecular weight alcohol such as ethanol, isopropanol, and the like. Acidic polymerization initiator such as the azo initiators, organic peroxides, or redox initiators such as the sulfite- persulfate system is then added in an amount calculated to yield a polymer product of desired molecular weight. (14 claims.

  12. Concurrent Covalent and Supramolecular Polymerization.

    PubMed

    Hou, Xisen; Ke, Chenfeng; Zhou, Yu; Xie, Zhuang; Alngadh, Ahmed; Keane, Denis T; Nassar, Majed S; Botros, Youssry Y; Mirkin, Chad A; Stoddart, J Fraser

    2016-08-22

    Covalent and supramolecular polymerizations, both of which offer their own unique advantages, have emerged as popular strategies for making artificial materials. Herein, we describe a concurrent covalent and supramolecular polymerization strategy-namely, one which utilizes 1) a bis-azide-functionalized diazaperopyrenium dication that undergoes polymeriation covalently with a bis-alkyne-functionalized biphenyl derivative in one dimension as a result of a rapid and efficient β-cyclodextrin(CD)-accelerated, cucurbit[6]uril(CB)-templated azide-alkyne cycloaddition, while 2) the aromatic core of the dication is able to dimerize in a criss-cross fashion by dint of π-π interactions, enabling simultaneous supramolecular assembly, resulting in an extended polymer network in an orthogonal dimension. PMID:27338246

  13. Radiation-hardened polymeric films

    DOEpatents

    Arnold, C. Jr.; Hughes, R.C.; Kepler, R.G.; Kurtz, S.R.

    1984-07-16

    The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10/sup 15/ to 10/sup 21/ molecules of dopant/cm/sup 3/. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

  14. Electrochemical polymerization of pyrrole derivatives

    SciTech Connect

    Inagaki, T.; Hunter, M.; Yang, X.Q.; Skotheim, T.A.; Lee, H.S.; Okamoto, Y.

    1988-01-01

    Electrochemical copolymerization of pyrrole and 3-(6-ferrocenyl-6-hydroxyhexyl)pyrrole (P-Fc) yields a ferrocene functionalized polypyrrole with a controlled amount of ferrocene functionalization. Similarly, copolymers of pyrrole and 3-(4-(2,5- dimethoxyphenyl)butyl)pyrrole (P-MP) can be made by electrochemical polymerization and converted to the copolymers containing pH dependent electroactive hydroquinone moieties. 16 refs., 6 figs.

  15. Radiation-hardened polymeric films

    DOEpatents

    Arnold, Jr., Charles; Hughes, Robert C.; Kepler, R. Glen; Kurtz, Steven R.

    1986-01-01

    The radiation-induced conductivity of polymeric dielectrics with low electronic mobility is reduced by doping with electron donor or electron acceptor compounds at a level of 10.sup.15 to 10.sup.21 molecules of dopant/cm.sup.3. Polyesters, polyolefins, perfluoropolyolefins, vinyl polymers, vinylidene polymers, polycarbonates, polysulfones and polyimides can benefit from such a treatment. Usable dopants include 2,4,7-trinitro-9-fluorenone, tetracyanethylene, 7,7,8,8-tetracyanoquinodimethane, m-dinitrobenzene, 2-isopropylcarbazole, and triphenylamine.

  16. Alcohol polymerization using electron emission

    NASA Astrophysics Data System (ADS)

    Matsuura, Hiroshi; Tanikawa, Tamio; Takaba, Hiromitsu; Fujiwara, Yutaka

    2004-04-01

    We report a means of instantaneous alcohol polymerization using electron emission at room temperature. We selected 1-butanol as a source of alcohol polymer. A 1-butanol molecule has a simple molecular structure and is a good candidate for analyzing reaction mechanisms. Direct electron emission onto the surface of volatile 1-butanol prevented intense discharge and gently composed 1-butanol-polymer at room temperature in air. The strategy enabled exciting liquids and instantaneously composing new materials at room temperature.

  17. Two Photon Polymerization of Ormosils

    NASA Astrophysics Data System (ADS)

    Matei, A.; Zamfirescu, M.; Jipa, F.; Luculescu, C.; Dinescu, M.; Buruiana, E. C.; Buruiana, T.; Sima, L. E.; Petrescu, S. M.

    2010-10-01

    In this work, 3D structures of hybrid polymers—ORMOSILS (organically modified silicates) were produced via Two Photon Polymerization (2PP) of hybrid methacrylates based on silane derivates. Synthetic routes have been used to obtain series of hybrid monomers, their structure and purity being checked by NMR Spectroscopy and Fourier Transform Infrared Spectroscopy. Two photon polymerization method (a relatively new technology which allows fast micro and nano processing of three-dimensional structures with application in medical devices, tissue scaffolds, photonic crystals etc) was used for monomers processing. As laser a Ti: Sapphire laser was used, with 200 fs pulse duration and 2 kHz repetition rate, emitting at 775 nm. A parametric study on the influence of the processing parameters (laser fluence, laser scanning velocity, photo initiator) on the written structures was carried out. The as prepared polymeric scaffolds were tested in mesenchymal stem cells and fibroblasts cell cultures, with the aim of further obtaining bone and dermal grafts. Cells morphology, proliferation, adhesion and alignment were analyzed for different experimental conditions.

  18. Bleach vs. Bacteria

    MedlinePlus

    ... Inside Life Science > Bleach vs. Bacteria Inside Life Science View All Articles | Inside Life Science Home Page Bleach vs. Bacteria By Sharon Reynolds ... For Proteins, Form Shapes Function This Inside Life Science article also appears on LiveScience . Learn about related ...

  19. Bacteria turn tiny gears

    SciTech Connect

    2009-01-01

    Swarms of bacteria turn two 380-micron long gears, opening the possibility of building hybrid biological machines at the microscopic scale. Read more at Wired: http://www.wired.com/wiredscience/2009/12/bacterial-micro-machine/#more-15684 or Scientific American: http://www.scientificamerican.com/article.cfm?id=brownian-motion-bacteria

  20. Ultrasound-Mediated Polymeric Micelle Drug Delivery.

    PubMed

    Xia, Hesheng; Zhao, Yue; Tong, Rui

    2016-01-01

    The synthesis of multi-functional nanocarriers and the design of new stimuli-responsive means are equally important for drug delivery. Ultrasound can be used as a remote, non-invasive and controllable trigger for the stimuli-responsive release of nanocarriers. Polymeric micelles are one kind of potential drug nanocarrier. By combining ultrasound and polymeric micelles, a new modality (i.e., ultrasound-mediated polymeric micelle drug delivery) has been developed and has recently received increasing attention. A major challenge remaining in developing ultrasound-responsive polymeric micelles is the improvement of the sensitivity or responsiveness of polymeric micelles to ultrasound. This chapter reviews the recent advance in this field. In order to understand the interaction mechanism between ultrasound stimulus and polymeric micelles, ultrasound effects, such as thermal effect, cavitation effect, ultrasound sonochemistry (including ultrasonic degradation, ultrasound-initiated polymerization, ultrasonic in-situ polymerization and ultrasound site-specific degradation), as well as basic micellar knowledge are introduced. Ultrasound-mediated polymeric micelle drug delivery has been classified into two main streams based on the different interaction mechanism between ultrasound and polymeric micelles; one is based on the ultrasound-induced physical disruption of the micelle and reversible release of payload. The other is based on micellar ultrasound mechanochemical disruption and irreversible release of payload. PMID:26486348

  1. Polymerization rate and mechanism of ultrasonically initiated emulsion polymerization of n-butyl acrylate.

    PubMed

    Xia, Hesheng; Wang, Qi; Liao, Yongqin; Xu, Xi; Baxter, Steven M; Slone, Robert V; Wu, Shuguang; Swift, Graham; Westmoreland, David G

    2002-07-01

    The factors affecting the induction period and polymerization rate in ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) were investigated. The induction period takes only an instant in ultrasonically initiated emulsion polymerization of BA without any added initiator by enhancing the N2 flow rate. Increasing temperature, power output and SDS concentration, decreasing the monomer concentration results in further decreasing induction period and enhanced polymerization rate. Under optimized reaction conditions the conversion of BA reaches 92% in 11 min. The polymerization rate can be controlled by varying reaction parameters. The apparatus of ultrasonically initiated semi-continuous and continuous emulsion polymerization were set up and the feasibility was first studied. Based on the experimental results, a free radical polymerization mechanism for ultrasonically initiated emulsion polymerization was proposed, including the sources of the radicals, the process of radical formation, the locus of polymerization and the polymerization process. Compared with conventional emulsion polymerization, where the radicals come from thermal decomposition of a chemical initiator, ultrasonically initiated emulsion polymerization has attractive features such as no need for a chemical initiator, lower reaction temperature, faster polymerization rate, and higher molecular weight of the polymer prepared. PMID:12154689

  2. Controlled release of ethylene via polymeric films for food packaging

    NASA Astrophysics Data System (ADS)

    Pisano, Roberto; Bazzano, Marco; Capozzi, Luigi Carlo; Ferri, Ada; Sangermano, Marco

    2015-12-01

    In modern fruit supply chain a common method to trigger ripening is to keep fruits inside special chambers and initiate the ripening process through administration of ethylene. Ethylene is usually administered through cylinders with inadequate control of its final concentration in the chamber. The aim of this study is the development of a new technology to accurately regulate ethylene concentration in the atmosphere where fruits are preserved: a polymeric film, containing an inclusion complex of α-cyclodextrin with ethylene, was developed. The complex was prepared by molecular encapsulation which allows the entrapment of ethylene into the cavity of α-cyclodextrin. After encapsulation, ethylene can be gradually released from the inclusion complex and its release rate can be regulated by temperature and humidity. The inclusion complex was dispersed into a thin polymeric film produced by UV-curing. This method was used because is solvent-free and involves low operating temperature; both conditions are necessary to prevent rapid release of ethylene from the film. The polymeric films were characterized with respect to thermal behaviour, crystalline structure and kinetics of ethylene release, showing that can effectively control the release of ethylene within confined volume.

  3. Inactivation of biofilm bacteria.

    PubMed Central

    LeChevallier, M W; Cawthon, C D; Lee, R G

    1988-01-01

    The current project was developed to examine inactivation of biofilm bacteria and to characterize the interaction of biocides with pipe surfaces. Unattached bacteria were quite susceptible to the variety of disinfectants tested. Viable bacterial counts were reduced 99% by exposure to 0.08 mg of hypochlorous acid (pH 7.0) per liter (1 to 2 degrees C) for 1 min. For monochloramine, 94 mg/liter was required to kill 99% of the bacteria within 1 min. These results were consistent with those found by other investigators. Biofilm bacteria grown on the surfaces of granular activated carbon particles, metal coupons, or glass microscope slides were 150 to more than 3,000 times more resistant to hypochlorous acid (free chlorine, pH 7.0) than were unattached cells. In contrast, resistance of biofilm bacteria to monochloramine disinfection ranged from 2- to 100-fold more than that of unattached cells. The results suggested that, relative to inactivation of unattached bacteria, monochloramine was better able to penetrate and kill biofilm bacteria than free chlorine. For free chlorine, the data indicated that transport of the disinfectant into the biofilm was a major rate-limiting factor. Because of this phenomenon, increasing the level of free chlorine did not increase disinfection efficiency. Experiments where equal weights of disinfectants were used suggested that the greater penetrating power of monochloramine compensated for its limited disinfection activity. These studies showed that monochloramine was as effective as free chlorine for inactivation of biofilm bacteria. The research provides important insights into strategies for control of biofilm bacteria. Images PMID:2849380

  4. Quality control of residual solvent content in polymeric microparticles.

    PubMed

    Dixit, Kalpana; Athawale, Rajani B; Singh, Sarabjit

    2015-01-01

    Organic solvents are the innate part of pharmaceutical industry, playing vital role in the bulk drug substance as well as finished product manufacturing. Even though they are used for various crucial purposes, they still lack therapeutic beneficial effect and can be toxic if present in unacceptable limits in final product. Hence, their concentration must be regulated in the final pharmaceutical formulation. With the major development in the market of polymeric microparticles in past few decades, drug product manufacturers are paying more attention towards the development of new techniques for reducing residual solvent content of microparticles. This article sheds light on the importance of removal of organic volatile impurities from the formulation and its regulatory aspects. It also highlights how residual solvent affects various physicochemical characteristics of polymeric microparticles and suggests certain solutions as per the current state of art for limiting organic solvent content in the final product. PMID:25560934

  5. Induction of HoxB Transcription by Retinoic Acid Requires Actin Polymerization

    PubMed Central

    Ferrai, Carmelo; Naum-Onganía, Gabriela; Longobardi, Elena; Palazzolo, Martina; Disanza, Andrea; Diaz, Victor M.; Crippa, Massimo P.; Scita, Giorgio

    2009-01-01

    We have analyzed the role of actin polymerization in retinoic acid (RA)-induced HoxB transcription, which is mediated by the HoxB regulator Prep1. RA induction of the HoxB genes can be prevented by the inhibition of actin polymerization. Importantly, inhibition of actin polymerization specifically affects the transcription of inducible Hox genes, but not that of their transcriptional regulators, the RARs, nor of constitutively expressed, nor of actively transcribed Hox genes. RA treatment induces the recruitment to the HoxB2 gene enhancer of a complex composed of “elongating” RNAPII, Prep1, β-actin, and N-WASP as well as the accessory splicing components p54Nrb and PSF. We show that inhibition of actin polymerization prevents such recruitment. We conclude that inducible Hox genes are selectively sensitive to the inhibition of actin polymerization and that actin polymerization is required for the assembly of a transcription complex on the regulatory region of the Hox genes. PMID:19477923

  6. Induction of HoxB transcription by retinoic acid requires actin polymerization.

    PubMed

    Ferrai, Carmelo; Naum-Onganía, Gabriela; Longobardi, Elena; Palazzolo, Martina; Disanza, Andrea; Diaz, Victor M; Crippa, Massimo P; Scita, Giorgio; Blasi, Francesco

    2009-08-01

    We have analyzed the role of actin polymerization in retinoic acid (RA)-induced HoxB transcription, which is mediated by the HoxB regulator Prep1. RA induction of the HoxB genes can be prevented by the inhibition of actin polymerization. Importantly, inhibition of actin polymerization specifically affects the transcription of inducible Hox genes, but not that of their transcriptional regulators, the RARs, nor of constitutively expressed, nor of actively transcribed Hox genes. RA treatment induces the recruitment to the HoxB2 gene enhancer of a complex composed of "elongating" RNAPII, Prep1, beta-actin, and N-WASP as well as the accessory splicing components p54Nrb and PSF. We show that inhibition of actin polymerization prevents such recruitment. We conclude that inducible Hox genes are selectively sensitive to the inhibition of actin polymerization and that actin polymerization is required for the assembly of a transcription complex on the regulatory region of the Hox genes. PMID:19477923

  7. Biofilm Matrix and Its Regulation in Pseudomonas aeruginosa

    PubMed Central

    Wei, Qing; Ma, Luyan Z.

    2013-01-01

    Biofilms are communities of microorganisms embedded in extracellular polymeric substances (EPS) matrix. Bacteria in biofilms demonstrate distinct features from their free-living planktonic counterparts, such as different physiology and high resistance to immune system and antibiotics that render biofilm a source of chronic and persistent infections. A deeper understanding of biofilms will ultimately provide insights into the development of alternative treatment for biofilm infections. The opportunistic pathogen Pseudomonas aeruginosa, a model bacterium for biofilm research, is notorious for its ability to cause chronic infections by its high level of drug resistance involving the formation of biofilms. In this review, we summarize recent advances in biofilm formation, focusing on the biofilm matrix and its regulation in P. aeruginosa, aiming to provide resources for the understanding and control of bacterial biofilms. PMID:24145749

  8. Multidrug Resistance in Bacteria

    PubMed Central

    Nikaido, Hiroshi

    2010-01-01

    Large amounts of antibiotics used for human therapy, as well as for farm animals and even for fish in aquaculture, resulted in the selection of pathogenic bacteria resistant to multiple drugs. Multidrug resistance in bacteria may be generated by one of two mechanisms. First, these bacteria may accumulate multiple genes, each coding for resistance to a single drug, within a single cell. This accumulation occurs typically on resistance (R) plasmids. Second, multidrug resistance may also occur by the increased expression of genes that code for multidrug efflux pumps, extruding a wide range of drugs. This review discusses our current knowledge on the molecular mechanisms involved in both types of resistance. PMID:19231985

  9. Antibiotics from predatory bacteria

    PubMed Central

    Korp, Juliane; Vela Gurovic, María S

    2016-01-01

    Summary Bacteria, which prey on other microorganisms, are commonly found in the environment. While some of these organisms act as solitary hunters, others band together in large consortia before they attack their prey. Anecdotal reports suggest that bacteria practicing such a wolfpack strategy utilize antibiotics as predatory weapons. Consistent with this hypothesis, genome sequencing revealed that these micropredators possess impressive capacities for natural product biosynthesis. Here, we will present the results from recent chemical investigations of this bacterial group, compare the biosynthetic potential with that of non-predatory bacteria and discuss the link between predation and secondary metabolism. PMID:27340451

  10. Antibiotics from predatory bacteria.

    PubMed

    Korp, Juliane; Vela Gurovic, María S; Nett, Markus

    2016-01-01

    Bacteria, which prey on other microorganisms, are commonly found in the environment. While some of these organisms act as solitary hunters, others band together in large consortia before they attack their prey. Anecdotal reports suggest that bacteria practicing such a wolfpack strategy utilize antibiotics as predatory weapons. Consistent with this hypothesis, genome sequencing revealed that these micropredators possess impressive capacities for natural product biosynthesis. Here, we will present the results from recent chemical investigations of this bacterial group, compare the biosynthetic potential with that of non-predatory bacteria and discuss the link between predation and secondary metabolism. PMID:27340451

  11. Anionic polymerization of azo substituted methacrylates

    SciTech Connect

    Dimov, D.K.; Dalton, L.R.; Hogen-Esch, T.E.

    1993-12-31

    The anionic polymerization of 4-phenylazophenyl methacrylate (PAM) and 6-(4-phenylazophenoxy)-hexyl methacrylate (PAHM) initiated by {open_quotes}living{close_quotes} PMMA with lithium counterion was studied in THF at {minus}78{degrees}C. The polymerization of PAM was prevented by a side termination reaction. The polymerization of PAHM proceeded smoothly to furnish PMMA/azopolymer block copolymers. The process showed features typical of {open_quotes}living{close_quotes} anionic polymerization. No phase transitions could be detected by DSC to prove liquid crystalline mesophase formation by the block copolymers.

  12. Ketoprofen as a photoinitiator for anionic polymerization.

    PubMed

    Wang, Yu-Hsuan; Wan, Peter

    2015-06-01

    A new photoinitiating system for anionic polymerization of acrylates based on the efficient photodecarboxylation of Ketoprofen (1) and the related derivatives 3 and 4 that generate the corresponding carbanion intermediates is presented. Carbanion intermediates are confirmed by deuterium incorporation in the trapped Michael adducts and by spectroscopic detection using laser flash photolysis (LFP). This novel anionic initiating system features excitation in the near UV and visible regions, potential characteristics of photocontrolled living polymerization, and metal-free photoinitiators generated from photoexcitation, different from typical anionic polymerization where the polymerizations are initiated by heat and strong base containing alkali metals. PMID:25917384

  13. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, Douglas B.; Shahinpoor, Mohsen; Segalman, Daniel J.; Witkowski, Walter R.

    1993-01-01

    Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots.

  14. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

    1993-10-05

    Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

  15. Ionene modified small polymeric beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor)

    1977-01-01

    Linear ionene polyquaternary cationic polymeric segments are bonded by means of the Menshutkin reaction (quaternization) to biocompatible, extremely small, porous particles containing halide or tertiary amine sites which are centers for attachment of the segments. The modified beads in the form of emulsions or suspensions offer a large, positively-charged surface area capable of irreversibly binding polyanions such as heparin, DNA, RNA or bile acids to remove them from solution or of reversibly binding monoanions such as penicillin, pesticides, sex attractants and the like for slow release from the suspension.

  16. Polymerized nanotube structures new zeolites?

    NASA Astrophysics Data System (ADS)

    Chernozatonskii, Leonid A.

    1998-11-01

    Polymers of single-wall carbon nanotubes - possible new zeolites - are modeled by molecular mechanics (MM2 calculation method). The polymerization at issue occurs by bonding of 6 sp 3 atomic pairs in each nanotube unit cell with similar atomic pairs located on 6 neighboring tubes like 2+2 cycloaddition in a rhombic two-dimensional C 60 polymer. It is shown these bonding in armchair ( n, n) SWNT ropes ( n=6, 8, 10, 12) changes positive radial curvature of tube segments to a negative one.

  17. Computational studies of polymeric systems

    NASA Astrophysics Data System (ADS)

    Carrillo, Jan-Michael Y.

    Polymeric systems involving polyelectrolytes in surfaces and interfaces, semiflexible polyelectrolytes and biopolymers in solution, complex polymeric systems that had applications in nanotechnology were modeled using coarse grained molecular dynamics simulation. In the area of polyelectrolytes in surfaces and interfaces, the phenomena of polyelectrolyte adsorption at oppositely charge surface was investigated. Simulations found that short range van der Waals interaction was a major factor in determining morphology and thickness of the adsorbed layer. Hydrophobic polyelectrolytes adsorbed in hydrophobic surfaces tend to be the most effective in forming multi-layers because short range attraction enhances the adsorption process. Adsorbed polyelectrolytes could move freely along the surface which was in contrast to polyelectrolyte brushes. The morphologies of hydrophobic polyelectrolyte brushes were investigated and simulations found that brushes had different morphologies depending on the strength of the short range monomer-monomer attraction, electrostatic interaction and counterion condensation. Planar polyelectrolyte brushes formed: (1) vertically oriented cylindrical aggregates, (2) maze-like aggregate structures, or (3) thin polymeric layer covering a substrate. While, the spherical polyelectrolyte brushes could be in any of the previous morphologies or be in a micelle-like conformation with a dense core and charged corona. In the area of biopolymers and semiflexible polyelectrolytes in solution, simulations demonstrated that the bending rigidity of these polymers was scale-dependent. The bond-bond correlation function describing a chain's orientational memory could be approximated by a sum of two exponential functions manifesting the existence of the two characteristic length scales. The existence of the two length scales challenged the current practice of describing chain stretching experiments using a single length scale. In the field of nanotechnology

  18. Marketing NASA Langley Polymeric Materials

    NASA Technical Reports Server (NTRS)

    Flynn, Diane M.

    1995-01-01

    A marketing tool was created to expand the knowledge of LaRC developed polymeric materials, in order to facilitate the technology transfer process and increase technology commercialization awareness among a non-technical audience. The created brochure features four materials, LaRC-CP, LaRC-RP46, LaRC-SI, and LaRC-IA, and highlights their competitive strengths in potential commercial applications. Excellent opportunities exist in the $40 million per year microelectronics market and the $6 billion adhesives market. It is hoped that the created brochure will generate inquiries regarding the use of the above materials in markets such as these.

  19. Effects of inulin chain length on fermentation by equine fecal bacteria and Streptococcus bovis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fructans from pasture can be fermented by Gram-positive bacteria (e.g., Streptococcus bovis) in the equine hindgut, increasing production of lactic acid and decreasing pH. The degree of polymerization (DP) of fructans has been suggested to influence fermentation rates. The objective of the current ...

  20. Durable Nanolayer Graft Polymerization of Functional Finishes Using Atmospheric Plasma

    NASA Astrophysics Data System (ADS)

    Mazloumpour, Maryam

    . Furthermore, spunbond nonwoven polypropylene fabric, commonly used for hygienic products, was treated with diallyldimethylammonium chloride (DADMAC). Atmospheric pressure glow discharge plasma was used to induce free radical chain polymerization of the ADMAC monomer, which conferred a graft polymerized network on the fabric with durable antimicrobial properties. The effect of different DADMAC concentration, and plasma conditions including the RF power and the time of plasma exposure were studied and the optimum treatment conditions were identified by calculating the surface charge density on the treated fabrics. The presence of poly-DADMAC on the polypropylene surface was confirmed using SEM, FT-IR and TOF-SIMS. Antibacterial performance was investigated using standard test methods (AATCC TM 100) for both gram positive and gram negative bacteria. The antimicrobial results showed 6 log reductions in the bacterial activities of K. pneumoniae and S .aureus, which was unprecedented using a plasma-induced graft polymerization approach.

  1. Toxicity: Polymeric materials in food-contact applications. January 1977-September 1989 (Citations from the Rubber and Plastics Research Association data base). Report for January 1977-September 1989

    SciTech Connect

    Not Available

    1989-09-01

    This bibliography contains citations concerning toxicity investigations of polymeric materials in food-contact applications. Polymeric food-packaging materials and regulations are discussed. Toxicity testing, polymeric equipment in food processing, and the use of additives in food packaging are included. Discussions also include coating materials for food containers and pigments for food packaging films. (This updated bibliography contains 275 citations, 10 of which are new entries to the previous edition.)

  2. Self-folding polymeric containers for encapsulation and delivery of drugs

    PubMed Central

    Fernandes, Rohan; Gracias, David H.

    2012-01-01

    Self-folding broadly refers to self-assembly processes wherein thin films or interconnected planar templates curve, roll-up or fold into three dimensional (3D) structures such as cylindrical tubes, spirals, corrugated sheets or polyhedra. The process has been demonstrated with metallic, semiconducting and polymeric films and has been used to curve tubes with diameters as small as 2 nm and fold polyhedra as small as 100 nm, with a surface patterning resolution of 15 nm. Self-folding methods are important for drug delivery applications since they provide a means to realize 3D, biocompatible, all-polymeric containers with well-tailored composition, size, shape, wall thickness, porosity, surface patterns and chemistry. Self-folding is also a highly parallel process, and it is possible to encapsulate or self-load therapeutic cargo during assembly. A variety of therapeutic cargos such as small molecules, peptides, proteins, bacteria, fungi and mammalian cells have been encapsulated in self-folded polymeric containers. In this review, we focus on self-folding of all-polymeric containers. We discuss the mechanistic aspects of self-folding of polymeric containers driven by differential stresses or surface tension forces, the applications of self-folding polymers in drug delivery and we outline future challenges. PMID:22425612

  3. Polymeric microfluidic devices for the monitoring and separation of water-borne pathogens utilizing insulative dielectrophoresis

    NASA Astrophysics Data System (ADS)

    McGraw, Greg J.; Davalos, Rafael V.; Brazzle, John D.; Hachman, John T.; Hunter, Marion C.; Chames, Jeffery M.; Fiechtner, Gregory J.; Cummings, Eric B.; Fintschenko, Yolanda; Simmons, Blake A.

