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1

Debunking BACT  

SciTech Connect

The US Clean Air Act's provisions for the Prevention of Significant Deterioration (PSD) of air quality require a new major stationary source to obtain a preconstruction permit that specifies the Best Available Control Technology (BACT) for each regulated pollutant that may be emitted in amounts greater than major source thresholds. The PSD regulations also impose BACT requirements on modifications to existing major sources that result in significant net emissions increases. Rather than a specific technology, BACT is an achievable emissions limitation (or work practice) determined by the permitting authority on a case-by- case basis, taking into account available technologies and energy, environmental, and economic impacts. BACT determinations are generally made by a state environmental agency after an opportunity for public comment. Increasingly, advocacy groups are challenging BACT decisions in administrative and judicial proceedings. As a result, the permitting process has been substantially delayed, even for facilities that have agreed to install state-of-the-art emissions control technology. This article outlines the key statutory and regulatory elements of BACT, how to analyze alternative technologies and emissions limitations, and prepare an application for an appropriate and final BACT determination. It is based largely on the regulatory definition of BACT and recent Environmental Appeals Board (EAB) decisions. Case-by-case BACT analyses do not necessarily yield a single, objectively correct BACT determination. The permitting agency must exercise a high degree of technical judgment in any BACT analysis, particularly for coal-fired plants, which use a wide variety of coals, combustion techniques, and other site-specific factors. 12 refs.

Finto, K.; Harrison, C.; Lomax, S. [Junton & Williams (United States)

2006-11-15

2

Serine utilization by Klebsiella aerogenes.  

PubMed Central

Klebsiella aerogenes was found to contain a specific L-serine dehydrase that was induced by threonine, glycine or leucine, but not by its substrate. Cellular concentrations were sensitive to carbon rather than nitrogen sources in the growth medium. A nonspecific isoleucine-sensitive L-threonine dehydrase supplemented the specific L-serine dehydrase activity. K. aerogenes also contains a leucine-inducible L-threonine dehydrogenase which probably initiated a threonine-utilization pathway in which the serine-specific dehydrate participated. Strains that were altered in their ability to metabolize serine differed in either L-serine dehydrase or L-threonine dehydrase activity. Thus, K. aerogenes growing on L-serine as a sole nitrogen source relies upon two enzymes that metabolize the amino acid as subsidiary functions.

Vining, L C; Magasanik, B

1981-01-01

3

Benchmark Active Controls Technology (BACT) Wing CFD Results  

NASA Technical Reports Server (NTRS)

The Benchmark Active Controls Technology (BACT) wing test (see chapter 8E) provides data for the validation of aerodynamic, aeroelastic, and active aeroelastic control simulation codes. These data provide a rich database for development and validation of computational aeroelastic and aeroservoelastic methods. In this vein, high-level viscous CFD analyses of the BACT wing have been performed for a subset of the test conditions available in the dataset. The computations presented in this section investigate the aerodynamic characteristics of the rigid clean wing configuration as well as simulations of the wing with a static and oscillating aileron and spoiler deflection. Two computational aeroelasticity codes extensively used at NASA Langley Research Center are implemented in this simulation. They are the ENS3DAE and CFL3DAE computational aeroelasticity programs. Both of these methods solve the three-dimensional compressible Navier-Stokes equations for both rigid and flexible vehicles, but they use significantly different approaches to the solution 6f the aerodynamic equations of motion. Detailed descriptions of both methods are presented in the following section.

Schuster, David M.; Bartels, Robert E.

2000-01-01

4

Differentiation of Enterobacter aerogenes from Klebsiellae by Deoxyribonucleic Acid Reassociation  

Microsoft Academic Search

Polynucleotide sequence relatedness tests were carried out to determine the extent of deoxyribonucleic acid (DNA) divergence among species of Klebsiella and Enterobacter aerogenes strains. Labeled, denatured DNA fragments from K. pneumoniae type 2 and E. aerogenes 1627-66 were each incubated with an excess of unlabeled DNA fragments from Klebsielia species and strains of E. aerogenes. Reassociated DNA duplexes were separated

DON J. BRENNER; A. G. STEIGERWALT; G. R. FANNING

1972-01-01

5

Robust Multivariable Flutter Suppression for the Benchmark Active Control Technology (BACT) Wind-Tunnel Model  

NASA Technical Reports Server (NTRS)

The Benchmark Active Controls Technology (BACT) project is part of NASA Langley Research Center s Benchmark Models Program for studying transonic aeroelastic phenomena. In January of 1996 the BACT wind-tunnel model was used to successfully demonstrate the application of robust multivariable control design methods (H and -synthesis) to flutter suppression. This paper addresses the design and experimental evaluation of robust multivariable flutter suppression control laws with particular attention paid to the degree to which stability and performance robustness was achieved.

Waszak, Martin R.

1997-01-01

6

mar Operon Involved in Multidrug Resistance of Enterobacter aerogenes  

Microsoft Academic Search

We determined the sequence of the entire marRAB operon in Enterobacter aerogenes. It is functionally and structurally analogous to the Escherichia coli operon. The overexpression of E. aerogenes MarA induces a multidrug resistance phenotype in a susceptible strain, demonstrated by a noticeable resistance to various antibiotics, a decrease in immunodetected porins, and active efflux of norfloxacin.

Renaud Chollet; Claude Bollet; Jacqueline Chevalier; M. Mallea; J.-M. Pages; Anne Davin-Regli

2002-01-01

7

Characterization of purified human Bact spliceosomal complexes reveals compositional and morphological changes during spliceosome activation and first step catalysis  

PubMed Central

To better understand the compositional and structural dynamics of the human spliceosome during its activation, we set out to isolate spliceosomal complexes formed after precatalytic B but prior to catalytically active C complexes. By shortening the polypyrimidine tract of the PM5 pre-mRNA, which lacks a 3? splice site and 3? exon, we stalled spliceosome assembly at the activation stage. We subsequently affinity purified human Bact complexes under the same conditions previously used to isolate B and C complexes, and analyzed their protein composition by mass spectrometry. A comparison of the protein composition of these complexes allowed a fine dissection of compositional changes during the B to Bact and Bact to C transitions, and comparisons with the Saccharomyces cerevisiae Bact complex revealed that the compositional dynamics of the spliceosome during activation are largely conserved between lower and higher eukaryotes. Human SF3b155 and CDC5L were shown to be phosphorylated specifically during the B to Bact and Bact to C transition, respectively, suggesting these modifications function at these stages of splicing. The two-dimensional structure of the human Bact complex was determined by electron microscopy, and a comparison with the B complex revealed that the morphology of the human spliceosome changes significantly during its activation. The overall architecture of the human and S. cerevisiae Bact complex is similar, suggesting that many of the higher order interactions among spliceosomal components, as well as their dynamics, are also largely conserved.

Bessonov, Sergey; Anokhina, Maria; Krasauskas, Andrius; Golas, Monika M.; Sander, Bjoern; Will, Cindy L.; Urlaub, Henning; Stark, Holger; Luhrmann, Reinhard

2010-01-01

8

Multicenter Evaluation of the MB\\/BACT System for Susceptibility Testing of Mycobacterium tuberculosis  

Microsoft Academic Search

The reliability of the MB\\/BACT system for susceptibility testing of Mycobacterium tuberculosis to pyrazin- amide, rifampin, isoniazid, streptomycin, and ethambutol was compared to the BACTEC 460TB system. The proportion method was used to resolve discrepant results by an independent arbiter. Two interpretative methods were used, with an undiluted control (direct control) and a diluted control (10 1 control). As no

Pascale Bemer; Thomas Bodmer; Juerg Munzinger; Monique Perrin; Veronique Vincent; Henri Drugeon

2004-01-01

9

BactQuant: An enhanced broad-coverage bacterial quantitative real-time PCR assay  

PubMed Central

Background Bacterial load quantification is a critical component of bacterial community analysis, but a culture-independent method capable of detecting and quantifying diverse bacteria is needed. Based on our analysis of a diverse collection of 16?S rRNA gene sequences, we designed a broad-coverage quantitative real-time PCR (qPCR) assay—BactQuant—for quantifying 16?S rRNA gene copy number and estimating bacterial load. We further utilized in silico evaluation to complement laboratory-based qPCR characterization to validate BactQuant. Methods The aligned core set of 4,938 16?S rRNA gene sequences in the Greengenes database were analyzed for assay design. Cloned plasmid standards were generated and quantified using a qPCR-based approach. Coverage analysis was performed computationally using >670,000 sequences and further evaluated following the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines. Results A bacterial TaqMan® qPCR assay targeting a 466?bp region in V3-V4 was designed. Coverage analysis showed that 91% of the phyla, 96% of the genera, and >80% of the 89,537 species analyzed contained at least one perfect sequence match to the BactQuant assay. Of the 106 bacterial species evaluated, amplification efficiencies ranged from 81 to 120%, with r2-value of >0.99, including species with sequence mismatches. Inter- and intra-run coefficient of variance was <3% and <16% for Ct and copy number, respectively. Conclusions The BactQuant assay offers significantly broader coverage than a previously reported universal bacterial quantification assay BactQuant in vitro performance was better than the in silico predictions.

2012-01-01

10

Multicenter Evaluation of the MB/BACT System for Susceptibility Testing of Mycobacterium tuberculosis  

PubMed Central

The reliability of the MB/BACT system for susceptibility testing of Mycobacterium tuberculosis to pyrazinamide, rifampin, isoniazid, streptomycin, and ethambutol was compared to the BACTEC 460TB system. The proportion method was used to resolve discrepant results by an independent arbiter. Two interpretative methods were used, with an undiluted control (direct control) and a diluted control (10?1 control). As no significant difference was observed between the two controls, the method with the direct control was adopted as the most accurate one. One hundred sixty-six strains were tested, with an overall agreement of 98.3%. After resolution of the 18 discrepant results by the proportion method, the sensitivity and specificity of the MB/BACT system were 100% for rifampin, isoniazid, and pyrazinamide. For ethambutol, sensitivity was 92.3% at the critical concentration and 33% at the high concentration, and specificity was 100% at both concentrations. For streptomycin, sensitivity was 100% at the critical concentration and 80% at the high concentration, and specificity was 98.6% at the critical concentration and 100% at the high concentration. The rifampin, isoniazid, streptomycin, and ethambutol susceptibility test results were obtained in 6.6 days with the MB/BACT versus 5 days with the BACTEC 460TB. The pyrazinamide susceptibility test results were obtained in 7.8 days with the MB/BACT, versus 6.7 days with the BACTEC 460TB. These data demonstrate that the fully automated MB/BACT system is a very reliable method for rapid susceptibility testing of M. tuberculosis against rifampin, isoniazid, and pyrazinamide. Sensitivity results have to be improved for ethambutol and streptomycin, especially at the high concentration.

Bemer, Pascale; Bodmer, Thomas; Munzinger, Juerg; Perrin, Monique; Vincent, Veronique; Drugeon, Henri

2004-01-01

11

Multicenter evaluation of the MB/BACT system for susceptibility testing of Mycobacterium tuberculosis.  

PubMed

The reliability of the MB/BACT system for susceptibility testing of Mycobacterium tuberculosis to pyrazinamide, rifampin, isoniazid, streptomycin, and ethambutol was compared to the BACTEC 460TB system. The proportion method was used to resolve discrepant results by an independent arbiter. Two interpretative methods were used, with an undiluted control (direct control) and a diluted control (10(-1) control). As no significant difference was observed between the two controls, the method with the direct control was adopted as the most accurate one. One hundred sixty-six strains were tested, with an overall agreement of 98.3%. After resolution of the 18 discrepant results by the proportion method, the sensitivity and specificity of the MB/BACT system were 100% for rifampin, isoniazid, and pyrazinamide. For ethambutol, sensitivity was 92.3% at the critical concentration and 33% at the high concentration, and specificity was 100% at both concentrations. For streptomycin, sensitivity was 100% at the critical concentration and 80% at the high concentration, and specificity was 98.6% at the critical concentration and 100% at the high concentration. The rifampin, isoniazid, streptomycin, and ethambutol susceptibility test results were obtained in 6.6 days with the MB/BACT versus 5 days with the BACTEC 460TB. The pyrazinamide susceptibility test results were obtained in 7.8 days with the MB/BACT, versus 6.7 days with the BACTEC 460TB. These data demonstrate that the fully automated MB/BACT system is a very reliable method for rapid susceptibility testing of M. tuberculosis against rifampin, isoniazid, and pyrazinamide. Sensitivity results have to be improved for ethambutol and streptomycin, especially at the high concentration. PMID:15004049

Bemer, Pascale; Bodmer, Thomas; Munzinger, Juerg; Perrin, Monique; Vincent, Véronique; Drugeon, Henri

2004-03-01

12

Regulatory region of the Klebsiella aerogenes tryptophan operon.  

PubMed Central

The trp operon of Klebsiella aerogenes was cloned, and its regulatory region was sequenced. Comparison with previously reported trp regulatory sequences of other enteric bacteria indicates that the K. aerogenes trp promoter-operator region is most similar to the corresponding region of Salmonella typhimurium. The trp leader regions of K. aerogenes and other enteric bacteria are organized similarly, but there are significant differences in the stabilities of the predicted secondary structures in their leader transcripts. These differences should make the K. aerogenes attenuator a weaker transcription termination site than any of the other attenuator regions studied; this was confirmed in in vitro transcription experiments. The sequence of the leader transcript and the precise site of in vitro termination were determined. Images

Blumenberg, M; Yanofsky, C

1982-01-01

13

Effects of Formate on Fermentative Hydrogen Production by Enterobacter aerogenes  

Microsoft Academic Search

This paper describes the effects of formate on fermentative hydrogen production by Enterobacter aerogenes by way of batch culture. When 20 mM formate was added to pH 6.3 and pH 5.8 E. aerogenes glucose cultures (formate culture) at the beginning of cultivation, hydrogen evolution through both glucose consumption and decomposition of the extrinsic formate occurred together, while hydrogen evolution occurred

Tatsuo Kurokawa; Shigeharu Tanisho

2005-01-01

14

TEM Derivative-Producing Enterobacter aerogenes Strains: Dissemination of a Prevalent Clone  

Microsoft Academic Search

TEM-24 (CAZ-6) extended-spectrum -lactamase (ESBL) was detected in 1988 in Clermont-Ferrand, France, in Klebsiella pneumoniae (blaTEM-24) and Enterobacter aerogenes (blaTEM-24b), and since 1994, a TEM- 24-producing E. aerogenes clonal strain has been observed elsewhere in the country. To determine if the spread of this clonal strain was restricted to TEM-24-producing E. aerogenes strains, 84 E. aerogenes strains (non- TEM\\/SHV-producing strains,

P. Dumarche; C. De Champs; D. Sirot; C. Chanal; R. Bonnet; J. Sirot

2002-01-01

15

Single-cell protein from methanol with Enterobacter aerogenes  

SciTech Connect

An identified Enterobacter aerogenes utilizing methanol as a sole carbon source was studied for the optimization of biomass production and the reduction of its nucleic acid content. Results indicated that the highest yield and conversion were obtained at 0.5% methanol. The addition of seawater as a source of trace elements has an adverse effect. However, the addition of urea as source of nitrogen enhanced the growth of E. aerogenes. Heat shock at 60 degrees C for one minute followed by incubation at 50 degrees C for 2 hours caused 72.6% reduction in the nucleic acid. 12 references.

Gnan, S.O.; Abodreheba, A.O.

1987-02-20

16

RACT/BACT/LAER clearinghouse: A compilation of control technology determinations. Third supplement to the 1990 edition. Volume 1  

SciTech Connect

The Clean Air Act as amended in 1977 prescribes several technology based limitations affecting new or modified air pollution sources: (1) new source performance stds. (NSPS); (2) best available control technology (BACT); and (3) lowest achievable emission rates (LAER). The basic purposes of the RACT/BACT/LAER Clearinghouse are to: (1) provide State and local air pollution control agencies with current information on case-by-case control technology determinations that are made nationwide and (2) promote communication, cooperation, and sharing of control technology information among the permitting agencies. The information presented in the compilation was abstracted from preconstruction permits and submitted voluntarily by the State and local agencies in making RACT/BACT/LAER decisions.

Steigerwald, J.E.

1993-08-01

17

Carbapenem Resistance in Enterobacter aerogenes is due to Lipopolysaccharide Alterations  

Microsoft Academic Search

The extensive characterization of 2 clinical Enterobacter aerogenes isolates resistant to all ?-lactam antibiotics including imipenem revealed that imipenem resistance could not be attributed to overproduction of the chromosomal ?-lactamase; moreover, it was lost after subcultivation and can be thus considered as unstable. The comparison of sensitive and resistant clones revealed that the ?-lactamase in the resistant clones was less

Hermann Leying; Wolfgang Cullmann; Wolfgang Dick

1991-01-01

18

Chloramphenicol and expression of multidrug efflux pump in Enterobacter aerogenes  

Microsoft Academic Search

Chloramphenicol has been reported to act as an inducer of the multidrug resistance in Escherichia coli. A resistant variant able to grow on plates containing 64?g\\/ml chloramphenicol was obtained from the Enterobacter aerogenes ATCC 13048-type strain. Chloramphenicol resistance was due to an active efflux of this antibiotic and it was associated with resistance to fluoroquinolones and tetracycline, but not to

Didier Ghisalberti; Muriel Masi; Jean-Marie Pagès; Jacqueline Chevalier

2005-01-01

19

Inhibitors of antibiotic efflux pump in resistant Enterobacter aerogenes strains  

Microsoft Academic Search

Enterobacter aerogenes, a nosocomial pathogen, is frequently exhibiting multidrug resistance mechanisms associated with a change in membrane permeability. In clinical isolates, active efflux plays a prominent role in antibiotic resistance. We report here the effect of three unrelated compounds that are able to restore a noticeable antibiotic susceptibility to resistant strains. The targeting of various parameters which contribute to the

Monique Malléa; Jacqueline Chevalier; Annie Eyraud; Jean-Marie Pagès

2002-01-01

20

Imipenem and expression of multidrug efflux pump in Enterobacter aerogenes  

Microsoft Academic Search

Imipenem is often used to treat intensive care unit patients infected by Enterobacter aerogenes, but it is leading to an increasing number of antibiotic resistant strains. Clinical isolates and imipenem resistant variants presented a high level of resistance to ?-lactam antibiotic group and to chemically unrelated drugs. We report here that imipenem selects strains which contain active efflux pumps ejecting

Charléric Bornet; Renaud Chollet; Monique Malléa; Jacqueline Chevalier; Anne Davin-Regli; Jean-Marie Pagès; Claude Bollet

2003-01-01

21

Effects of Nitrogen Supplements on Nitrogen Fixation by Aerobacter Aerogenes.  

National Technical Information Service (NTIS)

The effects of limiting concentrations of NH4(+) and amino acids on nitrogen fixation by Aerobacter aerogenes have been compared. The organism exhibited typical diphasic growth during the fixation of nitrogen in the presence of NH4(+), whereas in the pres...

R. B. Patil R. M. Pengra D. C. Yoch

1966-01-01

22

RACT/BACT/LAER clearinghouse: A compilation of control technology determinations. Fifth supplement to the 1990 edition. Final report  

SciTech Connect

The basic purposes of the RACT/BACT/LAER Clearinghouse are (1) to provide State and local air pollution control agencies with current information on case-by-case control technology determinations that are made nationwide and (2) promote communication, cooperation, and sharing of control technology information among the permitting agencies. The information presented in this compilation was abstracted from per-construction permits and submitted voluntarily by the State and local air pollution control agencies. The Clearinghouse is intended as a reference for States and local agencies in making RACT/BACT/LAER decisions.

Steigerwald, J.E.

1995-08-01

23

Tryptophan biosynthesis genes in Lactococcus lactis subsp. lactis.  

PubMed Central

The Lactococcus lactis chromosomal region containing the seven structural genes required for tryptophan biosynthesis was characterized by cloning and sequencing. All of the trp genes were identified by the homology of their products with known Trp proteins from other organisms. The identification was confirmed for five genes by their ability to complement trp mutations in Escherichia coli. The seven structural genes are present in the order trpEGDCFBA and span a 7,968-bp segment. Each gene is preceded by a putative ribosome binding site complementary to the 3' end of the L. lactis 16S rRNA. Three pairs of genes (trpG-trpD, trpC-trpF, and trpB-trpA) overlap, and there is intercistronic spacing of 124, 46, and 585 bp between the trpE-trpG, trpD-trpC, and trpF-trpB gene pairs, respectively. No gene fusion was found. Upstream of the trp genes, a 457-bp noncoding DNA segment contains several regions fitting the consensus for gram-positive promoters and one region strongly resembling a transcription terminator. However, it seems unlikely that an attenuation mechanism similar to the one found in E. coli regulates tryptophan biosynthesis in L. lactis, since no potential leader peptide was detected. We propose that a mechanisms resembling that described in Bacillus spp. can regulate trp genes expression in L. lactis.

Bardowski, J; Ehrlich, S D; Chopin, A

1992-01-01

24

Enterobacter aerogenes Needle Stick Leads to Improved Biological Management System  

SciTech Connect

A laboratory worker who received a needle stick from a contaminated needle while working with a culture containing Enterobactor aerogenes developed a laboratory acquired infection. Although this organism has been shown to cause community and nosocomial infections, there have been no documented cases of a laboratory acquired infections. Lessons learned from the event led to corrective actions which included modification of lab procedures, development of a biological inventory tracking and risk identification system and the establishment of an effective biological safety program.

Johanson, Richard E.

2004-08-01

25

Thermodynamic study and optimization of hydrogen production by Enterobacter aerogenes  

Microsoft Academic Search

This paper investigates the influence of pH and temperature on hydrogen bioproduction by Enterobacter aerogenes (NCIMB 10102) utilizing starch hydrolysate as substrate. An optimum pH range corresponding to 6.1–6.6 is the main evidence of batch runs carried out at different pHs. An optimum value of temperature corresponding to 40°C is experimentally determined by means of batch fermentation runs carried out

B. Fabiano; P. Perego

2002-01-01

26

Molecular Analysis of Tetracycline Resistance in Pasteurella aerogenes  

PubMed Central

Tetracycline-resistant Pasteurella aerogenes isolates obtained from the intestinal tract of swine were investigated for their tet genes by PCR analysis and hybridization experiments. In contrast to Pasteurella isolates from the respiratory tract, tet(H) genes were detected in the chromosomal DNA of only 2 of the 24 isolates, one of which also carried two copies of a tet(B) gene. All other P. aerogenes isolates carried tet(B) genes, which are the predominant tet genes among Enterobacteriaceae. A single isolate harbored a tet(B) gene as part of a truncated Tn10 element on the 4.8-kb plasmid pPAT2. Comparative analysis of the pPAT2 sequence suggested that the Tn10 relic on plasmid pPAT2 is the result of several illegitimate recombination events. The remaining 21 P. aerogenes isolates carried one or two copies of the tet(B) gene in their chromosomal DNA. In the majority of the cases, these tet(B) genes were associated with copies of Tn10 as confirmed by their SfuI and BamHI hybridization patterns. No correlation between the number of tet gene copies and the MICs of tetracycline, doxycyline and minocycline was observed.

Kehrenberg, Corinna; Schwarz, Stefan

2001-01-01

27

Biological Conversion of Glycerol to Ethanol by Enterobacter aerogenes  

NASA Astrophysics Data System (ADS)

In a search to turn the economically and environmentally non-valuable "waste" streams of biodiesel production into a profitable byproduct, a mutant strain of Enterobacter aerogenes ATCC 13048 was developed by six-tube subculturing technique. This technique is based on the principle of adaptive evolution, and involved subculturing the bacterium in a tryptic soy broth without dextrose (TSB) containing specific glycerol and ethanol concentration for six consecutive times. Then, the six consecutive subculturing was repeated in a fresh TSB of higher glycerol and ethanol concentrations. A new mutant strain, E. aerogenes S012, which could withstand a combination of 200 g/l glycerol and 30 g/l ethanol concentrations, was developed. The wild and mutant strains were used for the fermentation of pure (P-) and recovered (R-) glycerol. Taguchi and full factorial methods of design of experiments were used to screen and optimize the important process factors that influence the microbial production of ethanol. A statistically sound regression model was used to establish the mathematical relationship between the process variables and ethanol production. Temperature of 38°C, agitation speed of 200 rpm, pH of 6.3-6.6, and microaerobic condition were the optimum process conditions. Different pretreatment methods to recover glycerol from the crude glycerol and the subsequent fermentation method showed that direct acidification using 85% H3PO4 was the best. The R-glycerol contained 51% pure glycerol and 21% methanol. The wild strain, E. aerogenes ATCC 13048, produced only 12 g/l and 12.8 g/l ethanol from 20 g/l P- and R-glycerol respectively, and could not utilize higher glycerol concentrations. The mutant, E. aerogenes S012, produced ethanol amount and yield of 43 g/l and 1.12 mol/mol-glycerol from P-glycerol, respectively within 96 h. It also produced ethanol amount and yield of 26.8 g/l and 1.07 mol/mol-glycerol, respectively, from R-glycerol within the same duration. In a fermentation to estimate hydrogen production using a respirometer, the hydrogen yield and volumetric rate of 1.06 mol/mol-glycerol and 217 ml/l/h, respectively were obtained from 6% P-glycerol in 72 h by E. aerogenes S012. The result was higher from R-glycerol, which produced hydrogen yield and productivity of 1.83 mol/mol-glycerol and 326 ml/l/h, respectively.

Nwachukwu, Raymond E. S.

28

Starvation-Induced Stress Resistance in Lactococcus lactis subsp. lactis IL1403.  

PubMed

Carbohydrate-starved cultures of Lactococcus lactis subsp. lactis IL1403 showed enhanced resistance to heat, ethanol, acid, osmotic, and oxidative stresses. This cross-protection seems to be established progressively during the transitional growth phase, with maximum resistance occurring when cells enter the stationary phase. Chloramphenicol or rifamycin treatment does not abolish the development of a tolerant cell state but, on the contrary, seems to provoke this response in L. lactis subsp. lactis. PMID:16349399

Hartke, A; Bouche, S; Gansel, X; Boutibonnes, P; Auffray, Y

1994-09-01

29

Genome Sequence of Lactococcus lactis subsp. lactis bv. diacetylactis LD61  

PubMed Central

Lactococcus lactis is widely used in the dairy industry. We report the draft genome sequence of L. lactis subsp. lactis bv. diacetylactis LD61, an industrial and extensively studied strain. In contrast to the closely related and plasmidless strain IL1403, LD61 contains 6 plasmids, and the genome sequence provides additional information related to adaptation to the dairy environment.

Falentin, Helene; Naquin, Delphine; Loux, Valentin; Barloy-Hubler, Frederique; Loubiere, Pascal; Nouaille, Sebastien; Lavenier, Dominique; Le Bourgeois, Pascal; Francois, Patrice; Schrenzel, Jacques; Hernandez, David; Even, Sergine

2014-01-01

30

Regulation of hydrogen production by Enterobacter aerogenes by external NADH and NAD +  

Microsoft Academic Search

Experiments involving the addition of external nicotinamide adenine dinucleotide, reduced form (NADH) or nicotinamide adenine dinucleotide (NAD+) have been designed to examine how the hydrogen in Enterobacter aerogenes is liberated by NADH or NAD+. The addition of external NADH or NAD+ was found to regulate hydrogen production by E. aerogenes in resting cells, batch cultures, and chemostat cultures. Particularly in chemostat

Chong Zhang; Kun Ma; Xin-Hui Xing

2009-01-01

31

Molecular Epidemiological Study of Nosocomial Enterobacter aerogenes Isolates in a Belgian Hospital  

Microsoft Academic Search

In 1995, the rate of isolation of Enterobacter aerogenes in the Saint-Pierre University Hospital in Brussels, Belgium, was higher than that in the preceding years. A total of 45 nosocomial E. aerogenes strains were collected from 33 patients of different units during that year, and they were isolated from 19 respiratory specimens, 13 pus specimens, 7 blood specimens, 4 urinary

SHEIKH JALALUDDIN; JEANNE-MARIE DEVASTER; ROBERT SCHEEN; MICHELE GERARD; JEAN-PAUL BUTZLER

1998-01-01

32

Induction by Klebsiella aerogenes of a Melanin-Like Pigment in Cryptococcus neoformans  

Microsoft Academic Search

While studying the interaction of Cryptococcus neoformans with Dictyostelium discoideum, we noticed that yeast colonies in agar with a feeder lawn of Klebsiella aerogenes were brown. This finding was intriguing because C. neoformans colonies are not pigmented unless they are provided with precursors for melanization. Strains of all C. neoformans serotypes produced brown pigment in response to K. aerogenes at

Susana Frases; Stuart Chaskes; Ekaterina Dadachova; Arturo Casadevall

2006-01-01

33

Chloramphenicol and expression of multidrug efflux pump in Enterobacter aerogenes.  

PubMed

Chloramphenicol has been reported to act as an inducer of the multidrug resistance in Escherichia coli. A resistant variant able to grow on plates containing 64 microg/ml chloramphenicol was obtained from the Enterobacter aerogenes ATCC 13048-type strain. Chloramphenicol resistance was due to an active efflux of this antibiotic and it was associated with resistance to fluoroquinolones and tetracycline, but not to aminoglycoside or beta-lactam antibiotics. MDR in the chloramphenicol-resistant variant is linked to the overexpression of the major AcrAB-TolC efflux system. This overexpression seems unrelated to the global Mar and the local AcrR regulatory pathways. PMID:15707992

Ghisalberti, Didier; Masi, Muriel; Pagès, Jean-Marie; Chevalier, Jacqueline

2005-03-25

34

Complete Genome Sequence of Lactococcus lactis subsp. cremoris A76  

PubMed Central

We report the complete genome sequence of Lactococcus lactis subsp. cremoris A76, a dairy strain isolated from a cheese production outfit. Genome analysis detected two contiguous islands fitting to the L. lactis subsp. lactis rather than to the L. lactis subsp. cremoris lineage. This indicates the existence of genetic exchange between the diverse subspecies, presumably related to the technological process.

Quinquis, Benoit; Ehrlich, Stanislas Dusko; Sorokin, Alexei

2012-01-01

35

Complete genome sequence of Lactococcus lactis subsp. cremoris A76.  

PubMed

We report the complete genome sequence of Lactococcus lactis subsp. cremoris A76, a dairy strain isolated from a cheese production outfit. Genome analysis detected two contiguous islands fitting to the L. lactis subsp. lactis rather than to the L. lactis subsp. cremoris lineage. This indicates the existence of genetic exchange between the diverse subspecies, presumably related to the technological process. PMID:22328746

Bolotin, Alexander; Quinquis, Benoit; Ehrlich, Stanislas Dusko; Sorokin, Alexei

2012-03-01

36

d-Apiose Reductase from Aerobacter aerogenes1  

PubMed Central

A strain of Aerobacter aerogenes PRL-R3 has been isolated which utilizes d-apiose as its sole source of carbon. A new enzyme, d-apiose reductase, was discovered in this strain. The enzyme was not present when the strain was grown on d-glucose. d-Apiose reductase catalyzes the nicotinamide adenine dinucleotide-dependent interconversion of d-apiose and d-apiitol. The enzyme is specific for d-apiose and d-apiitol, with a few possible exceptions. The Km for d-apiose is 0.02 m. The Km for d-apiitol is 0.01 m. The enzyme is almost completely specific for the reduced and oxidized forms of nicotinamide adenine dinucleotide. When cell-free extracts were centrifuged at 100,000 × g for 1 hr, the enzyme remained in solution. Optimal activity for the reduction of d-apiose was obtained at pH 7.5 in glycylglycine buffer, whereas for the oxidation of d-apiitol it was obtained at pH 10.5 in glycine buffer. Enzymatic reduction of d-apiose was not appreciably affected by the presence of 0.02 m ethylenediaminetetraacetate. Paper chromatography and specific spray reagents were used to identify d-apiitol and d-apiose as the products of this reversible reaction. d-Apiose and d-apiitol did not serve as substrates for ribitol dehydrogenase and d-arabitol dehydrogenase from A. aerogenes PRL-R3.

Neal, Donna L.; Kindel, Paul K.

1970-01-01

37

Uridine Diphosphate d-Glucose Dehydrogenase of Aerobacter aerogenes  

PubMed Central

Uridine diphosphate d-glucose dehydrogenase (EC 1.1.1.22) from Aerobacter aerogenes has been partially purified and its properties have been investigated. The molecular weight of the enzyme is between 70,000 and 100,000. Uridine diphosphate d-glucose is a substrate; the diphosphoglucose derivatives of adenosine, cytidine, guanosine, and thymidine are not substrates. Nicotinamide adenine dinucleotide (NAD), but not nicotinamide adenine dinucleotide phosphate, is active as hydrogen acceptor. The pH optimum is between 9.4 and 9.7; the Km is 0.6 mm for uridine diphosphate d-glucose and 0.06 mm for NAD. Inhibition of the enzyme by uridine diphosphate d-xylose is noncooperative and of mixed type; the Ki is 0.08 mm. Thus, uridine diphosphate d-glucose dehydrogenase from A. aerogenes differs from the enzyme from mammalian liver, higher plants, and Cryptococcus laurentii, in which uridine diphosphate d-xylose functions as a cooperative, allosteric feedback inhibitor.

Bdolah, Avener; Feingold, David S.

1968-01-01

38

Purification and characterization of a bacteriocin produced by Lactococcus lactis subsp. lactis H-559 isolated from kimchi  

Microsoft Academic Search

Lactic acid bacteria were isolated from kimchi and screened for bacteriocin production. Strain H-559, identified as Lactococcus lactis subsp. lactis, exhibited the strongest antibacterial activity among them and was active against pathogenic bacteria such as Listeria monocytogenes and Staphylococcus aureus as well as many lactic acid bacteria. The antimicrobial substance produced by L. lactis subsp. lactis H-559 was inactivated by

Hun-Joo Lee; Yun-Jung Joo; Chan-Sun Park; Seung-Ho Kim; In-Kyeong Hwang; Jong-Seog Ahn; Tae-Ick Mheen

1999-01-01

39

Histidine biosynthesis genes in Lactococcus lactis subsp. lactis.  

PubMed

The genes of Lactococcus lactis subsp. lactis involved in histidine biosynthesis were cloned and characterized by complementation of Escherichia coli and Bacillus subtilis mutants and DNA sequencing. Complementation of E. coli hisA, hisB, hisC, hisD, hisF, hisG, and hisIE genes and the B. subtilis hisH gene (the E. coli hisC equivalent) allowed localization of the corresponding lactococcal genes. Nucleotide sequence analysis of the 11.5-kb lactococcal region revealed 14 open reading frames (ORFs), 12 of which might form an operon. The putative operon includes eight ORFs which encode proteins homologous to enzymes involved in histidine biosynthesis. The operon also contains (i) an ORF encoding a protein homologous to the histidyl-tRNA synthetases but lacking a motif implicated in synthetase activity, which suggests that it has a role different from tRNA aminoacylation, and (ii) an ORF encoding a protein that is homologous to the 3'-aminoglycoside phosphotransferases but does not confer antibiotic resistance. The remaining ORFs specify products which have no homology with proteins in the EMBL and GenBank data bases. PMID:1400209

Delorme, C; Ehrlich, S D; Renault, P

1992-10-01

40

Klebsiella aerogenes catabolite gene activator protein and the gene encoding it (crp).  