    2005-01-01

    We have successfully demonstrated selective trapping, concentration, and release of various biological organisms and inert beads by insulator-based dielectrophoresis within a polymeric microfluidic device. The microfluidic channels and internal features, in this case arrays of insulating posts, were initially created through standard wet-etch techniques in glass. This glass chip was then transformed into a nickel stamp through the process of electroplating. The resultant nickel stamp was then used as the replication tool to produce the polymeric devices through injection molding. The polymeric devices were made of Zeonor 1060R, a polyolefin copolymer resin selected for its superior chemical resistance and optical properties. These devices were then optically aligned with another polymeric substrate that had been machined to form fluidic vias. These two polymeric substrates were then bonded together through thermal diffusion bonding. The sealed devices were utilized to selectively separate and concentrate a variety of biological pathogen simulants and organisms. These organisms include bacteria and spores that were selectively concentrated and released by simply applying D.C. voltages across the plastic replicates via platinum electrodes in inlet and outlet reservoirs. The dielectrophoretic response of the organisms is observed to be a function of the applied electric field and post size, geometry and spacing. Cells were selectively trapped against a background of labeled polystyrene beads and spores to demonstrate that samples of interest can be separated from a diverse background. We have implemented a methodology to determine the concentration factors obtained in these devices.

  4. Indicator For Pseudomonas Bacteria

    NASA Technical Reports Server (NTRS)

    Margalit, Ruth

    1990-01-01

    Characteristic protein extracted and detected. Natural protein marker found in Pseudomonas bacteria. Azurin, protein containing copper readily extracted, purified, and used to prepare antibodies. Possible to develop simple, fast, and accurate test for marker carried out in doctor's office.

  5. Bacteria subsisting on antibiotics.

    PubMed

    Dantas, Gautam; Sommer, Morten O A; Oluwasegun, Rantimi D; Church, George M

    2008-04-01

    Antibiotics are a crucial line of defense against bacterial infections. Nevertheless, several antibiotics are natural products of microorganisms that have as yet poorly appreciated ecological roles in the wider environment. We isolated hundreds of soil bacteria with the capacity to grow on antibiotics as a sole carbon source. Of 18 antibiotics tested, representing eight major classes of natural and synthetic origin, 13 to 17 supported the growth of clonal bacteria from each of 11 diverse soils. Bacteria subsisting on antibiotics are surprisingly phylogenetically diverse, and many are closely related to human pathogens. Furthermore, each antibiotic-consuming isolate was resistant to multiple antibiotics at clinically relevant concentrations. This phenomenon suggests that this unappreciated reservoir of antibiotic-resistance determinants can contribute to the increasing levels of multiple antibiotic resistance in pathogenic bacteria. PMID:18388292

  6. Gut bacteria and cancer

    PubMed Central

    Erdman, Susan E.; Poutahidis, Theofilos

    2015-01-01

    Microbiota on the mucosal surfaces of the gastrointestinal (GI) tract greatly outnumber the cells in the human body. Effects of antibiotics indicate that GI tract bacteria may be determining the fate of distal cancers. Recent data implicate dysregulated host responses to enteric bacteria leading to cancers in extra-intestinal sites. Together these findings point to novel anti-cancer strategies aimed at promoting GI tract homeostasis. PMID:26050963

  7. Nanomechanical testing of polymeric nanofibers

    NASA Astrophysics Data System (ADS)

    Tan, E. P. S.; Lim, C. T.

    2005-04-01

    Biodegradable polymeric nanofibrous scaffold comprises individual nanofibers where their stiffnesses can promote or undermine the various cellular functions as well as structural integrity of the scaffold. As such, there is a need to investigate the nanomechanical properties of these individual nanofibers. However, conducting mechanical tests of individual fibers at the nanometer scale can pose great challenges and difficulties. Here, we present novel techniques to perform nanomechanical testing of individual polymeric nanofibers. For demonstration of the nano tensile tests, polycaprolactone (PCL) nanofibers were produced via electrospinning. These fibers were deposited across two parallel edges of a cardboard frame so that a single nanofiber can be isolated for tensile test using a nano tensile tester. For nanoscale three-point bend test, a Poly (L-lactic acid) (PLLA) nanofiber was suspended across a microsized groove etched on a silicon wafer. An atomic force microscope (AFM) tip was then used to apply a point load on the mid-span of the suspended fiber. Beam bending theory was then used to calculate the elastic modulus of the nanofiber. For nanoindentation test, a PLLA nanofiber was deposited on a mica substrate and an AFM tip used to indent the nanofiber. Modified Hertz theory for normal contact was then used to evaluate the elastic modulus of the nanofiber.

  8. Aerobic Anoxygenic Phototrophic Bacteria

    PubMed Central

    Yurkov, Vladimir V.; Beatty, J. Thomas

    1998-01-01

    The aerobic anoxygenic phototrophic bacteria are a relatively recently discovered bacterial group. Although taxonomically and phylogenetically heterogeneous, these bacteria share the following distinguishing features: the presence of bacteriochlorophyll a incorporated into reaction center and light-harvesting complexes, low levels of the photosynthetic unit in cells, an abundance of carotenoids, a strong inhibition by light of bacteriochlorophyll synthesis, and the inability to grow photosynthetically under anaerobic conditions. Aerobic anoxygenic phototrophic bacteria are classified in two marine (Erythrobacter and Roseobacter) and six freshwater (Acidiphilium, Erythromicrobium, Erythromonas, Porphyrobacter, Roseococcus, and Sandaracinobacter) genera, which phylogenetically belong to the α-1, α-3, and α-4 subclasses of the class Proteobacteria. Despite this phylogenetic information, the evolution and ancestry of their photosynthetic properties are unclear. We discuss several current proposals for the evolutionary origin of aerobic phototrophic bacteria. The closest phylogenetic relatives of aerobic phototrophic bacteria include facultatively anaerobic purple nonsulfur phototrophic bacteria. Since these two bacterial groups share many properties, yet have significant differences, we compare and contrast their physiology, with an emphasis on morphology and photosynthetic and other metabolic processes. PMID:9729607

  9. Characterization of microbes which polymerize and depolymerize lignite coals

    SciTech Connect

    Polman, J.K.; Breckenridge, C.R.; Quigley, D.R.

    1991-01-01

    Several bacteria were tested for their ability to modify the macromolecular structure of different coals. When grown in the presence of Mississippi Wilcox lignite, North Dakota Beulah Zap lignite, and North Dakota lenoardite, strain Con5-1L produces polymerization products that are derived from coal. This bacterium was characterized extensively with respect to physiology and morphology and may be a member of the genus Arthrobacter. Strain UPLCPS2-B, which was identified as Pseudomonas chlororaphis, may be capable of limited depolymerization of Mississippi Wilcox lignite and leonardite, but not Beulah Zap lignite. Fermentative strain Con5-5C, which may extensively depolymerize Mississippi Wilcox lignite, was characterized according to morphology and physiology. Other strains tested had little or no effect on coal macromolecular structure. These included Escherichia coli, Arthrobacter paraffineus, and strain BED1. 21 refs., 2 figs.

  10. Characterization of microbes which polymerize and depolymerize lignite coals

    SciTech Connect

    Polman, J.K.; Breckenridge, C.R.; Quigley, D.R.

    1991-12-01

    Several bacteria were tested for their ability to modify the macromolecular structure of different coals. When grown in the presence of Mississippi Wilcox lignite, North Dakota Beulah Zap lignite, and North Dakota lenoardite, strain Con5-1L produces polymerization products that are derived from coal. This bacterium was characterized extensively with respect to physiology and morphology and may be a member of the genus Arthrobacter. Strain UPLCPS2-B, which was identified as Pseudomonas chlororaphis, may be capable of limited depolymerization of Mississippi Wilcox lignite and leonardite, but not Beulah Zap lignite. Fermentative strain Con5-5C, which may extensively depolymerize Mississippi Wilcox lignite, was characterized according to morphology and physiology. Other strains tested had little or no effect on coal macromolecular structure. These included Escherichia coli, Arthrobacter paraffineus, and strain BED1. 21 refs., 2 figs.

  11. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, M.

    1995-02-14

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

  12. Polymeric Additives For Graphite/Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Kourtides, D. A.; Nir, Z.

    1990-01-01

    Report describes experimental studies of properties of several graphite/epoxy composites containing polymeric additives as flexibilizing or toughening agents. Emphasizes effects of brominated polymeric additives (BPA's) with or without carboxy-terminated butadiene acrylonitrile rubber. Reviews effects of individual and combined additives on fracture toughnesses, environmental stabilities, hot/wet strengths, thermomechanical behaviors, and other mechanical properties of composites.

  13. Radiation polymerization of diethyl fumarate [rapid communication

    NASA Astrophysics Data System (ADS)

    Alkassiri, Haroun

    2005-05-01

    Diethyl fumarate (DEF) has been polymerized by gamma irradiation using doses in the range 50-300 kGy, and in this dose range the polymerization yield increased almost linearly. The polymer has a glass transition temperature of about -20 °C, softening point about 15 °C, and decomposition temperature 300 °C.

  14. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, Mohsen

    1995-01-01

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

  15. Genetics in methylotrophic bacteria: Appendix. Final report

    SciTech Connect

    Lidstrom, M.E.

    1998-09-01

    This research has focused primarily on promoters in Methylobacterium extorquens AM1 and in methanotrophic bacteria. In Methylobacterium extorquens work continued on the moxF promoter. The author constructed chromosomal lacZ fusions of this promoter to avoid the regulation problems of plasmid-borne fragments and has shown that this is regulated normally in the chromosome. She has constructed lacZ fusions to some of the mox genes involved in the synthesis of the cofactor, PQQ, in order to carry out similar analysis of transcription of PQQ genes. The author has continued to isolate mox genes in methanotrophs for the purpose of studying their promoters and transcriptional regulation.

  16. Platelet Interaction with Bacteria

    PubMed Central

    Clawson, C. C.

    1973-01-01

    The interaction of several common strains of bacteria with rabbit or human platelets in vitro has been examined sequentially with scanning and transmission electron microscopy. Bacteria were added to platelets in their native plasma or to washed platelets in a balanced salt solution at ratios of about 1:1 or at low bacteria to platelet ratios (down to 1:100). The platelet-bacterial interaction (PBI) was studied with recording nephelometry. Matched samples were fixed for microscopy at various points in the aggregation response. The results support these conclusions: a) Bacteria stimulate platelet aggregation by direct contact and adhesion with the platelet surface. b) Adhesion between the two cell types requires divalent cations, occurs through fusion of normal cell-surface coats and appears identical in the presence or absence of extracellular plasma protein. c) The morphologic transformation of platelets during PBI is identical to that produced by collagen. d) During PBI the bacteria are incorporated into the forming platelet aggregates and reside predominantly intercellularly. e) Phagocytosis of bacteria by a single platelet is very rare. f) Bacteria which have resided within platelet aggregates for one hour are unaltered morphologically. g) PBI occurs even at very low bacterial numbers and produces platelet-bacterial aggregates in small numbers without stimulating generalized platelet aggregation. Methods for concentration of thrombocytopenic plasma and washing human platelets are presented. ImagesFig 6Fig 7Fig 8Fig 9Fig 10Fig 11Fig 1Fig 2Fig 12Fig 13Fig 3Fig 14Fig 4Fig 5 PMID:4632008

  17. Targeted polymeric nanoparticles for cancer gene therapy

    PubMed Central

    Kim, Jayoung; Wilson, David R.; Zamboni, Camila G.; Green, Jordan J.

    2015-01-01

    In this article, advances in designing polymeric nanoparticles for targeted cancer gene therapy are reviewed. Characterization and evaluation of biomaterials, targeting ligands, and transcriptional elements are each discussed. Advances in biomaterials have driven improvements to nanoparticle stability and tissue targeting, conjugation of ligands to the surface of polymeric nanoparticles enable binding to specific cancer cells, and the design of transcriptional elements has enabled selective DNA expression specific to the cancer cells. Together, these features have improved the performance of polymeric nanoparticles as targeted non-viral gene delivery vectors to treat cancer. As polymeric nanoparticles can be designed to be biodegradable, non-toxic, and to have reduced immunogenicity and tumorigenicity compared to viral platforms, they have significant potential for clinical use. Results of polymeric gene therapy in clinical trials and future directions for the engineering of nanoparticle systems for targeted cancer gene therapy are also presented. PMID:26061296

  18. Kinetics and thermodynamics of reversible polymerization in closed systems

    NASA Astrophysics Data System (ADS)

    Lahiri, Sourabh; Wang, Yang; Esposito, Massimiliano; Lacoste, David

    2015-08-01

    Motivated by a recent study on the metabolism of carbohydrates in bacteria, we study the kinetics and thermodynamics of two classic models for reversible polymerization, one preserving the total polymer concentration and the other one not. The chemical kinetics is described by rate equations following the mass-action law. We consider a closed system and nonequilibrium initial conditions and show that the system dynamically evolves towards equilibrium where a detailed balance is satisfied. The entropy production during this process can be expressed as the time derivative of a Lyapunov function. When the solvent is not included in the description and the dynamics conserves the total concentration of polymer, the Lyapunov function can be expressed as a Kullback-Leibler divergence between the nonequilibrium and the equilibrium polymer length distribution. The same result holds true when the solvent is explicitly included in the description and the solution is assumed dilute, whether or not the total polymer concentration is conserved. Furthermore, in this case a consistent nonequilibrium thermodynamic formulation can be established and the out-of-equilibrium thermodynamic enthalpy, entropy and free energy can be identified. Such a framework is useful in complementing standard kinetics studies with the dynamical evolution of thermodynamic quantities during polymerization.

  19. Gating mechanosensitive channels in bacteria with an atomic force microscope

    NASA Astrophysics Data System (ADS)

    Garces, Renata; Miller, Samantha; Schmidt, Christoph F.; Third Institute of Physics Team; School of Medical Sciences Collaboration

    The regulation of growth and integrity of bacteria is critically linked to mechanical stress. Bacteria typically maintain a high difference of osmotic pressure (turgor pressure) with respect to the environment. This pressure difference (on the order of 1 atm) is supported by the cell envelope, a composite of lipid membranes and a rigid cell wall. Turgor pressure is controlled by the ratio of osmolytes inside and outside bacteria and thus, can abruptly increase upon osmotic downshock. For structural integrity bacteria rely on the mechanical stability of the cell wall and on the action of mechanosensitive (MS) channels: membrane proteins that release solutes in response to stress in the cell envelope. We here present experimental data on MS channels gating. We activate channels by indenting living bacteria with the cantilever of an atomic force microscope (AFM). We compare responses of wild-type and mutant bacteria in which some or all MS channels have been eliminated.

  20. Antimicrobial Peptide Mimicking Primary Amine and Guanidine Containing Methacrylamide Copolymers Prepared by Raft Polymerization

    PubMed Central

    Exley, Sarah E.; Paslay, Lea C.; Sahukhal, Gyan S.; Abel, Brooks A.; Brown, Tyler D.; McCormick, Charles L.; Heinhorst, Sabine; Koul, Veena; Choudhary, Veena; Elasri, Mohamed O.; Morgan, Sarah E.

    2016-01-01

    Naturally occurring antimicrobial peptides (AMPs) display the ability to eliminate a wide variety of bacteria, without toxicity to the host eukaryotic cells. Synthetic polymers containing moieties mimicking lysine and arginine components found in AMPs have been reported to show effectiveness against specific bacteria, with the mechanism of activity purported to depend on the nature of the amino acid mimic. In an attempt to incorporate the antimicrobial activity of both amino acids into a single water-soluble copolymer, a series of copolymers containing lysine mimicking aminopropyl methacrylamide (APMA) and arginine mimicking guanadinopropyl methacrylamide (GPMA) were prepared via aqueous RAFT polymerization. Copolymers were prepared with varying ratios of the comonomers, with degree of polymerization of 35–40 and narrow molecular weight distribution to simulate naturally occurring AMPs. Antimicrobial activity was determined against Gram-negative and Gram-positive bacteria under conditions with varying salt concentration. Toxicity to mammalian cells was assessed by hemolysis of red blood cells and MTT assays of MCF-7 cells. Antimicrobial activity was observed for APMA homopolymer and copolymers with low concentrations of GPMA against all bacteria tested, with low toxicity toward mammalian cells. PMID:26558609

  1. Modeling liquid crystal polymeric devices

    NASA Astrophysics Data System (ADS)

    Gimenez Pinto, Vianney Karina

    The main focus of this work is the theoretical and numerical study of materials that combine liquid crystal and polymer. Liquid crystal elastomers are polymeric materials that exhibit both the ordered properties of the liquid crystals and the elastic properties of rubbers. Changing the order of the liquid crystal molecules within the polymer network can induce shape change. These materials are very valuable for applications such as actuators, sensors, artificial muscles, haptic displays, etc. In this work we apply finite element elastodynamics simulations to study the temperature induced shape deformation in nematic elastomers with complex director microstructure. In another topic, we propose a novel numerical method to model the director dynamics and microstructural evolution of three dimensional nematic and cholesteric liquid crystals. Numerical studies presented in this work are in agreement with experimental observations and provide insight into the design of application devices.

  2. The talking language in some major Gram-negative bacteria.

    PubMed

    Banerjee, Goutam; Ray, Arun Kumar

    2016-08-01

    Cell-cell interaction or quorum sensing (QS) is a vital biochemical/physiological process in bacteria that is required for various physiological functions, including nutrient uptake, competence development, biofilm formation, sporulation, as well as for toxin secretion. In natural environment, bacteria live in close association with other bacteria and interaction among them is crucial for survival. The QS-regulated gene expression in bacteria is a cell density-dependent process and the initiation process depends on the threshold level of the signaling molecule, N-acyl-homoserine lactone (AHL). The present review summarizes the QS signal and its respective circuit in Gram-negative bacteria. Most of the human pathogens belong to Gram-negative group, and only a few of them cause disease through QS system. Thus, inhibition of pathogenic bacteria is important. Use of antibiotics creates a selective pressure (antibiotics act as natural selection factor to promote one group of bacteria over another group) for emerging multidrug-resistant bacteria and will not be suitable for long-term use. The alternative process of inhibition of QS in bacteria using different natural and synthetic molecules is called quorum quenching. However, in the long run, QS inhibitors or blockers may also develop resistance, but obviously it will solve some sort of problems. In this review, we also have stated the mode of action of quorum-quenching molecule. The understanding of QS network in pathogenic Gram-negative bacteria will help us to solve many health-related problems in future. PMID:27062655

  3. Polymeric materials from renewable resources

    NASA Astrophysics Data System (ADS)

    Frollini, Elisabete; Rodrigues, Bruno V. M.; da Silva, Cristina G.; Castro, Daniele O.; Ramires, Elaine C.; de Oliveira, Fernando; Santos, Rachel P. O.

    2016-05-01

    The goals of our studies have been the use of renewable raw materials in the preparation of polymeric materials with diversified properties. In this context, lignosulfonate, which is produced in large scale around the world, but not widely used in the production of polymeric materials, was used to replace phenol and polyols in the preparation of phenolic- (Ligno-PH) and polyurethane-type (Ligno-PU) polymers, respectively. These polymers were used to prepare composites reinforced with sisal lignocellulosic fibers. The use of lignosulfonate in the formulation of both types of polymers was beneficial, because in general composites with improved properties, specially impact strength, were obtained. Composites were also prepared from the so called "biopolyethylene" (HDPE), curaua lignocellulosic fiber, and castor oil (CO). All composites HDBPE/CO/Fiber exhibited higher impact strength, when compared to those of the corresponding HDBPE/Fiber. These results, combined with others (eg SEM images of the fractured surfaces) indicated that, in addition to acting as a plasticizer, this oil may have acted as a compatibilizer of the hydrophilic fiber with the hydrophobic polymer. The set of results indicated that (i) mats with nano (diameter ≤ 100nm) and/or ultrafine (submicron scale) fibers were produced, (ii) hybrid fibers were produced (bio-based mats composites), (iii) cellulosic pulp (CP) and/or lignin (Lig) can be combined with PET matrices to control properties such as stiffness and hydrophilicity of the respective mats. Materials with diversified properties were prepared from high content of renewable raw materials, thus fulfilling the proposed targets.

  4. Pilins in gram-positive bacteria: A structural perspective.

    PubMed

    Krishnan, Vengadesan

    2015-07-01

    Pilins or fimbrilins are a class of proteins found in bacterial surface pilus, a hair-like surface appendage. Both the Gram-negative and -positive bacteria produce pilins to assemble pili on their cell-surface for different purposes including adherence, twitching motility, conjugation, immunomodulation, biofilm formation, and electron transfer. Immunogenic properties of the pilins make them attractive vaccine candidates. The polymerized pilins play a key role in the initiation of host adhesion, which is a critical step for bacterial colonization and infection. Because of their key role in adhesion and exposure on the cell surface, targeting the pilins-mediated adhesion (anti-adhesion therapy) is also seen as a promising alternative approach for preventing and treating bacterial infections, one that may overcome their ever-increasing repertoires of resistance mechanisms. Individual pilins interact with each other non-covalently to assemble the pilus fiber with the help of associated proteins like chaperones and Usher in Gram-negative bacteria. In contrast, the pilins in Gram-positive bacteria often connect with each other covalently, with the help of sortases. Certain unique structural features present on the pilins distinguish them from one another across different bacterial strains, and these dictate their cellular targets and functions. While the structure of pilins has been extensively studied in Gram-negative pathogenic bacteria, the pilins in Gram-positive pathogenic bacteria have been in only during the last decade. Recently, the discovery of pilins in non-pathogenic bacteria, such as Lactobacillus rhamnosus GG, has received great attention, though traditionally the attention was on pathogenic bacteria. This review summarizes and discusses the current structural knowledge of pilins in Gram-positive bacteria with emphasis on those pilins which are sortase substrates. PMID:26178080

  5. Ice-Nucleating Bacteria

    NASA Astrophysics Data System (ADS)

    Obata, Hitoshi

    Since the discovery of ice-nucleating bacteria in 1974 by Maki et al., a large number of studies on the biological characteristics, ice-nucleating substance, ice nucleation gene and frost damage etc. of the bacteria have been carried out. Ice-nucleating bacteria can cause the freezing of water at relatively warm temperature (-2.3°C). Tween 20 was good substrates for ice-nucleating activity of Pseudomonas fluorescens KUIN-1. Major fatty acids of Isolate (Pseudomonas fluorescens) W-11 grown at 30°C were palmitic, cis-9-hexadecenoic and cis-11-octadecenoic which amounted to 90% of the total fatty acids. Sequence analysis shows that an ice nucleation gene from Pseudomonas fluorescens is related to the gene of Pseudomonas syringae.

  6. Studies on cyanobacterial extracellular polymeric substances: functional groups, calcite biomineralization and formation of capsular polymeric substances

    NASA Astrophysics Data System (ADS)

    Dittrich, M.; Sibler, S.; Matsko, N.

    2006-12-01

    Extracellular polymeric substances (EPS) of microbial origin are an important class of polymeric materials which have been involved in different processes such as biofilm development or mineral precipitation. Cyanobacteria have been known as potential EPS producers for a long time. Despite their ubiquitous distribution, there is still a great lack of knowledge concerning the diversity of EPS binding sites of different picocyanobacterial strains on the one hand and the specific components of EPS which are responsible for calcite precipitation and crystal morphology on the other hand. It is generally accepted that capsular extracellular polymeric substances are the main components of biofilm matrixes. In this context, it is important to understand under which conditions cyanobacteria produce surface polysaccharides. In a recent study, we characterized the binding sites of EPS of three unicellular autotrophic picocyanobacterial strains of the Synechococcus-type. Potentiometric titrations were conducted to determine different types of functional groups present at the various sites. Precipitation experiments with EPS of different strains allowed for estimating the potential of EPS to precipitate calcium carbonate and the impact of functional groups composition on crystal morphology. In order to clarify the conditions under which cyanobacteria formed capsular EPS, we performed growth experiments in nutrients medium with different phosphorus concentrations (0.4, 4.1, 8.2 and 41 mgP/l). Cyanobacterial cells produced capsular EPS under phosphorus concentrations of 0.4, 4.1 and 8.2 mgP/l, while no capsular EPS were observed for the highest P concentration (41 mgP/l). At this concentration, however, calcium rich storage products were detected in the cells. The results thus suggest that both extracellular and intracellular products are regulated through phosphorus concentrations in growth solutions. Titrations reveal five or six distinct sites on surfaces of picocyanobacterial

  7. Immobilized N-alkylated polyethylenimine avidly kills bacteria by rupturing cell membranes with no resistance developed.

    PubMed

    Milović, Nebojsa M; Wang, Jun; Lewis, Kim; Klibanov, Alexander M

    2005-06-20

    Several critical mechanistic and phenomenological aspects of the microbicidal surface coatings based on immobilized hydrophobic polycations, previously developed by us, are addressed. Using Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria, remarkable bactericidal action (up to a 10(9)-fold reduction in live bacteria count in the surface-exposed solution and a 100% inactivation of the surface-adhered bacteria) of an amino-glass slide covalently derivatized with N-hexyl,methyl-polyethylenimine (PEI) is found to be due to rupturing bacterial cell membranes by the polymeric chains. The bacteria fail to develop noticeable resistance to this lethal action over the course of many successive generations. Finally, the immobilized N-alkyl-PEI, while deadly to bacteria, is determined to be harmless to mammalian (monkey kidney) cells. PMID:15803464

  8. ESR studies of semicontinuous emulsion polymerization

    SciTech Connect

    Lau, W.; Westmoreland, D.G.

    1993-12-31

    Electron spin resonance (ESR) is used in the detection and quantification of propagating radicals during a semicontinuous emulsion polymerization. The propagating radical concentration is crucial for the determination of kinetic parameters of the emulsion polymerization process. A flow reactor was built which involves a closed-loop flow system that circulates latex from the polymerization reactor through the ESR cavity for free-radical measurements and back to the reactor. With the continuous measurement of the radical concentrations during a polymerization of methyl methacrylate (MMA), {bar n} (average number of radicals per particle) and k{sub p} (propagating rate constant), are measured throughout the entire polymerization. For the polymerization of the MMA system studied, the authors observed a gradual increased in n and decrease in k{sub p} during the run, suggesting a diffusionally controlled process and that the polymerization is not occurring homogeneously throughout the polymer particles. In the glassy pMMA matrix, radicals can be {open_quotes}trapped{close_quotes} within a minimum volume and remain unterminated.