PubMed Central

The catabolite gene activator protein from Klebsiella aerogenes (CAPK) and the corresponding protein from Escherichia coli (CAPE) were shown to be nearly identical. Both CAPK and CAPE activated transcription from the CAP-dependent promoters derived from E. coli and K. aerogenes. The crp gene from K. aerogenes (encoding CAP) is tightly linked to rpsL. The nucleotide sequence of crp predicts an amino acid sequence for CAPK that differs in only one position from that of CAPE. Images FIG. 2 FIG. 3 FIG. 4 FIG. 5

Osuna, R; Bender, R A

1991-01-01

41

Glutathione Protects Lactococcus lactis against Oxidative Stress  

PubMed Central

Glutathione was found in several dairy Lactococcus lactis strains grown in M17 medium. None of these strains was able to synthesize glutathione. In chemically defined medium, L. lactis subsp. cremoris strain SK11 was able to accumulate up to ?60 mM glutathione when this compound was added to the medium. Stationary-phase cells of strain SK11 grown in chemically defined medium supplemented with glutathione showed significantly increased resistance (up to fivefold increased resistance) to treatment with H2O2 compared to the resistance of cells without intracellular glutathione. The resistance to H2O2 treatment was found to be dependent on the accumulation of glutathione in 16 strains of L. lactis tested. We propose that by taking up glutathione, L. lactis might activate a glutathione-glutathione peroxidase-glutathione reductase system in stationary-phase cells, which catalyzes the reduction of H2O2. Glutathione reductase, which reduces oxidized glutathione, was detectable in most strains of L. lactis, but the activities of different strains were very variable. In general, the glutathione reductase activities of L. lactis subsp. lactis are higher than those of L. lactis subsp. cremoris, and the activities were much higher when strains were grown aerobically. In addition, glutathione peroxidase is detectable in strain SK11, and the level was fivefold greater when the organism was grown aerobically than when the organism was grown anaerobically. Therefore, the presence of glutathione in L. lactis could result in greater stability under storage conditions and quicker growth upon inoculation, two important attributes of successful starter cultures.

Li, Yin; Hugenholtz, Jeroen; Abee, Tjakko; Molenaar, Douwe

2003-01-01

42

RACT/BACT/LAER clearinghouse: A compilation of control technology determinations. Sixth supplement to the 1990 edition. Final report  

SciTech Connect

The basic purposes of the RACT/BACT/LAER Clearinghouse are (1) to provide State and local air pollution control agencies with current information on case-by-case control technology determinations that are made nationwide and (2) promote communication, cooperation, and sharing of control technology information among the permitting agencies. The information presented in this compilation was abstracted from per-construction permits and submitted voluntarily by the State and local air pollution control agencies. A mast edition containing all new/revised determinations completed during the past 5 years was published in 1990. This is the sixth supplement to that edition.

Steigerwald, J.E.

1996-08-01

43

Possible role of membrane proteins in mercury resistance of Enterobacter aerogenes  

Microsoft Academic Search

Mercury resistance shown by a strain of Enterobacter aerogenes was found to be determined by a plasmid. The resistance appeared to be not due to enzymatic volatilization of mercury, but due to the alteration in cellular permeability to mercury.

Hidemitsu S Pan-Hou; Masayo Nishimoto; Nobumasa Imura

1981-01-01

44

Further studies on the sources of Klebsiella aerogenes in hospital patients.  

PubMed Central

We report an investigation into faecal carriage of Klebsiella aerogenes and the distribution of this organism in the environment of three wards. In all three wards faecal carriage rates were high (60-70%). The faecal carriage rate increased with antibiotic administration and with length of in-patient stay. K. aerogenes was widely distributed in the ward environment and was found on the hands of nursing staff. Clusters of isolations of K. aerogenes of the same serotype were demonstrated indicating either patient-to-patient transfer or a common source of infection. The results indicate that even under conditions in which there are no outbreaks of K. aerogenes infection, there is a large reservoir of this organism both in the bowel of patients and in the ward environment.

Cooke, E. M.; Pool, R.; Brayson, J. C.; Edmondson, A. S.; Munro, M. E.; Shinebaum, R.

1979-01-01

45

Plasmid-Mediated Resistance to Expanded-Spectrum Cephalosporins among Enterobacter aerogenes Strains  

Microsoft Academic Search

Resistance to expanded-spectrum cephalosporins commonly develops in Enterobacter aerogenes during ther- apy due to selection of mutants producing high levels of the chromosomal Bush group 1 b-lactamase. Recently, resistant strains producing plasmid-mediated extended-spectrum b-lactamases (ESBLs) have been isolated as well. A study was designed to investigate ESBL production among 31 clinical isolates of E. aerogenes from Richmond, Va., with decreased

JOHANN D. D. PITOUT; KENNETH S. THOMSON; NANCY D. HANSON; ANTON F. EHRHARDT; PHILIP COUDRON; CHRISTINE C. SANDERS

1998-01-01

46

Resistance to imipenem, cefepime, and cefpirome associated with mutation in Omp36 osmoporin of Enterobacter aerogenes  

Microsoft Academic Search

Enterobacter aerogenes develops increased multidrug resistance via a functional alteration of outer-membrane permeability associated with a decrease in porin function. We have sequenced the gene coding the major porin of Enterobacter aerogenes, omp36. The sequence shows a high similarity with the Klebsiella pneumoniae ompK36 gene and is closely related to the enterobacterial OmpC family. Sequence analysis of several Omp36 issued

Aurélie Thiolas; Charléric Bornet; Anne Davin-Régli; Jean-Marie Pagès; Claude Bollet

2004-01-01

47

RamA Is an Alternate Activator of the Multidrug Resistance Cascade in Enterobacter aerogenes  

Microsoft Academic Search

Multidrug resistance (MDR) in Enterobacter aerogenes can be mediated by induction of MarA, which is triggered by certain antibiotics and phenolic compounds. In this study, we identified the gene encoding RamA, a 113-amino-acid regulatory protein belonging to the AraC-XylS transcriptional activator family, in the Enterobacter aerogenes ATCC 13048 type strain and in a clinical multiresistant isolate. Overexpression of RamA induced

Renaud Chollet; Jacqueline Chevalier; Claude Bollet; Jean-Marie Pages; Anne Davin-Regli

2004-01-01

48

A model for multiproduct-inhibited growth of Enterobacter aerogenes in 2,3-butanediol fermentation  

Microsoft Academic Search

Ethanol is identified as a strongly inhibitory metabolite in addition to acetic acid and 2,3-butanediol in 2,3-butanediol production by Enterobacter aerogenes. A model is proposed to describe the multiproduct-inhibited growth of E. aerogenes in 2,3-butanediol fermentation. The model is verified with data from anaerobic and microaerobic continuous culture. On the basis of this model the difference in biomass production and

An-Ping Zeng; Wolf-Dieter Deckwer

1991-01-01

49

Enhanced hydrogen production in altered mixed acid fermentation of glucose by Enterobacter aerogenes  

Microsoft Academic Search

Hydrogen (H2) production by mutants of Enterobacter aerogenes HU-101, a strain isolated and characterized in our laboratory, was found to be enhanced compared with that of HU-101 due to blockage of production of other metabolites. The mutants were isolated by the allyl alcohol (AA) and\\/or proton suicide method. Among the AA resistant mutants isolated after NTG treatment of E. aerogenes

Mahyudin Abdul Rachman; Yoshinori Furutani; Yutaka Nakashimada; Toshihide Kakizono; Naomichi Nishio

1997-01-01

50

Bioreactor for glycerol conversion into H 2 by bacterium Enterobacter aerogenes  

Microsoft Academic Search

Glycerol was used as a substrate for H2 production by bacterium Enterobacter aerogenes in the test tubes and bioreactor. A BioFlo\\/CelliGen 115 bioreactor (10 L working volume) was utilized to conduct the experiments for conversion of glycerol into H2 by E. aerogenes cells. The highest H2 production rate was observed under 2% glycerol in the culture medium. The glycerol uptake efficiency

Sergei A. Markov; Jared Averitt; Barbara Waldron

2011-01-01

51

DNA analysis of nosocomial infection by Enterobacter aerogenes in three cases of septicaemia in Japan  

Microsoft Academic Search

Ceftazidime-resistant Enterobacter aerogenes was isolated from blood cultures of three patients with fever. DNA analysis using pulsed-field gel electrophoresis and ribosomal RNA gene restriction digest pattern analysis revealed that the strains were clonally similar to each other with a 79.3–96.0% homology. The same strain of E. aerogenes was isolated from a three-way stopcock connected to the indwelling catheter in one

S. Goshi; I. Taneike; S. Nakagawa; S. Kojio; Y. Tamura; T. Ohara; K. Ozaki; H. Tsukada; Y. Aoki; H. Asakura; F. Gejyo; M. Itoh; T. Yamamoto

2002-01-01

52

Endocarditis caused by Lactococcus lactis subsp. lactis in a patient with atrial myxoma: a case report.  

PubMed

We report a case of subacute endocarditis in a 55-year-old patient affected by left atrial myxoma and with a severe mitral regurgitation. Lactococcus lactis subsp. lactis was isolated from blood cultures and infection was eliminated by treatment with amoxicillin-clavulanic acid. PMID:16757143

Zechini, Barbara; Cipriani, Paola; Papadopoulou, Styliani; Di Nucci, Giandomenico; Petrucca, Andrea; Teggi, Antonella

2006-11-01

53

Comparative Phenotypic and Molecular Genetic Profiling of Wild Lactococcus lactis subsp. lactis Strains of the L. lactis subsp. lactis and L. lactis subsp. cremoris Genotypes, Isolated from Starter-Free Cheeses Made of Raw Milk?  

PubMed Central

Twenty Lactococcus lactis strains with an L. lactis subsp. lactis phenotype isolated from five traditional cheeses made of raw milk with no added starters belonging to the L. lactis subsp. lactis and L. lactis subsp. cremoris genotypes (lactis and cremoris genotypes, respectively; 10 strains each) were subjected to a series of phenotypic and genetic typing methods, with the aims of determining their phylogenetic relationships and suitability as starters. Pulsed-field gel electrophoresis (PFGE) analysis of intact genomes digested with SalI and SmaI proved that all strains were different except for three isolates of the cremoris genotype, which showed identical PFGE profiles. Multilocus sequence typing (MLST) analysis using internal sequences of seven loci (namely, atpA, rpoA, pheS, pepN, bcaT, pepX, and 16S rRNA gene) revealed considerable intergenotype nucleotide polymorphism, although deduced amino acid changes were scarce. Analysis of the MLST data for the present strains and others from other dairy and nondairy sources showed that all of them clustered into the cremoris or lactis genotype group, by using both independent and combined gene sequences. These two groups of strains also showed distinctive carbohydrate fermentation and enzyme activity profiles, with the strains in the cremoris group showing broader profiles. However, the profiles of resistance/susceptibility to 16 antibiotics were very similar, showing no atypical resistance, except for tetracycline resistance in three identical cremoris genotype isolates. The numbers and concentrations of volatile compounds produced in milk by the strains belonging to these two groups were clearly different, with the cremoris genotype strains producing higher concentrations of more branched-chain, derived compounds. Together, the present results support the idea that the lactis and cremoris genotypes of phenotypic Lactococcus lactis subsp. lactis actually represent true subspecies. Some strains of the two subspecies in this study appear to be good starter candidates.

Fernandez, Elena; Alegria, Angel; Delgado, Susana; Martin, M. Cruz; Mayo, Baltasar

2011-01-01

54

Insertion and amplification of foreign genes in the Lactococcus lactis subsp. lactis chromosome.  

PubMed Central

The plasmid pE194 is unable to replicate in Lactococcus lactis subsp. lactis (formerly Streptococcus lactis). When linked to resident bacteriophage sequences, pE194 was able to integrate into the L. lactis subsp. lactis chromosome either by Campbell-like recombination or by double crossing over with deletion. Integration occurred into the DNA of the prophage and prevented its multiplication. When a selective pressure was applied to an integrant in which pE194 was flanked by two direct repeats of prophage fragment, amplification of pE194 and the prophage fragment was observed. The pE194 copy number was assessed at six to nine, and amplification was stable upon growth under nonselective conditions. Images

Chopin, M C; Chopin, A; Rouault, A; Galleron, N

1989-01-01

55

Peritonitis due to Lactococcus lactis in a CAPD patient.  

PubMed

Lactococcus lactis is a gram-positive bacterium, commonly used in the dairy industry. Although Lactococcus lactis is known to be non-pathogenic for humans, it can cause infection in immunocompromised patients. We report a case of peritonitis due to L. lactis in a continuous ambulatory peritoneal dialysis patient, which is the second reported case in the literature. PMID:16857618

Guz, Galip; Colak, Bulent; Hizel, Kenan; Suyani, Elif; Sindel, Sukru

2006-01-01

56

Methionine-to-Cysteine Recycling in Klebsiella aerogenes  

PubMed Central

In the enteric bacteria Escherichia coli and Salmonella enterica, sulfate is reduced to sulfide and assimilated into the amino acid cysteine; in turn, cysteine provides the sulfur atom for other sulfur-bearing molecules in the cell, including methionine. These organisms cannot use methionine as a sole source of sulfur. Here we report that this constraint is not shared by many other enteric bacteria, which can use either cysteine or methionine as the sole source of sulfur. The enteric bacterium Klebsiella aerogenes appears to use at least two pathways to allow the reduced sulfur of methionine to be recycled into cysteine. In addition, the ability to recycle methionine on solid media, where cys mutants cannot use methionine as a sulfur source, appears to be different from that in liquid media, where they can. One pathway likely uses a cystathionine intermediate to convert homocysteine to cysteine and is induced under conditions of sulfur starvation, which is likely sensed by low levels of the sulfate reduction intermediate adenosine-5?-phosphosulfate. The CysB regulatory proteins appear to control activation of this pathway. A second pathway may use a methanesulfonate intermediate to convert methionine-derived methanethiol to sulfite. While the transsulfurylation pathway may be directed to recovery of methionine, the methanethiol pathway likely represents a general salvage mechanism for recovery of alkane sulfide and alkane sulfonates. Therefore, the relatively distinct biosyntheses of cysteine and methionine in E. coli and Salmonella appear to be more intertwined in Klebsiella.

Seiflein, Thomas A.; Lawrence, Jeffrey G.

2001-01-01

57

Extended-Spectrum ?-lactamase (ESBL) producing Enterobacter aerogenes phenotypically misidentified as Klebsiella pneumoniae or K. terrigena  

PubMed Central

Background Enterobacter aerogenes and Klebsiella pneumoniae are common isolates in clinical microbiology and important as producers of extended spectrum ?-lactamases (ESBL). The discrimination between both species, which is routinely based on biochemical characteristics, is generally accepted to be straightforward. Here we report that genotypically unrelated strains of E. aerogenes can be misidentified as K. pneumoniae by routine laboratories using standard biochemical identification and using identification automates. Results Ten clinical isolates, identified as K. pneumoniae or K. terrigena with the routinely used biochemical tests and with API-20E, were identified as E. aerogenes by tDNA-PCR – an identification that was confirmed by 16S rRNA gene sequencing for five of these isolates. Misidentification also occurred when using the automated identification systems Vitek 2 and Phoenix, and was due to delayed positivity for ornithine decarboxylase and motility. Subculture and prolonged incubation resulted in positive results for ornithine decarboxylase and for motility. It could be shown by RAPD-analysis that the E. aerogenes strains belonged to different genotypes. Conclusions Clinical E. aerogenes isolates can be easily misidentified as Klebsiella due to delayed positivity for ornithine decarboxylase and motility. The phenomenon may be widespread, since it was shown to occur among genotypically unrelated strains from different hospitals and different isolation dates. A useful clue for correct identification is the presence of an inducible ?-lactamase, which is highly unusual for K. pneumoniae. In several instances, the use of genotypic techniques like tDNA-PCR may circumvent problems of phenotypic identification.

Claeys, Geert; De Baere, Thierry; Wauters, Georges; Vandecandelaere, Patricia; Verschraegen, Gerda; Muylaert, An; Vaneechoutte, Mario

2004-01-01

58

The AcrAB-TolC Efflux Pump Contributes to Multidrug Resistance in the Nosocomial Pathogen Enterobacter aerogenes  

Microsoft Academic Search

For the last decade, Enterobacter aerogenes, a commensal gram-negative bacterium of human intestinal flora, has been rapidly emerging as an important nosocomial pathogen (14, 18). Of concern is the increasing frequency of E. aerogenes isolates that are resistant to antibiotics and antiseptics (3). Several types of systems have evolved in gram-negative bac- teria to pump deleterious molecules out of the

Elizabeth Pradel; Jean-Marie Pages

2002-01-01

59

Necrotising pneumonia caused by Lactococcus lactis cremoris.  

PubMed

Lactococcus lactis cremoris is a facultative anaerobic, gram-positive coccus whose natural host is bovine livestock. It may form part of the normal human bacterial flora found in the oropharynx, the gastrointestinal tract and the vagina. This bacterium is essential in the food industry, where it is used in milk fermentation to obtain cheese, yoghurt, etc. Exposure to unpasteurised dairy products has thus been recognised as a risk factor for infection by this organism. It is generally considered to be non-pathogenic, although it appears that pathogenicity may be emerging. We present an atypical case of necrotising pneumonia caused by L. lactis cremoris. PMID:23485391

Buchelli-Ramirez, H L; Alvarez-Alvarez, C; Rojo-Alba, S; García-Clemente, M; Cimadevilla-Suárez, R; Pando-Sandoval, A; Casan-Clará, P

2013-04-01

60

Cloning of a chromosomal fragment from Lactococcus lactis subsp. lactis partially complementing Escherichia coli recA functions.  