  9. Method for forming polymerized microfluidic devices

    SciTech Connect

    Sommer, Gregory J.; Hatch, Anson V.; Wang, Ying-Chih; Singh, Anup K.; Renzi, Ronald F.; Claudnic, Mark R.

    2013-03-12

    Methods for making a microfluidic device according to embodiments of the present invention include defining.about.cavity. Polymer precursor solution is positioned in the cavity, and exposed to light to begin the polymerization process and define a microchannel. In some embodiments, after the polymerization process is partially complete, a solvent rinse is performed, or fresh polymer precursor introduced into the microchannel. This may promote removal of unpolymerized material from the microchannel and enable smaller feature sizes. The polymer precursor solution may contain an iniferter. Polymerized features therefore may be capped with the iniferter, which is photoactive. The iniferter may aid later binding of a polyacrylamide gel to the microchannel surface.

  10. Method for forming polymerized microfluidic devices

    DOEpatents

    Sommer, Gregory J.; Hatch, Anson V.; Wang, Ying-Chih; Singh, Anup K.; Renzi, Ronald F.; Claudnic, Mark R.

    2011-11-01

    Methods for making a micofluidic device according to embodiments of the present invention include defining a cavity. Polymer precursor solution is positioned in the cavity, and exposed to light to begin the polymerization process and define a microchannel. In some embodiments, after the polymerization process is partially complete, a solvent rinse is performed, or fresh polymer precursor introduced into the microchannel. This may promote removal of unpolymerized material from the microchannel and enable smaller feature sizes. The polymer precursor solution may contain an iniferter. Polymerized features therefore may be capped with the iniferter, which is photoactive. The iniferter may aid later binding of a polyacrylamide gel to the microchannel surface.

  11. Polymeric MST - high precision at low cost

    NASA Astrophysics Data System (ADS)

    Elderstig, Håkan; Larsson, Olle

    1997-09-01

    A low-cost production process for fabrication of polymeric microstructures from micromachined silicon is demonstrated in a splice for the splicing of optical fibers and an optical motherboard. Measurements on splices showed less than 0.5 dB insertion losses. The prototype polymeric motherboard concisted of an optical receiver module. The detector that was mounted on the polymeric optical motherboard detected about 70% of the transferred light. Measurements with modulated light indicates an optical bandwidth of 5 GHz at 2 V reverse current on the pin-diode.

  12. Mechanical force-induced polymerization and depolymerization of F-actin at water/solid interfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Xueqiang; Hu, Xiuyuan; Lei, Haozhi; Hu, Jun; Zhang, Yi

    2016-03-01

    Actin molecules are among the three main cytoskeleton proteins of cells and undergo rapid cycling to regulate critical processes such as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. Although extensive studies have been carried out on the dynamics as well as biological functions of actin polymerization and depolymerization both in vivo and in vitro, the molecular mechanisms by which cells sense and respond to mechanical signals are not fully understood. In particular, little attention has been paid to the effect of a physical force that is exerted directly on the actin cytoskeleton. In this paper, we have explored how the mechanical force affects the actin polymerization and depolymerization behaviors at water/solid interfaces using an atomic force microscope (AFM) operated in liquid. By raster scanning an AFM probe on a substrate surface with a certain load, it was found that actin monomers could polymerize into filaments without the help of actin related proteins (ARPs). Further study indicated that actin monomers were inclined to form filaments only under a small scanning load. The polymerized actin filaments would be depolymerized when the mechanical force was stronger. A possible mechanism has been suggested to explain the mechanical force induced actin polymerization.Actin molecules are among the three main cytoskeleton proteins of cells and undergo rapid cycling to regulate critical processes such as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. Although extensive studies have been carried out on the dynamics as well as biological functions of actin polymerization and depolymerization both in vivo and in vitro, the molecular mechanisms by which cells sense and respond to mechanical signals are not fully understood. In particular, little attention has been paid to the effect of a physical force that is exerted directly on the actin cytoskeleton. In this paper, we have explored how the mechanical force affects the actin

  13. 49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... compound. 173.221 Section 173.221 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non... molding compound in dough, sheet or extruded rope form, evolving flammable vapor must be packed in:...

  14. 49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... compound. 173.221 Section 173.221 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non... molding compound in dough, sheet or extruded rope form, evolving flammable vapor must be packed in:...

  15. 49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... compound. 173.221 Section 173.221 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non... molding compound in dough, sheet or extruded rope form, evolving flammable vapor must be packed in:...

  16. 49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... compound. 173.221 Section 173.221 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non... molding compound in dough, sheet or extruded rope form, evolving flammable vapor must be packed in:...

  17. 49 CFR 173.221 - Polymeric beads, expandable and Plastic molding compound.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... compound. 173.221 Section 173.221 Transportation Other Regulations Relating to Transportation PIPELINE AND... Than Class 1 and Class 7 § 173.221 Polymeric beads, expandable and Plastic molding compound. (a) Non... molding compound in dough, sheet or extruded rope form, evolving flammable vapor must be packed in:...

  18. Polymerization in emulsion microdroplet reactors

    NASA Astrophysics Data System (ADS)

    Carroll, Nick J.

    The goal of this research project is to utilize emulsion droplets as chemical reactors for execution of complex polymerization chemistries to develop unique and functional particle materials. Emulsions are dispersions of immiscible fluids where one fluid usually exists in the form of drops. Not surprisingly, if a liquid-to-solid chemical reaction proceeds to completion within these drops, the resultant solid particles will possess the shape and relative size distribution of the drops. The two immiscible liquid phases required for emulsion polymerization provide unique and complex chemical and physical environments suitable for the engineering of novel materials. The development of novel non-ionic fluorosurfactants allows fluorocarbon oils to be used as the continuous phase in a water-free emulsion. Such emulsions enable the encapsulation of almost any hydrocarbon compound in droplets that may be used as separate compartments for water-sensitive syntheses. Here, we exemplify the promise of this approach by suspension polymerization of polyurethanes (PU), in which the liquid precursor is emulsified into droplets that are then converted 1:1 into polymer particles. The stability of the droplets against coalescence upon removal of the continuous phase by evaporation confirms the formation of solid PU particles. These results prove that the water-free environment of fluorocarbon based emulsions enables high conversion. We produce monodisperse, cross-linked, and fluorescently labeled PU-latexes with controllable mesh size through microfluidic emulsification in a simple one-step process. A novel method for the fabrication of monodisperse mesoporous silica particles is presented. It is based on the formation of well-defined equally sized emulsion droplets using a microfluidic approach. The droplets contain the silica precursor/surfactant solution and are suspended in hexadecane as the continuous oil phase. The solvent is then expelled from the droplets, leading to

  19. PATHOGENICITY OF BIOFILM BACTERIA

    EPA Science Inventory

    There is a paucity of information concerning any link between the microorganisms commonly found in biofilms of drinking water systems and their impacts on human health. For bacteria, culture-based techniques detect only a limited number of the total microorganisms associated wit...

  20. Antibiotic-Resistant Bacteria.

    ERIC Educational Resources Information Center

    Longenecker, Nevin E.; Oppenheimer, Dan

    1982-01-01

    A study conducted by high school advanced bacteriology students appears to confirm the hypothesis that the incremental administration of antibiotics on several species of bacteria (Escherichia coli, Staphylococcus epidermis, Bacillus sublitus, Bacillus megaterium) will allow for the development of antibiotic-resistant strains. (PEB)

  1. Polymeric Coatings for Electrodynamic Tethers

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.; Kamenetzky, Rachel R.; Finckenor, Miria M.; Schuler, Peter

    2000-01-01

    Two polymeric coatings have been developed for the Propulsive Small Expendable Deployer System (ProSEDS) mission. ProSEDS is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta II unmanned expendable booster scheduled for launch in August 2000. A 5-km conductive tether is attached to the Delta 11 second stage and collects current from the low Earth orbit (LEO) plasma to facilitate de-orbit of the spent stage. The conductive tether is attached to a 10-km non-conductive tether, the other end of which is attached to an endmass containing several scientific instruments. A bare metal tether would have the best conductivity but thermal concerns preclude this design. A conductive polymer developed by Triton Systems has been optimized for conductivity and thermo-optical properties. The current design for the ProSEDS conductive tether is seven strands of 28 AWG aluminum wire individually coated with 8.7 micrometers (0.35 mil) of an atomic oxygen-resistant conductive polymer composed of a mixture of 87% Clear Oxygen-Resistant polymer (COR) and 13% polyanaline (PANi), wrapped around a braided Kevlar (TM) 49 core. Extensive testing has been performed at the Marshall Space Flight Center (MSFC) to qualify this material for flight on ProSEDS. Atomic oxygen exposure was performed, with solar absorptance and infrared emittance measured before and after exposure. Conductivity was measured before and after atomic oxygen exposure. High voltage tests, up to 1500 V, of the current collecting ability of the COR/PANi have been completed. Approximately 160 meters of the conductive tether closest to the Delta 11 second stage is insulated to prevent any electron reconnection to the tether from the plasma contactor. The insulation is composed of polyimide overcoated with TOR-BP, another polymeric coating developed by Triton for this mission. TOR-BP acts as both insulator

  2. Clay-Bacteria Systems and Biofilm Production

    NASA Astrophysics Data System (ADS)

    Steiner, J.; Alimova, A.; Katz, A.; Steiner, N.; Rudolph, E.; Gottlieb, P.

    2007-12-01

    Soil clots and the aerosol transport of bacteria and spores are promoted by the formation of biofilms (bacteria cells in an extracellular polymeric matrix). Biofilms protect microorganisms by promoting adhesion to both organic and inorganic surfaces. Time series experiments on bacteria-clay suspensions demonstrate that biofilm growth is catalyzed by the presence of hectorite in minimal growth media for the studied species: Gram negatives (Pseudomonas syringae and Escherichia coli,) and Gram positives (Staphylococcus aureus and Bacillus subtilis). Soil organisms (P. syringae, B. subtilis) and organisms found in the human population (E. coli, S. aureus) are both used to demonstrate the general applicability of clay involvement. Fluorescent images of the biofilms are acquired by staining with propidium iodide, a component of the BacLightTM Live/Dead bacterial viability staining kit (Molecular Probes, Eugene, OR). The evolving polysaccharide-rich biofilm reacts with the clay interlayer site causing a complex substitution of the two-water hectorite interlayer with polysaccharide. The result is often a three-peak composite of the (001) x-ray diffraction maxima resulting from polysaccharide-expanded clays and an organic-driven contraction of a subset of the clays in the reaction medium. X-ray diffractograms reveal that the expanded set creates a broad maximum with clay subsets at 1.84 nm and 1.41 nm interlayer spacings as approximated by a least squares double Lorentzian fit, and a smaller shoulder at larger 2q, deriving from a contraction of the interlayer spacing. Washing with chlorox removes organic material from the contracted clay and creates a 1-water hectorite single peak in place of the double peak. The clay response can be used as an indirect indicator of biofilm in an environmental system.

  3. 21 CFR 177.2250 - Filters, microporous polymeric.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Filters, microporous polymeric. 177.2250 Section... Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in... liquid food. (a) Microporous polymeric filters consist of a suitably permeable, continuous,...

  4. Polymerization as a Model Chain Reaction

    ERIC Educational Resources Information Center

    Morton, Maurice

    1973-01-01

    Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

  5. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

    Lonsdale, H.K.; Babcock, W.C.; Friensen, D.T.; Smith, K.L.; Johnson, B.M.; Wamser, C.C.

    1990-08-14

    Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclosed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers. 3 figs.

  6. Reverse-osmosis membranes by plasma polymerization

    NASA Technical Reports Server (NTRS)

    Hollahan, J. R.; Wydeven, T.

    1972-01-01

    Thin allyl amine polymer films were developed using plasma polymerization. Resulting dry composite membranes effectively reject sodium chloride during reverse osmosis. Films are 98% sodium chloride rejective, and 46% urea rejective.

  7. Hydrocarbon polymeric binder for advanced solid propellant

    NASA Technical Reports Server (NTRS)

    Potts, J. E. (Editor)

    1972-01-01

    A series of DEAB initiated isoprene polymerizations were run in the 5-gallon stirred autoclave reactor. Polymerization run parameters such as initiator concentration and feed rate were correlated with the molecular weight to provide a basis for molecular weight control in future runs. Synthetic methods were developed for the preparation of n-1,3-alkadienes. By these methods, 1,3-nonadiene was polymerized using DEAB initiator to give an ester-telechelic polynonadiene. This was subsequently hydrogenated with copper chromite catalyst to give a hydroxyl terminated saturated liquid hydrocarbon prepolymer having greatly improved viscosity characteristics and a Tg 18 degrees lower than that of the hydrogenated polyisoprenes. The hydroxyl-telechelic saturated polymers prepared by the hydrogenolysis of ester-telechelic polyisoprene were reached with diisocyanates under conditions favoring linear chain extension gel permeation chromatography was used to monitor this condensation polymerization. Fractions having molecular weights above one million were produced.

  8. Dielectric films improve life of polymeric insulators

    NASA Technical Reports Server (NTRS)

    Hudis, M.; Wydeven, T.

    1975-01-01

    Degradation of polymeric insulators may be significantly reduced when polymer surfaces are coated with film having gradation of dielectric constants, larger where it is in contact with polymer and smaller at its exposed surface.

  9. Physicochemically functional ultrathin films by interfacial polymerization

    DOEpatents

    Lonsdale, Harold K.; Babcock, Walter C.; Friensen, Dwayne T.; Smith, Kelly L.; Johnson, Bruce M.; Wamser, Carl C.

    1990-01-01

    Interfacially-polymerized ultrathin films containing physicochemically functional groups are disclosed, both with and without supports. Various applications are disclsoed, including membrane electrodes, selective membranes and sorbents, biocompatible materials, targeted drug delivery, and narrow band optical absorbers.

  10. PERMEABILITY OF POLYMERIC MEMBRANE LINING MATERIALS

    EPA Science Inventory

    Permeabilities to three gases (carbon dioxide, methane, and nitrogen), water vapor, and five solvents (methanol, acetone, cyclohexane, xylene, and chloroform) are reported for a broad range of commercial polymeric membranes. Gas and water vapor transmission (WVT) data were determ...

  11. Radiation effects on polymeric materials

    NASA Technical Reports Server (NTRS)

    Kiefer, Richard L.

    1988-01-01

    It is important to study changes in properties of polymeres after irradiation with charged particles, with ultraviolet radiation, and with combinations of both. An apparatus for this purpose has been built at the NASA Langley Research Center. It consists of a chamber 9 inches in diameter and 9 inches high with a port for an electron gun, another port for a mass spectrometer, and a quartz window through which an ultraviolet lamp can be focused. The chamber, including the electron gun and the mass spectrometer, can be evacuated to a pressure of 10 to the 8th power torr. A sample placed in the chamber can be irradiated with electrons and ultraviolet radiation separately, sequentially, or simultaneously, while volatile products can be monitored during all irradiations with the mass spectrometer. The apparatus described above has been used to study three different polymer films: lexan; a polycarbonate; P1700, a polysulfone; and mylar, a polyethylene terephthalate. All three polymers had been studied extensively with both electrons and ultraviolet radiation separately, but not simultaneously. Also, volatile products had not been monitored during irradiation for the materials. A high electron dose rate of 530 Mrads/hr was used so that a sufficient concentration of volatile products would be formed to yield a reasonable mass spectrum.

  12. Highly elastic conductive polymeric MEMS

    NASA Astrophysics Data System (ADS)

    Ruhhammer, J.; Zens, M.; Goldschmidtboeing, F.; Seifert, A.; Woias, P.

    2015-02-01

    Polymeric structures with integrated, functional microelectrical mechanical systems (MEMS) elements are increasingly important in various applications such as biomedical systems or wearable smart devices. These applications require highly flexible and elastic polymers with good conductivity, which can be embedded into a matrix that undergoes large deformations. Conductive polydimethylsiloxane (PDMS) is a suitable candidate but is still challenging to fabricate. Conductivity is achieved by filling a nonconductive PDMS matrix with conductive particles. In this work, we present an approach that uses new mixing techniques to fabricate conductive PDMS with different fillers such as carbon black, silver particles, and multiwalled carbon nanotubes. Additionally, the electrical properties of all three composites are examined under continuous mechanical stress. Furthermore, we present a novel, low-cost, simple three-step molding process that transfers a micro patterned silicon master into a polystyrene (PS) polytetrafluoroethylene (PTFE) replica with improved release features. This PS/PTFE mold is used for subsequent structuring of conductive PDMS with high accuracy. The non sticking characteristics enable the fabrication of delicate structures using a very soft PDMS, which is usually hard to release from conventional molds. Moreover, the process can also be applied to polyurethanes and various other material combinations.

  13. Polymeric conjugates for drug delivery

    PubMed Central

    Larson, Nate; Ghandehari, Hamidreza

    2012-01-01

    The field of polymer therapeutics has evolved over the past decade and has resulted in the development of polymer-drug conjugates with a wide variety of architectures and chemical properties. Whereas traditional non-degradable polymeric carriers such as poly(ethylene glycol) (PEG) and N-(2-hydroxypropyl methacrylamide) (HPMA) copolymers have been translated to use in the clinic, functionalized polymer-drug conjugates are increasingly being utilized to obtain biodegradable, stimuli-sensitive, and targeted systems in an attempt to further enhance localized drug delivery and ease of elimination. In addition, the study of conjugates bearing both therapeutic and diagnostic agents has resulted in multifunctional carriers with the potential to both “see and treat” patients. In this paper, the rational design of polymer-drug conjugates will be discussed followed by a review of different classes of conjugates currently under investigation. The design and chemistry used for the synthesis of various conjugates will be presented with additional comments on their potential applications and current developmental status. PMID:22707853

  14. Stress-Induced Mutagenesis in Bacteria

    PubMed Central

    Foster, Patricia L.

    2009-01-01

    Bacteria spend their lives buffeted by changing environmental conditions. To adapt to and survive these stresses, bacteria have global response systems that result in sweeping changes in gene expression and cellular metabolism. These responses are controlled by master regulators, which include: alternative sigma factors, such as RpoS and RpoH; small molecule effectors, such as ppGpp; gene repressors such as LexA; and, inorganic molecules, such as polyphosphate. The response pathways extensively overlap and are induced to various extents by the same environmental stresses. These stresses include nutritional deprivation, DNA damage, temperature shift, and exposure to antibiotics. All of these global stress responses include functions that can increase genetic variability. In particular, up-regulation and activation of error-prone DNA polymerases, down-regulation of error-correcting enzymes, and movement of mobile genetic elements are common features of several stress responses. The result is that under a variety of stressful conditions, bacteria are induced for genetic change. This transient mutator state may be important for adaptive evolution. PMID:17917873

  15. Biaxially oriented film on flexible polymeric substrate

    DOEpatents

    Finkikoglu, Alp T.; Matias, Vladimir

    2009-10-13

    A flexible polymer-based template having a biaxially oriented film grown on the surface of a polymeric substrate. The template having the biaxially oriented film can be used for further epitaxial growth of films of interest for applications such as photovoltaic cells, light emitting diodes, and the like. Methods of forming such a flexible template and providing the polymeric substrate with a biaxially oriented film deposited thereon are also described.

  16. Containerless polymeric microsphere production for biomedical applications

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Hyson, M. T.; Chung, S. K.; Colvin, M.; Chang, M.

    1987-01-01

    A containerless method that produces highly uniform microspheres (greater than 50 microns in diameter) from many materials has been developed for biomedical applications. A piezoelectrically vibrated drop generator forms uniform (monodisperse) monomer droplets that are either electrostatistically levitated and polymerized using UV irradiation, or free-radical polymerized. Spheres of 2-hydroxyethyl methacrylate polymer have been produced with diameters of 155 microns + or - 1.57 percent.

  17. DNA detection with a polymeric nanochannel device.

    PubMed

    Fanzio, Paola; Mussi, Valentina; Manneschi, Chiara; Angeli, Elena; Firpo, Giuseppe; Repetto, Luca; Valbusa, Ugo

    2011-09-01

    We present the development and the electrical characterization of a polymeric nanochannel device. Standard microfabrication coupled to Focused Ion Beam (FIB) nanofabrication is used to fabricate a silicon master, which can be then replicated in a polymeric material by soft lithography. Such an elastomeric nanochannel device is used to study DNA translocation events during electrophoresis experiments. Our results demonstrate that an easy and low cost fabrication technique allows creation of a low noise device for single molecule analysis. PMID:21750811

  18. Post polymerization cure shape memory polymers

    DOEpatents

    Wilson, Thomas S; Hearon, Michael Keith; Bearinger, Jane P

    2014-11-11

    This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

  19. Polymeric Micelles for Acyclovir Drug Delivery

    PubMed Central

    Sawdon, Alicia J.; Peng, Ching-An

    2014-01-01

    Polymeric prodrug micelles for delivery of acyclovir (ACV) were synthesized. First, ACV was used directly to initiate ring-opening polymerization of ε-caprolactone to form ACV-polycaprolactone (ACV-PCL). Through conjugation of hydrophobic ACV-PCL with hydrophilic methoxy poly(ethylene glycol) (MPEG) or chitosan, polymeric micelles for drug delivery were formed. 1H NMR, FTIR, and gel permeation chromatography were employed to show successful conjugation of MPEG or chitosan to hydrophobic ACV-PCL. Through dynamic light scattering, zeta potential analysis, transmission electron microscopy, and critical micelle concentration (CMC), the synthesized ACV-tagged polymeric micelles were characterized. It was found that the average size of the polymeric micelles was under 200 nm and the CMCs of ACV-PCLMPEG and ACV-PCL-chitosan were 2.0 mg L−1 and 6.6 mg L−1, respectively. The drug release kinetics of ACV was investigated and cytotoxicity assay demonstrates that ACV-tagged polymeric micelles were non-toxic. PMID:25193154

  20. Catalytic living ring-opening metathesis polymerization

    NASA Astrophysics Data System (ADS)

    Nagarkar, Amit A.; Kilbinger, Andreas F. M.

    2015-09-01

    In living ring-opening metathesis polymerization (ROMP), a transition-metal-carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well-defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst.

  1. Nonperturbative Renormalization Group Approach to Polymerized Membranes

    NASA Astrophysics Data System (ADS)

    Essafi, Karim; Kownacki, Jean-Philippe; Mouhanna, Dominique

    2014-03-01

    Membranes or membrane-like materials play an important role in many fields ranging from biology to physics. These systems form a very rich domain in statistical physics. The interplay between geometry and thermal fluctuations lead to exciting phases such flat, tubular and disordered flat phases. Roughly speaking, membranes can be divided into two group: fluid membranes in which the molecules are free to diffuse and thus no shear modulus. On the other hand, in polymerized membranes the connectivity is fixed which leads to elastic forces. This difference between fluid and polymerized membranes leads to a difference in their critical behaviour. For instance, fluid membranes are always crumpled, whereas polymerized membranes exhibit a phase transition between a crumpled phase and a flat phase. In this talk, I will focus only on polymerized phantom, i.e. non-self-avoiding, membranes. The critical behaviour of both isotropic and anisotropic polymerized membranes are studied using a nonperturbative renormalization group approach (NPRG). This allows for the investigation of the phase transitions and the low temperature flat phase in any internal dimension D and embedding d. Interestingly, graphene behaves just as a polymerized membrane in its flat phase.

  2. Antifouling activities of marine bacteria associated with sponge ( Sigmadocia sp.)

    NASA Astrophysics Data System (ADS)

    Satheesh, S.; Soniamby, A. R.; Sunjaiy Shankar, C. V.; Mary Josephine Punitha, S.

    2012-09-01

    The present study aimed at assessing the antifouling activity of bacteria associated with marine sponges. A total of eight bacterial strains were isolated from the surface of sponge Sigmadocia sp., of them, SS02, SS05 and SS06 showed inhibitory activity against biofilm-forming bacteria. The extracts of these 3 strains considerably affected the extracellular polymeric substance producing ability and adhesion of biofilm-forming bacterial strains. In addition to disc diffusion assay, microalgal settlement assay was carried out with the extracts mixed with polyurethane wood polish and coated onto stainless steel coupons. The extract of strain SS05 showed strong microalgal settlement inhibitory activity. Strain SS05 was identified as Bacillus cereus based on its 16S rRNA gene. Metabolites of the bacterial strains associated with marine invertebrates promise to be developed into environment-friendly antifouling agents.

  3. Lipoprotein sorting in bacteria.

    PubMed

    Okuda, Suguru; Tokuda, Hajime

    2011-01-01

    Bacterial lipoproteins are synthesized as precursors in the cytoplasm and processed into mature forms on the cytoplasmic membrane. A lipid moiety attached to the N terminus anchors these proteins to the membrane surface. Many bacteria are predicted to express more than 100 lipoproteins, which play diverse functions on the cell surface. The Lol system, composed of five proteins, catalyzes the localization of Escherichia coli lipoproteins to the outer membrane. Some lipoproteins play vital roles in the sorting of other lipoproteins, lipopolysaccharides, and β-barrel proteins to the outer membrane. On the basis of results from biochemical, genetic, and structural studies, we discuss the biogenesis of lipoproteins in bacteria, their importance in cellular functions, and the molecular mechanisms underlying efficient sorting of hydrophobic lipoproteins to the outer membrane through the hydrophilic periplasm. PMID:21663440

  4. Sociomicrobiology and Pathogenic Bacteria.

    PubMed

    Xavier, Joao B

    2016-06-01

    The study of microbial pathogenesis has been primarily a reductionist science since Koch's principles. Reductionist approaches are essential to identify the causal agents of infectious disease, their molecular mechanisms of action, and potential drug targets, and much of medicine's success in the treatment of infectious disease stems from that approach. But many bacteria-caused diseases cannot be explained by a single bacterium. Several aspects of bacterial pathogenesis will benefit from a more holistic approach that takes into account social interaction among bacteria of the same species and between species in consortia such as the human microbiome. The emerging discipline of sociomicrobiology provides a framework to dissect microbial interactions in single and multi-species communities without compromising mechanistic detail. The study of bacterial pathogenesis can benefit greatly from incorporating concepts from other disciplines such as social evolution theory and microbial ecology, where communities, their interactions with hosts, and with the environment play key roles. PMID:27337482

  5. Manufacture of Probiotic Bacteria

    NASA Astrophysics Data System (ADS)

    Muller, J. A.; Ross, R. P.; Fitzgerald, G. F.; Stanton, C.