PubMed

A recA-like gene was isolated from a gene library of Lactococcus lactis subsp. lactis by intergeneric complementation of an E. coli recA mutant. A plasmid was obtained which fully complemented the RecA response to DNA damaging agents and UV inducibility of prophage, but not P1 plating efficiency in an E. coli recA mutant. The cloned DNA fragment also partially complemented the rec mutation in Lc. lactis MMS36. Hybridization studies showed that there was no detectable sequence homology between the recA gene of E. coli and Lc. lactis subsp. lactis chromosomal DNA. PMID:2150659

Novel, M; Huang, X F; Novel, G

1990-11-01

61

Is thermotolerance correlated to heat-shock protein synthesis in Lactococcus lactis subsp. lactis?  

PubMed

Exposure of Lactococcus lactis subsp. lactis cells to a heat shock at 40 degrees C for 30 min induces thermotolerance, the increased ability of bacterial cells to survive exposure to lethal temperature (52 degrees C for 25 min). This transient state of thermal resistance is accompanied, as in Escherichia coli, by the synthesis of a new set of specific proteins termed heat-shock proteins (Hsps). Pre-treatment of the bacterial cells by antibiotics (streptomycin, spiramycin, kanamycin and erythromycin) known to act on translation, induces the major Hsps synthesis but no thermal protection; conversely, puromycin and amino acid analogues treatments, known to produce abnormal and incomplete peptides, triggers the thermotolerance state without inducing significant Hsps synthesis. These results demonstrate that heat-shock response and induced thermotolerance are not tightly correlated phenomena in L. lactis subsp. lactis. PMID:1445769

Boutibonnes, P; Tranchard, C; Hartke, A; Thammavongs, B; Auffray, Y

1992-07-01

62

Anaerobic biotransformation of dinitrotoluene isomers by Lactococcus lactis subsp. lactis strain 27 isolated from earthworm intestine  

Microsoft Academic Search

Dinitrotoluenes are widely used as solvents and are intermediates in the synthesis of dyes, explosives, and pesticides. Environmental concerns regarding DNTs have increased due to their widespread use and their discharge into the environment. In this study, the anaerobic biodegradation of four dinitrotoluene isomers, 2,3-, 2,4-, 2,6- and 3,4-DNT, was investigated using Lactococcus lactis subsp. lactis strain 27, which was

Kwang-Hee Shin; Yoongho Lim; Joong-Hoon Ahn; Jinmo Khil; Chang-Joon Cha; Hor-Gil Hur

2005-01-01

63

Cloning and Characterization of a Novel tuf Promoter from Lactococcus lactis subsp. lactis IL1403  

Microsoft Academic Search

Genetic engineering of lactic acid bacteria (LAB) requires a reliable gene expression system. Especially, a stable promoter\\u000a is an important genetic element to induce gene expression in such a system. We report on a novel tuf promoter (Ptuf) of Lactococcus lactis subsp. lactis IL1403 that was screened and selected through analysis of previously published microarray data. Ptuf activity was examined

Eun Bae Kim; Da Chuan Piao; Jee Soo Son; Yun Jaie Choi

2009-01-01

64

Environmental stress responses in Lactococcus lactis  

Microsoft Academic Search

Bacteria can encounter a variety of physical conditions during their life. Bacterial cells are able to survive these (often adverse) conditions by the induction of specific or general protection mechanisms. The lactic acid bacterium Lactococcus lactis is widely used for the production of cheese. Before and during this process as well as in its natural habitats, it is subjected to

Jan Willem Sanders; Gerard Venema; Jan Kok

1999-01-01

65

The non-oxidative decarboxylation of p -hydroxybenzoic acid, gentisic acid, protocatechuic acid and gallic acid by Klebsiella aerogenes (Aerobacter aerogenes)  

Microsoft Academic Search

Klebsiella aerogenes adapted to a chemically-defined mineral salts medium with glucose orp-hydroxybenzoate as sole source of carbon and energy possessed constitutive decarboxylases for gentisate (2,5-dihydroxybenzoate), protocatechuate (3,4-dihydroxybenzoate) and gallate (3,4,5-trihydroxybenzoate) whose pH optima were respectively 5.9, 5.6 and 5.8. A decarboxylase for PHB was induced by PHB in both growing and resting cells; the induction was delayed or inhibited by

D. J. W. Grant; J. C. Patel

1969-01-01

66

Amphotericin B resistance and membrane fluidity in Kluyveromyces lactis strains.  

PubMed

The membrane fluidity of reduced-amphotericin B (AmB)-sensitivity Kluyveromyces lactis mutant strain is higher than that of the wild-type K. lactis strain. After culture of the K. lactis and K. lactis mutant cells in the presence of subinhibitory doses of AmB (10 and 125 mg/liter, respectively), the plasma membranes of both yeast strains also showed a higher fluidity than did those of control cells. High membrane fluidity was associated with changes in the structural properties of the membranes. Culture of the K. lactis and K. lactis mutant cells in the presence of AmB induced changes in membrane lipid contents. In particular, phospholipid contents were increased in both strains treated with AmB, compared with their corresponding counterparts. As a result, the sterol/phospholipid ratio decreased. The relative proportion of monounsaturated fatty acids also increased after AmB treatment. The saturated fatty acid/monounsaturated fatty acid ratio decreased in K. lactis and K. lactis mutant cells treated with AmB but also in K. lactis mutant control cells compared to that in the K. lactis wild strain. These changes in lipid composition explain the higher fluidity, which could represent a process of metabolic resistance of the yeasts to AmB. PMID:10858353

Younsi, M; Ramanandraibe, E; Bonaly, R; Donner, M; Coulon, J

2000-07-01

67

Porin alteration and active efflux: two in vivo drug resistance strategies used by Enterobacter aerogenes  

Microsoft Academic Search

Entembacter aemgenes is among the five most frequently isolated nosocomial pathogens in France, and this bacterium also shows increasing multidrug resistance. In this study, various E. aerogenes strains isolated from hospital units were characterized for their outer-membrane proteins, antibiotic susceptibilities (inhibition diameters and MICs) and resistance mechanisms associated with modification of envelope permeability (porin alteration and active efflux). Diminished outer-membrane

Monique Mallea; Jacqueline Chevalier; Charleric Bornet; Annie Eyraud; Anne Davin-Regli; Claude Bollet; Jean-Marie Pages

1998-01-01

68

An adaptive response of Enterobacter aerogenes to imipenem: regulation of porin balance in clinical isolates.  

PubMed

Imipenem (IPM) is a carbapenem antibiotic frequently used in severe hospital infections. Several reports have mentioned the emergence of resistant isolates exhibiting membrane modifications. A study was conducted between September 2005 and August 2007 to survey infections due to Enterobacter aerogenes in patients hospitalised in a French university hospital. Resistant E. aerogenes clinical isolates obtained from patients treated with IPM and collected during the 3 months following initiation of treatment were phenotypically and molecularly characterised for ?-lactamases, efflux pumps activity and outer membrane proteins. Among the 339 patients infected with E. aerogenes during the study period, 41 isolates (12.1%) were resistant to extended-spectrum cephalosporins and 17 patients (5.0%) were treated with IPM. The isolates from these 17 patients presented TEM-24 and basal efflux expression. Following IPM treatment, an IPM-intermediate-susceptible (IPM-I) isolate emerged in 11 patients and an IPM-resistant (IPM-R) isolate in 6 patients. A change in the porin balance (Omp35/Omp36) was observed in IPM-I isolates exhibiting ertapenem resistance. Finally, a porin deficiency (Omp35 and Omp36 absence) was detected in IPM-R isolates associated with efflux pump expression. This study indicates that the alteration in porin expression, including the shift of porin expression and lack of porins, contribute to the E. aerogenes adaptive response to IPM treatment. PMID:23280442

Lavigne, Jean-Philippe; Sotto, Albert; Nicolas-Chanoine, Marie-Hélène; Bouziges, Nicole; Pagès, Jean-Marie; Davin-Regli, Anne

2013-02-01

69

Repeated cadmium biosorption by regenerated Enterobacter aerogenes biofilm attached to activated carbon  

Microsoft Academic Search

Summary The bacteriumEnterobacter aerogenes has been used to develop a biofilm over activated carbon for biosorption from various strength cadmium solutions (25–500ppm). High bacterial resistance to metal poisoning allowed biofilm regeneration to raise the net loading of cadmium over the carbon by repeated biosorption runs.

J. A. Scott; A. M. Karanjkar

1992-01-01

70

Hydrogen production of Enterobacter aerogenes altered by extracellular and intracellular redox states  

Microsoft Academic Search

Enterobacter aerogenes HU-101, tested for its hydrogen production in batch cultures on various substrates, produced the highest amount of hydrogen when the substrate was glycerol. The yield of hydrogen is a function of the degree to which the substrates are reduced. To examine the effect of intracellular redox state on hydrogen yield, glucose-limiting chemostat cultures were carried out at various

Y. Nakashimada; M. A. Rachman; T. Kakizono; N. Nishio

2002-01-01

71

Hydrogen production by immobilized cells of aciduric Enterobacter aerogenes strain HO39  

Microsoft Academic Search

Cell immobilization of Enterobacter aerogenes strain HO-39 in agar gel or on porous glass beads was effective for hydrogen production in batch cultures of cells immobilized by the entrapment and adsorption methods. Stirring of the culture was indispensable for effective hydrogen production using cells immobilized in agar gel. However, relatively good hydrogen-production performance was obtained with cells immobilized on porous

Haruhiko Yokoi; Tadafumi Tokushige; Jun Hirose; Sachio Hayashi; Yoshiyuki Takasaki

1997-01-01

72

In Vivo Modification of Porin Activity Conferring Antibiotic Resistance to Enterobacter aerogenes  

Microsoft Academic Search

Cephalosporins are widely used in chemotherapy of bacterial infections and resistance mechanisms seriously impair their antibacterial activity. Several resistant strains of Enterobacter aerogenes, a frequently isolated nosocomial pathogen, were analyzed. One isolate exhibited a strong modification of the porin antigenic pattern, especially with an immunological probe directed against an epitope located inside the pore lumen. A strong decrease of cefepime

Jacqueline Chevalier; Jean-Marie Pagès; Monique Malléa

1999-01-01

73

Optimization of key process variables for enhanced hydrogen production by Enterobacter aerogenes using statistical methods  

Microsoft Academic Search

The individual and mutual effects of glucose concentration, temperature and pH on the hydrogen production by Enterobacter aerogenes were investigated in a batch system. A Box–Behnken design and response surface methodology (RSM) were employed to determine the optimum condition for enhanced hydrogen production. The hydrogen production rate was investigated by simultaneously changing the three independent variables, which all had significant

Ji Hye Jo; Dae Sung Lee; Donghee Park; Woo-Seok Choe; Jong Moon Park

2008-01-01

74

Differentiation of Escherichia coil and Aerobacter aerogenes by Gas Liquid Chromatography  

Microsoft Academic Search

Six isolates of Aerobacter aerogenes; one Pseudomonas aergenoidcs ; five Escherichia coli; one Escherichia freundii; and one Escherichia intermedia were obtained from different sources and classified according to Bergey's 5(anual. Cultures of each were prepared in heat- and vacuum-treated milk and incubated 30 hr at 35 C. An attempt was made to differentiate these species by gas chromatography (GLC) of

R. E. BAWDON; R. BASSETTE

75

Complete genome sequence of Bifidobacterium animalis subsp. lactis BLC1.  

PubMed

Bifidobacterium animalis subsp. lactis BLC1 is a probiotic bacterium that is widely exploited by food industries as the active ingredient of various functional foods. Here we report the complete genome sequence of B. animalis subsp. lactis BLC1, which is expected to provide insights into the biology of this health-promoting microorganism and improve our understanding of its phylogenetic relatedness with other members of the B. animalis subsp. lactis taxon. PMID:22038957

Bottacini, Francesca; Dal Bello, Fabio; Turroni, Francesca; Milani, Christian; Duranti, Sabrina; Foroni, Elena; Viappiani, Alice; Strati, Francesco; Mora, Diego; van Sinderen, Douwe; Ventura, Marco

2011-11-01

76

Complete Genome Sequence of Bifidobacterium animalis subsp. lactis BLC1  

PubMed Central

Bifidobacterium animalis subsp. lactis BLC1 is a probiotic bacterium that is widely exploited by food industries as the active ingredient of various functional foods. Here we report the complete genome sequence of B. animalis subsp. lactis BLC1, which is expected to provide insights into the biology of this health-promoting microorganism and improve our understanding of its phylogenetic relatedness with other members of the B. animalis subsp. lactis taxon.

Bottacini, Francesca; Dal Bello, Fabio; Turroni, Francesca; Milani, Christian; Duranti, Sabrina; Foroni, Elena; Viappiani, Alice; Strati, Francesco; Mora, Diego; van Sinderen, Douwe; Ventura, Marco

2011-01-01

77

Antimicrobial potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 against selected bacteria.  

PubMed

Immobilization of living cells of lactic acid bacteria could be an alternative or complementary method of immobilizing organic acids and bacteriocins and inhibit undesirable bacteria in foods. This study evaluated the inhibition potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 on selected bacteria by a modified method of the agar spot test. L. lactis was immobilized in calcium alginate (1 to 2%)-whey protein concentrate (0 and 1%) beads. The antimicrobial potential of immobilized L. lactis was evaluated in microbiological media against pathogenic bacteria (Escherichia coli, Salmonella, and Staphylococcus aureus) or Pseudomonas putida, a natural meat contaminant, and against seven gram-positive bacteria used as indicator strains. Results obtained in this study indicated that immobilized L. lactis inhibited the growth of S. aureus, Enterococcus faecalis, Enterococcus faecium, Lactobacillus curvatus, Lactobacillus sakei, Kocuria varians, and Pediococcus acidilactici. Only 4 h of incubation at 35 degrees C resulted in a clear inhibition zone around the beads that increased with time. With the addition of 10 mM of a chelating agent (EDTA) to the media, results showed growth inhibition of E. coli; however, P. putida and Salmonella Typhi were unaffected by this treatment. These results indicate that immobilized lactic acid bacteria strains can be successfully used to produce nisin and inhibit bacterial growth in semisolid synthetic media. PMID:15222547

Millette, M; Smoragiewicz, W; Lacroix, M

2004-06-01

78

Brain abscess caused by Lactococcus lactis cremoris in a child.  

PubMed

Lactococcus lactis cremoris infections are very rare in humans. It is recognized as a commensal organism of mucocutaneous surfaces of cattle, and is occasionally isolated from human mucocutaneous surfaces. We report a brain abscess caused by L. lactis cremoris in an immunocompetent child. A 19-month-old female patient was admitted with fever and vomiting. Brain computed tomography (CT) revealed brain abscess. L. lactis cremoris was isolated from culture of the abscess material. The patient was treated with pus drainage from brain abscess and antibiotics including vancomycin and meropenem. The patient recovered completely. To our knowledge, this is the first report of a L. lactis cremoris infection in children. PMID:21953033

Topçu, Yasemin; Ak?nc?, Gülçin; Bayram, Erhan; H?z, Semra; Türkmen, Mehmet

2011-12-01

79

Galactose and lactose transport in Kluyveromyces lactis.  

PubMed

Transport of lactose into Kluyveromyces lactis was accomplished by a highly specific system inducible by lactose and galactose. The biosynthesis of the transport enzyme was strongly repressed by glucose. For non-induced cells, lactose penetrated by passive transport, like galactose in any type of cells. The lactose transport showed aK (m) 1.2 -4 mm, was temperature-dependent (76 kJ/mol) and was blocked by metabolic inhibitors. PMID:18425681

Boze, H; Moulin, G; Galzy, P

1987-01-01

80

Anaerobic biotransformation of dinitrotoluene isomers by Lactococcus lactis subsp. lactis strain 27 isolated from earthworm intestine.  

PubMed

Dinitrotoluenes are widely used as solvents and are intermediates in the synthesis of dyes, explosives, and pesticides. Environmental concerns regarding DNTs have increased due to their widespread use and their discharge into the environment. In this study, the anaerobic biodegradation of four dinitrotoluene isomers, 2,3-, 2,4-, 2,6- and 3,4-DNT, was investigated using Lactococcus lactis subsp. lactis strain 27, which was isolated from the intestines of earthworms. Liquid chromatography/mass spectrometry and NMR spectroscopy showed that L. lactis strain 27 non-specifically reduced the nitro groups on the tested dinitrotoluenes to their corresponding aminonitrotoluenes. L. lactis strain 27, however, did not reduce either sequentially or simultaneously two nitro groups of the dinitrotoluenes, resulting in the formation of the corresponding diaminotoluenes. In vitro formation of dinitroazoxytoluenes suggested the presence of oxygen-sensitive hydroxylaminonitrotoluenes. L. lactis strain 27 was capable of reducing 2,4-, 2,6-, 2,3-, and 3,4-dinitrotoluenes up to 173.6, 66.6, 287.1, and 355 microM, respectively in 12 h incubation. A relatively rapid reduction was observed in the case of the 2,3-, and 3,4-dinitrotoluenes, which have vicinal nitro groups on their arene structure. Non-specific anaerobic reduction of dinitrotoluenes by the intestinal bacterium L. lactis strain 27 differentiated the extent of reduction of DNTs according to the substitutional position of the nitro groups and produced in vitro more toxic dinitroazoxytoluenes, suggesting that anaerobic biotransformation of dinitrotoluenes could increase environmental risk. PMID:16157167

Shin, Kwang-Hee; Lim, Yoongho; Ahn, Joong-Hoon; Khil, Jinmo; Cha, Chang-Joon; Hur, Hor-Gil

2005-09-01

81

Branched-chain amino acid biosynthesis genes in Lactococcus lactis subsp. lactis.  

PubMed Central

The genes for biosynthesis of the branched-chain amino acids leucine, isoleucine, and valine in Lactococcus lactis subsp. lactis NCDO2118 were characterized by cloning, complementation in Escherichia coli and Bacillus subtilis, and nucleotide sequence analysis. Nine structural genes are clustered on a 12-kb DNA fragment in the order leuABCD ilvDBNCA. Upstream of these genes, the nucleotide sequence suggests the existence of regulation by transcriptional attenuation. Between the leuD and ilvD genes is an unexpected gene, encoding a protein which belongs to the ATP-binding cassette protein superfamily.