    Lactic acid bacteria (LAB) have been used for many years as natural biopreservatives in fermented foods. A small group of LAB are also believed to have beneficial health effects on the host, so called probiotic bacteria. Probiotics have emerged from the niche industry from Asia into European and American markets. Functional foods are one of the fastest growing markets today, with estimated growth to 20 billion dollars worldwide by 2010 (GIA, 2008). The increasing demand for probiotics and the new food markets where probiotics are introduced, challenges the industry to produce high quantities of probiotic cultures in a viable and stable form. Dried concentrated probiotic cultures are the most convenient form for incorporation into functional foods, given the ease of storage, handling and transport, especially for shelf-stable functional products. This chapter will discuss various aspects of the challenges associated with the manufacturing of probiotic cultures.

  6. Exopolysaccharides from marine bacteria

    NASA Astrophysics Data System (ADS)

    Chi, Zhenming; Fang, Yan

    2005-01-01

    Microbial polysaccharides represent a class of important products of growing interest for many sectors of industry. In recent years, there has been a growing interest in isolating new exopolysaccharides (EPSs)-producing bacteria from marine environments, particularly from various extreme marine environments. Many new marine microbial EPSs with novel chemical compositions, properties and structures have been found to have potential applications in fields such as adhesives, textiles, Pharmaceuticals and medicine for anti-cancer, food additives, oil recovery and metal removal in mining and industrial waste treatments, etc This paper gives a brief summary of the information about the EPSs produced by marine bacteria, including their chemical compositions, properties and structures, together with their potential applications in industry.

  7. Force-Driven Polymerization and Turgor-Induced Wall Expansion.

    PubMed

    Ali, Olivier; Traas, Jan

    2016-05-01

    While many molecular players involved in growth control have been identified in the past decades, it is often unknown how they mechanistically act to induce specific shape changes during development. Plant morphogenesis results from the turgor-induced yielding of the extracellular and load-bearing cell wall. Its mechanochemical equilibrium appears as a fundamental link between molecular growth regulation and the effective shape evolution of the tissue. We focus here on force-driven polymerization of the cell wall as a central process in growth control. We propose that mechanical forces facilitate the insertion of wall components, in particular pectins, a process that can be modulated through genetic regulation. We formalize this idea in a mathematical model, which we subsequently test with published experimental results. PMID:26895732

  8. Bacteria in Confined Spaces

    NASA Astrophysics Data System (ADS)

    Wilking, Connie; Weitz, David

    2010-03-01

    Bacterial cells can display differentiation between several developmental pathways, from planktonic to matrix-producing, depending upon the colony conditions. We study the confinement of bacteria in hydrogels as well as in liquid-liquid double emulsion droplets and observe the growth and morphology of these colonies as a function of time and environment. Our results can give insight into the behavior of bacterial colonies in confined spaces that can have applications in the areas of food science, cosmetics, and medicine.

  9. Denitrification by extremely halophilic bacteria

    NASA Technical Reports Server (NTRS)

    Hochstein, L. I.; Tomlinson, G. A.

    1985-01-01

    Extremely halophilic bacteria were isolated from widely separated sites by anaerobic enrichment in the presence of nitrate. The anaerobic growth of several of these isolates was accompanied by the production of nitrite, nitrous oxide, and dinitrogen. These results are a direct confirmation of the existence of extremely halophilic denitrifying bacteria, and suggest that such bacteria may be common inhabitants of hypersaline environments.

  10. Growing Unculturable Bacteria

    PubMed Central

    2012-01-01

    The bacteria that can be grown in the laboratory are only a small fraction of the total diversity that exists in nature. At all levels of bacterial phylogeny, uncultured clades that do not grow on standard media are playing critical roles in cycling carbon, nitrogen, and other elements, synthesizing novel natural products, and impacting the surrounding organisms and environment. While molecular techniques, such as metagenomic sequencing, can provide some information independent of our ability to culture these organisms, it is essentially impossible to learn new gene and pathway functions from pure sequence data. A true understanding of the physiology of these bacteria and their roles in ecology, host health, and natural product production requires their cultivation in the laboratory. Recent advances in growing these species include coculture with other bacteria, recreating the environment in the laboratory, and combining these approaches with microcultivation technology to increase throughput and access rare species. These studies are unraveling the molecular mechanisms of unculturability and are identifying growth factors that promote the growth of previously unculturable organisms. This minireview summarizes the recent discoveries in this area and discusses the potential future of the field. PMID:22661685

  11. Biocide tolerance in bacteria.

    PubMed

    Ortega Morente, Elena; Fernández-Fuentes, Miguel Angel; Grande Burgos, Maria José; Abriouel, Hikmate; Pérez Pulido, Rubén; Gálvez, Antonio

    2013-03-01

    Biocides have been employed for centuries, so today a wide range of compounds showing different levels of antimicrobial activity have become available. At the present time, understanding the mechanisms of action of biocides has also become an important issue with the emergence of bacterial tolerance to biocides and the suggestion that biocide and antibiotic resistance in bacteria might be linked. While most of the mechanisms providing antibiotic resistance are agent specific, providing resistance to a single antimicrobial or class of antimicrobial, there are currently numerous examples of efflux systems that accommodate and, thus, provide tolerance to a broad range of structurally unrelated antimicrobials, both antibiotics and biocides. If biocide tolerance becomes increasingly common and it is linked to antibiotic resistance, not only resistant (even multi-resistant) bacteria could be passed along the food chain, but also there are resistance determinants that can spread and lead to the emergence of new resistant microorganisms, which can only be detected and monitored when the building blocks of resistance traits are understood on the molecular level. This review summarizes the main advances reached in understanding the mechanism of action of biocides, the mechanisms of bacterial resistance to both biocides and antibiotics, and the incidence of biocide tolerance in bacteria of concern to human health and the food industry. PMID:23340387

  12. Primary innate immune cells respond efficiently to polymeric peptidoglycan but not to peptidoglycan monomers1

    PubMed Central

    Iyer, Janaki K.; Coggeshall, K. Mark

    2011-01-01

    The cell wall of bacteria induces pro-inflammatory cytokines in monocytes and neutrophils in human blood. The nature of the stimulating component of bacterial cell walls is not well understood. We have previously shown polymeric peptidoglycan (PGN2) has this activity, and the cytokine response requires PGN internalization and trafficking to lysosomes. Here, we demonstrate that peptidoglycan monomers like muramyl dipeptide and soluble peptidoglycan fail to induce robust cytokine production in immune cells although they activate the NOD proteins in transfected cell models. We further show that lysosomal extracts from immune cells degrade intact peptidoglycan into simpler products and that the lysosomal digestion products activate the NOD proteins. We conclude that naïve innate immune cells recognize PGN in its polymeric form rather than monomers such as muramyl dipeptide and require PGN lysosomal hydrolysis to respond. These findings offer new opportunities in the treatment of sepsis, especially sepsis arising from Gram-positive organisms. PMID:21357534

  13. Engineering an artificial amoeba propelled by nanoparticle-triggered actin polymerization.

    PubMed

    Yi, Jinsoo; Schmidt, Jacob; Chien, Aichi; Montemagno, Carlo D

    2009-02-25

    We have engineered an amoeba system combining nanofabricated inorganic materials with biological components, capable of propelling itself via actin polymerization. The nanofabricated materials have a mechanism similar to the locomotion of the Listeria monocytogenes, food poisoning bacteria. The propulsive force generation utilizes nanoparticles made from nickel and gold functionalized with the Listeria monocytogenes transmembrane protein, ActA. These Listeria-mimic nanoparticles were in concert with actin, actin binding proteins, ATP (adenosine triphosphate) and encapsulated within a lipid vesicle. This system is an artificial cell, such as a vesicle, where artificial nanobacteria and actin polymerization machinery are used in driving force generators inside the cell. The assembled structure was observed to crawl on a glass surface analogously to an amoeba, with the speed of the movement dependent on the amount of actin monomers and ATP present. PMID:19417437

  14. Engineering an artificial amoeba propelled by nanoparticle-triggered actin polymerization

    NASA Astrophysics Data System (ADS)

    Yi, Jinsoo; Schmidt, Jacob; Chien, Aichi; Montemagno, Carlo D.

    2009-02-01

    We have engineered an amoeba system combining nanofabricated inorganic materials with biological components, capable of propelling itself via actin polymerization. The nanofabricated materials have a mechanism similar to the locomotion of the Listeria monocytogenes, food poisoning bacteria. The propulsive force generation utilizes nanoparticles made from nickel and gold functionalized with the Listeria monocytogenes transmembrane protein, ActA. These Listeria-mimic nanoparticles were in concert with actin, actin binding proteins, ATP (adenosine triphosphate) and encapsulated within a lipid vesicle. This system is an artificial cell, such as a vesicle, where artificial nanobacteria and actin polymerization machinery are used in driving force generators inside the cell. The assembled structure was observed to crawl on a glass surface analogously to an amoeba, with the speed of the movement dependent on the amount of actin monomers and ATP present.

  15. Polymerization in emulsion microdroplet reactors

    NASA Astrophysics Data System (ADS)

    Carroll, Nick J.

    The goal of this research project is to utilize emulsion droplets as chemical reactors for execution of complex polymerization chemistries to develop unique and functional particle materials. Emulsions are dispersions of immiscible fluids where one fluid usually exists in the form of drops. Not surprisingly, if a liquid-to-solid chemical reaction proceeds to completion within these drops, the resultant solid particles will possess the shape and relative size distribution of the drops. The two immiscible liquid phases required for emulsion polymerization provide unique and complex chemical and physical environments suitable for the engineering of novel materials. The development of novel non-ionic fluorosurfactants allows fluorocarbon oils to be used as the continuous phase in a water-free emulsion. Such emulsions enable the encapsulation of almost any hydrocarbon compound in droplets that may be used as separate compartments for water-sensitive syntheses. Here, we exemplify the promise of this approach by suspension polymerization of polyurethanes (PU), in which the liquid precursor is emulsified into droplets that are then converted 1:1 into polymer particles. The stability of the droplets against coalescence upon removal of the continuous phase by evaporation confirms the formation of solid PU particles. These results prove that the water-free environment of fluorocarbon based emulsions enables high conversion. We produce monodisperse, cross-linked, and fluorescently labeled PU-latexes with controllable mesh size through microfluidic emulsification in a simple one-step process. A novel method for the fabrication of monodisperse mesoporous silica particles is presented. It is based on the formation of well-defined equally sized emulsion droplets using a microfluidic approach. The droplets contain the silica precursor/surfactant solution and are suspended in hexadecane as the continuous oil phase. The solvent is then expelled from the droplets, leading to

  16. Stereo- and Temporally Controlled Coordination Polymerization Triggered by Alternating Addition of a Lewis Acid and Base.

    PubMed

    Liu, Bo; Cui, Dongmei; Tang, Tao

    2016-09-19

    Significant progress has been made with regard to temporally controlled radical and ring-opening polymerizations, for example, by means of chemical reagents, light, and voltage, whereas quantitative switch coordination polymerization is still challenging. Herein, we report the temporally and stereocontrolled 3,4-polymerization of isoprene through allosterically regulating the active metal center by alternating addition of Lewis basic pyridine to "poison" the Lewis acidic active metal species through acid-base interactions and Lewis acidic Al(i) Bu3 to release the original active species through pyridine abstraction. This process is quick, quantitative, and can be repeated multiple times while maintaining high 3,4-selectivity. Moreover, this strategy is also effective for the switch copolymerization of isoprene and styrene with dual 3,4- and syndiotactic selectivity. Tuning the switch cycles and intervals enables the isolation of various copolymers with different distributions of 3,4-polyisoprene and syndiotactic polystyrene sequences. PMID:27539866

  17. Synthesis of hollow polymeric nanoparticles for protein delivery via inverse miniemulsion periphery RAFT polymerization.

    PubMed

    Utama, Robert H; Guo, Yi; Zetterlund, Per B; Stenzel, Martina H

    2012-11-21

    Hollow polymeric nanoparticles with a hydrophilic liquid core have been synthesized in a one-pot approach via a novel inverse miniemulsion periphery RAFT polymerization process. Successful encapsulation and release of a model protein is reported as a potential application. PMID:23041953

  18. Polarity and the diversity of growth mechanisms in bacteria

    PubMed Central

    Brown, Pamela J.B.; Kysela, David T.; Brun, Yves V.

    2011-01-01

    Bacterial cell growth is a complex process consisting of two distinct phases: cell elongation and septum formation prior to cell division. Although bacteria have evolved several different mechanisms for cell growth, it is clear that tight spatial and temporal regulation of peptidoglycan synthesis is a common theme. In this review, we discuss bacterial cell growth with a particular emphasis on bacteria that utilize tip extension as a mechanism for cell elongation. We describe polar growth among diverse bacteria and consider the advantages and consequences of this mode of cell elongation. PMID:21736947

  19. Mechanical force-induced polymerization and depolymerization of F-actin at water/solid interfaces.

    PubMed

    Zhang, Xueqiang; Hu, Xiuyuan; Lei, Haozhi; Hu, Jun; Zhang, Yi

    2016-03-21

    Actin molecules are among the three main cytoskeleton proteins of cells and undergo rapid cycling to regulate critical processes such as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. Although extensive studies have been carried out on the dynamics as well as biological functions of actin polymerization and depolymerization both in vivo and in vitro, the molecular mechanisms by which cells sense and respond to mechanical signals are not fully understood. In particular, little attention has been paid to the effect of a physical force that is exerted directly on the actin cytoskeleton. In this paper, we have explored how the mechanical force affects the actin polymerization and depolymerization behaviors at water/solid interfaces using an atomic force microscope (AFM) operated in liquid. By raster scanning an AFM probe on a substrate surface with a certain load, it was found that actin monomers could polymerize into filaments without the help of actin related proteins (ARPs). Further study indicated that actin monomers were inclined to form filaments only under a small scanning load. The polymerized actin filaments would be depolymerized when the mechanical force was stronger. A possible mechanism has been suggested to explain the mechanical force induced actin polymerization. PMID:26928199

  20. Fluorescent dye-labelled polymer synthesis by nitroxide mediated radical polymerization

    NASA Astrophysics Data System (ADS)

    Kollár, Jozef; Chmela, Štefan; Hrčková, Ľudmila; Hrdlovič, Pavol

    2012-07-01

    New applications of polymers at advanced technologies demand increased requirements on their properties. These properties are influenced by molecular as well as supramolecular structure. Controlled radical polymerization mediated by stable nitroxides (NMP) or substituted alkoxyamines offers simple method for preparation of polymers with programmable structure of macromolecules which possess remarkable better physical as well as chemical properties. They can be used as a macro initiators for the synthesis of block copolymers. At the present time it has been generally accepted that the extent of "livingness" is high for all conversions [1-4]. To verify this statement a series of fluorescent dye-labelled regulators has been synthesized, spectrally characterized and used as the mediators of styrene and n-butyl acrylate polymerization. Direct quantification of dormant species concentration (extent of livingness) and calculation of molar mass of marked polymers was performed by absorption and/or emission spectroscopy. Controlled radical polymerization mediated by stable nitroxides bearing fluorescence mark represents unconventional approach for monitoring and evaluation of mechanism and kinetics of polymerization process. Results indicate that the extent of livingness is strongly influenced by conversion as well as mediator concentration. There is a clear tendency toward to decreasing amount of dormant species with increasing monomer conversion. Moreover, lower mediator concentration decreases livingness of polymerization process.

  1. BioNLP Shared Task - The Bacteria Track

    PubMed Central

    2012-01-01

    Background We present the BioNLP 2011 Shared Task Bacteria Track, the first Information Extraction challenge entirely dedicated to bacteria. It includes three tasks that cover different levels of biological knowledge. The Bacteria Gene Renaming supporting task is aimed at extracting gene renaming and gene name synonymy in PubMed abstracts. The Bacteria Gene Interaction is a gene/protein interaction extraction task from individual sentences. The interactions have been categorized into ten different sub-types, thus giving a detailed account of genetic regulations at the molecular level. Finally, the Bacteria Biotopes task focuses on the localization and environment of bacteria mentioned in textbook articles. We describe the process of creation for the three corpora, including document acquisition and manual annotation, as well as the metrics used to evaluate the participants' submissions. Results Three teams submitted to the Bacteria Gene Renaming task; the best team achieved an F-score of 87%. For the Bacteria Gene Interaction task, the only participant's score had reached a global F-score of 77%, although the system efficiency varies significantly from one sub-type to another. Three teams submitted to the Bacteria Biotopes task with very different approaches; the best team achieved an F-score of 45%. However, the detailed study of the participating systems efficiency reveals the strengths and weaknesses of each participating system. Conclusions The three tasks of the Bacteria Track offer participants a chance to address a wide range of issues in Information Extraction, including entity recognition, semantic typing and coreference resolution. We found commond trends in the most efficient systems: the systematic use of syntactic dependencies and machine learning. Nevertheless, the originality of the Bacteria Biotopes task encouraged the use of interesting novel methods and techniques, such as term compositionality, scopes wider than the sentence. PMID:22759457

  2. Structure, Function, and Assembly of Adhesive Organelles by Uropathogenic Bacteria

    PubMed Central

    Chahales, Peter; Thanassi, David G.

    2015-01-01

    Bacteria assemble a wide range of adhesive proteins, termed adhesins, to mediate binding to receptors and colonization of surfaces. For pathogenic bacteria, adhesins are critical for early stages of infection, allowing the bacteria to initiate contact with host cells, colonize different tissues, and establish a foothold within the host. The adhesins expressed by a pathogen are also critical for bacterial-bacterial interactions and the formation of bacterial communities such as biofilms. The ability to adhere to host tissues is particularly important for bacteria that colonize sites such as the urinary tract, where the flow of urine functions to maintain sterility by washing away non-adherent pathogens. Adhesins vary from monomeric proteins that are directly anchored to the bacterial surface to polymeric, hairlike fibers that extend out from the cell surface. These latter fibers are termed pili or fimbriae, and were among the first identified virulence factors of uropathogenic Escherichia coli. Studies since then have identified a range of both pilus and non-pilus adhesins that contribute to bacterial colonization of the urinary tract, and have revealed molecular details of the structures, assembly pathways, and functions of these adhesive organelles. In this review, we describe the different types of adhesins expressed by both Gram-negative and Gram-positive uropathogens, what is known about their structures, how they are assembled on the bacterial surface, and the functions of specific adhesins in the pathogenesis of urinary tract infections. PMID:26542038

  3. Bacteria counting method based on polyaniline/bacteria thin film.

    PubMed

    Zhihua, Li; Xuetao, Hu; Jiyong, Shi; Xiaobo, Zou; Xiaowei, Huang; Xucheng, Zhou; Tahir, Haroon Elrasheid; Holmes, Mel; Povey, Malcolm

    2016-07-15

    A simple and rapid bacteria counting method based on polyaniline (PANI)/bacteria thin film was proposed. Since the negative effects of immobilized bacteria on the deposition of PANI on glass carbon electrode (GCE), PANI/bacteria thin films containing decreased amount of PANI would be obtained when increasing the bacteria concentration. The prepared PANI/bacteria film was characterized with cyclic voltammetry (CV) technique to provide quantitative index for the determination of the bacteria count, and electrochemical impedance spectroscopy (EIS) was also performed to further investigate the difference in the PANI/bacteria films. Good linear relationship of the peak currents of the CVs and the log total count of bacteria (Bacillus subtilis) could be established using the equation Y=-30.413X+272.560 (R(2)=0.982) over the range of 5.3×10(4) to 5.3×10(8)CFUmL(-1), which also showed acceptable stability, reproducibility and switchable ability. The proposed method was feasible for simple and rapid counting of bacteria. PMID:26921555

  4. Fire-Retardant Polymeric Additives

    NASA Technical Reports Server (NTRS)

    Williams, Martha K.; Smith, Trent M.

    2011-01-01

    component forms polybenzoxazole (PBO) in a reaction that absorbs heat from its surroundings. PBO under thermal stress cross-links, forming a protective char layer, which thermally insulates the polymer. Thus, the formation of the char layer further assists to extinguish the fire by preventing vaporization of the polymeric fuel.

  5. Mixing in polymeric microfluidic devices.

    SciTech Connect

    Schunk, Peter Randall; Sun, Amy Cha-Tien; Davis, Robert H.; Brotherton, Christopher M. (University of Colorado at Boulder, Boulder, CO)

    2006-04-01

    This SAND report describes progress made during a Sandia National Laboratories sponsored graduate fellowship. The fellowship was funded through an LDRD proposal. The goal of this project is development and characterization of mixing strategies for polymeric microfluidic devices. The mixing strategies under investigation include electroosmotic flow focusing, hydrodynamic focusing, physical constrictions and porous polymer monoliths. For electroosmotic flow focusing, simulations were performed to determine the effect of electroosmotic flow in a microchannel with heterogeneous surface potential. The heterogeneous surface potential caused recirculations to form within the microchannel. These recirculations could then be used to restrict two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the mixing region surface potential to the average channel surface potential was made large in magnitude and negative in sign, and when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Based on these results, experiments were performed to evaluate the manipulation of surface potential using living-radical photopolymerization. The material chosen to manipulate typically exhibits a negative surface potential. Using living-radical surface grafting, a positive surface potential was produced using 2-(Dimethylamino)ethyl methacrylate and a neutral surface was produced using a poly(ethylene glycol) surface graft. Simulations investigating hydrodynamic focusing were also performed. For this technique, mixing is enhanced by using a tertiary fluid stream to constrict the two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the tertiary flow stream flow-rate to the mixing streams flow-rate was maximized. Also, like the electroosmotic focusing mixer, mixing was also maximized when the ratio of the characteristic convection time to the

  6. Bacteria in solitary confinement.

    PubMed

    Mullineaux, Conrad W

    2015-02-15

    Even in clonal bacterial cultures, individual bacteria can show substantial stochastic variation, leading to pitfalls in the interpretation of data derived from millions of cells in a culture. In this issue of the Journal of Bacteriology, as part of their study on osmoadaptation in a cyanobacterium, Nanatani et al. describe employing an ingenious microfluidic device that gently cages individual cells (J Bacteriol 197:676-687, 2015, http://dx.doi.org/10.1128/JB.02276-14). The device is a welcome addition to the toolkit available to probe the responses of individual cells to environmental cues. PMID:25488297

  7. Bacteria in Solitary Confinement

    PubMed Central

    2014-01-01

    Even in clonal bacterial cultures, individual bacteria can show substantial stochastic variation, leading to pitfalls in the interpretation of data derived from millions of cells in a culture. In this issue of the Journal of Bacteriology, as part of their study on osmoadaptation in a cyanobacterium, Nanatani et al. describe employing an ingenious microfluidic device that gently cages individual cells (J Bacteriol 197:676–687, 2015, http://dx.doi.org/10.1128/JB.02276-14). The device is a welcome addition to the toolkit available to probe the responses of individual cells to environmental cues. PMID:25488297

  8. Surface layers of bacteria.

    PubMed Central

    Beveridge, T J; Graham, L L

    1991-01-01

    Since bacteria are so small, microscopy has traditionally been used to study them as individual cells. To this end, electron microscopy has been a most powerful tool for studying bacterial surfaces; the viewing of macromolecular arrangements of some surfaces is now possible. This review compares older conventional electron-microscopic methods with new cryotechniques currently available and the results each has produced. Emphasis is not placed on the methodology but, rather, on the importance of the results in terms of our perception of the makeup and function of bacterial surfaces and their interaction with the surrounding environment. Images PMID:1723487

  9. Reversible addition-fragmentation chain transfer polymerization in microemulsion.

    PubMed

    O'Donnell, Jennifer M

    2012-04-21

    This tutorial review first details the uncontrolled microemulsion polymerization mechanism, and the RAFT polymerization mechanism to provide the necessary background for examining the RAFT microemulsion polymerization mechanism. The effect of the chain transfer agent per micelle ratio and the chain transfer agent aqueous solubility on the RAFT microemulsion polymerization kinetics, polymer molecular weight and polydispersity, and polymer nanoparticle size are discussed with a focus on oil-in-water microemulsions. Modeling of RAFT microemulsion polymerization kinetics and the resulting final polymer molecular weight are presented to assist with the analysis of observed experimental trends. Lastly, the current significance of RAFT microemulsion polymerization and the future directions are discussed. PMID:22246214

  10. Equilibrium polymerization on the equivalent-neighbor lattice

    NASA Technical Reports Server (NTRS)

    Kaufman, Miron

    1989-01-01

    The equilibrium polymerization problem is solved exactly on the equivalent-neighbor lattice. The Flory-Huggins (Flory, 1986) entropy of mixing is exact for this lattice. The discrete version of the n-vector model is verified when n approaches 0 is equivalent to the equal reactivity polymerization process in the whole parameter space, including the polymerized phase. The polymerization processes for polymers satisfying the Schulz (1939) distribution exhibit nonuniversal critical behavior. A close analogy is found between the polymerization problem of index the Schulz r and the Bose-Einstein ideal gas in d = -2r dimensions, with the critical polymerization corresponding to the Bose-Einstein condensation.

  11. Investigation of Solution Polymerizations in Microgravity and 1 G

    NASA Technical Reports Server (NTRS)

    Kennedy, Alvin P.

    1998-01-01

    The in-situ dielectric spectra for the solution polymerization of polydiacetylene has been successfully measured. The results show a distinct difference between the response for the bulk solution and surface polymerization. It also shows a low frequency peak in the dissipation factor which is present in both the bulk and surface polymerizations. These features may prove to be significant indicators for important polymerization processes. Future studies will investigate the mechanisms responsible for these dielectric responses. This technique will eventually be used to monitor microgravity polymerizations and provide in-situ data on how microgravity affects solution polymerization.

  12. Cyclic diguanylate signaling in Gram-positive bacteria.

    PubMed

    Purcell, Erin B; Tamayo, Rita

    2016-09-01

    The nucleotide second messenger 3'-5' cyclic diguanylate monophosphate (c-di-GMP) is a central regulator of the transition between motile and non-motile lifestyles in bacteria, favoring sessility. Most research investigating the functions of c-di-GMP has focused on Gram-negative species, especially pathogens. Recent work in Gram-positive species has revealed that c-di-GMP plays similar roles in Gram-positives, though the precise targets and mechanisms of regulation may differ. The majority of bacterial life exists in a surface-associated state, with motility allowing bacteria to disseminate and colonize new environments. c-di-GMP signaling regulates flagellum biosynthesis and production of adherence factors and appears to be a primary mechanism by which bacteria sense and respond to surfaces. Ultimately, c-di-GMP influences the ability of a bacterium to alter its transcriptional program, physiology and behavior upon surface contact. This review discusses how bacteria are able to sense a surface via flagella and type IV pili, and the role of c-di-GMP in regulating the response to surfaces, with emphasis on studies of Gram-positive bacteria. PMID:27354347

  13. Universal metastability of sickle hemoglobin polymerization

    NASA Astrophysics Data System (ADS)

    Weng, Weijun

    Sickle hemoglobin (HbS) is a natural mutation of the normal hemoglobin (HbA) found in the red blood cells of human body. Polymerization of HbS occurs when the concentration of deoxyHbS exceeds a well-defined solubility, which is the underlying cause of the Sickle Cell Disease. It has long been assumed that thermodynamic equilibrium is reached when polymerization comes to an end. However, in this thesis we demonstrate that in confined volume as well as in bulk solution, HbS polymerization terminates prematurely, leaving the solution in a metastable state. A newly developed Reservoir method as well as modulated excitation method were adopted for the study. This discovery of universal metastability gives us new insights into understanding the mechanism of sickle cell disease.