Godon, J J; Chopin, M C; Ehrlich, S D

1992-01-01

82

Production of adenine arabinoside by gel-entrapped cells of Enterobacter aerogenes in water-organic cosolvent system  

Microsoft Academic Search

Gel-entrapped whole cells of Enterobacter aerogenes, which has a transglycosylation activity, were used to produce adenine arabinoside from uracil arabinoside and adenine, in an appropriate water-organic cosolvent system. Cells of E. aerogenes entrapped with a hydrophilic photo-crosslinkable resin prepolymer, ENT-4000, or a urethane prepolymer, PU-6, had a high and stable transglycosylation activity. To improve the poor solubility in water of

Kenzo Yokozekil; Shigeru Yamanaka; Takashi Utagawa; Koichi Takinami; Yoshio Hirose; Atsuo Tanaka; Kenji Sonomoto; Saburo Fukui

1982-01-01

83

Transfer of Plasmids between Bacillus subtilis and Streptococcus lactis  

PubMed Central

The shuttle plasmid pGK12, as well as several Staphylococcus aureus plasmids, was introduced into Streptococcus lactis by intergeneric protoplast fusion with Bacillus subtilis. The S. aureus plasmids were stably inherited in S. lactis, and so they may possibly be used as cloning vectors in lactic streptococci.

Baigori, Mario; Sesma, Fernando; de Ruiz Holgado, Aida P.; de Mendoza, Diego

1988-01-01

84

Engineered Enterobacter aerogenes for efficient utilization of sugarcane molasses in 2,3-butanediol production.  

PubMed

Sugarcane molasses is considered to be a good carbon source for biorefinery due to its high sugar content and low price. Sucrose occupies more than half of the sugar in the molasses. Enterobacter aerogenes is a good host strain for 2,3-butanediol production, but its utilization of sucrose is not very efficient. To improve sucrose utilization in E. aerogenes, a sucrose regulator (ScrR) was disrupted from the genomic DNA. The deletion mutation increased the sucrose consumption rate significantly when sucrose or sugarcane molasses was used as a carbon source. The 2,3-butanediol production from sugarcane molasses by the mutant was enhanced by 60% in batch fermentation compared to that by the wild type strain. In fed-batch fermentation, 98.69 g/L of 2,3-butanediol production was achieved at 36 h. PMID:23644066

Jung, Moo-Young; Park, Bu-Soo; Lee, Jinwon; Oh, Min-Kyu

2013-07-01

85

A novel bioflocculant produced by Enterobacter aerogenes and its use in defecating the trona suspension  

Microsoft Academic Search

In this paper, a bioflocculant-producing bacterium, named W-23, was isolated from soil and identified as Enterobacter aerogenes. The bioflocculant (named WF-1) produced by W-23 was an acidic polysaccharide composed mainly of uronic acid (13.2%), pyruvic acid (7.4%) and acetic acid (1.6%). The three components sugars of WF-1 were glucose, fructose and manose, and the molar ratio was 10.3:5.4:1 for glucose:fructose:manose.

Wen-Yu Lu; Tong Zhang; Dong-Yan Zhang; Cai-Hong Li; Jian-Ping Wen; Lian-Xiang Du

2005-01-01

86

Nucleotide Sequence of the Chromosomal ampC Gene of Enterobacter aerogenes  

Microsoft Academic Search

The AmpC b-lactamase gene and a small portion of the regulatory ampR sequence of Enterobacter aerogenes 97B were cloned and sequenced. The b-lactamase had an isoelectric point of 8 and conferred cephalosporin and cephamycin resistance on the host. The sequence of the cloned gene is most closely related to those of the ampC genes of E. cloacae and C. freundii.

KAREN E. PRESTON; CHRISTOPHER C. A. RADOMSKI; RICHARD A. VENEZIA

2000-01-01

87

2,3Butanediol production by Enterobacter aerogenes in continuous culture: role of oxygen supply  

Microsoft Academic Search

The influence of oxygen on growth and production of 2,3-butanediol and acetoin by Enterobacter aerogenes was studied in continuous culture. At all dilution rates (D) studied cell mass increased steadily with increasing oxygen uptake rate (OUR), hence the micro-aerobic cultivation was energy-limited. The biomass yield on oxygen increased with D which suggests that cells need more energy for maintenance functions

An-Ping Zeng; Hanno Biebl; Wolf-Dieter Deckwer

1990-01-01

88

Production of l-asparaginase in Enterobacter aerogenes expressing Vitreoscilla hemoglobin for efficient oxygen uptake  

Microsoft Academic Search

This study is the first utilizing Vitreoscilla hemoglobin in a heterologous bacterium, Enterobacter aerogenes, to determine the effect of such a highly efficient oxygen-uptake system on the production of l-asparaginase, an enzyme that has attracted considerable attention due to its anti-tumor activity. Here, we show that the Vitreoscilla hemoglobin expressing strain has from 10-fold to more than two orders of

H. Geckil; S. Gencer

2004-01-01

89

Fluorescence monitoring during cultivation of Enterobacter aerogenes at different oxygen levels  

Microsoft Academic Search

On-line monitoring of NAD(P)H fluorescence and 2D fluorescence spectroscopy was performed with Enterobacter aerogenes, a bacterium sensitive to oxygen availability. The organism was grown in a reactor under low and high dissolved oxygen concentrations\\u000a and circulated through a bypass attached to the reactor. Under low dissolved oxygen concentration in the reactor, NAD(P)H\\u000a fluorescence in the reactor and the bypass showed

J. Mukherjee; C. Lindemann; T. Scheper

1999-01-01

90

H2 production from starch by a mixed culture of Clostridium butyricum and Enterobacter aerogenes  

Microsoft Academic Search

A mixed continuous culture of Clostridium butyricum and Enterobacter aerogenes removed O2 in a reactor and produced H2 from starch with yield of more than 2 mol H2\\/mol glucose without any reducing agents in the medium. Co-immobilized cells of the bacteria on porous glass beads evolved H2 from starch at 1.3 l\\/l.h, with H2 yield of 2.6 mol H2\\/ mol

Haruhiko Yokoi; Tadafumi Tokushige; Jun Hirose; Sachio Hayashi; Yoshiyuki Takasaki

1998-01-01

91

Enterobacter aerogenes OmpX, a cation-selective channel mar- and osmo-regulated  

Microsoft Academic Search

The ompX gene of Enterobacter aerogenes was cloned. Its overexpression induced a decrease in the major porin Omp36 production and consequently a ?-lactam resistance was noted. Purified outer membrane protein X (OmpX) was reconstituted into artificial membranes and formed ion channels with a conductance of 20 pS in 1 M NaCl and a cationic selectivity. Both MarA expression and high

Myrielle Dupont; Emmanuelle Dé; Renaud Chollet; Jacqueline Chevalier; Jean-Marie Pagès

2004-01-01

92

Biodegradation of 2-methylquinoline by Enterobacter aerogenes TJ-D isolated from activated sludge.  

PubMed

Bacterial strain Enterobacter aerogenes TJ-D capable of utilizing 2-methylquinoline as the sole carbon and energy source was isolated from acclimated activated sludge under denitrifying conditions. The ability to degrade 2-methylquinoline by E. aerogenes TJ-D was investigated under denitrifying conditions. Under optimal conditions of temperature (35 degrees C) and initial pH 7, 2-methylquinoline of 100 mg/L was degraded within 176 hr. The degradation of 2-methylquinoline by E. aerogenes TJ-D could be well described by the Haldane model (R2 > 0.91). During the degradation period of 2-methylquinoline (initial concentration 100 mg/L), nitrate was almost completely consumed (the removal efficiency was 98.5%), while nitrite remained at low concentration (< 0.62 mg/L) during the whole denitrification period. 1,2,3,4-Tetrahydro-2-methylquinoline, 4-ethyl-benzenamine, N-butyl-benzenamine, N-ethyl-benzenamine and 2,6-diethyl-benzenamine were metabolites produced during the degradation. The degradation pathway of 2-methylquinoline by E. aerogenes TJ-D was proposed. 2-Methylquinoline is initially hydroxylated at C-4 to form 2-methyl-4-hydroxy-quinoline, and then forms 2-methyl-4-quinolinol as a result of tautomerism. Hydrogenation of the heterocyclic ring at positions 2 and 3 produces 2,3-dihydro-2-methyl-4-quinolinol. The carbon-carbon bond at position 2 and 3 in the heterocyclic ring may cleave and form 2-ethyl-N-ethyl-benzenamine. Tautomerism may result in the formation of 2,6-diethyl-benzenamine and N-butyl-benzenamine. 4-Ethyl-benzenamine and N-ethyl-benzenamine were produced as a result of losing one ethyl group from the above molecules. PMID:24218841

Wang, Lin; Li, Yongmei; Duan, Jingyuan

2013-07-01

93

Studies on nutritional and oxygen requirements for production of L-asparaginase by Enterobacter aerogenes  

Microsoft Academic Search

The carbon and nitrogen sources most suitable for L-asparaginase production by Enterobacter aerogenes were selected and their concentrations optimized in shake-flask cultures. Sodium citrate (1.0%) and diammonium hydrogen phosphate\\u000a (0.16%) proved to be the best sources of carbon and nitrogen, respectively. Nitrogen catabolite repression of enzyme formation\\u000a was absent in this bacterium. Cultivation in a reactor showed that the dissolved

J. Mukherjee; S. Majumdar; T. Scheper

2000-01-01

94

Characteristics of hydrogen production by aciduric Enterobacter aerogenes strain HO39  

Microsoft Academic Search

An aciduric facultative anaerobe with a hydrogen-producing ability was isolated and identified as Enterobacter aerogenes strain HO-39. The bacterium was able to grow at acidic pH of 3.3 aerobically and at 4.0 anaerobically. Although the optimum pH for hydrogen production was 6.0 to 7.0, hydrogen could be produced at acidic pH of 4.0. The optimum temperature for hydrogen production and

Haruhiko Yokoi; Takanobu Ohkawara; Jun Hirose; Satio Hayashi; Yoshiyuki Takasaki

1995-01-01

95

Rapid detection of a gfp-marked Enterobacter aerogenes under anaerobic conditions by aerobic fluorescence recovery  

Microsoft Academic Search

A gfp- and kanamycin-resistance gene-containing plasmid pUCGK was successfully constructed and transformed into Enterobacter aerogenes to develop a rapid GFP-based method for quantifying the bacterial concentration under anaerobic conditions for production of biohydrogen. Since the use of GFP as a molecular reporter is restricted by its requirement for oxygen in the development of the fluorophore, fluorescence detection for the fluorescent

Chong Zhang; Xin-Hui Xing; Kai Lou

2005-01-01

96

Aerogenic vaccination with a Burkholderia mallei auxotroph protects against aerosol-initiated glanders in mice  

Microsoft Academic Search

Burkholderia mallei is an obligate mammalian pathogen that causes the zoonotic disease glanders. Two live attenuated B. mallei strains, a capsule mutant and a branched-chain amino acid auxotroph, were evaluated for use as vaccines against aerosol-initiated glanders in mice. Animals were aerogenically vaccinated and serum samples were obtained before aerosol challenge with a high-dose (>300 times the LD50) of B.

Ricky L. Ulrich; Kei Amemiya; David M. Waag; Chad J. Roy; David DeShazer

2005-01-01

97

Effect of the extremely low frequency magnetic field on nisin production by Lactococcus lactis subsp. lactis using cheese whey permeate  

Microsoft Academic Search

The effect of the extremely low frequency (ELF) magnetic field on nisin production by Lactococcus lactis subsp. lactis using cheese whey permeate was studied during batch fermentation. The cellular suspension from the fermentor was externally recycled through a stainless steel tube inserted between the magnetic bars. The exposure time, recycle velocity and intensity of the magnetic field varied in a

David Chacón Alvarez; Victor Haber Pérez; Oselys Rodríguez Justo; Ranulfo Monte Alegre

2006-01-01

98

Molecular Epidemiological Study of Nosocomial Enterobacter aerogenes Isolates in a Belgian Hospital  

PubMed Central

In 1995, the rate of isolation of Enterobacter aerogenes in the Saint-Pierre University Hospital in Brussels, Belgium, was higher than that in the preceding years. A total of 45 nosocomial E. aerogenes strains were collected from 33 patients of different units during that year, and they were isolated from 19 respiratory specimens, 13 pus specimens, 7 blood specimens, 4 urinary specimens, 1 catheter specimen, and 1 heparin vial. The strains were analyzed to determine their epidemiological relatedness and were characterized by their antibiotic resistance pattern determination, plasmid profiling, and genomic fingerprinting by macrorestriction analysis with pulsed-field gel electrophoresis (PFGE). The majority of the strains (82%) were multiply resistant to different commonly used antibiotics. Two major plasmid profiles were found: most strains (64%) harbored two plasmids of different sizes, whereas the others (20%) contained a single plasmid. PFGE with SpeI and/or XbaI restriction enzymes revealed that a single clone (80%) was responsible for causing infections or colonizations throughout the year, and this result was concordant with those obtained by plasmid profiling, with slight variations. By comparing the results of these three methods, PFGE and plasmid profiling were found to be the techniques best suited for investigating the epidemiological relatedness of E. aerogenes strains, and they are therefore proposed as useful tools for the investigation of nosocomial outbreaks caused by this organism.

Jalaluddin, Sheikh; Devaster, Jeanne-Marie; Scheen, Robert; Gerard, Michele; Butzler, Jean-Paul

1998-01-01

99

Inactivation of Enterobacter aerogenes in reconstituted skim milk by high- and low-frequency ultrasound.  

PubMed

The inactivation of Enterobacter aerogenes in skim milk using low-frequency (20kHz) and high-frequency (850kHz) ultrasonication was investigated. It was found that low-frequency acoustic cavitation resulted in lethal damage to E. aerogenes. The bacteria were more sensitive to ultrasound in water than in reconstituted skim milk having different protein concentrations. However, high-frequency ultrasound was not able to inactivate E. aerogenes in milk even when powers as high as 50W for 60min were used. This study also showed that high-frequency ultrasonication had no influence on the viscosity and particle size of skim milk, whereas low-frequency ultrasonication resulted in the decrease in viscosity and particle size of milk. The decrease in particle size is believed to be due to the breakup of the fat globules, and possibly to the cleavage of the ?-casein present at the surface of the casein micelles. Whey proteins were also found to be slightly affected by low-frequency ultrasound, with the amounts of ?-lactalbumin and ?-lactoglobulin slightly decreasing. PMID:24394387

Gao, Shengpu; Hemar, Yacine; Lewis, Gillian D; Ashokkumar, Muthupandian

2014-11-01

100

Occurrence of Efflux Mechanism and Cephalosporinase Variant in a Population of Enterobacter aerogenes and Klebsiella pneumoniae Isolates Producing Extended-Spectrum ?-Lactamases?  

PubMed Central

We investigated the occurrence of multidrug resistance in 44 Enterobacter aerogenes and Klebsiella pneumoniae clinical isolates. Efflux was involved in resistance in E. aerogenes isolates more frequently than in K. pneumoniae isolates (100 versus 38% of isolates) and was associated with the expression of phenylalanine arginine ?-naphthylamide-susceptible active efflux. AcrA-TolC overproduction in E. aerogenes isolates was noted. An analysis of four E. aerogenes isolates for which cefepime MICs were high revealed no modification in porin expression but a new specific mutation in the AmpC ?-lactamase.

Tran, Que-Tien; Dupont, Myrielle; Lavigne, Jean-Philippe; Chevalier, Jacqueline; Pages, Jean-Marie; Sotto, Albert; Davin-Regli, Anne

2009-01-01

101

RACT/BACT/LAER Clearinghouse Clean Air Technology Center annual report for 1999: A compilation of control technology determinations. Ninth supplement to 1990 edition  

SciTech Connect

The basic purposes of the RBLC are to: (1) provide state and local air pollution control agencies, industry, and the public with current information on case-by-case control technology determinations that are made nationwide, and (2) promote communication, cooperation, and sharing of control technology information among the permitting agencies. The information presented in this compilation was abstracted from preconstruction permits and submitted by the state and local air pollution control agencies and EPA regional offices. The Clearinghouse is intended as a reference for state and local agencies in making RACT/BACT/LAER decisions.

NONE

1999-06-01

102

RACT/BACT/LAER Clearinghouse [RBLC] Clean Air Technology Center: A compilation of control technology determinations. Seventh supplement to the 1990 edition; Final report  

SciTech Connect

The basic purposes of the RBLC are to: (1) provide state and local air pollution control agencies with current information on case-by-case control technology determinations that are made nationwide, and (2) promote communication, cooperation, and sharing of control technology information among the permitting agencies. The information presented in this compilation was abstracted from preconstruction permits and submitted by the state and local air pollution control agencies and EPA regional offices. The Clearinghouse is intended as a reference for state and local agencies in making decision on RACT/BACT/LAER [Reasonably Achievable Control Technology/Best Achievable Control Technology/Lowest Achievable Emission Rates].

Steigerwald, J.E.

1997-06-01

103

RACT/BACT/LAER Clearinghouse annual report for 1998: A compilation of control technology determinations. Eighth supplement to the 1990 edition  

SciTech Connect

The basic purposes of the RBLC are to: (1) provide state and local air pollution control agencies with current information on case-by-case control technology determinations that are made nationwide, and (2) promote communication, cooperation, and sharing of control technology information among the permitting agencies. The information presented in this compilation was abstracted from preconstruction permits and submitted by the state and local air pollution control agencies and EPA regional offices. The Clearinghouse is intended as a reference for state and local agencies in making RACT/BACT/LAER decisions.