  14. Immobilization of Polymeric Luminophor on Nanoparticles Surface

    NASA Astrophysics Data System (ADS)

    Bolbukh, Yuliia; Podkoscielna, Beata; Lipke, Agnieszka; Bartnicki, Andrzej; Gawdzik, Barbara; Tertykh, Valentin

    2016-04-01

    Polymeric luminophors with reduced toxicity are of the priorities in the production of lighting devices, sensors, detectors, bioassays or diagnostic systems. The aim of this study was to develop a method of immobilization of the new luminophor on a surface of nanoparticles and investigation of the structure of the grafted layer. Monomer 2,7-(2-hydroxy-3-methacryloyloxypropoxy)naphthalene (2,7-NAF.DM) with luminophoric properties was immobilized on silica and carbon nanotubes in two ways: mechanical mixing with previously obtained polymer and by in situ oligomerization with chemisorption after carrier's modification with vinyl groups. The attached polymeric (or oligomeric) surface layer was studied using thermal and spectral techniques. Obtained results confirm the chemisorption of luminophor on the nanotubes and silica nanoparticles at the elaborated synthesis techniques. The microstructure of 2,7-NAF.DM molecules after chemisorption was found to be not changed. The elaborated modification approach allows one to obtain nanoparticles uniformly covered with polymeric luminophor.

  15. Supramolecular Polymerization Engineered with Molecular Recognition.

    PubMed

    Haino, Takeharu

    2015-10-01

    Supramolecular polymeric assemblies represent an emerging, promising class of molecular assemblies with enormous versatility compared with their covalent polymeric counterparts. Although a large number of host-guest motifs have been produced over the history of supramolecular chemistry, only a limited number of recognition motifs have been utilized as supramolecular connections in polymeric assemblies. This account describes the molecular recognition of host molecules based on calix[5]arene and bisporphyrin that demonstrate unique guest encapsulations; subsequently, these host-guest motifs are applied to the synthesis of supramolecular polymers that display polymer-like properties in solution and solid states. In addition, new bisresorcinarenes are developed to form supramolecular polymers that are connected via a rim-to-rim hydrogen-bonded dimeric structure, which is composed of two resorcinarene moieties. PMID:26178364

  16. Molecular Probe Fluorescence Monitoring of Polymerization

    NASA Technical Reports Server (NTRS)

    Bunton, Patrick

    2002-01-01

    This project investigated the feasibility of using fluorescence spectroscopy to determine viscosity of polymer/monomer in support of Transient Interfacial Phenomena in Miscible Polymer Systems (TIPMPS). This project will attempt to measure gradient induced flow at a miscible interface during and / or after in-flight polymerization of dodecyl acrylate (lauryl acrylate). Concentration and temperature gradients will be intentionally introduced during polymerization and the resultant fluid flow determined by Particle Imaging Velocimetry (PIV). This report describes an investigation of the feasibility of using fluorescence of a probe molecule to monitor viscosity and/or concentration during and after polymerization. The probe used was pyrene which has been shown to be sensitive to its local environment in methyl methacrylate.

  17. Quorum sensing in plant-pathogenic bacteria.

    PubMed

    Von Bodman, Susanne B; Bauer, W Dietz; Coplin, David L

    2003-01-01

    Quorum sensing (QS) allows bacteria to assess their local population density and/or physical confinement via the secretion and detection of small, diffusible signal molecules. This review describes how phytopathogenic bacteria have incorporated QS mechanisms into complex regulatory cascades that control genes for pathogenicity and colonization of host surfaces. Traits regulated by QS include the production of extracellular polysaccharides, degradative enzymes, antibiotics, siderophores, and pigments, as well as Hrp protein secretion, Ti plasmid transfer, motility, biofilm formation, and epiphytic fitness. Since QS regulatory systems are often required for pathogenesis, interference with QS signaling may offer a means of controlling bacterial diseases of plants. Several bacterial pathogens of plants that have been intensively studied and have revealed information of both fundamental and practical importance are reviewed here: Agrobacterium tumefaciens, Pantoea stewartii, Erwinia carotovora, Ralstonia solanacearum, Pseudomonas syringae, Pseudomonas aeruginosa, and Xanthomonas campestris. PMID:12730390

  18. Pattern Formation in Growing Polar Bacteria

    NASA Astrophysics Data System (ADS)

    Yang, Xingbo; Marchetti, M.; Marenduzzo, Davide

    2013-03-01

    We analyze a continuum model of a bacterial suspension that includes motility suppression from steric repulsion, polar alignment, and bacteria reproduction and death. Using a combination of linear stability analysis and numerical solution of the nonlinear equations, we demonstrate that the model exhibits a rich variety of emergent structures, corresponding to generic patterns seen in experiments. Motility suppression in a crowded environment gives rise to a density phase separation, regulated by the growth/death of the bacteria, as demonstrated earlier by Cates et al. [PNAS 107, 11715-11720(2010)], with spherically symmetric patterns similar to those observed in S. typhimurium. The addition of polar alignment yields new ring/band and swirl/spiral structures resembling those observed in E.coli colonies. The stationary/traveling nature of the patterns and their symmetry is classified and summarized in a phase diagram. This work was supported by the NSF through grant DMR-1004789.

  19. Bacterial cell surface properties: role of loosely bound extracellular polymeric substances (LB-EPS).

    PubMed

    Zhao, Wenqiang; Yang, Shanshan; Huang, Qiaoyun; Cai, Peng

    2015-04-01

    This study investigated the effect of loosely bound extracellular polymeric substances (LB-EPS) on the comprehensive surface properties of four bacteria (Bacillus subtilis, Streptococcus suis, Escherichia coli and Pseudomonas putida). The removal of LB-EPS from bacterial surfaces by high-speed centrifugation (12,000×g) was confirmed by SEM images. Viability tests showed that the percentages of viable cells ranged from 95.9% to 98.0%, and no significant difference was found after treatment (P>0.05). FTIR spectra revealed the presence of phosphodiester, carboxylic, phosphate, and amino functional groups on bacteria surfaces, and the removal of LB-EPS did not alter the types of cell surface functional groups. Potentiometric titration results suggested the total site concentrations on the intact bacteria were higher than those on LB-EPS free bacteria. Most of the acidity constants (pKa) were almost identical, except the increased pKa values of phosphodiester groups on LB-EPS free S. suis and E. coli surfaces. The electrophoretic mobilities and hydrodynamic diameters of the intact and LB-EPS free bacteria were statistically unchanged (P>0.05), indicating LB-EPS had no influence on the net surface charges and size distribution of bacteria. However, LB-ESP could enhance cell aggregation processes. The four LB-EPS free bacteria all exhibited fewer hydrophobicity values (26.1-65.0%) as compared to the intact cells (47.4-69.3%), suggesting the removal of uncharged nonpolar compounds (e.g., carbohydrates) in LB-EPS. These findings improve our understanding of the changes in cell surface characterizations induced by LB-EPS, and have important implications for assessing the role of LB-EPS in bacterial adhesion and transport behaviors. PMID:25805151

  20. Fabrication of triazinedithiol functional polymeric nanofilm by potentiostatic polymerization on aluminum surface

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Wang, Yabin; Li, Yanni; Wang, Qian

    2011-01-01

    The functional polymeric nanofilm of 6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-dithiol monosodium (AF17N) was prepared on pure aluminum surface by potentiostatic polymerization at different potentials. The thickness and weight of polymeric nanofilm increased proportionally to electro-polymerization potential following linear equation. The chemical structure of nanofilm was characterized by Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Adsorption peaks in FT-IR and C1s, N1s, S2p, F1s and Al2p peaks in XPS spectra indicated that the polymeric nanofilm was poly(6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-disulfide) (PAF17). The morphologies of polymeric nanofilm were also observed by atomic force microscopy (AFM). All the results showed that the optimal electro-polymerization potential and time were 8 V and 20 s, respectively. Uniform and compact nanofilm of PAF17 could be obtained under these conditions. It is expected that this technique will be applied in the preparation of lubricating, dielectric and hydrophobic surface on aluminum substrate.

  1. Surface properties of an indirect composite polymerized with five laboratory light polymerization systems.

    PubMed

    Murakami, Mahoko

    2009-06-01

    A study was conducted to evaluate the influence of laboratory light polymerization systems on the post-curing properties of a composite. An indirect composite (Sinfony) was polymerized with five polymerization systems (Visio system, Hyper LII, Pearlcure Light, Twinkle MIII, and UniXS II) using nine polymerization modes. After light exposure, Knoop hardness number, wear depth, and changes in gloss were determined. The highest hardness number was recorded with the use of the Hyper LII (120 s) and Pearlcure Light (120 s) units, whereas the lowest value was obtained with the Visio system and UniXS II (60 s). Six groups demonstrated comparable as well as higher wear resistance to toothbrush abrasion (Hyper LII 60 and 120 s, UniXS II 120 s, Pearlcure Light 60 and 120 s, and Twinkle MIII 120 s), and two groups exhibited lower wear resistance (Visio system and UniXS II 60 s). Gloss of the composite was not dependent on the polymerization mode used before wear testing. However, surface gloss was significantly reduced by toothbrush dentifrice abrasion. Within the limitations of the present experiment, it can be concluded that the Sinfony composite can be polymerized sufficiently with high-intensity light polymerization units. PMID:19550089

  2. Polymeric matrix materials for infrared metamaterials

    DOEpatents

    Dirk, Shawn M; Rasberry, Roger D; Rahimian, Kamyar

    2014-04-22

    A polymeric matrix material exhibits low loss at optical frequencies and facilitates the fabrication of all-dielectric metamaterials. The low-loss polymeric matrix material can be synthesized by providing an unsaturated polymer, comprising double or triple bonds; partially hydrogenating the unsaturated polymer; depositing a film of the partially hydrogenated polymer and a crosslinker on a substrate; and photopatterning the film by exposing the film to ultraviolet light through a patterning mask, thereby cross-linking at least some of the remaining unsaturated groups of the partially hydrogenated polymer in the exposed portions.

  3. Elasto-Inertial Turbulence in polymeric flows

    NASA Astrophysics Data System (ADS)

    Terrapon, Vincent; Dubief, Yves; Soria, Julio

    2013-11-01

    The dynamics of elasto-inertial turbulence (EIT) is investigated numerically from the perspective of the coupling between polymer dynamics and flow structures. In particular, direct numerical simulations of channel flow with Reynolds numbers ranging from 1000 to 6000 are used to study the formation and dynamics of elastic instabilities and their effects on the flow. Based on the splitting of the pressure into inertial and polymeric contributions, it is shown that the trains of cylindrical structures around thin sheets of high polymer extension that are characteristics to elasto-inertial turbulence are mostly driven by polymeric contributions. Also King Abdulaziz University, Jeddah.

  4. A Fluidic Device with Polymeric Textured Ratchets

    PubMed Central

    Sekeroglu, Koray; Demirel, Melik C.

    2014-01-01

    Nanotextured surfaces are widely used throughout nature for adhesion, wetting, and transport. Chemistry, geometry, and morphology are important factors for creating tunable textured surfaces, in which directionality of droplets can be controlled. Here, we fabricated nano textured polymeric surfaces, and studied the effect of tilting on the mobility of frequency modulated water droplet transported on asymmetric nano-PPX tracks. Plastically-deformed tracks guided water droplets for sorting, gating, and merging them as a function on their volume. Polymeric ratchets open up new avenues for the fields of digital fluidics and flexible device fabrication. PMID:25641987

  5. Polymeric materials science in the microgravity environment

    NASA Technical Reports Server (NTRS)

    Coulter, Daniel R.

    1989-01-01

    The microgravity environment presents some interesting possibilities for the study of polymer science. Properties of polymeric materials depend heavily on their processing history and environment. Thus, there seem to be some potentially interesting and useful new materials that could be developed. The requirements for studying polymeric materials are in general much less rigorous than those developed for studying metals, for example. Many of the techniques developed for working with other materials, including heat sources, thermal control hardware and noncontact temperature measurement schemes should meet the needs of the polymer scientist.

  6. Fiber optical beam shaping using polymeric structures

    NASA Astrophysics Data System (ADS)

    Rodrigues Ribeiro, R. S.; Queirós, R. B.; Guerreiro, A.; Ecoffet, C.; Soppera, O.; Jorge, P. A. S.

    2014-05-01

    A method to control the output intensity profile of optical fibers is presented. Using guided wave photopolymerization in multimode structures the fabrication with modal assisted shaping of polymeric micro lenses is demonstrated. Results showing that a given linear polarized mode can be selectively excited controlling the intensity distribution at the fiber tip are presented. This pattern is then reproduced in the polymeric micro structure fabricated at the fiber tip thus modulating its output intensity distribution. Such structures can therefore be used to obtain at the fiber tip predetermined intensity patterns for attaining optical trapping or patterned illumination.

  7. Producing ORMOSIL scaffolds by femtosecond laser polymerization

    NASA Astrophysics Data System (ADS)

    Matei, A.; Zamfirescu, M.; Radu, C.; Buruiana, E. C.; Buruiana, T.; Mustaciosu, C.; Petcu, I.; Radu, M.; Dinescu, M.

    2012-07-01

    Structures with different geometries and sizes were built via direct femtosecond laser writing, starting from new organic/inorganic hybrid monomers based on hybrid methacrylate containing triethoxysilane, in addition to urethane and urea groups. Multifunctional oligomer of urethane dimethacrylate type was chosen as comonomer in polymerization experiments because dimethacrylates give rise to the formation of a polymer network, having a number of favorable properties including biocompatibility and surface nanostructuring. Free standing polymeric structures were designed and created in order to be tested in fibroblast cells culture. Investigations of the cellular adhesion, proliferation, and viability of L929 mouse fibroblasts on free-standing laser processed scaffolds were performed for different scaffold designs.

  8. PEG based hyperbranched polymeric hollow nanospheres

    NASA Astrophysics Data System (ADS)

    Cao, Hongliang; Dong, Yixiao; O'Rorke, Suzanne; Wang, Wenxin; Pandit, Abhay

    2011-02-01

    The synthesis of a new PEG based hyperbranched copolymer of poly(ethylene glycol) methyl ether methacrylate-co-ethylene glycol dimethacrylate (PEGMEMA-co-EGDMA) was achieved via a one-step in situ deactivation enhanced atom transfer radical polymerization (DE-ATRP). Then, hollow PEG based nanospheres were fabricated from this polymer using a solvent evaporation method and post-stabilisation strategy. Furthermore, the analysis using a cellular metabolic activity assay proved that the copolymer did not affect cellular metabolism, indicating that this PEG based polymeric nanosphere has potential for use in drug delivery applications.

  9. Polymerization Initiated by Organic Electron Donors.

    PubMed

    Broggi, Julie; Rollet, Marion; Clément, Jean-Louis; Canard, Gabriel; Terme, Thierry; Gigmes, Didier; Vanelle, Patrice

    2016-05-10

    Polymerization reactions with organic electron donors (OED) as initiators are presented herein. The metal-free polymerization of various activated alkene and cyclic ester monomers was performed in short reaction times, under mild conditions, with small amounts of organic reducing agents, and without the need for co-initiators or activation by photochemical, electrochemical, or other methods. Hence, OED initiators enabled the development of an efficient, rapid, room-temperature process that meets the technical standards expected for industrial processes, such as energy savings, cost-effectiveness and safety. Mechanistic investigations support an electron-transfer initiation pathway that leads to the reduction of the monomer. PMID:27061743

  10. Biomimetic radical polymerization via cooperative assembly of segregating templates

    NASA Astrophysics Data System (ADS)

    McHale, Ronan; Patterson, Joseph P.; Zetterlund, Per B.; O'Reilly, Rachel K.

    2012-06-01

    Segregation and templating approaches have been honed by billions of years of evolution to direct many complex biological processes. Nature uses segregation to improve biochemical control by organizing reactants into defined, well-regulated environments, and the transfer of genetic information is a primary function of templating. The ribosome, wherein messenger RNA is translated into polypeptides, combines both techniques to allow for ideal biopolymer syntheses. Herein is presented a biomimetic segregation/templating approach to synthetic radical polymerization. Polymerization of a nucleobase-containing vinyl monomer in the presence of a complementary block copolymer template of low molecular weight yields high molecular weight (Mw up to ~400,000 g mol-1), extremely low polydispersity (≤1.08) daughter polymers. Control is attained by segregation of propagating radicals in discrete micelle cores (via cooperative assembly of dynamic template polymers). Significantly reduced bimolecular termination, combined with controlled propagation along a defined number of templates, ensures unprecedented control to afford well-defined high molecular weight polymers.

  11. Multiscale Model of Swarming Bacteria

    NASA Astrophysics Data System (ADS)

    Alber, Mark

    2011-03-01

    Many bacteria can rapidly traverse surfaces from which they are extracting nutrient for growth. They generate flat, spreading colonies, called swarms because they resemble swarms of insects. In the beginning of the talk, swarms of the M. xanthus will be described in detail. Individual M. xanthus cells are elongated; they always move in the direction of their long axis; and they are in constant motion, repeatedly touching each other. As a cell glides, the slime capsule of a cell interacts with the bare agar surface, non-oriented slime which arises from the surface contact with the slime capsule, or oriented slime trails. Remarkably, cells regularly reverse their gliding directions. In this talk a detailed cell- and behavior-based computational model of M. xanthus swarming will be used to demonstrate that reversals of gliding direction and cell bending are essential for swarming and that specific reversal frequencies result in optimal swarming rate of the whole population. This suggests that the circuit regulating reversals evolved to its current sensitivity under selection for growth achieved by swarming.

  12. Phenotypic switching in bacteria

    NASA Astrophysics Data System (ADS)

    Merrin, Jack

    Living matter is a non-equilibrium system in which many components work in parallel to perpetuate themselves through a fluctuating environment. Physiological states or functionalities revealed by a particular environment are called phenotypes. Transitions between phenotypes may occur either spontaneously or via interaction with the environment. Even in the same environment, genetically identical bacteria can exhibit different phenotypes of a continuous or discrete nature. In this thesis, we pursued three lines of investigation into discrete phenotypic heterogeneity in bacterial populations: the quantitative characterization of the so-called bacterial persistence, a theoretical model of phenotypic switching based on those measurements, and the design of artificial genetic networks which implement this model. Persistence is the phenotype of a subpopulation of bacteria with a reduced sensitivity to antibiotics. We developed a microfluidic apparatus, which allowed us to monitor the growth rates of individual cells while applying repeated cycles of antibiotic treatments. We were able to identify distinct phenotypes (normal and persistent) and characterize the stochastic transitions between them. We also found that phenotypic heterogeneity was present prior to any environmental cue such as antibiotic exposure. Motivated by the experiments with persisters, we formulated a theoretical model describing the dynamic behavior of several discrete phenotypes in a periodically varying environment. This theoretical framework allowed us to quantitatively predict the fitness of dynamic populations and to compare survival strategies according to environmental time-symmetries. These calculations suggested that persistence is a strategy used by bacterial populations to adapt to fluctuating environments. Knowledge of the phenotypic transition rates for persistence may provide statistical information about the typical environments of bacteria. We also describe a design of artificial

  13. Microbial influenced corrosion by thermophilic bacteria

    NASA Astrophysics Data System (ADS)

    Lata, Suman; Sharma, Chhaya; Singh, Ajay K.

    2012-03-01

    The present study was undertaken to investigate microbial influenced corrosion (MIC) on stainless steels due to thermophilic bacteria Desulfotomaculum nigrificans. The objective of the study was to measure the extent of corrosion and correlate it with the growth of the biofilm by monitoring the composition of its extracellular polymeric substances (EPS). The toxic effect of heavy metals on MIC was also observed. For this purpose, stainless steels 304L, 316L and 2205 were subjected to electrochemical polarization and immersion tests in the modified Baar's media, control and inoculated, in anaerobic conditions at room temperature. Scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) were used to identify the chemicals present in/outside the pit. The results show maximum corrosive conditions when bacterial activity is highest, which in turn minimizes the amount of carbohydrate and protein along with the increase in the fraction of uronic acid in carbohydrate in EPS of the biofilm. However, although bacterial activity and corrosion rate decreases, the amount of biofilm components continue to increase. It is also observed that the toxicity of metals ions affect the bacterial activity and EPS production. It was observed that Desulfotomaculum sp. has the ability to biodegrade its own EPS.

  14. Method of Making Thermally Stable, Piezoelectric and Proelectric Polymeric Substrates

    NASA Technical Reports Server (NTRS)

    Simpson, Joycelyn O. (Inventor); St.Clair, Terry L. (Inventor)

    1999-01-01

    A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers, acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors. in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors, weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 100 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium: applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

  15. Polymerization Initiated at the Sidewalls of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Tour, James M.; Hudson, Jared L.

    2011-01-01

    A process has been developed for growing polymer chains via anionic, cationic, or radical polymerization from the side walls of functionalized carbon nanotubes, which will facilitate greater dispersion in polymer matrices, and will greatly enhance reinforcement ability in polymeric material.

  16. The Pho regulon: a huge regulatory network in bacteria

    PubMed Central

    Santos-Beneit, Fernando

    2015-01-01

    One of the most important achievements of bacteria is its capability to adapt to the changing conditions of the environment. The competition for nutrients with other microorganisms, especially in the soil, where nutritional conditions are more variable, has led bacteria to evolve a plethora of mechanisms to rapidly fine-tune the requirements of the cell. One of the essential nutrients that are normally found in low concentrations in nature is inorganic phosphate (Pi). Bacteria, as well as other organisms, have developed several systems to cope for the scarcity of this nutrient. To date, the unique mechanism responding to Pi starvation known in detail is the Pho regulon, which is normally controlled by a two component system and constitutes one of the most sensible and efficient regulatory mechanisms in bacteria. Many new members of the Pho regulon have emerged in the last years in several bacteria; however, there are still many unknown questions regarding the activation and function of the whole system. This review describes the most important findings of the last three decades in relation to Pi regulation in bacteria, including: the PHO box, the Pi signaling pathway and the Pi starvation response. The role of the Pho regulon in nutritional regulation cross-talk, secondary metabolite production, and pathogenesis is discussed in detail. PMID:25983732

  17. Metabolic regulation via enzyme filamentation

    PubMed Central

    Aughey, Gabriel N.; Liu, Ji-Long

    2016-01-01

    Abstract Determining the mechanisms of enzymatic regulation is central to the study of cellular metabolism. Regulation of enzyme activity via polymerization-mediated strategies has been shown to be widespread, and plays a vital role in mediating cellular homeostasis. In this review, we begin with an overview of the filamentation of CTP synthase, which forms filamentous structures termed cytoophidia. We then highlight other important examples of the phenomenon. Moreover, we discuss recent data relating to the regulation of enzyme activity by compartmentalization into cytoophidia. Finally, we hypothesize potential roles for enzyme filament formation in the regulation of metabolism, development and disease. PMID:27098510

  18. Impregnated metal-polymeric functional beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Volksen, Willi (Inventor)

    1980-01-01

    Amine containing polymeric microspheres such as polyvinyl pyridine are complexed with metal salts or acids containing metals such as gold, platinum or iron. After reduction with sodium borohydride, the salt is reduced to finely divided free metal or metal oxides, useful as catalysts. Microspheres containing covalent bonding sites can be used for labeling or separating proteins.

  19. The Morphology of Emulsion Polymerized Latex Particles

    DOE R&D Accomplishments Database

    Wignall, G. D.; Ramakrishnan, V. R.; Linne, M. A.; Klein, A.; Sperling, L. H.; Wai, M. P.; Gelman, R. A.; Fatica, M. G.; Hoerl, R. H.; Fisher, L. W.

    1987-11-01

    Under monomer starved feed conditions, emulsion polymerization of perdeuterated methyl methacrylate and styrene in the presence of preformed polymethylmethacrylate latexes resulted in particles with a core-shell morphology, as determined by small-angle neutron scattering (SANS) analysis for a hollow sphere. The locus of polymerization of the added deuterated monomer is therefore at the particle surface. In similar measurements a statistical copolymer of styrene and methyl methacrylate was used as seed particles for further polymerization of trideuteromethyl methacrylate. The resulting polymer latex was again shown to have a core-shell morphological structure as determined by SANS. SANS experiments were also undertaken on polystyrene latexes polymerized by equilibrium swelling methods, with deuterated polymer forming the first or second step. The experiments covered a molecular weight range of 6 x 10{sup 4} 10{sup 6} the molecular weights are consistent with the experimental errors, indicating that the deuterium labeled molecules are randomly distributed in the latex. These results led to the finding that the polymer chains were constrained in the latex particles by factors of 2 to 4 from the relaxed coil dimensions. For M < 10{sup 6} g/mol SANS gave zero angle scattering intensities much higher than expected on the basis of a random distribution of labeled molecules. Several models were examined, including the possible development of core-shell structures at lower molecular weights.

  20. Next-generation polymeric photonic devices

    NASA Astrophysics Data System (ADS)

    Eldada, Louay A.; Shacklette, Lawrence W.; Norwood, Robert A.; Yardley, James T.

    1997-07-01

    A versatile polymeric waveguide technology is proposed for low-cost high-performance photonic devices that address the needs of both the telecom and the datacom industries. We have developed advanced organic polymeric materials that can be readily made into both multimode and single-mode optical waveguide structures of controlled numerical aperture and geometry. These materials are formed from highly-crosslinked acrylate monomers with specific linkages that determine properties such as flexibility, toughness, loss, and stability with temperature and humidity. These monomers are intermiscible, providing for precise adjustment of the refractive index from 1.3 to 1.6. Waveguides are formed photolithographically, with the liquid monomer mixture polymerizing upon illumination in the UV via either mask exposure or laser direct-writing. A wide range of rigid and flexible substrates can be used, including glass, quartz, oxidized silicon, glass-filled epoxy printed circuit board substrate, and flexible polyimide film. We discuss the use of these materials on chips, on multi-chip modules, on boards, and on backplanes. Light coupling from and to chips is achieved by cutting 45 degree(s) mirrors using excimer laser ablation. Fabrication of the planar polymeric structures directly on the modules provides for stability, ruggedness, and hermeticity in packaging.

  1. Polymeric components for telecom and datacom

    NASA Astrophysics Data System (ADS)

    Diemeer, Mart; Dekker, Ronald; Hilderink, Lucie; Leinse, Arne; Balakrishnan, Muralidharan; Faccini, Mirko; Driessen, Alfred

    2005-09-01

    Polymeric optical waveguide components offer attractive properties for applications in optical telecom and datacom systems. These are high speed for electro-optic modulators, low power dissipation for thermo-optic (digital) switches and low-cost for all active and passive components. We report on active and passive components realized by utilizing polymer-specific attractive techniques such as planarizing spincoating, low-temperature reflowing and direct photodefinition. Examples are multimode photodefined passive polymeric waveguides for optical interconnect applications; photodefined monomode polymeric waveguides loaded with rare-earth doped nanoparticles for planar waveguide amplifiers and with non-linear chromophores for electro-optic modulators. We will show that polymer waveguide technology allows vertical stacking of electro-optic microringresonators with their port waveguides to realize high-speed modulators. By reflowing the reactive-ion-etched microring we could reduce the scattering by wall roughness considerably. Thermo-optic polymeric microringresonators combine the high thermo-optic coefficient and low thermal conductivity of polymers with the small size of the microring. It will be shown that this yields a broad wavelength tuning range at low power dissipation.

  2. Dynamic modeling of emulsion polymerization reactors

    SciTech Connect

    Penlidis, A.; Hamielec, A.E.; MacGregor, J.F.

    1985-06-01

    This paper is a survey of recent published works on the dynamic and steady state modeling of emulsion homo- and copolymerization in batch, semicontinuous , and continuous latex reactors. Contributions to our understanding of diffusion-controlled termination and propagation reactions, molecular weight, long chain branching and crosslinking development, polymer particle nucleation, and of the dynamics of continuous emulsion polymerization are critically reviewed.

  3. Dynamics of polymeric drop breakup in microchannels

    NASA Astrophysics Data System (ADS)

    Arratia, Paulo; Gollub, Jerry; Durian, Douglas

    2006-11-01

    The dynamics of drop formation of sheared polymeric and Newtonian fluids are investigated in a 50 μm microchannel. Inverse emulsions are obtained in a cross-like geometry by impinging a continuous oil phase (with surfactant) onto either a polymeric or a Newtonian aqueous solution. The viscosity ratio between the continuous and dispersed phases is kept close to unity, and both flow rates are varied. Solutions containing small amounts (100 ppm) of flexible polymers strongly affect the filament and drop breakup processes when compared to a Newtonian solution of similar viscosity. We find that the thinning of the filament for the Newtonian case is characterized by linear decline followed by a rapid approach to breakup. The polymeric case shows an initial Newtonian-like thinning followed by a slower, elasticity- dominated thinning. Consequently, the filament breakup time and length are considerably increased for the polymeric solutions. Also, larger primary drops and beads-on-string phenomena are found for the polymer solutions.

  4. Biocompatibility of Experimental Polymeric Tracheal Matrices.

    PubMed

    Kiselevskii, M V; Chikileva, I O; Vlasenko, R Ya; Sitdikova, S M; Tenchurin, T Kh; Mamagulashvili, V G; Shepelev, A D; Grigoriev, T A; Chvalun, S N

    2016-08-01

    Biocompatibility of a new tracheal matrix is studied. The new matrix is based on polymeric ultra-fiber material colonized by mesenchymal multipotent stromal cells. The experiments demonstrate cytoconductivity of the synthetic matrices and no signs of their degradation within 2 months after their implantation to recipient mice. These data suggest further studies of the synthetic tracheal matrices on large laboratory animals. PMID:27591876

  5. Polymeric Electrolytic Hygrometer For Harsh Environments

    NASA Technical Reports Server (NTRS)

    Lawson, Daniel D.; Shakkottai, Parthasarathy; Venkateshan, Shakkottai P.

    1989-01-01

    Design of polymeric electrolytic hygrometer improved to meet need for reliable measurements of relative humidity in harsh environments of pulpmills and papermills. Redesigned sensor head features shorter, more-rigidly-held sensing element, less vulnerable than previous version to swell and loss of electrical contact. Useful for control of batch dryers in food and pharmaceutical industries.

  6. Non-traditional plasticization of polymeric films.

    PubMed

    Wu, C; McGinity, J W

    1999-01-15

    The objective of this study was to investigate the influence of methylparaben, ibuprofen, chlorpheniramine maleate and theophylline on the thermal and mechanical properties of polymeric films of Eudragit RS 30 D. The effects of methylparaben and ibuprofen in the film coating on the rate of drug release from Eudragit RS 30 D coated beads were also studied. The physical and mechanical properties of the cast films and coated beads were investigated using thermal analysis, tensile testing, X-ray diffraction analysis and dissolution testing. The results demonstrated that the glass transition temperature of the Eudragit RS 30 D decreased with increasing levels of methylparaben, ibuprofen and chlorpheniramine maleate in the film. Theophylline exerted no influence on the thermal properties of the polymer. The higher levels of the ibuprofen and methylparaben incorporated into the film resulted in a decrease in the tensile strength of the film. The decrease in Young's modulus of Eudragit RS 30 D coated beads was attributed to an increase in the flexibility of the polymeric films when the level of methylparaben or ibuprofen in the polymeric dispersion was increased. The dissolution data demonstrated that the rate of release of the ibuprofen from coated beads was decreased by increasing the amount of ibuprofen and methylparaben in the polymeric film coating. PMID:10205601

  7. Nanofibers And Related Structures Formed By Polymerization

    NASA Astrophysics Data System (ADS)

    Doiphode, S. V.

    2005-03-01

    Nanofibers of cyanoacrylate were obtained by polymerization from the monomer vapor at a temperature near room temperature. The nanofibers had diameters ranging from 20 nm to 100 nm and lengths of up to several millimeters. Water molecules present on the substrate initiated the living anionic polymerization. As growth continued, the living ends were carried on the tip of each growing nanofiber. These nanofibers formed on glass, metal, plastic, electrospun nanofibers of other polymers, and other surfaces. Some fibers were tapered, some were branched, and some were bent. The number of fibers was varied by controlling the exposure of the substrate to water vapor. Under different conditions the monomer vapor was collected as droplets along electrospun nanofibers, or as droplets at the points where two electrospun nanofibers crossed. The addition of the initiator caused the droplets to polymerize, forming permanent beads on the fibers, and strong mechanical connections at the cross points. This phenomenon provides new ways to construct nanofiber structures engineered on nanometer scales. For example, filters constructed from an open structure of fibers can be coated with nanofibers polymerized from a vapor of nanometer scale droplets flowing through the structure, to improve the capture of molecules or particles.

  8. Polymerization of adamantane vapors during electrical discharge

    SciTech Connect

    Fedoseev, D.V.; Lavrent'ev, A.V.; Barshavskaya, I.G.

    1987-06-01

    The authors describe the polymerization and deposition of adamantane films on quartz and molybdenum substrates under arc spraying conditions and use infrared spectroscopy, electron diffraction, and transmission electron microscopy to determine the crystal and molecular structure of the resulting film. Film microhardness and electrical conductivity were also determined as was the temperature dependence of these properties.

  9. Polymerization of epoxidized triglycerides with fluorosulfonic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of triglycerides as agri-based renewable raw materials for the development of new products is highly desirable in view of uncertain future petroleum prices. A new method of polymerizing epoxidized soybean oil has been devised with the use of fluorosulfonic acid. Depending on the reaction con...

  10. The morphology of emulsion polymerized latex particles

    SciTech Connect

    Wignall, G.D.; Ramakrishnan, V.R.; Linne, M.A.; Klein, A.; Sperling, L.H.; Wai, M.P.; Gelman, R.A.; Fatica, M.G.; Hoerl, R.H.; Fisher, L.W.

    1987-11-01

    Under monomer starved feed conditions, emulsion polymerization of perdeuterated methyl methacrylate and styrene in the presence of preformed polymethylmethacrylate latexes resulted in particles with a core-shell morphology, as determined by small-angle neutron scattering (SANS) analysis for a hollow sphere. The locus of polymerization of the added deuterated monomer is therefore at the particle surface. In similar measurements a statistical copolymer of styrene and methyl methacrylate was used as seed particles for further polymerization of trideuteromethyl methacrylate. The resulting polymer latex was again shown to have a core-shell morphological structre as determined by SANS. SANS experiments were also undertaken on polystyrene latexes polymerized by equilibrium swelling methods, with deuterated polymer forming the first or second step. The experiments covered a molecular weight range of 6 x 10/sup 4/ < M < 6 x 10/sup 6/ g/mol. For M > 10/sup 6/ the molecular weights are consistent with the experimental errors, indicating that the deuterium labeled molecules are randomly distributed in the latex. These results led to the finding that the polymer chains were constrained in the latex particles by factors of 2 to 4 from the relaxed coil dimensions. For M < 10/sup 6/ g/mol SANS gave zero angle scattering intensities much higher than expected on the basis of a random distribution of labeled molecules. Several models were examined, including the possible development of core-shell structures at lower molecular weights. 25 refs., 6 figs., 3 tabs.

  11. Impregnated metal-polymeric functional beads

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Volksen, Willi (Inventor)

    1978-01-01

    Amine containing polymeric microspheres such as polyvinyl pyridine are complexed with metal salts or acids containing metals such as gold, platinum or iron. After reduction with sodium borohydride, the salt is reduced to finely divided free metal or metal oxides, useful as catalysts. Microspheres containing covalent bonding sites can be used for labeling or separating proteins.

  12. A simple polymeric model describes cell nuclear mechanical response

    NASA Astrophysics Data System (ADS)

    Banigan, Edward; Stephens, Andrew; Marko, John

    The cell nucleus must continually resist inter- and intracellular mechanical forces, and proper mechanical response is essential to basic cell biological functions as diverse as migration, differentiation, and gene regulation. Experiments probing nuclear mechanics reveal that the nucleus stiffens under strain, leading to two characteristic regimes of force response. This behavior depends sensitively on the intermediate filament protein lamin A, which comprises the outer layer of the nucleus, and the properties of the chromatin interior. To understand these mechanics, we study a simulation model of a polymeric shell encapsulating a semiflexible polymer. This minimalistic model qualitatively captures the typical experimental nuclear force-extension relation and observed nuclear morphologies. Using a Flory-like theory, we explain the simulation results and mathematically estimate the force-extension relation. The model and experiments suggest that chromatin organization is a dominant contributor to nuclear mechanics, while the lamina protects cell nuclei from large deformations.

  13. Acyltransferases in bacteria.

    PubMed

    Röttig, Annika; Steinbüchel, Alexander

    2013-06-01

    Long-chain-length hydrophobic acyl residues play a vital role in a multitude of essential biological structures and processes. They build the inner hydrophobic layers of biological membranes, are converted to intracellular storage compounds, and are used to modify protein properties or function as membrane anchors, to name only a few functions. Acyl thioesters are transferred by acyltransferases or transacylases to a variety of different substrates or are polymerized to lipophilic storage compounds. Lipases represent another important enzyme class dealing with fatty acyl chains; however, they cannot be regarded as acyltransferases in the strict sense. This review provides a detailed survey of the wide spectrum of bacterial acyltransferases and compares different enzyme families in regard to their catalytic mechanisms. On the basis of their studied or assumed mechanisms, most of the acyl-transferring enzymes can be divided into two groups. The majority of enzymes discussed in this review employ a conserved acyltransferase motif with an invariant histidine residue, followed by an acidic amino acid residue, and their catalytic mechanism is characterized by a noncovalent transition state. In contrast to that, lipases rely on completely different mechanism which employs a catalytic triad and functions via the formation of covalent intermediates. This is, for example, similar to the mechanism which has been suggested for polyester synthases. Consequently, although the presented enzyme types neither share homology nor have a common three-dimensional structure, and although they deal with greatly varying molecule structures, this variety is not reflected in their mechanisms, all of which rely on a catalytically active histidine residue. PMID:23699259

  14. Acyltransferases in Bacteria

    PubMed Central

    Röttig, Annika

    2013-01-01

    SUMMARY Long-chain-length hydrophobic acyl residues play a vital role in a multitude of essential biological structures and processes. They build the inner hydrophobic layers of biological membranes, are converted to intracellular storage compounds, and are used to modify protein properties or function as membrane anchors, to name only a few functions. Acyl thioesters are transferred by acyltransferases or transacylases to a variety of different substrates or are polymerized to lipophilic storage compounds. Lipases represent another important enzyme class dealing with fatty acyl chains; however, they cannot be regarded as acyltransferases in the strict sense. This review provides a detailed survey of the wide spectrum of bacterial acyltransferases and compares different enzyme families in regard to their catalytic mechanisms. On the basis of their studied or assumed mechanisms, most of the acyl-transferring enzymes can be divided into two groups. The majority of enzymes discussed in this review employ a conserved acyltransferase motif with an invariant histidine residue, followed by an acidic amino acid residue, and their catalytic mechanism is characterized by a noncovalent transition state. In contrast to that, lipases rely on completely different mechanism which employs a catalytic triad and functions via the formation of covalent intermediates. This is, for example, similar to the mechanism which has been suggested for polyester synthases. Consequently, although the presented enzyme types neither share homology nor have a common three-dimensional structure, and although they deal with greatly varying molecule structures, this variety is not reflected in their mechanisms, all of which rely on a catalytically active histidine residue. PMID:23699259

  15. 40 CFR 721.10299 - Polymeric MDI based polyurethanes (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Polymeric MDI based polyurethanes... Specific Chemical Substances § 721.10299 Polymeric MDI based polyurethanes (generic). (a) Chemical... as polymeric MDI based polyurethanes (PMNs P-00-2, P-00-5, and P-00-6) are subject to reporting...

  16. 40 CFR 721.10299 - Polymeric MDI based polyurethanes (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Polymeric MDI based polyurethanes... Specific Chemical Substances § 721.10299 Polymeric MDI based polyurethanes (generic). (a) Chemical... as polymeric MDI based polyurethanes (PMNs P-00-2, P-00-5, and P-00-6) are subject to reporting...

  17. 40 CFR 721.10299 - Polymeric MDI based polyurethanes (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Polymeric MDI based polyurethanes... Specific Chemical Substances § 721.10299 Polymeric MDI based polyurethanes (generic). (a) Chemical... as polymeric MDI based polyurethanes (PMNs P-00-2, P-00-5, and P-00-6) are subject to reporting...

  18. Sulfhydryl Binding Sites within Bacterial Extracellular Polymeric Substances.

    PubMed

    Yu, Qiang; Fein, Jeremy B

    2016-06-01

    In this study, the concentration of sulfhydryl sites on bacterial biomass samples with and without extracellular polymeric substances (EPS) was measured in order to determine the distribution of sulfhydryl sites on bacteria. Three different approaches were employed for EPS removal from Pseudomonas putida, and the measured sulfhydryl concentrations on bacterial EPS molecules are independent of the EPS removal protocols used. Prior to EPS removal, the measured sulfhydryl sites within P. putida samples was 34.9 ± 9.5 μmol/g, and no sulfhydryl sites were detected after EPS removal, indicating that virtually all of the sulfhydryl sites are located on the EPS molecules produced by P. putida. In contrast, the sulfhydryl sites within the S. oneidensis samples increased from 32.6 ± 3.6 μmol/g to 51.9 ± 7.2 μmol/g after EPS removal, indicating that the EPS produced by S. oneidensis contained fewer sulfhydryl sites than those present on the untreated cells. This study suggests that the sulfhydryl concentrations on EPS molecules may vary significantly from one bacterial species to another, thus it is crucial to quantify the concentration of sulfhydryl sites on EPS molecules of other bacterial species in order to determine the effect of bacterial EPS on metal cycling in the environment. PMID:27177017

  19. Running and tumbling with E. coli in polymeric solutions

    NASA Astrophysics Data System (ADS)

    Patteson, Alison; Gopinath, Arvind; Arratia, Paulo

    2015-11-01

    Bacteria commonly utilize a run-and-tumble swimming behavior to navigate through complex environments such as mucus in the lungs or digestive system. This swimming behavior has been extensively studied in water-like fluids; yet, investigations on the role of particles or polymers in the ambient fluid on the run-and-tumble behavior are limited. Here, we experimentally investigate the swimming dynamics of E. coli in polymeric solutions. We find that small amounts of polymer drastically change the run-and-tumble behavior of E. coli cells, significantly enhancing translational diffusion and reducing rotational diffusion. The average cell velocity increases with polymer concentration (and viscosity) and the mean run times are enhanced. By varying polymer molecular weight and visualizing interactions between single E. coli and fluorescently-stained DNA-polymer molecules, we show that enhanced translation is a result of two mechanisms: (1) suppression of cell wobbling due to elasticity and (2) enhancement of run times due to viscosity. Our results show that the transport of chemotactic cells can be independently modified by viscosity and elasticity. This work was supported by NSF-DMR-1104705 and NSF-CBET-1437482.

  20. Small Talk: Cell-to-Cell Communication in Bacteria

    ScienceCinema

    Bassler, Bonnie [Princeton University, Princeton, New Jersey, United States

    2010-01-08

    Cell-cell communication in bacteria involves the production, release, and subsequent detection of chemical signaling molecules called autoinducers. This process, called quorum sensing, allows bacteria to regulate gene expression on a population-wide scale. Processes controlled by quorum sensing are usually ones that are unproductive when undertaken by an individual bacterium but become effective when undertaken by the group. For example, quorum sensing controls bioluminescence, secretion of virulence factors, biofilm formation, sporulation, and the exchange of DNA. Thus, quorum sensing is a mechanism that allows bacteria to function as multi-cellular organisms. Bacteria make, detect, and integrate information from multiple autoinducers, some of which are used exclusively for intra-species communication while others enable communication between species. Research is now focused on the development of therapies that interfere with quorum sensing to control bacterial virulence.

  1. Small Talk: Cell-to-Cell Communication in Bacteria

    SciTech Connect

    Bassler, Bonnie

    2008-12-03

    Cell-cell communication in bacteria involves the production, release, and subsequent detection of chemical signaling molecules called autoinducers. This process, called quorum sensing, allows bacteria to regulate gene expression on a population-wide scale. Processes controlled by quorum sensing are usually ones that are unproductive when undertaken by an individual bacterium but become effective when undertaken by the group. For example, quorum sensing controls bioluminescence, secretion of virulence factors, biofilm formation, sporulation, and the exchange of DNA. Thus, quorum sensing is a mechanism that allows bacteria to function as multi-cellular organisms. Bacteria make, detect, and integrate information from multiple autoinducers, some of which are used exclusively for intra-species communication while others enable communication between species. Research is now focused on the development of therapies that interfere with quorum sensing to control bacterial virulence.

  2. Small Talk: Cell-to-Cell Communication in Bacteria

    SciTech Connect

    Bassler, Bonnie

    2008-05-14

    Cell-cell communication in bacteria involves the production, release, and subsequent detection of chemical signaling molecules called autoinducers. This process, called quorum sensing, allows bacteria to regulate gene expression on a population-wide scale. Processes controlled by quorum sensing are usually ones that are unproductive when undertaken by an individual bacterium but become effective when undertaken by the group. For example, quorum sensing controls bioluminescence, secretion of virulence factors, biofilm formation, sporulation, and the exchange of DNA. Thus, quorum sensing is a mechanism that allows bacteria to function as multi-cellular organisms. Bacteria make, detect, and integrate information from multiple autoinducers, some of which are used exclusively for intra-species communication while others enable communication between species. Research is now focused on the development of therapies that interfere with quorum sensing to control bacterial virulence.

  3. Evolution of transcriptional regulatory circuits in bacteria

    PubMed Central

    Perez, J. Christian; Groisman, Eduardo A.

    2009-01-01

    Related organisms typically respond to a given cue by altering the level or activity of orthologous transcription factors, which, paradoxically, often regulate expression of distinct gene sets. Although promoter rewiring of shared genes is primarily responsible for regulatory differences among related eukaryotic species, in bacteria, species-specific genes are often controlled by ancestral transcription factors and regulatory circuit evolution has been further shaped by horizontal gene transfer. Modifications in transcription factors and in promoter structure also contribute to divergence in bacterial regulatory circuits. PMID:19632175

  4. The growth-suppressive function of the polycomb group protein polyhomeotic is mediated by polymerization of its sterile alpha motif (SAM) domain.

    PubMed

    Robinson, Angela K; Leal, Belinda Z; Chadwell, Linda V; Wang, Renjing; Ilangovan, Udayar; Kaur, Yogeet; Junco, Sarah E; Schirf, Virgil; Osmulski, Pawel A; Gaczynska, Maria; Hinck, Andrew P; Demeler, Borries; McEwen, Donald G; Kim, Chongwoo A

    2012-03-16

    Polyhomeotic (Ph), a member of the Polycomb Group (PcG), is a gene silencer critical for proper development. We present a previously unrecognized way of controlling Ph function through modulation of its sterile alpha motif (SAM) polymerization leading to the identification of a novel target for tuning the activities of proteins. SAM domain containing proteins have been shown to require SAM polymerization for proper function. However, the role of the Ph SAM polymer in PcG-mediated gene silencing was uncertain. Here, we first show that Ph SAM polymerization is indeed required for its gene silencing function. Interestingly, the unstructured linker sequence N-terminal to Ph SAM can shorten the length of polymers compared with when Ph SAM is individually isolated. Substituting the native linker with a random, unstructured sequence (RLink) can still limit polymerization, but not as well as the native linker. Consequently, the increased polymeric Ph RLink exhibits better gene silencing ability. In the Drosophila wing disc, Ph RLink expression suppresses growth compared with no effect for wild-type Ph, and opposite to the overgrowth phenotype observed for polymer-deficient Ph mutants. These data provide the first demonstration that the inherent activity of a protein containing a polymeric SAM can be enhanced by increasing SAM polymerization. Because the SAM linker had not been previously considered important for the function of SAM-containing proteins, our finding opens numerous opportunities to manipulate linker sequences of hundreds of polymeric SAM proteins to regulate a diverse array of intracellular functions. PMID:22275371

  5. Free heme and sickle hemoglobin polymerization

    NASA Astrophysics Data System (ADS)

    Uzunova, Veselina V.

    This work investigates further the mechanism of one of the most interesting of the protein self-assembly systems---the polymerization of sickle hemoglobin and the role of free heme in it. Polymerization of sickle hemoglobin is the primary event in the pathology of a chronic hemolytic condition called sickle cell anemia with complex pathogenesis, unexplained variability and symptomatic treatment. Auto-oxidation develops in hemoglobin solutions exposed to room temperature and causes release of ferriheme. The composition of such solutions is investigated by mass spectrometry. Heme dimers whose amount corresponds to the initial amounts of heme released from the protein are followed. Differences in the dimer peak height are established for hemoglobin variants A, S and C and depending on the exposure duration. The effects of free heme on polymerization kinetics are studied. Growth rates and two characteristic parameters of nucleation are measured for stored Hb S. After dialysis of polymerizing solutions, no spherulites are detected at moderately high supersaturation and prolonged exposure times. The addition of 0.16-0.26 mM amounts of heme to dialyzed solutions leads to restoration of polymerization. The measured kinetic parameters have higher values compared to the ones before dialysis. The amount of heme in non-dialyzed aged solution is characterized using spectrophotometry. Three methods are used: difference in absorbance of dialyzed and non-dialyzed solutions, characteristic absorbance of heme-albumin complex and absorbance of non-dialyzed solutions with added potassium cyanide. The various approaches suggest the presence of 0.12 to 0.18 mM of free ferriheme in such solutions. Open questions are whether the same amounts of free heme are present in vivo and whether the same mechanism operates intracellulary. If the answer to those questions is positive, then removal of free heme from erythrocytes can influence their readiness to sickle.

  6. Chromatin binding and polymerization of the endogenous Xenopus egg lamins: the opposing effects of glycogen and ATP.

    PubMed

    Lourim, D; Krohne, G

    1998-12-18

    We have previously identified and quantitated three B-type lamin isoforms present in the nuclei of mature Xenopus laevis oocytes, and in cell-free egg extracts. As Xenopus egg extracts are frequently used to analyze nuclear envelope assembly and lamina functions, we felt it was imperative that the polymerization and chromatin-binding properties of the endogenous B-type egg lamins be investigated. While we have demonstrated that soluble B-type lamins bind to chromatin, we have also observed that the polymerization of egg lamins does not require membranes or chromatin. Lamin assembly is enhanced by the addition of glycogen/glucose, or by the depletion of ATP from the extract. Moreover, the polymerization of egg cytosol lamins and their binding to demembranated sperm or chromatin assembled from naked lambda-DNA is inhibited by an ATP regeneration system. These ATP-dependent inhibitory activities can be overcome by the coaddition of glycogen to egg cytosol. We have observed that glycogen does not alter ATP levels during cytosol incubation, but rather, as glycogen-enhanced lamin polymerization is inhibited by okadaic acid, we conclude that glycogen activates protein phosphatases. Because protein phosphatase 1 (PP1) is the only phosphatase known to be specifically regulated by glycogen our data indicate that PP1 is involved in lamin polymerization. Our results show that ATP and glycogen effect lamin polymerization and chromatin binding by separate and opposing mechanisms. PMID:9819358

  7. Automatic, continuous online monitoring of polymerization reactions (ACOMP): Progress in characterization of polymers and polymerization reactions

    NASA Astrophysics Data System (ADS)

    Alb, Alina M.

    An original method is presented as an efficient technique for characterizing polymers, and understanding the kinetics of the polymerization reactions. The Automatic Continuous Online Monitoring of Polymerization Reactions (ACOMP) method developed at Tulane University involves following one or more characteristics of a polymerization reaction: monomer conversion, different molecular weight averages, intrinsic viscosity, etc. By performing an automatic withdrawal and dilution of the polymer solution to create a small stream which flows through a detector train, including light scattering, viscometer, refractive index, Ultraviolet/Visible detectors, a continuum of data points can be obtained, allowing powerful analysis methods to be developed. The goal of this work is to expand ACOMP to new polymerization reactions, such as free radical copolymerization, controlled radical polymerization, inverse emulsion polymerization, both to achieve a complete physical characterization of the polymers synthesized and a better understanding of the reaction mechanisms. For each of the reactions ACOMP brings significant innovations in the analysis of the kinetics. Other new methods, such as Automatic Continuous Mixing (ACM) and Simultaneous Multiple Sample Light Scattering (SMSLS) are also used, as well as traditional multi-detector Size Exclusion Chromatography (SEC). As an immediate consequence it is hoped that the information on reaction kinetics and mechanisms offer a better fundamental knowledge, control and ability to optimize reactions. At the industrial scale, online monitoring should allow a more efficient use of resources, energy, reactor and personnel time as well as a higher product quality.