NONE

1998-06-01

104

Physiological Role of ?-Phosphoglucomutase in Lactococcus lactis  

PubMed Central

A ?-phosphoglucomutase (?-PGM) mutant of Lactococcus lactis subsp. lactis ATCC 19435 was constructed using a minimal integration vector and double-crossover recombination. The mutant and the wild-type strain were grown under controlled conditions with different sugars to elucidate the role of ?-PGM in carbohydrate catabolism and anabolism. The mutation did not significantly affect growth, product formation, or cell composition when glucose or lactose was used as the carbon source. With maltose or trehalose as the carbon source the wild-type strain had a maximum specific growth rate of 0.5 h?1, while the deletion of ?-PGM resulted in a maximum specific growth rate of 0.05 h?1 on maltose and no growth at all on trehalose. Growth of the mutant strain on maltose resulted in smaller amounts of lactate but more formate, acetate, and ethanol, and approximately 1/10 of the maltose was found as ?-glucose 1-phosphate in the medium. Furthermore, the ?-PGM mutant cells grown on maltose were considerably larger and accumulated polysaccharides which consisted of ?-1,4-bound glucose units. When the cells were grown at a low dilution rate in a glucose and maltose mixture, the wild-type strain exhibited a higher carbohydrate content than when grown at higher growth rates, but still this content was lower than that in the ?-PGM mutant. In addition, significant differences in the initial metabolism of maltose and trehalose were found, and cell extracts did not digest free trehalose but only trehalose 6-phosphate, which yielded ?-glucose 1-phosphate and glucose 6-phosphate. This demonstrates the presence of a novel enzymatic pathway for trehalose different from that of maltose metabolism in L. lactis.

Levander, Fredrik; Andersson, Ulrika; Radstrom, Peter

2001-01-01

105

Acanthamoeba castellanii of the T4 genotype is a potential environmental host for Enterobacter aerogenes and Aeromonas hydrophila  

PubMed Central

Background Acanthamoeba can interact with a wide range of microorganisms such as viruses, algae, yeasts, protists and bacteria including Legionella pneumophila, Pseudomonas aeruginosa, Vibrio cholerae, Helicobacter pylori, Listeria monocytogenes, Mycobacterium spp., and Escherichia coli. In this capacity, Acanthamoeba has been suggested as a vector in the transmission of bacterial pathogens to the susceptible hosts. Methods Here, we used a keratitis isolate of A. castellanii of the T4 genotype and studied its interactions with two bacterial genera which have not been tested before, Enterobacter aerogenes, and Aeromonas hydrophila, as well as E. coli. Assays were performed to determine bacterial association with and invasion of A. castellanii. Additionally, bacterial survival intracellular of A. castellanii trophozoites as well as cysts was determined. Results All three bacterial isolates tested, associated, invaded, and survived inside A. castellanii trophozoites as well as A. castellanii cysts. However, E. aerogenes and E. coli exhibited significantly reduced association with and invasion of A. castellanii as compared with A. hydrophila (P?aerogenes (3.96?±?0.7 bacteria:amoeba ratio) and E. coli (5.85?±?1.1 bacteria:amoeba ratio). A. hydrophila, E. coli, and E. aerogenes remained viable during the encystment process and exhibited higher levels of recovery from mature cysts (14.13?±?0.89 A. hydrophila:amoeba ratio, 10.13?±?1.17 E. aerogenes:amoeba ratio, and 11.95?±?0.7 E. coli:amoeba ratio). Conclusions A. hydrophila and E. aerogenes also joined the ranks of other bacteria that could benefit from A. castellanii. Because cysts can be airborne, these findings suggest that Acanthamoeba is a potential vector in the transmission of A. hydrophila and E. aerogenes to susceptible hosts.

2013-01-01

106

Optimization of nisin production by Lactococcus lactis  

Microsoft Academic Search

The production of nisin by batch culture of Lactococcus lactis ATCC 11454 in MRS broth (pH 6.5), as treated in 30 assays, that were set up by a fractional factorial design of two levels\\u000a (2[4–1]), was improved. The minimum and maximum concentrations of sucrose (5.0–12.5 g\\/L), asparagine (7.5–75 g\\/L), potassium phosphate\\u000a (6.0–18.0 g\\/L), and Tween-80 (1.0–6.6 g\\/L) were added to

Thereza Christina Vessoni Penna; Dante Augusto Moraes

2002-01-01

107

Stimulation of respiratory immunity by oral administration of Lactococcus lactis.  

PubMed

This work demonstrates that non-recombinant Lactococcus lactis NZ, administered by the oral route at the proper dose, is able to improve resistance against pneumococcal infection. Lactococcus lactis NZ oral administration was able to improve pathogen lung clearance, increased survival of infected mice, and reduced lung injuries. This effect was related to an upregulation of the respiratory innate and specific immune responses. Administration of L. lactis NZ improved production of bronchoalveolar lavage (BAL) fluid TNF-alpha, enhanced recruitment of neutrophils into the alveolar spaces, and induced a higher activation of BAL phagocytes compared with the control group. Lactococcus lactis NZ administered orally stimulated the IgA cycle, increased IgA+ cells in intestine and bronchus, and improved production of BAL IL-4 and IL-10 during infection. Moreover, mice treated with L. lactis NZ showed higher levels of BAL anti-pneumococcal IgA and IgG. Taking into consideration that orally administered L. lactis NZ stimulates both the innate and the specific immune responses in the respiratory tract and that bacterial and viral antigens have been efficiently produced in this strain, L. lactis NZ is an excellent candidate for the development of an effective pneumococcal oral vaccine. PMID:18772925

Villena, Julio; Medina, Marcela; Vintiñi, Elisa; Alvarez, Susana

2008-08-01

108

Rewiring Lactococcus lactis for ethanol production.  

PubMed

Lactic acid bacteria (LAB) are known for their high tolerance toward organic acids and alcohols (R. S. Gold, M. M. Meagher, R. Hutkins, and T. Conway, J. Ind. Microbiol. 10:45-54, 1992) and could potentially serve as platform organisms for production of these compounds. In this study, we attempted to redirect the metabolism of LAB model organism Lactococcus lactis toward ethanol production. Codon-optimized Zymomonas mobilis pyruvate decarboxylase (PDC) was introduced and expressed from synthetic promoters in different strain backgrounds. In the wild-type L. lactis strain MG1363 growing on glucose, only small amounts of ethanol were obtained after introducing PDC, probably due to a low native alcohol dehydrogenase activity. When the same strains were grown on maltose, ethanol was the major product and lesser amounts of lactate, formate, and acetate were formed. Inactivating the lactate dehydrogenase genes ldhX, ldhB, and ldh and introducing codon-optimized Z. mobilis alcohol dehydrogenase (ADHB) in addition to PDC resulted in high-yield ethanol formation when strains were grown on glucose, with only minor amounts of by-products formed. Finally, a strain with ethanol as the sole observed fermentation product was obtained by further inactivating the phosphotransacetylase (PTA) and the native alcohol dehydrogenase (ADHE). PMID:23377945

Solem, Christian; Dehli, Tore; Jensen, Peter Ruhdal

2013-04-01

109

Cloning and DNA sequence analysis of an X-prolyl dipeptidyl aminopeptidase gene from Lactococcus lactis subsp. lactis NCDO 763.  

PubMed Central

Lactococcus lactis subsp. lactis NCDO 763 (also designated ML3) possesses an X-prolyl dipeptidyl aminopeptidase (X-PDAP; EC 3.4.14.5). X-PDAP mutants were selected by an enzymatic plate assay on the basis of their inability to hydrolyze an L-phenylalanyl-L-proline-beta-naphthylamide substrate. A DNA bank from L. lactis subsp. lactis NCDO 763 was constructed in one of these X-PDAP mutants, and one clone in which the original X-PDAP phenotype was restored was detected by the enzymatic plate assay. The X-PDAP gene, designated pepXP, was further subcloned and sequenced. It codes for a protein containing 763 residues. Comparison of the amino-terminal sequence of the X-PDAP enzyme with the amino acid sequence deduced from the pepXP gene indicated that the enzyme is not subjected to posttranslational modification or exported via processing of a signal peptide. The pepXP gene from L. lactis subsp. lactis NCDO 763 in more than 99% homologous to the pepXP gene from L. lactis subsp. cremoris P8-2-47 described elsewhere (B. Mayo, J. Kok, K. Venema, W. Bockelmann, M. Teuber, H. Reinke, and G. Venema, Appl. Environ. Microbiol. 57:38-44, 1991) and is also conserved in other lactococcal strains.

Nardi, M; Chopin, M C; Chopin, A; Cals, M M; Gripon, J C

1991-01-01

110

Antioxidant activity of phosphorylated exopolysaccharide produced by Lactococcus lactis subsp. lactis.  

PubMed

Exopolysaccharide (EPS) of Lactococcus lactis subsp. lactis was isolated and purified from MRS culture broth. Phosphorylated exopolysaccharide (P-EPS) was synthesized by using the purified EPS and sodium hexametaphosphate (SHMP). The in vitro and in vivo antioxidant activity of EPS and P-EPS was analyzed. Both EPS and P-EPS displayed superoxide anion (O(2-•)), hydroxyl radical (OH•) and DPPH scavenging activity. Catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity increased in serum and the livers of mice treated with EPS and P-EPS, while malondialdehyde (MDA) levels decreased. P-EPS was shown to prevent the progression of D-galactose-induced oxidative stress in hepatocytes in vivo. P-EPS showed stronger in vitro and in vivo antioxidant activity than EPS. PMID:23911523

Guo, Yuxing; Pan, Daodong; Sun, Yangying; Xin, Lingying; Li, Hua; Zeng, Xiaoqun

2013-09-12

111

Cloning of the citrate permease gene of Lactococcus lactis subsp. lactis biovar diacetylactis and expression in Escherichia coli.  

PubMed Central

The citrate plasmid (Cit+ plasmid) from Lactococcus lactis subsp. lactis biovar diacetylactis was cloned into the EcoRI site of plasmid pUC18. This recombinant plasmid enabled Escherichia coli K-12 to transport and utilize citrate as a source of energy, indicating expression of the citrate permease from L. lactis biovar diacetylactis. The citrate permease was under the control of the lac promoter of pUC18. Genetic expression of the Cit+ plasmid in maxicells revealed that the plasmid encoded two polypeptides of 47 and 32 kilodaltons, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Images

Sesma, F; Gardiol, D; de Ruiz Holgado, A P; de Mendoza, D

1990-01-01

112

DNA Macroarray Profiling of Lactococcus lactis subsp. lactis IL1403 Gene Expression during Environmental Stresses†  

PubMed Central

This report describes the use of an oligonucleotide macroarray to profile the expression of 375 genes in Lactococcus lactis subsp. lactis IL1403 during heat, acid, and osmotic stress. A set of known stress-associated genes in IL1403 was used as the internal control on the array. Every stress response was accurately detected using the macroarray, compared to data from previous reports. As a group, the expression patterns of the investigated metabolic genes were significantly altered by heat, acid, and osmotic stresses. Specifically, 13 to 18% of the investigated genes were differentially expressed in each of the environmental stress treatments. Interestingly, the methionine biosynthesis pathway genes (metA-metB1 and metB2-cysK) were induced during heat shock, but methionine utilization genes, such as metK, were induced during acid stress. These data provide a possible explanation for the differences between acid tolerance mechanisms of L. lactis strains IL1403 and MG1363 reported previously. Several groups of transcriptional responses were common among the stress treatments, such as repression of peptide transporter genes, including the opt operon (also known as dpp) and dtpT. Reduction of peptide transport due to environmental stress will have important implications in the cheese ripening process. Although stress responses in lactococci were extensively studied during the last decade, additional information about this bacterium was gained from the use of this metabolic array.

Xie, Yi; Chou, Lan-szu; Cutler, Adele; Weimer, Bart

2004-01-01

113

Genetic transformation of intact Lactococcus lactis subsp. lactis by high-voltage electroporation  

SciTech Connect

The objective of this study was to develop a system for electroporating intact cells of Lactococcus lactis subsp. lactis LM0230 (previously designated Streptococcus lactis LM0230) with a commercially available electroporation unit. Parameters which influenced the efficiency of transformation included growth phase and final concentration of cells, ionic strength of the suspending medium, concentration of plasmid DNA, and the amplitude and duration of the pulse. Washed suspensions of intact cells suspended in deionized distilled water were subjected to one high-voltage electric pulse varying in voltage (300 to 900 V corresponding to field strengths of 5 to 17 kV/cm) and duration (100 {mu}s to 1 s). Transformation efficiencies of 10{sup 3} transformants per {mu}g of DNA were obtained when dense suspensions (final concentration, 5 {times} 10{sup 10} CFU/ml) of stationary-phase cells were subjected to one pulse with a peak voltage of 900 V (field strength, 17 kV/cm) and a pulse duration of 5 ms in the presence of plasmid DNA. Dilution of porated cells in broth medium followed by an expression period of 2 h at 30{degree}C was beneficial in enhancing transformation efficiencies. Plasmids ranging in size from 9.8 to 30.0 kilobase pairs could be transformed by this procedure.

McIntyre, D.A.; Harlander, S.K. (Univ. of Minnesota, St. Paul (USA))

1989-03-01

114

Liver abscess and empyema due to Lactococcus lactis cremoris.  

PubMed

Lactococcus lactis cremoris infections are very rare in humans. We experienced liver abscess and empyema due to L. lactis cremoris in an immunocompetent adult. A 42-yr-old man was admitted with fever and abdominal pain. Abdominal computed tomography (CT) revealed a liver abscess and chest CT showed loculated pleural effusion consistent with empyema. L. lactis cremoris was isolated from culture of the abscess material and blood. The patient was treated with pus drainage from liver abscess, video-assisted thoracoscopic decortications for empyema, and antibiotics including cefotaxime and levofloxacin. The patient was completely recovered with the treatment. To our knowledge, this is the first report of a L. lactis cremoris infection in Korea. PMID:21060760

Kim, Hye Sook; Park, Dae Won; Youn, Young Kyoung; Jo, Yu Mi; Kim, Jeong Yeon; Song, Joon Young; Sohn, Jang-Wook; Cheong, Hee Jin; Kim, Woo Joo; Kim, Min Ja; Choi, Won Suk

2010-11-01

115

Liver abscess caused by Lactococcus lactis cremoris: a new pathogen.  

PubMed

We describe the first case reported in the literature of liver abscess due to Lactococcus lactis cremoris in an immunocompetent adult patient. The patient was treated with catheter drainage and antibiotics, which resulted in improvement and resolution. PMID:15307576

Antolín, J; Cigüenza, R; Salueña, I; Vázquez, E; Hernández, J; Espinós, D

2004-01-01

116

Selenomethionine incorporation in proteins expressed in Lactococcus lactis  

PubMed Central

Lactococcus lactis is a promising host for (membrane) protein overproduction. Here, we describe a protocol for incorporation of selenomethionine (SeMet) into proteins expressed in L. lactis. Incorporation efficiencies of SeMet in the membrane protein complex OpuA (an ABC transporter) and the soluble protein OppA, both from L. lactis, were monitored by mass spectrometry. Both proteins incorporated SeMet with high efficiencies (>90%), which greatly extends the usefulness of the expression host L. lactis for X-ray crystallography purposes. The crystal structure of ligand-free OppA was determined at 2.4 Å resolution by a semiautomatic approach using selenium single-wavelength anomalous diffraction phasing.

Berntsson, Ronnie P-A; Alia Oktaviani, Nur; Fusetti, Fabrizia; Thunnissen, Andy-Mark W H; Poolman, Bert; Slotboom, Dirk-Jan

2009-01-01

117

Plasmid-Mediated Resistance to Expanded-Spectrum Cephalosporins among Enterobacter aerogenes Strains  

PubMed Central

Resistance to expanded-spectrum cephalosporins commonly develops in Enterobacter aerogenes during therapy due to selection of mutants producing high levels of the chromosomal Bush group 1 ?-lactamase. Recently, resistant strains producing plasmid-mediated extended-spectrum ?-lactamases (ESBLs) have been isolated as well. A study was designed to investigate ESBL production among 31 clinical isolates of E. aerogenes from Richmond, Va., with decreased susceptibility to expanded-spectrum cephalosporins and a positive double-disk potentiation test. Antibiotic susceptibility was determined by standard disk diffusion and agar dilution procedures. ?-Lactamases were investigated by an isoelectric focusing overlay technique which simultaneously determined isoelectric points (pIs) and substrate or inhibitor profiles. Decreased susceptibility to cefotaxime, ceftazidime, and aztreonam (MIC range, 1 to 64 ?g/ml) was detected and associated with resistance to gentamicin and trimethoprim-sulfamethoxazole. All strains produced an inducible Bush group 1 ?-lactamase (pI 8.3). Twenty-nine of the 31 isolates also produced an enzyme similar to SHV-4 (pI 7.8), while 1 isolate each produced an enzyme similar to SHV-3 (pI 6.9) and to SHV-5 (pI 8.2). The three different SHV-derived ESBLs were transferred by transconjugation to Escherichia coli C600N and amplified by PCR. Plasmid profiles of the clinical isolates showed a variety of different large plasmids. Because of the linkage of resistance to aminoglycosides and trimethoprim-sulfamethoxazole with ESBL production, it is possible that the usage of these drugs was responsible for selecting plasmid-mediated resistance to extended-spectrum cephalosporins in E. aerogenes. Furthermore, it is important that strains such as these be recognized, because they can be responsible for institutional spread of resistance genes.

Pitout, Johann D. D.; Thomson, Kenneth S.; Hanson, Nancy D.; Ehrhardt, Anton F.; Coudron, Philip; Sanders, Christine C.

1998-01-01

118

Rapid fluorescence assessment of the viability of stressed Lactococcus lactis  

Microsoft Academic Search

The aim of this study was to establish the use of the fluorescent probes carboxyfluorescein (cF) and propidium iodide (PI) for rapid assessment of viability, using Lactococcus lactis subsp. lactis ML3 exposed to different stress treatments. The cF labeling indicated the reproductive capacity of mixtures of nontreated cells and cells killed at 70°C very well. However, after treatment up to

CHRISTINE J. BUNTHOF; SABINA VAN DEN BRAAK; PIETER BREEUWER; FRANK M. ROMBOUTS; TJAKKO ABEE

1999-01-01

119

Portal vein thrombosis and liver abscess due to Lactococcus lactis.  