  8. Nontoxic hydrophilic polymeric nanocomposites containing silver nanoparticles with strong antimicrobial activity

    PubMed Central

    Pozdnyakov, Alexander S; Emel’yanov, Artem I; Kuznetsova, Nadezhda P; Ermakova, Tamara G; Fadeeva, Tat’yana V; Sosedova, Larisa M; Prozorova, Galina F

    2016-01-01

    New nontoxic hydrophilic nanocomposites containing metallic silver nanoparticles (AgNPs) in a polymer matrix were synthesized by the chemical reduction of silver ions in an aqueous medium. A new nontoxic water soluble copolymer of 1-vinyl-1,2,4-triazole and N-vinylpyrrolidone synthesized by free radical-initiated polymerization was used as a stabilizing agent. Transmission electron microscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, atomic absorption, and thermogravimetric analysis were used to characterize polymeric AgNPs nanocomposites. The results showed that the diameter of the synthesized AgNPs ranged from 2 to 6 nm. The toxicity of the initial copolymer of 1-vinyl-1,2,4-triazole and N-vinylpyrrolidone and its nanocomposite with AgNPs was found to be more than 5,000 mg/kg. The synthesized AgNP polymeric nanocomposite showed significant antimicrobial activity against different strains of Gram-negative and -positive bacteria. The minimum inhibitory concentrations suppressing the growth of the microorganisms ranged from 0.5 to 8 µg/mL and the minimum bactericidal concentrations ranged from 0.5 to 16 µg/mL. The fabricated AgNP nanocomposites are promising materials for the design of novel nontoxic hydrophilic antiseptics and antimicrobial components for medical purposes. PMID:27099492

  9. Pathophysiological Effects of Synthetic Derivatives of Polymeric Alkylpyridinium Salts from the Marine Sponge, Reniera sarai

    PubMed Central

    Grandič, Marjana; Frangež, Robert

    2014-01-01

    Polymeric 3-alkylpyridinium salts (poly-APS) are among the most studied natural bioactive compounds extracted from the marine sponge, Reniera sarai. They exhibit a wide range of biological activities, and the most prominent among them are the anti-acetylcholinesterase and membrane-damaging activity. Due to their membrane activity, sAPS can induce the lysis of various cells and cell lines and inhibit the growth of bacteria and fungi. Because of their bioactivity, poly-APS are possible candidates for use in the fields of medicine, pharmacy and industry. Due to the small amounts of naturally occurring poly-APS, methods for the synthesis of analogues have been developed. They differ in chemical properties, such as the degree of polymerization, the length of the alkyl chains (from three to 12 carbon atoms) and in the counter ions present in their structures. Such structurally defined analogues with different chemical properties and degrees of polymerization possess different levels of biological activity. We review the current knowledge of the biological activity and toxicity of synthetic poly-APS analogues, with particular emphasis on the mechanisms of their physiological and pharmacological effects and, in particular, the mechanisms of toxicity of two analogues, APS12-2 and APS3, in vivo and in vitro. PMID:24796301

  10. Swimming bacteria in liquid crystal

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrey; Zhou, Shuang; Aranson, Igor; Lavrentovich, Oleg

    2014-03-01

    Dynamics of swimming bacteria can be very complex due to the interaction between the bacteria and the fluid, especially when the suspending fluid is non-Newtonian. Placement of swimming bacteria in lyotropic liquid crystal produces a new class of active materials by combining features of two seemingly incompatible constituents: self-propelled live bacteria and ordered liquid crystals. Here we present fundamentally new phenomena caused by the coupling between direction of bacterial swimming, bacteria-triggered flows and director orientations. Locomotion of bacteria may locally reduce the degree of order in liquid crystal or even trigger nematic-isotropic phase transition. Microscopic flows generated by bacterial flagella disturb director orientation. Emerged birefringence patterns allow direct optical observation and quantitative characterization of flagella dynamics. At high concentration of bacteria we observed the emergence of self-organized periodic texture caused by bacteria swimming. Our work sheds new light on self-organization in hybrid bio-mechanical systems and can lead to valuable biomedical applications. Was supported by the US DOE, Office of Basic Energy Sciences, Division of Materials Science and Engineering, under the Contract No. DE AC02-06CH11357.

  11. Manganese homeostasis and utilization in pathogenic bacteria.

    PubMed

    Juttukonda, Lillian J; Skaar, Eric P

    2015-07-01

    Manganese (Mn) is a required cofactor for all forms of life. Given the importance of Mn to bacteria, the host has devised strategies to sequester Mn from invaders. In the macrophage phagosome, NRAMP1 removes Mn and other essential metals to starve intracellular pathogens; in the extracellular space, calprotectin chelates Mn and Zn. Calprotectin-mediated Mn sequestration is a newly appreciated host defense mechanism, and recent findings are highlighted herein. In order to acquire Mn when extracellular concentrations are low, bacteria have evolved efficient Mn acquisition systems that are under elegant transcriptional control. To counteract Mn overload, some bacteria possess Mn-specific export systems that are important in vivo, presumably for control of intracellular Mn levels. Mn transporters, their transcriptional regulators and some Mn-requiring enzymes are necessary for virulence of certain bacterial pathogens, as revealed by animal models of infection. Furthermore, Mn is an important facet of the cellular response to oxidative stress, a host antibacterial strategy. The battle for Mn between host and pathogen is now appreciated to be a major determinant of the outcome of infection. In this MicroReview, the contribution of Mn to the host-pathogen interaction is reviewed, and key questions are proposed for future study. PMID:25898914

  12. Prebiotic potential of Agave angustifolia Haw fructans with different degrees of polymerization.

    PubMed

    Velázquez-Martínez, José Rodolfo; González-Cervantes, Rina M; Hernández-Gallegos, Minerva Aurora; Mendiola, Roberto Campos; Aparicio, Antonio R Jiménez; Ocampo, Martha L Arenas

    2014-01-01

    Inulin-type fructans are the most studied prebiotic compounds because of their broad range of health benefits. In particular, plants of the Agave genus are rich in fructans. Agave-derived fructans have a branched structure with both β-(2→1) and β-(2→6) linked fructosyl chains attached to the sucrose start unit with a degree of polymerization (DP) of up to 80 fructose units. The objective of this work was to assess the prebiotic potential of three Agave angustifolia Haw fructan fractions (AFF) with different degrees of polymerization. The three fructan fractions were extracted from the agave stem by lixiviation and then purified by ultrafiltration and ion exchange chromatography: AFF1, AFF2 and AFF3 with high (3-60 fructose units), medium (2-40) and low (2-22) DP, respectively. The fructan profile was determined with high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), which confirmed a branched fructan structure. Structural elucidation was performed by Fourier Transform Infra-Red Spectroscopy. The AFF spectrum shows characteristic fructan bands. The prebiotic effect of these fractions was assessed in vitro through fermentation by Bifidobacterium and Lactobacillus strains. Four growth patterns were observed. Some bacteria did not grow with any of the AFF, while other strains grew with only AFF3. Some bacteria grew according to the molecular weight of the AFF and some grew indistinctly with the three fructan fractions. PMID:25153877

  13. Thromboxane-induced actin polymerization in hypoxic neonatal pulmonary arterial myocytes involves Cdc42 signaling.

    PubMed

    Fediuk, Jena; Sikarwar, Anurag S; Nolette, Nora; Dakshinamurti, Shyamala

    2014-12-01

    In hypoxic pulmonary arterial (PA) myocytes, challenge with thromboxane mimetic U46619 induces marked actin polymerization and contraction, phenotypic features of persistent pulmonary hypertension of the newborn (PPHN). Rho GTPases regulate the actin cytoskeleton. We previously reported that U46619-induced actin polymerization in hypoxic PA myocytes occurs independently of the RhoA pathway and hypothesized involvement of the Cdc42 pathway. PA myocytes grown in normoxia or hypoxia for 72 h were stimulated with U46619, then analyzed for Rac/Cdc42 activation by affinity precipitation, phosphatidylinositide-3-kinase (PI3K) activity by phospho-Akt, phospho-p21-activated kinase (PAK) by immunoblot, and association of Cdc42 with neuronal Wiskott Aldrich Syndrome protein (N-WASp) by immunoprecipitation. The effect of Rac or PAK inhibition on filamentous actin was quantified by laser-scanning cytometry and by cytoskeletal fractionation; effects of actin-modifying agents were measured by isometric myography. Basal Cdc42 activity increased in hypoxia, whereas Rac activity decreased. U46619 challenge increased Cdc42 and Rac activity in hypoxic cells, independently of PI3K. Hypoxia increased phospho-PAK, unaltered by U46619. Association of Cdc42 with N-WASp decreased in hypoxia but increased after U46619 exposure. Hypoxia doubled filamentous-to-globular ratios of α- and γ-actin isoforms. Jasplakinolide stabilized γ-filaments, increasing force; cytochalasin D depolymerized all actin isoforms, decreasing force. Rac and PAK inhibition decreased filamentous actin in tissues although without decrease in force. Rho inhibition decreased myosin phosphorylation and force. Hypoxia induces actin polymerization in PA myocytes, particularly increasing filamentous α- and γ-actin, contributing to U46619-induced contraction. Hypoxic PA myocytes challenged with a thromboxane mimetic polymerize actin via the Cdc42 pathway, reflecting increased Cdc42 association with N-WASp. Mechanisms

  14. Genetics of Bacteria That Oxidize On-Carbon Compounds

    SciTech Connect

    Hanson, Richard S.

    2001-01-01

    Facultative methanol oxidizing bacteria contain large amounts of methanol dehydrogenase which is expressed only in the presence of methanol. This technical report describes two-two component regulatory systems encoding histidine kinases and response regulators and another response regulator all of which are required for the expression of mxaF, the open reading frame encoding methanol dehydrogenase. The response regulators bind to sequences upstream of the mxaF when phosphoryled in a reaction catalyzed by the histidine kinases. The binding of the response regulators is required for the transcription of mxaF.

  15. Autoacceleration and kinetics of electrochemical polymerization of aniline

    SciTech Connect

    Wei, Yen; Sun, Yan; Tang, Xun )

    1989-06-15

    A convenient method is presented for determining the rate of polyaniline formation in the electrochemical polymerization of aniline in aqueous HCl solution utilizing cyclic potential sweep techniques. In this method, the mass of polyaniline deposited on a platinum electrode is correlated with the polymer anodic peak current that is recorded during the polymerization. The rates of polymer deposition were therefore monitored by the increases in the anodic peak current at various concentrations of aniline. A kinetic expression obtained for the polymerization accounts well for the autoacceleration process in the electrochemical polymerization of aniline and supports the mechanism of polymerization in which monomeric aniline is incorporated in the growing polymer.

  16. Metabolic engineering of bacteria.

    PubMed

    Kumar, Ravi R; Prasad, Satish

    2011-07-01

    Yield and productivity are critical for the economics and viability of a bioprocess. In metabolic engineering the main objective is the increase of a target metabolite production through genetic engineering. Metabolic engineering is the practice of optimizing genetic and regulatory processes within cells to increase the production of a certain substance. In the last years, the development of recombinant DNA technology and other related technologies has provided new tools for approaching yields improvement by means of genetic manipulation of biosynthetic pathway. Industrial microorganisms like Escherichia coli, Actinomycetes, etc. have been developed as biocatalysts to provide new or to optimize existing processes for the biotechnological production of chemicals from renewable plant biomass. The factors like oxygenation, temperature and pH have been traditionally controlled and optimized in industrial fermentation in order to enhance metabolite production. Metabolic engineering of bacteria shows a great scope in industrial application as well as such technique may also have good potential to solve certain metabolic disease and environmental problems in near future. PMID:22754024

  17. Sociomicrobiology and pathogenic bacteria

    PubMed Central

    Xavier, Joao B.

    2015-01-01

    The study of microbial pathogenesis has been primarily a reductionist science since Koch's principles. Reductionist approaches are essential to identify the causal agents of infectious disease, their molecular mechanisms of action and potential drug targets, and much of medicine's success in the treatment of infectious disease comes from this approach. But many bacterial caused diseases cannot be explained by focusing on a single bacterium. Many aspects of bacterial pathogenesis will benefit from a more holistic approach that takes into account social interaction within bacteria of the same species and between different species in consortia such as the human microbiome. I discuss recent advances in the emerging discipline of sociomicrobiology and how it provides a framework to dissect microbial interactions in single and multispecies communities without compromising mechanistic detail. The study of bacterial pathogenesis can benefit greatly from incorporating concepts from other disciplines such as social evolution theory and microbial ecology where communities, their interactions with hosts and with the environment play key roles. PMID:27337482

  18. Extracellular polymeric substances govern the development of biofilm and mass transfer of polycyclic aromatic hydrocarbons for improved biodegradation.

    PubMed

    Zhang, Yinping; Wang, Fang; Zhu, Xiaoshu; Zeng, Jun; Zhao, Qiguo; Jiang, Xin

    2015-10-01

    The hypothesis that extracellular polymeric substances (EPS) affect the formation of biofilms for subsequent enhanced biodegradation of polycyclic aromatic hydrocarbons was tested. Controlled formation of biofilms on humin particles and biodegradation of phenanthrene and pyrene were performed with bacteria and EPS-extracted bacteria of Micrococcus sp. PHE9 and Mycobacterium sp. NJS-P. Bacteria without EPS extraction developed biofilms on humin, in contrast the EPS-extracted bacteria could not attach to humin particles. In the subsequent biodegradation of phenanthrene and pyrene, the biodegradation rates by biofilms were significantly higher than those of EPS-extracted bacteria. Although, both the biofilms and EPS-extracted bacteria showed increases in EPS contents, only the EPS contents in biofilms displayed significant correlations with the biodegradation efficiencies of phenanthrene and pyrene. It is proposed that the bacterial-produced EPS was a key factor to mediate bacterial attachment to other surfaces and develop biofilms, thereby increasing the bioavailability of poorly soluble PAH for enhanced biodegradation. PMID:26141288

  19. Mechanisms of Drug Diffusion from Polymeric Devices.

    NASA Astrophysics Data System (ADS)

    Sharma, Kuldeepak

    1987-09-01

    A detailed mechanistic study of drug diffusion and the factors which influence drug diffusion through polymeric controlled release systems was undertaken to understand drug diffusion through hydrophilic and hydrophobic polymeric systems. The effect of improved aqueous solubility of the salt form (ionizable form) of selected drugs on diffusion through hydrophilic and hydrophobic polymeric membranes was compared to diffusion of the less soluble (unionizable form) of the drugs. Model drugs chosen for these studies were prednisolone, prednisolone phosphate sodium (prednisolone phosphoric acid disodium salt), pilocarpine, pilocarpine hydrochloride, sulfacetamide and sodium sulfacetamide. The hydrophilic polymers were hydrogels of hydroxyethylmethacrylate (PHEMA) and hydrophobic polymers were copolyether-urethane -urea (Biomer) and polydimethylsiloxane (PDMS). Salt forms of the drugs permeated faster than the free forms through the hydrophilic polymers because of higher aqueous solubility. The free forms of the drugs had higher diffusion rates than the salt forms due to increased solubility in the hydrophobic polymers. Drug solubility in polymers and the water fraction of the polymeric membrane were determined to be the primary factors in diffusion through polymeric membranes. Drug aqueous solubility was of secondary importance. Two controlled release systems were then designed to further study drug release. The Biomer and copolymers of polystyrene and PHEMA were chosen as the polymers for the fabrication of the devices. These copolymers incorporated the favorable attributes of hydrophobic and hydrophilic homopolymers into single polymers. Prednisolone was used as a model drug for these studies. The effects of initial drug load, drug loading solvents and the drug polymer interactions on drug release from the devices were then studied. The drug release from these devices increased as the initial drug load increased. Drug loading solvents had a marked effect on drug

  20. Bacteriophage Infection of Model Metal Reducing Bacteria

    NASA Astrophysics Data System (ADS)

    Weber, K. A.; Bender, K. S.; Gandhi, K.; Coates, J. D.

    2008-12-01

    Microbially-mediated metal reduction plays a significant role controlling contaminant mobility in aqueous, soil, and sedimentary environments. From among environmentally relevant microorganisms mediating metal reduction, Geobacter spp. have been identified as predominant metal-reducing bacteria under acetate- oxidizing conditions. Due to the significance of these bacteria in environmental systems, it is necessary to understand factors influencing their metabolic physiology. Examination of the annotated finished genome sequence of G. sulfurreducens PCA, G. uraniumreducens Rf4, G. metallireduceans GS-15 as well as a draft genome sequence of Geobacter sp. FRC-32 have identified gene sequences of putative bacteriophage origin. Presence of these sequences indicates that these bacteria are susceptible to phage infection. Polymerase chain reaction (PCR) primer sets designed tested for the presence of 12 of 25 annotated phage-like sequences in G. sulfurreducens PCA and 9 of 17 phage-like sequences in FRC- 32. The following genes were successfully amplified in G. sulfurreducens PCA: prophage type transcription regulator, phage-induced endonuclease, phage tail sheath, 2 phage tail proteins, phage protein D, phage base plate protein, phage-related DNA polymerase, integrase, phage transcriptional regulator, and Cro-like transcription regulator. Nine of the following sequences were present in FRC-32: 4 separate phage- related proteins, phage-related tail component, viron core protein, phage Mu protein, phage base plate, and phage tail sheath. In addition to the bioinformatics evidence, incubation of G. sulfurreducens PCA with 1 μg mL-1 mytomycin C (mutagen stimulating prophage induction) during mid-log phase resulted in significant cell lysis relative to cultures that remained unamended. Cell lysis was concurrent with an increase in viral like particles enumerated using epifluorescent microscopy. In addition, samples collected following this lytic event (~44hours) were

  1. Evaluation of antibacterial activity of nitric oxide-releasing polymeric particles against Staphylococcus aureus and Escherichia coli from bovine mastitis.

    PubMed

    Cardozo, Viviane F; Lancheros, Cesar A C; Narciso, Adélia M; Valereto, Elaine C S; Kobayashi, Renata K T; Seabra, Amedea B; Nakazato, Gerson

    2014-10-01

    Bovine mastitis is a serious veterinary disease that causes great loss to the dairy industry worldwide. It is a major infectious disease and is difficult to manage and control. Furthermore, emerging multidrug resistant bacteria that cause mastitis have complicated such management. The free radical nitric oxide (NO) is a potent antimicrobial agent. Thus, the aims of this study were to prepare and evaluate the antibacterial activity of nitric oxide-releasing polymeric particles against Staphylococcus aureus (MBSA) and Escherichia coli (MBEC), which were isolated from bovine mastitis. Fifteen MBSA isolates and fifteen MBEC were collected from subclinical and clinical bovine mastitis. Biocompatible polymeric particles composed of alginate/chitosan or chitosan/sodium tripolyphosphate (TPP) were prepared and used to encapsulate mercaptosuccinic acid (MSA), which is a thiol-containing molecule. Nitrosation of thiol groups of MSA-containing particles formed S-nitroso-MSA particles, which are NO donors. The NO release kinetics from the S-nitroso-MSA particles showed sustained and controlled NO release over several hours. The antibacterial activity of NO-releasing particles was evaluated by incubating the particles with an MBSA multi-resistant strain, which is responsible for bovine mastitis. The minimum inhibitory concentration for S-nitroso-MSA-alginate/chitosan particles against MBSA ranged from 125 μg/mL to 250 μg/mL. The results indicate that NO-releasing polymeric particles are an interesting approach to combating bacteria resistance in bovine mastitis treatment and prevention. PMID:24979535

  2. Interactions between Diatoms and Bacteria

    PubMed Central

    Amin, Shady A.; Parker, Micaela S.

    2012-01-01

    Summary: Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans. PMID:22933565

  3. Suspended polymeric photonic crystals: simulation and fabrication

    NASA Astrophysics Data System (ADS)

    Rebigan, R.; Dinescu, A.; Kusko, C.; Gavrila, R.; Cristea, D.; Obreja, C.; Schiopu, P.

    2010-11-01

    In this paper we present simulation of transmission / reflection spectra of polymeric rectangular and hexagonal photonic crystals (PC) as well as the propagation of radiation in a hexagonal PC - based waveguide. The polymeric PC are periodic structures consisting in square arrays of holes configured in suspended membranes of PMMA with different diameters and pitch (100 nm diameter with 500 nm, respectively 800 nm pitch; 200 nm diameter with 500 nm pitch; 400 nm diameter with 700 nm pitch). For fabrication, we propose the bi-layer EBL technique based on simultaneous patterning of a bottom sacrificial layer (LOR 5A - Microchem Corporation) and a positive electron resist (PMMA of different molecular weights). Characterization of nanostructures was performed using SEM imaging and AFM measurements .

  4. All-polymeric control of nanoferronics

    PubMed Central

    Xu, Beibei; Li, Huashan; Hall, Asha; Gao, Wenxiu; Gong, Maogang; Yuan, Guoliang; Grossman, Jeffrey; Ren, Shenqiang

    2015-01-01

    In the search for light and flexible nanoferronics, significant research effort is geared toward discovering the coexisting magnetic and electric orders in crystalline charge-transfer complexes. We report the first example of multiferroicity in centimeter-sized crystalline polymeric charge-transfer superstructures that grow at the liquid-air interface and are controlled by the regioregularity of the polymeric chain. The charge order–driven ferroic mechanism reveals spontaneous and hysteretic polarization and magnetization at the donor-acceptor interface. The charge transfer and ordering in the ferroic assemblies depend critically on the self-organizing and molecular packing of electron donors and acceptors. The invention described here not only represents a new coupling mechanism of magnetic and electric ordering but also creates a new class of emerging all-organic nanoferronics. PMID:26824068

  5. Durability of Polymeric Glazing and Absorber Materials

    SciTech Connect

    Jorgensen, G.; Terwilliger, K.; Bingham, C.; Milbourne, M.

    2005-01-01

    The Solar Heating and Lighting Program has set the goal of reducing the cost of solar water heating systems by at least 50%. An attractive approach to such large cost reduction is to replace glass and metal parts with less-expensive, lighter-weight, more-integrated polymeric components. The key challenge with polymers is to maintain performance and assure requisite durability for extended lifetimes. The objective of this task is to quantify lifetimes through measurement of the optical and mechanical stability of candidate polymeric glazing and absorber materials. Polycarbonate sheet glazings, as proposed by two industry partners, have been tested for resistance to UV radiation with three complementary methods. Incorporation of a specific 2-mil thick UV-absorbing screening layer results in glazing lifetimes of at least 15 years; improved screens promise even longer lifetimes. Proposed absorber materials were tested for creep and embrittlement under high temperature, and appear adequate for planned ICS absorbers.

  6. Living anionic polymerization using a microfluidic reactor

    SciTech Connect

    Iida, Kazunori; Chastek, Thomas Q.; Beers, Kathryn L.; Cavicchi, Kevin A.; Chun, Jaehun; Fasolka, Michael J.

    2009-02-01

    Living anionic polymerizations were conducted within aluminum-polyimide microfluidic devices. Polymerizations of styrene in cyclohexane were carried out at various conditions, including elevated temperature (60 °C) and high monomer concentration (42%, by volume). The reactions were safely maintained at a controlled temperature at all points in the reactor. Conducting these reactions in a batch reactor results in uncontrolled heat generation with potentially dangerous rises in pressure. Moreover, the microfluidic nature of these devices allows for flexible 2D designing of the flow channel. Four flow designs were examined (straight, periodically pinched, obtuse zigzag, and acute zigzag channels). The ability to use the channel pattern to increase the level of mixing throughout the reactor was evaluated. When moderately high molecular mass polymers with increased viscosity were made, the patterned channels produced polymers with narrower PDI, indicating that passive mixing arising from the channel design is improving the reaction conditions.

  7. Chemical characterization of selected LDEF polymeric materials

    NASA Technical Reports Server (NTRS)

    Young, Philip R.; Slemp, Wayne S.

    1991-01-01

    Chemical characterization of selected polymeric materials which received exposure on the Long Duration Exposure Facility (LDEF) is reported. The specimens examined include silvered fluorinated ethylene propylene Teflon thermal blanket material, polysulfone, epoxy, polyimide matrix resin/graphite fiber reinforced composites, and several high performance polymer films. These specimens came from numerous LDEF locations, and thus received different environmental exposures. The results to date show no significant change at the molecular level in the polymer that survived exposure. Scanning electron and scanning tunneling microscopes show resin loss and a texturing of some specimens which resulted in a change in optical properties. The potential effect of a silicon-containing molecular contamination on these materials is addressed. The possibility of continued post-exposure degradation of some polymeric films is also proposed.

  8. Simultaneous covalent and noncovalent hybrid polymerizations

    NASA Astrophysics Data System (ADS)

    Yu, Zhilin; Tantakitti, Faifan; Yu, Tao; Palmer, Liam C.; Schatz, George C.; Stupp, Samuel I.

    2016-01-01

    Covalent and supramolecular polymers are two distinct forms of soft matter, composed of long chains of covalently and noncovalently linked structural units, respectively. We report a hybrid system formed by simultaneous covalent and supramolecular polymerizations of monomers. The process yields cylindrical fibers of uniform diameter that contain covalent and supramolecular compartments, a morphology not observed when the two polymers are formed independently. The covalent polymer has a rigid aromatic imine backbone with helicoidal conformation, and its alkylated peptide side chains are structurally identical to the monomer molecules of supramolecular polymers. In the hybrid system, covalent chains grow to higher average molar mass relative to chains formed via the same polymerization in the absence of a supramolecular compartment. The supramolecular compartments can be reversibly removed and re-formed to reconstitute the hybrid structure, suggesting soft materials with novel delivery or repair functions.

  9. Simultaneous covalent and noncovalent hybrid polymerizations.

    PubMed

    Yu, Zhilin; Tantakitti, Faifan; Yu, Tao; Palmer, Liam C; Schatz, George C; Stupp, Samuel I

    2016-01-29

    Covalent and supramolecular polymers are two distinct forms of soft matter, composed of long chains of covalently and noncovalently linked structural units, respectively. We report a hybrid system formed by simultaneous covalent and supramolecular polymerizations of monomers. The process yields cylindrical fibers of uniform diameter that contain covalent and supramolecular compartments, a morphology not observed when the two polymers are formed independently. The covalent polymer has a rigid aromatic imine backbone with helicoidal conformation, and its alkylated peptide side chains are structurally identical to the monomer molecules of supramolecular polymers. In the hybrid system, covalent chains grow to higher average molar mass relative to chains formed via the same polymerization in the absence of a supramolecular compartment. The supramolecular compartments can be reversibly removed and re-formed to reconstitute the hybrid structure, suggesting soft materials with novel delivery or repair functions. PMID:26823427

  10. Latent and delayed action polymerization systems.

    PubMed

    Naumann, Stefan; Buchmeiser, Michael R

    2014-04-01

    Various approaches to latent polymerization processes are described. In order to highlight recent advances in this field, the discussion is subdivided into chapters dedicated to diverse classes of polymers, namely polyurethanes, polyamides, polyesters, polyacrylates, epoxy resins, and metathesis-derived polymers. The described latent initiating systems encompass metal-containing as well as purely organic compounds that are activated by external triggers such as light, heat, or mechanical force. Special emphasis is put on the different chemical venues that can be taken to achieve true latency, which include masked N-heterocyclic carbenes, latent metathesis catalysts, and photolatent radical initiators, among others. Scientific challenges and the advantageous application of latent polymerization processes are discussed. PMID:24519912

  11. All-polymeric control of nanoferronics.

    PubMed

    Xu, Beibei; Li, Huashan; Hall, Asha; Gao, Wenxiu; Gong, Maogang; Yuan, Guoliang; Grossman, Jeffrey; Ren, Shenqiang

    2015-12-01

    In the search for light and flexible nanoferronics, significant research effort is geared toward discovering the coexisting magnetic and electric orders in crystalline charge-transfer complexes. We report the first example of multiferroicity in centimeter-sized crystalline polymeric charge-transfer superstructures that grow at the liquid-air interface and are controlled by the regioregularity of the polymeric chain. The charge order-driven ferroic mechanism reveals spontaneous and hysteretic polarization and magnetization at the donor-acceptor interface. The charge transfer and ordering in the ferroic assemblies depend critically on the self-organizing and molecular packing of electron donors and acceptors. The invention described here not only represents a new coupling mechanism of magnetic and electric ordering but also creates a new class of emerging all-organic nanoferronics. PMID:26824068

  12. Cooperative polymerization of one-patch colloids

    SciTech Connect

    Vissers, Teun; Smallenburg, Frank; Munaò, Gianmarco; Preisler, Zdeněk; Sciortino, Francesco

    2014-04-14

    We numerically investigate cooperative polymerization in an off-lattice model based on a pairwise additive potential using particles with a single attractive patch that covers 30% of the colloid surface. Upon cooling, these particles self-assemble into small clusters which, below a density-dependent temperature, spontaneously reorganize into long straight tubes. We evaluate the partition functions of clusters of all sizes to provide an accurate description of the chemical reaction constants governing this process. Our calculations show that, for intermediate sizes, the partition functions retain contributions from two different structures, differing in both energy and entropy. We illustrate the microscopic mechanism behind the complex polymerization process in this system and provide a detailed evaluation of its thermodynamics.

  13. Strategies for design of polymeric nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Jiwu; Mackay, Michael; Duxbury, Phillip

    2008-03-01

    Recently polymer nanoparticles have been synthesized using single chains as macromolecular precursors, providing unprecedented control of nanoparticle size and function. We present the results of molecular dynamics simulations which provide detailed insight into the formation kinetics of specific polymeric nanoparticles and which also predict design strategies for formation of interesting new targets. Nanoparticles are formed through chemical crosslinking which is possible when reactive species on the chain backbone are in close proximity. Since the chemical crosslinking is highly irreversible, nanoparticles formed in this way do not unfold on heating, in contrast to the familiar case of thermal denaturing of proteins. Synthesis of precursors with an alphabet of orthogonal crosslinkers provides a rich phase space for design of polymeric nanoparticles. For example, our simulations indicate that an alphabet of three orthogonal crosslinkers enables self-assembly of two-faced or Janus nanoparticles and a variety of other morphologies.

  14. Charge-transfer magnetoelectrics of polymeric multiferroics.

    PubMed

    Qin, Wei; Jasion, Daniel; Chen, Xiaomin; Wuttig, Manfred; Ren, Shenqiang

    2014-04-22

    The renaissance of multiferroics has yielded a deeper understanding of magneto-electric coupling of inorganic single-phase multiferroics and composites. Here, we report charge-transfer polymeric multiferroics, which exhibit external field-controlled magnetic, ferroelectric, and microwave response, as well as magneto-dielectric coupling. The charge-transfer-controlled ferroic properties result from the magnetic field-tunable triplet exciton which has been validated by the dynamic polaron-bipolaron transition model. In addition, the temperature-dependent dielectric discontinuity and electric-field-dependent polarization confirms room temperature ferroelectricity of crystalline charge-transfer polymeric multiferroics due to the triplet exciton, which allows the tunability of polarization by the photoexcitation. PMID:24654686

  15. Orthogonal gradient networks via post polymerization reaction

    NASA Astrophysics Data System (ADS)

    Chinnayan Kannan, Pandiyarajan; Genzer, Jan

    2015-03-01

    We report a novel synthetic route to generate orthogonal gradient networks through post polymerization reaction using pentaflurophenylmethacrylate (PFPMAc) active ester chemistry. These chemoselective monomers were successfully copolymerized with 5 mole% of the photo (methacryloyloxybenzophenone) and thermal (styrenesulfonylazide) crosslinkers. Subsequently, the copolymers were modified by a series of amines having various alkyl chain lengths. The conversion of post polymerization reaction was monitored using Fourier Transform Infrared Spectroscopy (FT-IR) and noticed that almost all pentaflurophenyl moieties are substituted by amines within in an hour without affecting the crosslinkers. In addition, the incorporation of photo and thermal crosslinkers in the polymer enabled us to achieve stable and covalently surface-bound polymer gradient networks (PGN) in an orthogonal manner, i.e. complete control over the crosslink density of the network in two opposite directions (i.e. heat vs photo). The network properties such as wettability, swelling and tensile modulus of the gradient coatings are studied and revealed in the paper.

  16. Therapeutic Strategies Based on Polymeric Microparticles

    PubMed Central

    Vilos, C.; Velasquez, L. A.

    2012-01-01

    The development of the field of materials science, the ability to perform multidisciplinary scientific work, and the need for novel administration technologies that maximize therapeutic effects and minimize adverse reactions to readily available drugs have led to the development of delivery systems based on microencapsulation, which has taken one step closer to the target of personalized medicine. Drug delivery systems based on polymeric microparticles are generating a strong impact on preclinical and clinical drug development and have reached a broad development in different fields supporting a critical role in the near future of medical practice. This paper presents the foundations of polymeric microparticles based on their formulation, mechanisms of drug release and some of their innovative therapeutic strategies to board multiple diseases. PMID:22665988

  17. Hemoglobin loaded polymeric nanoparticles: preparation and characterizations.

    PubMed

    Dessy, Alberto; Piras, Anna M; Schirò, Giorgio; Levantino, Matteo; Cupane, Antonio; Chiellini, Federica

    2011-05-18

    In the present work polymeric nanoparticles based on Poly (maleic anhydride-alt-butyl vinyl ether) 5% grafted with m-PEG (2000) and 95% grafted with 2-methoxyethanol (VAM41-PEG) were loaded with human hemoglobin (Hb) and characterized from a physicochemical point of view. The assessment of structural and functional features of the loaded Hb was performed and the effect of the introduction of different reducing agents as aimed at minimizing Hb oxidation during the nanoparticles formulation process, was also investigated. Nanoparticles possessing an average diameter of 138±10 nm and physicochemical features suitable for this kind of application were successfully obtained. Although the oxidation of the protein was not avoided during its loading into nanoparticles, the presence of acidic moieties in the polymeric structure is proposed to be directly involved in the protein inactivation mechanism. PMID:21443949

  18. Preparation of hydrogels via ultrasonic polymerization.

    PubMed

    Cass, Peter; Knower, Warren; Pereeia, Eliana; Holmes, Natalie P; Hughes, Tim

    2010-02-01

    Several acrylic hydrogels were prepared via ultrasonic polymerization of water soluble monomers and macromonomers. Ultrasound was used to create initiating radicals in viscous aqueous monomer solutions using the additives glycerol, sorbitol or glucose in an open system at 37 degrees C. The water soluble additives were essential for the hydrogel production, glycerol being the most effective. Hydrogels were prepared from the monomers 2-hydroxyethyl methacrylate, poly(ethylene glycol) dimethacrylate, dextran methacrylate, acrylic acid/ethylene glycol dimethacrylate and acrylamide/bis-acrylamide. For example a 5% w/w solution of dextran methacrylate formed a hydrogel in 6.5min in a 70% w/w solution of glycerol in water at 37 degrees C with 20kHz ultrasound, 56Wcm(-2). The ultrasonic polymerization method described here has a wide range of applications such a biomaterial synthesis where initiators are not desired. PMID:19762267

  19. Constructing monocrystalline covalent organic networks by polymerization

    NASA Astrophysics Data System (ADS)

    Beaudoin, Daniel; Maris, Thierry; Wuest, James D.

    2013-10-01

    An emerging strategy for making ordered materials is modular construction, which connects preformed molecular subunits to neighbours through interactions of properly selected reactive sites. This strategy has yielded remarkable materials, including metal-organic frameworks joined by coordinative bonds, supramolecular networks linked by strong non-covalent interactions, and covalent organic frameworks in which atoms of carbon and other light elements are bonded covalently. However, the strategy has not yet produced covalently bonded organic materials in the form of large single crystals. Here we show that such materials can result from reversible self-addition polymerizations of suitably designed monomers. In particular, monomers with four tetrahedrally oriented nitroso groups polymerize to form diamondoid azodioxy networks that can be fully characterized by single-crystal X-ray diffraction. This work forges a strong new link between polymer science and supramolecular chemistry by showing how predictably ordered covalent or non-covalent structures can both be built using a single modular strategy.

  20. Probiotic Lactic Acid Bacteria and Skin Health.

    PubMed

    Jeong, Ji Hye; Lee, Chang Y; Chung, Dae Kyun

    2016-10-25

    Human skin is the first defense barrier against the external environment, especially microbial pathogens and physical stimulation. Many studies on skin health with Lactic acid bacteria (LAB) have been published for many years, including prevention of skin disease and improvement of skin conditions. LAB, a major group of gram-positive bacteria, are known to be beneficial to human health by acting as probiotics. Recent studies have shown that LAB and their extracts have beneficial effects on maintenance and improvement of skin health. Oral administration of Lactobacillus delbrueckii inhibits the development of atopic disease. In addition, LAB and LAB extracts are known to have beneficial effects on intestinal diseases, with Lactobacillus plantarum having been shown to attenuate IL-10 deficient colitis. In addition to intestinal health, L. plantarum also has beneficial effects on skin. pLTA, which is lipoteichoic acid isolated from L. plantarum, has anti-photoaging effects on human skin cells by regulating the expression matrix meralloprotionase-1 (MMP-1) expression. While several studies have proposed a relationship between diseases of the skin and small intestines, there are currently no published reviews of the effects of LAB for skin health through regulation of intestinal conditions and the immune system. In this review, we discuss recent findings on the effects of LAB on skin health and its potential applications in beauty foods. PMID:26287529

  1. Transcriptional cross-regulation between Gram-negative and gram-positive bacteria, demonstrated using ArgP-argO of Escherichia coli and LysG-lysE of Corynebacterium glutamicum.

    PubMed

    Marbaniang, Carmelita N; Gowrishankar, J

    2012-10-01

    The protein-gene pairs ArgP-argO of Escherichia coli and LysG-lysE of Corynebacterium glutamicum are orthologous, with the first member of each pair being a LysR-type transcriptional regulator and the second its target gene encoding a basic amino acid exporter. Whereas LysE is an exporter of arginine (Arg) and lysine (Lys) whose expression is induced by Arg, Lys, or histidine (His), ArgO exports Arg alone, and its expression is activated by Arg but not Lys or His. We have now reconstituted in E. coli the activation of lysE by LysG in the presence of its coeffectors and have shown that neither ArgP nor LysG can regulate expression of the noncognate orthologous target. Of several ArgP-dominant (ArgP(d)) variants that confer elevated Arg-independent argO expression, some (ArgP(d)-P274S, -S94L, and, to a lesser extent, -P108S) activated lysE expression in E. coli. However, the individual activating effects of LysG and ArgP(d) on lysE were mutually extinguished when both proteins were coexpressed in Arg- or His-supplemented cultures. In comparison with native ArgP, the active ArgP(d) variants exhibited higher affinity of binding to the lysE regulatory region and less DNA bending at both argO and lysE. We conclude that the transcription factor LysG from a Gram-positive bacterium, C. glutamicum, is able to engage appropriately with the RNA polymerase from a Gram-negative bacterium, E. coli, for activation of its cognate target lysE in vivo and that single-amino-acid-substitution variants of ArgP can also activate the distantly orthologous target lysE, but by a subtly different mechanism that renders them noninterchangeable with LysG. PMID:22904281

  2. Superposition flows of entangled polymeric solutions

    NASA Astrophysics Data System (ADS)

    Ianniruberto, Giovanni; Unidad, Herwin Jerome

    2015-12-01

    Parallel and orthogonal superposition experiments by Vermant et al. (1998) on a polydisperse, entangled polymeric solution are here analyzed by using a simple, multi-mode differential constitutive equation based on the tube model, and also accounting for convective constraint release effects. Model predictions are in very good qualitative and quantitative agreement with parallel superposition data, while some discrepancies are found with orthogonal data, thus suggesting that orthogonal superposition experiments represent a more severe test for molecularly-based constitutive equations.

  3. INHIBITING THE POLYMERIZATION OF NUCLEAR COOLANTS

    DOEpatents

    Colichman, E.L.

    1959-10-20

    >The formation of new reactor coolants which contain an additive tbat suppresses polymerization of the primary dissoclation free radical products of the pyrolytic and radiation decomposition of the organic coolants is described. The coolants consist of polyphenyls and condensed ring compounds having from two to about four carbon rings and from 0.1 to 5% of a powdered metal hydride chosen from the group consisting of the group IIA and IVA dispersed in the hydrocarbon.

  4. Polymeric assemblies for sensitive colorimetric assays

    DOEpatents

    Charych, Deborah

    2000-01-01

    The presently claimed invention relates to polymeric assemblies which visibly change color in the presence of analyte. In particular, the presently claimed invention relates to liposomes comprising a plurality of lipid monomers, which comprises a polymerizable group, a hydrophilic head group and a hydrophobic tail group, and one or more ligands. Overall carbon chain length, and polymerizable group positioning on the monomer influence color change sensitivity to analyte concentrations.

  5. Bimetallic complexes and polymerization catalysts therefrom

    DOEpatents

    Patton, Jasson T.; Marks, Tobin J.; Li, Liting

    2000-11-28

    Group 3-6 or Lanthanide metal complexes possessing two metal centers, catalysts derived therefrom by combining the same with strong Lewis acids, Bronsted acid salts, salts containing a cationic oxidizing agent or subjected to bulk electrolysis in the presence of compatible, inert non-coordinating anions and the use of such catalysts for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers are disclosed.

  6. Biologically produced acid precipitable polymeric lignin

    DOEpatents

    Crawford, Don L.; Pometto, III, Anthony L.

    1984-01-01

    A water soluble, acid precipitable polymeric degraded lignin (APPL), having a molecular weight of at least 12,000 daltons, and comprising, by percentage of total weight, at least three times the number of phenolic hydroxyl groups and carboxylic acid groups present in native lignin. The APPL may be modified by chemical oxidation and reduction to increase its phenolic hydroxyl content and reduce the number of its antioxidant inhibitory side chains, thereby improving antioxidant properties.

  7. Sampling bacteria with a laser

    NASA Astrophysics Data System (ADS)

    Schwarzwälder, Kordula; Rutschmann, Peter

    2014-05-01

    Water quality is a topic of high interest and it's getting more and more important due to climate change and the implementation of European Water Framework Directive (WFD). One point of interest here is the inflow of bacteria into a river caused by combined sewer overflows which lead untreated wastewater including bacteria directly into a river. These bacteria remain in the river for a certain time, they settle down and can be remobilised again. In our study we want to investigate these processes of sedimentation and resuspension and use the results for the development of a software module coupled with the software Flow3D. Thereby we should be able to simulate and therefore predict the water quality influenced by combined sewer overflows. Hence we need to get information about the bacteria transport and fate. We need to know about the size of the bacteria or of the bacteria clumps and the size of the particles the bacteria are attached to. The agglomerates lead to different characteristics and velocities of settlement. The timespan during this bacteria can be detected in the bulk phase depends on many factors like the intensity of UV light, turbidity of the water, the temperature of the water, if there are grazers and a lot more. The size, density and composition of the agglomerates is just a part of all these influencing factors, but it is extremely difficult to differ between the other effects if we have no information about the simple sedimentation in default of these basic information. However we have a big problem getting the data. The chaining between bacteria or bacteria and particles is not too strong, so filtering the water to get a sieving curve may destroy these connections. We did some experiments similar to PIV (particle image velocimetry) measurements and evaluated the pictures with a macro written for the software ImageJ. Doing so we were able to get the concentration of bacteria in the water and collect information about the size of the bacteria. We

  8. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, T.J.; Eisen, M.S.; Giardello, M.A.

    1994-07-19

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C[sub 5]R[prime][sub 4[minus]x]R*[sub x])-A-(C[sub 5]R[double prime][sub 4[minus]y]R[prime][double prime][sub y])-M-Q[sub p], where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R[prime], R[double prime], R[prime][double prime], and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3 [<=] p [<=] 0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form cation-like'' species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other [alpha]-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

  9. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

    1994-01-01

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R'".sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R'", and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

  10. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

    1995-01-01

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R"'.sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R"', and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

  11. Homogeneous catalysts for stereoregular olefin polymerization

    DOEpatents

    Marks, T.J.; Eisen, M.S.; Giardello, M.A.

    1995-10-03

    The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C{sub 5}R{prime}{sub 4{minus}x}R*{sub x})A(C{sub 5}R{double_prime}{sub 4{minus}y}R{double_prime}{prime}{sub y})MQ{sub p}, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R{prime}, R{double_prime}, R{double_prime}{prime}, and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3{>=}p{>=}0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form ``cation-like`` species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other {alpha}-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

  12. Polymerization initated at sidewalls of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

    2011-01-01

    The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

  13. Performance of selected polymeric materials on LDEF

    NASA Technical Reports Server (NTRS)

    Young, Philip R.; Slemp, Wayne S.; Stein, Bland A.

    1993-01-01

    The NASA Long Duration Exposure Facility (LDEF) provided a unique environmental exposure of a wide variety of materials for potential advanced spacecraft application. This paper examines the molecular level response of selected polymeric materials which flew onboard this vehicle. Polymers include epolyimide, polysulfone, and polystyrene film and polyimide, polysulfone, and epoxy matrix resin/graphite fiber reinforced composites. Several promising experimental films were also studied. Most specimens received 5.8 years of low Earth orbital (LEO) exposure on LDEF. Several samples received on 10 months of exposure. Chemical characterization techniques included ultraviolet-visible and infrared spectroscopy, thermal analysis, x-ray photoelectron spectroscopy, and selected solution property measurements. Results suggest that many molecular level effects present during the first 10 months of exposure were not present after 5.8 years of exposure for specimens on or near Row 9. Increased AO fluence near the end of the mission likely eroded away much environmentally induced surface phenomena. The objective of this work is to provide fundamental information for use in improving the performance of polymeric materials for LEO application. A secondary objective is to gain an appreciation for the constraints and limitations of results from LDEF polymeric materials experiments.

  14. Immobilization of Polymeric Luminophor on Nanoparticles Surface.

    PubMed

    Bolbukh, Yuliia; Podkoscielna, Beata; Lipke, Agnieszka; Bartnicki, Andrzej; Gawdzik, Barbara; Tertykh, Valentin

    2016-12-01

    Polymeric luminophors with reduced toxicity are of the priorities in the production of lighting devices, sensors, detectors, bioassays or diagnostic systems. The aim of this study was to develop a method of immobilization of the new luminophor on a surface of nanoparticles and investigation of the structure of the grafted layer. Monomer 2,7-(2-hydroxy-3-methacryloyloxypropoxy)naphthalene (2,7-NAF.DM) with luminophoric properties was immobilized on silica and carbon nanotubes in two ways: mechanical mixing with previously obtained polymer and by in situ oligomerization with chemisorption after carrier's modification with vinyl groups. The attached polymeric (or oligomeric) surface layer was studied using thermal and spectral techniques. Obtained results confirm the chemisorption of luminophor on the nanotubes and silica nanoparticles at the elaborated synthesis techniques. The microstructure of 2,7-NAF.DM molecules after chemisorption was found to be not changed. The elaborated modification approach allows one to obtain nanoparticles uniformly covered with polymeric luminophor. PMID:27090657

  15. Identification of bacteria coexisting with anammox bacteria in an upflow column type reactor.

    PubMed

    Qiao, Sen; Kawakubo, Yuki; Cheng, Yingjun; Nishiyama, Takashi; Fujii, Takao; Furukawa, Kenji

    2009-02-01

    Anammox process has attracted considerable attention in the recent years as an alternative to conventional nitrogen removal technologies. In this study, a column type reactor using a novel net type acrylic fiber (Biofix) support material was used for anammox treatment. The Biofix reactor was operated at a temperature of 25 degrees C (peak summer temperature, 31.5 degrees C). During more than 340 days of operation for synthetic wastewater treatment, the nitrogen loading rates of the reactor were increased to 3.6 kg-N/m(3)/d with TN removal efficiencies reaching 81.3%. When the reactor was used for raw anaerobic sludge digester liquor treatment, an average TN removal efficiency of 72% was obtained with highest removal efficiency of 81.6% at a nitrogen loading rate of 2.2 kg-N/m(3)/d. Results of extracellular polymeric substances (EPS) quantification revealed that protein was the most abundant component in the granular sludge and was found to be almost twice than that in the sludge attached to the biomass carriers. The anammox granules in the Biofix reactor illustrated a dense morphology substantiated by scanning electron microscopy and EPS results. The results of DNA analyses indicated that the anammox strain KSU-1 might prefer relatively low nutrient levels, while the anammox strain KU2 strain might be better suited at high nutrient concentration. Other types of bacteria were also identified with the potential of consuming dissolved oxygen in the influent and facilitating survival of anammox bacteria under aerobic conditions. PMID:18651231

  16. Phage-bacteria interaction network in human oral microbiome.

    PubMed

    Wang, Jinfeng; Gao, Yuan; Zhao, Fangqing

    2016-07-01

    Although increasing knowledge suggests that bacteriophages play important roles in regulating microbial ecosystems, phage-bacteria interaction in human oral cavities remains less understood. Here we performed a metagenomic analysis to explore the composition and variation of oral dsDNA phage populations and potential phage-bacteria interaction. A total of 1,711 contigs assembled with more than 100 Gb shotgun sequencing data were annotated to 104 phages based on their best BLAST matches against the NR database. Bray-Curtis dissimilarities demonstrated that both phage and bacterial composition are highly diverse between periodontally healthy samples but show a trend towards homogenization in diseased gingivae samples. Significantly, according to the CRISPR arrays that record infection relationship between bacteria and phage, we found certain oral phages were able to invade other bacteria besides their putative bacterial hosts. These cross-infective phages were positively correlated with commensal bacteria while were negatively correlated with major periodontal pathogens, suggesting possible connection between these phages and microbial community structure in oral cavities. By characterizing phage-bacteria interaction as networks rather than exclusively pairwise predator-prey relationships, our study provides the first insight into the participation of cross-infective phages in forming human oral microbiota. PMID:26036920

  17. Ammonia-Oxidizing Bacteria in Biofilters Removing Trihalomethanes Are Related to Nitrosomonas oligotropha

    EPA Science Inventory

    Nitrifying biofilters degrading the four regulated trihalomethanes (THMs) trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) -were analyzed for the presence and activity of ammonia-oxidizing bacteria (AOB). Biofilter perfor...

  18. Clinical microbiology of coryneform bacteria.

    PubMed Central

    Funke, G; von Graevenitz, A; Clarridge, J E; Bernard, K A

    1997-01-01

    Coryneform bacteria are aerobically growing, asporogenous, non-partially-acid-fast, gram-positive rods of irregular morphology. Within the last few years, there has been a massive increase in the number of publications related to all aspects of their clinical microbiology. Clinical microbiologists are often confronted with making identifications within this heterogeneous group as well as with considerations of the clinical significance of such isolates. This review provides comprehensive information on the identification of coryneform bacteria and outlines recent changes in taxonomy. The following genera are covered: Corynebacterium, Turicella, Arthrobacter, Brevibacterium, Dermabacter. Propionibacterium, Rothia, Exiguobacterium, Oerskovia, Cellulomonas, Sanguibacter, Microbacterium, Aureobacterium, "Corynebacterium aquaticum," Arcanobacterium, and Actinomyces. Case reports claiming disease associations of coryneform bacteria are critically reviewed. Minimal microbiological requirements for publications on disease associations of coryneform bacteria are proposed. PMID:8993861

  19. Magnetosome biogenesis in magnetotactic bacteria.

    PubMed

    Uebe, René; Schüler, Dirk

    2016-09-13

    Magnetotactic bacteria derive their magnetic orientation from magnetosomes, which are unique organelles that contain nanometre-sized crystals of magnetic iron minerals. Although these organelles have evident potential for exciting biotechnological applications, a lack of genetically tractable magnetotactic bacteria had hampered the development of such tools; however, in the past decade, genetic studies using two model Magnetospirillum species have revealed much about the mechanisms of magnetosome biogenesis. In this Review, we highlight these new insights and place the molecular mechanisms of magnetosome biogenesis in the context of the complex cell biology of Magnetospirillum spp. Furthermore, we discuss the diverse properties of magnetosome biogenesis in other species of magnetotactic bacteria and consider the value of genetically 'magnetizing' non-magnetotactic bacteria. Finally, we discuss future prospects for this highly interdisciplinary and rapidly advancing field. PMID:27620945

  20. Environmental sources of fecal bacteria

    USGS Publications Warehouse

    Byappanahalli, Muruleedhara N.; Ishii, Satoshi

    2011-01-01

    This chapter provides a review of the research on environmental occurrences of faecal indicator bacteria in a variety of terrestrial and aquatic habitats under different geographic and climatic conditions, and discusses how these external sources may affect surface water quality.