PubMed

A 26-year-old man was admitted with fever and abdominal pain. Abdominal ultrasonography and Doppler ultrasound eventually revealed portal vein thrombosis and a pyogenic liver abscess (17x11x11 cm). Lactococcus lactis was isolated from a culture of the abscess material. This organism is not a common pathogen in humans. This is the first published description of portal vein thrombosis and pyogenic liver abscess due to L. lactis. PMID:16830302

Güz, Galip; Ye?in, Zeynep Arzu; Do?an, Ibrahim; Hizel, Kenan; Bali, Musa; Sindel, Sükrü

2006-06-01

120

Cold shock response in Lactococcus lactis ssp. diacetylactis  

Microsoft Academic Search

The acquired freeze-thaw tolerance was investigated forLactococcus lactis ssp.diacetylactis. Pretreatment of microorganisms at less severe temperatures to initiate cold tolerance gaveL. lactis ssp.diacetylactis improved cell viability after successive freezings and thawings. The ability of cells to survive freeze-thaw was dependent\\u000a on factors experienced prior to freezing. Factors affecting lactic acid bacteria survival during freeze-thaw cycles were found\\u000a to be different

Ki Beom Lee; Russell Cail; Seung-Hyeon Moon; Man Bock Gu

1999-01-01

121

Lepidic predominant adenocarcinoma with aerogenous spread of mucin in a young patient - A case report.  

PubMed

We present a unique case of a 26year-old female non-smoker who expired following treatment for presumed pneumonias. At autopsy, lepidic predominant adenocarcinoma with aerogenous spread of mucin without evidence of invasion, a rare diagnosis that previously would have fallen under the umbrella of "bronchioloalveolar carcinoma," was found. Histopathology showed mucin-secreting neoplastic cells lining the alveolar walls, as well as exfoliated and dense aggregates of mucinous debris filling the alveoli. The immediate cause of death was respiratory failure, most likely due to the significant amount of tumor-produced mucin that filled the alveolar spaces, which literally drowned the patient. PMID:24768586

Nguyen, Elise; Hakimi, Matthew; Chavoshan, Bahman; Stringer, William; French, Samuel W

2014-06-01

122

[Isolation and various properties of alpha-aminocaprolactam hydrolase from Klebsiella aerogenes].  

PubMed

L-alpha-aminocaprolactam hydrolase possessing the L lysine amidase activity was isolated from Klebsiella aerogenes and purified. The procedure of enzymes purification included cell destruction on USDN-I, fractionation by ammonium sulfate, gel chromatography on G-200. The preparation of the purified enzyme possessed specific activity of 50 mumol of lysin per 1 mg of protein per hour. Km was 2.6 mM in case of phosphate buffer (ph 7.2) for I-alpha-aminocaprolactam. Besides L-alpha-aminocaprolactam the enzyme hydrolyses lysine amide, leucine amide tryptophanamide. Magnesium ions are necessary for manifestation of catalytic activity of the enzyme. PMID:1519339

Kliment'eva, T A; Brel', A K

1992-01-01

123

Incidence of nisin Z production in Lactococcus lactis subsp. lactis TFF 221 isolated from Thai fermented foods.  

PubMed

Lactic acid bacteria isolated from various Thai fermented foods were screened for the presence of nisin gene by using PCR with primers specific to nisin A structural gene. Only one strain, Lactococcus lactis subsp. lactis TFF 221, isolated from kung jom, a traditional shrimp paste, was found to carry a nisin gene. The TFF 221 nisin had antimicrobial activity against not only closely related lactic acid bacteria but also some foodborne pathogens. It was heat stable and inactivated by alpha-chymotrypsin and proteinase K. Some characteristics of TFF 221 nisin were found to be very similar to those of nisin A produced by Lactococcus lactis subsp. lactis NCDO 2111. Both of them had the same antimicrobial spectrum and MICs against all indicator bacteria. However, when assayed with indicator organisms, in all cases the TFF 221 nisin produced larger zones of inhibition in agar diffusion assays than the nisin A did. Sequencing of the TFF 221 nisin gene showed that it was the natural nisin variant, nisin Z, as indicated by the substitution of asparagine residue instead of histidine at position 27. The nisin determinant in strain TFF 221 was found to be located on a conjugative transposon residing in the chromosome. The ability of the nisin produced by L. lactis subsp. lactis TFF 221 to inhibit a wide range of foodborne pathogens may be useful in improving the food safety of the fermented product, especially in the Thai environment, which suffers from perennial problems of poor food hygiene. PMID:18939747

Rattanachaikunsopon, Pongsak; Phumkhachorn, Parichat

2008-10-01

124

21 CFR 184.1388 - Lactase enzyme preparation from Kluyveromyces lactis.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Lactase enzyme preparation from Kluyveromyces lactis...Affirmed as GRAS § 184.1388 Lactase enzyme preparation from Kluyveromyces lactis. (a) This enzyme preparation is derived from the...

2013-04-01

125

Hospital clonal dissemination of Enterobacter aerogenes producing carbapenemase KPC-2 in a Chinese teaching hospital.  

PubMed

Carbapenems are first-line agents for the treatment of serious nosocomial infections caused by multidrug-resistant Enterobacteriaceae. However, resistance to carbapenems has increased dramatically among Enterobacteriaceae in our hospital. In this study, we report clonal dissemination caused by carbapenem-resistant Enterobacter aerogenes (CREA). In 2011, CREA was identified from 12 patients admitted to the neurosurgical ward. All 12 clinical isolates were non-susceptible to cefotaxime, ceftazidime, cefoxitin, ertapenem, imipenem or meropenem. All isolates carried the gene encoding Klebsiella pneumoniae carbapenemase-2 (KPC-2), except for the isolate E4. However, a remarkably lower expression level of the porin OmpF was detected in the non-KPC-2-producing isolate E4 on SDS-PAGE compared with the carbapenem-susceptible isolate. Epidemiological and molecular investigations showed that a single E. aerogenes strain (PFGE type A), including seven KPC-2-producing clinical isolates, was primarily responsible for the first isolation and subsequent dissemination. In a case-control study, we identified risk factors for infection/colonization with CREA. Mechanical ventilation, the changing of sickbeds and previous use of broad-spectrum antibiotics were identified as potential risk factors. Our findings suggest that further studies should focus on judicious use of available antibiotics, implementation of active antibiotic resistance surveillance and strict implementation of infection-control measures to avoid the rapid spread or clonal dissemination caused by carbapenem-resistant Enterobacteriaceae in healthcare facilities. PMID:24273320

Qin, Xiaohua; Yang, Yang; Hu, Fupin; Zhu, Demei

2014-02-01

126

Inhibition of the ?-lactamases of Escherichia coli and Klebsiella aerogenes by semi-synthetic penicillins  

PubMed Central

1. A new automated micro-iodometric method is described for screening compounds for inhibitory action against ?-lactamase enzymes. 2. Over 1000 semi-synthetic penicillins were tested for inhibitory activity against the ?-lactamase of Escherichia coli B11 and 18 showed a fractional inhibition similar to or higher than that of methicillin. 3. The best inhibitors were alkoxy- and halogen-substituted phenyl-, naphthyl- or quinolyl-penicillins. 2-Isopropoxy-1-naphthylpenicillin (BRL 1437) was clearly the best and had a Ki value about 1% of that of methicillin. 4. The inhibition of the ?-lactamase of E. coli B11 by BRL 1437 was shown to be reversible and competitive. The Ki was 0.004?m and Ki/Km with ampicillin and p-hydroxyampicillin (BRL 2333) was about 0.0001. The Km and Vmax. values were determined for the ?-lactamases of E. coli B11 and Klebsiella aerogenes A against a variety of penicillins. Cell-bound and solubilized enzymes gave similar Ki and Km values. 5. BRL 1437 was superior to cloxacillin and methicillin for inhibition of the ?-lactamase of live, fully grown cultures of several strains of E. coli and K. aerogenes. Of a group of inhibitors BRL 1437 was the most stable to the ?-lactamase of E. coli B11.

Cole, M.; Elson, S.; Fullbrook, P. D.

1972-01-01

127

Outbreak of TEM-24-producing Enterobacter aerogenes in a Spanish hospital.  

PubMed

Organisms encoding multidrug resistance genes are becoming increasingly prevalent. During a 2-month period (December, 2000, to January, 2001), 83 consecutive isolates of Enterobacter spp. were collected in our microbiology department. Antibiotic susceptibility was determined using the Vitek II automatic system. We selected strains with decreased susceptibility to extended-spectrum cephalosporins. The double-disk potentiation test was positive in 10 of these strains, indicating the presence of extended-spectrum beta-lactamases (ESBLs). Polymerase chain reaction (PCR), isoelectric focusing (IEF), and sequencing identified TEM 24 beta-lactamase in the 10 selected E. aerogenes. Random amplification of polymorphic DNA (RAPD-PCR) revealed the same clonal origin for all the strains tested and strongly suggest an outbreak of multidrug-resistant E. aerogenes. To follow up the trends in ESBLs-producing Enterobacter infections in the hospital over time, we repeated the study 1 year later (December, 2001, to February, 2002). Only three ESBLs-producing Enterobacter were found. All of them corresponded to the previously characterized clone. PMID:12959409

Salso, S; Culebras, E; Andrade, R; Picazo, J J

2003-01-01

128

[Isolation and identification of degradation bacteria Enterobacter aerogenes for pyrethriods pesticide residues and its degradation characteristics].  

PubMed

By incubation experiment, the bacterial strain labeled as M6R9 was isolated from the tame sludge in water course of Pesticide Factory of Hangzhou, and was identified as Enterobacter aerogenes, which had highly efficient degradation for Bifenthrin, Fenpropathrin and Cypermethrin. By investigating the physiological characteristics of the strain, the results show that the bacterium is a gram-negative aerobe bacilli, size is (0.8-1.9) microm x (0.5-1.0) microm, and is capable of utilizing Bifenthrin, Fenpropathrin and Cypermethrin as sole carbon source. Under the condition of ventilation, (25-30) degrees C, inoculated amount at D(415 nm) 0.2, pH 7.0, pesticide concentration 100 mg x L(-1) and vibrational speed 180 r x min(-1), the degradation efficiencies to Bifenthrin, Fenpropathrin and Cypermethrin are the highest by strain M6R9. Under such condition, in the mixture culture medium with 100 mg x L(-1) Bifenthrin, Fenpropathrin and Cypermethrin, the degradation ratios are 55.74%, 55.11% and 55.96% after culturing 3 d, respectively, the degradation processes are fitted for first-order kinetic equation and the half lives (t(1/2)) are 65.4,70.7 and 68.6 h respectively. The degradation ability of Enterobacter aerogenes M6R9 on Bifenthrin, Fenpropathrin and Cypermethrin is positively correlated to inoculated amount,vibrational speed and ventilation. PMID:19799315

Liao, Min; Zhang, Hai-jun; Xie, Xiao-mei

2009-08-15

129

Transcriptome Analysis Reveals Mechanisms by Which Lactococcus lactis Acquires Nisin Resistance  

Microsoft Academic Search

Nisin, a posttranslationally modified antimicrobial peptide produced by Lactococcus lactis, is widely used as a food preservative. Yet, the mechanisms leading to the development of nisin resistance in bacteria are poorly understood. We used whole-genome DNA microarrays of L. lactis IL1403 to identify the factors underlying acquired nisin resistance mechanisms. The transcriptomes of L. lactis IL1403 and L. lactis IL1403

Naomi E. Kramer; Jan Knol; Jan Kok; Oscar P. Kuipers

2006-01-01

130

Protein secretion in Lactococcus lactis : an efficient way to increase the overall heterologous protein production  

Microsoft Academic Search

Lactococcus lactis, the model lactic acid bacterium (LAB), is a food grade and well-characterized Gram positive bacterium. It is a good candidate for heterologous protein delivery in foodstuff or in the digestive tract. L. lactis can also be used as a protein producer in fermentor. Many heterologous proteins have already been produced in L. lactis but only few reports allow

Yves Le Loir; Vasco Azevedo; Sergio C Oliveira; Daniela A Freitas; Anderson Miyoshi; Luis G Bermúdez-Humarán; Sébastien Nouaille; Luciana A Ribeiro; Sophie Leclercq; Jane E Gabriel; Maricê N Oliveira; Cathy Charlier; Michel Gautier; Philippe Langella

2005-01-01

131

Modification of Outer Membrane Protein Profile and Evidence Suggesting an Active Drug Pump in Enterobacter aerogenes Clinical Strains  

Microsoft Academic Search

Two clinical strains of Enterobacter aerogenes that exhibited phenotypes of multiresistance to -lactam antibiotics, fluoroquinolones, chloramphenicol, tetracycline, and kanamycin were investigated. Both strains showed a porin pattern different from that of a susceptible strain, with a drastic reduction in the amount of the major porin but with an apparently conserved normal structure (size and immunogenicity), together with overproduction of two

Stephane Gayet; Renaud Chollet; Gerard Molle; Jean-Marie Pages

2003-01-01

132

Roles of Glutamate Synthase, gltBD, and gltF in Nitrogen Metabolism of Escherichia coli and Klebsiella aerogenes  

Microsoft Academic Search

Mutants of Escherichia coli and Klebsiella aerogenes that are deficient in glutamate synthase (glutamate- oxoglutarate amidotransferase (GOGAT)) activity have difficulty growing with nitrogen sources other than ammonia. Two models have been proposed to account for this inability to grow. One model postulated an imbalance between glutamine synthesis and glutamine degradation that led to a repression of the Ntr system and

THOMAS J. GOSS; ANA PEREZ-MATOS; ROBERT A. BENDER

2001-01-01

133

Identification and Evolution of Drug Efflux Pump in Clinical Enterobacter aerogenes Strains Isolated in 1995 and 2003  

PubMed Central

Background The high mortality impact of infectious diseases will increase due to accelerated evolution of antibiotic resistance in important human pathogens. Development of antibiotic resistance is a evolutionary process inducing the erosion of the effectiveness of our arsenal of antibiotics. Resistance is not necessarily limited to a single class of antibacterial agents but may affect many unrelated compounds; this is termed ‘multidrug resistance’ (MDR). The major mechanism of MDR is the active expulsion of drugs by bacterial pumps; the treatment of Gram negative bacterial infections is compromised due to resistance mechanisms including the expression of efflux pumps that actively expel various usual antibiotics (ß-lactams, quinolones, …). Methodology/Principal Findings Enterobacter aerogenes has emerged among Enterobacteriaceae associated hospital infections during the last twenty years due to its faculty of adaptation to antibiotic stresses. Clinical isolates of E. aerogenes belonging to two strain collections isolated in 1995 and 2003 respectively, were screened to assess the involvement of efflux pumps in antibiotic resistance. Drug susceptibility assays were performed on all bacterial isolates and an efflux pump inhibitor (PAßN) previously characterized allowed to decipher the role of efflux in the resistance. Accumulation of labelled chloramphenicol was monitored in the presence of an energy poison to determine the involvement of active efflux on the antibiotic intracellular concentrations. The presence of the PAßN-susceptible efflux system was also identified in resistant E. aerogenes strains. Conclusions/Significance For the first time a noticeable increase in clinical isolates containing an efflux mechanism susceptible to pump inhibitor is report within an 8 year period. After the emergence of extended spectrum ß-lactamases in E. aerogenes and the recent characterisation of porin mutations in clinical isolates, this study describing an increase in inhibitor-susceptible efflux throws light on a new step in the evolution of mechanism in E. aerogenes.

Garnotel, Eric; Nicolas, Pierre; Davin-Regli, Anne; Pages, Jean-Marie

2008-01-01

134

The Complete Genome Sequence of the Lactic Acid Bacterium Lactococcus lactis ssp. lactis IL1403  

PubMed Central

Lactococcus lactis is a nonpathogenic AT-rich gram-positive bacterium closely related to the genus Streptococcus and is the most commonly used cheese starter. It is also the best-characterized lactic acid bacterium. We sequenced the genome of the laboratory strain IL1403, using a novel two-step strategy that comprises diagnostic sequencing of the entire genome and a shotgun polishing step. The genome contains 2,365,589 base pairs and encodes 2310 proteins, including 293 protein-coding genes belonging to six prophages and 43 insertion sequence (IS) elements. Nonrandom distribution of IS elements indicates that the chromosome of the sequenced strain may be a product of recent recombination between two closely related genomes. A complete set of late competence genes is present, indicating the ability of L. lactis to undergo DNA transformation. Genomic sequence revealed new possibilities for fermentation pathways and for aerobic respiration. It also indicated a horizontal transfer of genetic information from Lactococcus to gram-negative enteric bacteria of Salmonella-Escherichia group. [The sequence data described in this paper has been submitted to the GenBank data library under accession no. AE005176.

Bolotin, Alexander; Wincker, Patrick; Mauger, Stephane; Jaillon, Olivier; Malarme, Karine; Weissenbach, Jean; Ehrlich, S. Dusko; Sorokin, Alexei

2001-01-01

135

Lactococcus lactis release from calcium alginate beads.  

PubMed

Cell release during milk fermentation by Lactococcus lactis immobilized in calcium alginate beads was examined. Numbers of free cells in the milk gradually increased from 1 x 10(6) to 3 x 10(7) CFU/ml upon successive reutilization of the beads. Rinsing the beads between fermentations did not influence the numbers of free cells in the milk. Cell release was not affected by initial cell density within the beads or by alginate concentration, although higher acidification rates were achieved with increased cell loading. Coating alginate beads with poly-L-lysine (PLL) did not significantly reduce the release of cells during five consecutive fermentations. A double coating of PLL and alginate reduced cell release by a factor of approximately 50. However, acidification of milk with beads having the PLL-alginate coating was slower than that with uncoated beads. Immersing the beads in ethanol to kill cells on the periphery reduced cell release, but acidification activity was maintained. Dipping the beads in aluminum nitrate or a hot CaCl2 solution was not as effective as dipping them in ethanol. Ethanol treatment or heating of the beads appears to be a promising method for maintaining acidification activity while minimizing viable cell release due to loosely entrapped cells near the surface of the alginate beads. PMID:1622208

Champagne, C P; Gaudy, C; Poncelet, D; Neufeld, R J

1992-05-01

136

Lactococcus lactis release from calcium alginate beads.  

PubMed Central

Cell release during milk fermentation by Lactococcus lactis immobilized in calcium alginate beads was examined. Numbers of free cells in the milk gradually increased from 1 x 10(6) to 3 x 10(7) CFU/ml upon successive reutilization of the beads. Rinsing the beads between fermentations did not influence the numbers of free cells in the milk. Cell release was not affected by initial cell density within the beads or by alginate concentration, although higher acidification rates were achieved with increased cell loading. Coating alginate beads with poly-L-lysine (PLL) did not significantly reduce the release of cells during five consecutive fermentations. A double coating of PLL and alginate reduced cell release by a factor of approximately 50. However, acidification of milk with beads having the PLL-alginate coating was slower than that with uncoated beads. Immersing the beads in ethanol to kill cells on the periphery reduced cell release, but acidification activity was maintained. Dipping the beads in aluminum nitrate or a hot CaCl2 solution was not as effective as dipping them in ethanol. Ethanol treatment or heating of the beads appears to be a promising method for maintaining acidification activity while minimizing viable cell release due to loosely entrapped cells near the surface of the alginate beads.

Champagne, C P; Gaudy, C; Poncelet, D; Neufeld, R J

1992-01-01

137

Genome-wide metabolic (re-) annotation of Kluyveromyces lactis  

PubMed Central

Background Even before having its genome sequence published in 2004, Kluyveromyces lactis had long been considered a model organism for studies in genetics and physiology. Research on Kluyveromyces lactis is quite advanced and this yeast species is one of the few with which it is possible to perform formal genetic analysis. Nevertheless, until now, no complete metabolic functional annotation has been performed to the proteins encoded in the Kluyveromyces lactis genome. Results In this work, a new metabolic genome-wide functional re-annotation of the proteins encoded in the Kluyveromyces lactis genome was performed, resulting in the annotation of 1759 genes with metabolic functions, and the development of a methodology supported by merlin (software developed in-house). The new annotation includes novelties, such as the assignment of transporter superfamily numbers to genes identified as transporter proteins. Thus, the genes annotated with metabolic functions could be exclusively enzymatic (1410 genes), transporter proteins encoding genes (301 genes) or have both metabolic activities (48 genes). The new annotation produced by this work largely surpassed the Kluyveromyces lactis currently available annotations. A comparison with KEGG’s annotation revealed a match with 844 (~90%) of the genes annotated by KEGG, while adding 850 new gene annotations. Moreover, there are 32 genes with annotations different from KEGG. Conclusions The methodology developed throughout this work can be used to re-annotate any yeast or, with a little tweak of the reference organism, the proteins encoded in any sequenced genome. The new annotation provided by this study offers basic knowledge which might be useful for the scientific community working on this model yeast, because new functions have been identified for the so-called metabolic genes. Furthermore, it served as the basis for the reconstruction of a compartmentalized, genome-scale metabolic model of Kluyveromyces lactis, which is currently being finished.

2012-01-01

138

Irreproducible and uninterpretable Polymyxin B MICs for Enterobacter cloacae and Enterobacter aerogenes.  

PubMed

Carbapenem-resistant Enterobacter species are emerging nosocomial pathogens. As with most multidrug-resistant Gram-negative pathogens, the polymyxins are often the only therapeutic option. In this study involving clinical isolates of E. cloacae and E. aerogenes, susceptibility testing methods with polymyxin B were analyzed. All isolates underwent testing by the broth microdilution (in duplicate) and agar dilution (in duplicate) methods, and select isolates were examined by the Etest method. Selected isolates were also examined for heteroresistance by population analysis profiling. Using a susceptibility breakpoint of ?2 ?g/ml, categorical agreement by all four dilution tests (two broth microdilution and two agar dilution) was achieved in only 76/114 (67%) of E. cloacae isolates (65 susceptible, 11 resistant). Thirty-eight (33%) had either conflicting or uninterpretable results (multiple skip wells, i.e., wells that exhibit no growth although growth does occur at higher concentrations). Of the 11 consistently resistant isolates, five had susceptible MICs as determined by Etest. Heteroresistant subpopulations were detected in eight of eight isolates tested, with greater percentages in isolates with uninterpretable MICs. For E. aerogenes, categorical agreement between the four dilution tests was obtained in 48/56 (86%), with conflicting and/or uninterpretable results in 8/56 (14%). For polymyxin susceptibility testing of Enterobacter species, close attention must be paid to the presence of multiple skip wells, leading to uninterpretable results. Susceptibility also should not be assumed based on the results of a single test. Until the clinical relevance of skip wells is defined, interpretation of polymyxin susceptibility tests for Enterobacter species should be undertaken with extreme caution. PMID:24088860

Landman, David; Salamera, Julius; Quale, John

2013-12-01

139

Irreproducible and Uninterpretable Polymyxin B MICs for Enterobacter cloacae and Enterobacter aerogenes  

PubMed Central

Carbapenem-resistant Enterobacter species are emerging nosocomial pathogens. As with most multidrug-resistant Gram-negative pathogens, the polymyxins are often the only therapeutic option. In this study involving clinical isolates of E. cloacae and E. aerogenes, susceptibility testing methods with polymyxin B were analyzed. All isolates underwent testing by the broth microdilution (in duplicate) and agar dilution (in duplicate) methods, and select isolates were examined by the Etest method. Selected isolates were also examined for heteroresistance by population analysis profiling. Using a susceptibility breakpoint of ?2 ?g/ml, categorical agreement by all four dilution tests (two broth microdilution and two agar dilution) was achieved in only 76/114 (67%) of E. cloacae isolates (65 susceptible, 11 resistant). Thirty-eight (33%) had either conflicting or uninterpretable results (multiple skip wells, i.e., wells that exhibit no growth although growth does occur at higher concentrations). Of the 11 consistently resistant isolates, five had susceptible MICs as determined by Etest. Heteroresistant subpopulations were detected in eight of eight isolates tested, with greater percentages in isolates with uninterpretable MICs. For E. aerogenes, categorical agreement between the four dilution tests was obtained in 48/56 (86%), with conflicting and/or uninterpretable results in 8/56 (14%). For polymyxin susceptibility testing of Enterobacter species, close attention must be paid to the presence of multiple skip wells, leading to uninterpretable results. Susceptibility also should not be assumed based on the results of a single test. Until the clinical relevance of skip wells is defined, interpretation of polymyxin susceptibility tests for Enterobacter species should be undertaken with extreme caution.

Landman, David; Salamera, Julius

2013-01-01

140

Fermented soymilk with a monoculture of Lactococcus lactis.  

PubMed

Lactococcus lactis strain (LL3) isolated from mothers' milk was used to produce fermented soymilk. The strain survived at levels of over 7 log cfu/ml for 3 weeks in the fermented soymilk. A consumer survey was carried out to compare the acceptability of the fermented product with a similar product made with L. lactis ATCC11545 originally isolated from cow's milk. Blind samples produced by fermentation with the two strains were rated equally attractive, whereas information on the origin of the strains significantly enhanced the pleasantness of the fermented soymilk. PMID:12457590

Beasley, S; Tuorila, H; Saris, P E J

2003-03-15

141

Chromosomal integration of plasmid DNA by homologous recombination in Enterococcus faecalis and Lactococcus lactis subsp. lactis hosts harboring Tn919.  

PubMed Central

Integration of pCI192, a pBR322-derived vector plasmid containing homology to the chromosomally located conjugative transposon Tn919 was observed in two strains that harbor Tn919, namely, Enterococcus faecalis GF590 and Lactococcus lactis subsp. lactis CH919. Hybridization analysis indicated that single-copy integration of the plasmid had occurred at low frequency. The Tn919::plasmid structure was conjugated from an E. faecalis donor to a L. lactis recipient, although at lower frequencies than was Tn919. Segregation of the tetracycline and chloramphenicol resistance markers during conjugation was observed. The integration strategy described allows for DNA manipulations to be performed in an easily manipulated model host strain with the subsequent transfer of integrated structures by conjugation to any strain capable of receiving Tn919. The results indicate that homologous recombination events may be used to introduce plasmid-encoded genes to the lactococcal chromosome. Images

Casey, J; Daly, C; Fitzgerald, G F

1991-01-01

142

The AcrAB-TolC Pump Is Involved in Macrolide Resistance but Not in Telithromycin Efflux in Enterobacter aerogenes and Escherichia coli  

Microsoft Academic Search

The role of the AcrAB-TolC pump in macrolide and ketolide susceptibility in Escherichia coli and Enterobacter aerogenes was studied. Efflux pump inhibitor restored erythromycin, clarithromycin, and telithromycin sus- ceptibilities to multidrug-resistant isolates. No modification of telithromycin accumulation was detected in E. aerogenes acrAB or tolC derivatives compared to that in the parental strain. Two independent efflux pumps, inhibited by phenylalanine

Renaud Chollet; Jacqueline Chevalier; A. Bryskier; J.-M. Pages

2004-01-01

143

Selection during Cefepime Treatment of a New Cephalosporinase Variant with Extended-Spectrum Resistance to Cefepime in an Enterobacter aerogenes Clinical Isolate  

Microsoft Academic Search

Enterobacter aerogenes resistant to cefepime (MIC, 32 g\\/ml) was isolated from a patient treated with cefepime for an infection caused by a strain of E. aerogenes overproducing its AmpC -lactamase (MIC of cefepime, 0.5 g\\/ml). The AmpC -lactamase of the resistant strain had an L-293-P amino acid substitution and a high kcat\\/Km ratio for cefepime. Both of these modifications were

G. Barnaud; Y. Benzerara; J. Gravisse; L. Raskine; M. J. Sanson-Le Pors; R. Labia; G. Arlet

2004-01-01

144

Vitreoscilla hemoglobin expressing Enterobacter aerogenes and Pseudomonas aeruginosa respond differently to carbon catabolite and oxygen repression for production of l-asparaginase, an enzyme used in cancer therapy  

Microsoft Academic Search

The production of antileukemic enzyme l-asparaginase in two distinctly related bacteria, Enterobacter aerogenes, Pseudomonas aeruginosa, and in their recombinants expressing the Vitresocilla hemoglobin (VHb) has been studied. Both bacteria showed a substantially different degree of carbon catabolite repression of the enzyme production. E. aerogenes grown under catabolite repression had more than 20-fold lower l-asparaginase activity than the controls. This figure

Hikmet Geckil; Salih Gencer; Mirac Uckun

2004-01-01

145

Insensitivity of 5-enolpyruvylshikimic acid-3-phosphate synthase to glyphosate confers resistance to this herbicide in a strain of Aerobacter aerogenes  

Microsoft Academic Search

The broadspectrum herbicide glyphosate (N-[phosphonomethyl]glycine), an inhibitor of the shikimate pathway enzyme 5-enolpyruvyl-shikimic acid-3-phosphate (EPSP)-synthase, inhibits the growth of Aerobacter aerogenes and causes the excretion of shikimic acid-3-phosphate. A strain of A. aerogenes, resistant to inhibition of growth by glyphosate, was isolated and found to have a glyphosate-insensitive EPSP-synthase and to no longer excrete shikimic acid-3-phosphate in the presence of

A. Schulz; D. Sost; N. Amrhein

1984-01-01

146

Gene inactivation in Lactococcus lactis: histidine biosynthesis.  

PubMed Central

Lactococcus lactis strains from dairy and nondairy sources were tested for the ability to grow in the absence of histidine. Among 60 dairy strains tested, 56 required histidine, whereas only 1 of 11 nondairy strains had this requirement. Moreover, 10 of the 56 auxotrophic strains were able to grow in the presence of histidinol (Hol+), the immediate histidine precursor. This indicates that adaptation to milk often results in histidine auxotrophy. The histidine operon was detected by Southern hybridization in eight dairy auxotrophic strains tested. A large part of the histidine operon (8 kb, containing seven histidine biosynthetic genes and three unrelated open reading frames [ORFs]) was cloned from an auxotroph, which had an inactive hisD gene, as judged by its inability to grow on histidinol. Complementation analysis of three genes, hisA, hisB, and hisG, in Escherichia coli showed that they also were inactive. Sequence analysis of the cloned histidine region, which revealed 98.6% overall homology with that of the previously analyzed prototrophic strain, showed the presence of frameshift mutations in three his genes, hisC, hisG, and hisH, and two genes unrelated to histidine biosynthesis, ORF3 and ORF6. In addition, several mutations were detected in the promoter region of the operon. Northern (RNA) hybridization analysis showed a much lower amount of the his transcript in the auxotrophic strain than in the prototrophic strain. The mutations detected account for the histidine auxotrophy of the analyzed strain. Certain other dairy auxotrophic strains carry a lower number of mutations, since they were able to revert either to a Hol+ phenotype or to histidine prototrophy. Images

Delorme, C; Godon, J J; Ehrlich, S D; Renault, P

1993-01-01

147

Towards enhanced galactose utilization by Lactococcus lactis.  

PubMed

Accumulation of galactose in dairy products due to partial lactose fermentation by lactic acid bacteria yields poor-quality products and precludes their consumption by individuals suffering from galactosemia. This study aimed at extending our knowledge of galactose metabolism in Lactococcus lactis, with the final goal of tailoring strains for enhanced galactose consumption. We used directed genetically engineered strains to examine galactose utilization in strain NZ9000 via the chromosomal Leloir pathway (gal genes) or the plasmid-encoded tagatose 6-phosphate (Tag6P) pathway (lac genes). Galactokinase (GalK), but not galactose permease (GalP), is essential for growth on galactose. This finding led to the discovery of an alternative route, comprising a galactose phosphotransferase system (PTS) and a phosphatase, for galactose dissimilation in NZ9000. Introduction of the Tag6P pathway in a galPMK mutant restored the ability to metabolize galactose but did not sustain growth on this sugar. The latter strain was used to prove that lacFE, encoding the lactose PTS, is necessary for galactose metabolism, thus implicating this transporter in galactose uptake. Both PTS transporters have a low affinity for galactose, while GalP displays a high affinity for the sugar. Furthermore, the GalP/Leloir route supported the highest galactose consumption rate. To further increase this rate, we overexpressed galPMKT, but this led to a substantial accumulation of ?-galactose 1-phosphate and ?-glucose 1-phosphate, pointing to a bottleneck at the level of ?-phosphoglucomutase. Overexpression of a gene encoding ?-phosphoglucomutase alone or in combination with gal genes yielded strains with galactose consumption rates enhanced up to 50% relative to that of NZ9000. Approaches to further improve galactose metabolism are discussed. PMID:20817811

Neves, Ana R; Pool, Wietske A; Solopova, Ana; Kok, Jan; Santos, Helena; Kuipers, Oscar P

2010-11-01

148

A Type IC Restriction-Modification System in Lactococcus lactis  

PubMed Central

Three genes coding for the endonuclease, methylase, and specificity subunits of a type I restriction-modification (R-M) system in the Lactococcus lactis plasmid pIL2614 have been characterized. Plasmid location, sequence homologies, and inactivation studies indicated that this R-M system is most probably of type IC.

Schouler, Catherine; Clier, Florence; Lerayer, Alda Luisa; Ehrlich, S. Dusko; Chopin, Marie-Christine

1998-01-01

149

Subdural Empyema Due to Lactococcus lactis cremoris: Case Report.  

PubMed

Lactococcus lactis cremoris (L. lactis cremoris) infections are very rare in humans. Only three case reports of brain abscess have been reported and the infectious routes and pathological features are still unknown. We experienced a subdural empyema due to L. lactis cremoris in an immunocompetent adult. A 33-year-old man was admitted with fever, right facial pain, left hemiparesis, and left hemianopsia. Computed tomography demonstrated low density fluid collection in the right falcotentorial subdural space. Magnetic resonance (MR) images revealed a high signal lesion on a diffusion-weighted image (DWI) and fluid attenuated inversion recovery (FLAIR) images in the right paratentorial and parafalcine subdural space, right maxillary sinus, and bilateral ethmoidal sinus. He underwent two sequential open surgeries for removal and drainage of empyema and was treated with antibiotics including meropenem and ampicillin. To our knowledge, this is the first report of subdural empyema caused by L. lactis cremoris infection. We report the case and discuss the pathological features with the previous literature. PMID:24257498

Inoue, Mizuho; Saito, Atsushi; Kon, Hiroyuki; Uchida, Hiroki; Koyama, Shinya; Haryu, Shinya; Sasaki, Tatsuya; Nishijima, Michiharu

2014-04-15

150

Specificity of Milk Peptide Utilization by Lactococcus lactis  

PubMed Central

To study the substrate specificity of the oligopeptide transport system of Lactococcus lactis for its natural substrates, the growth of L. lactis MG1363 was studied in a chemically defined medium containing milk peptides or a tryptic digest of ?s2-casein as the source of amino acids. Peptides were separated into acidic, neutral, and basic pools by solid-phase extraction or by cation-exchange liquid chromatography. Their ability to sustain growth and the time course of their utilization demonstrated the preferential use of hydrophobic basic peptides with molecular masses ranging between 600 and 1,100 Da by L. lactis MG1363 and the inability to use large, acidic peptides. These peptide utilization preferences reflect the substrate specificity of the oligopeptide transport system of the strain, since no significant cell lysis was inferred. Considering the free amino acid content of milk and these findings on peptide utilization, it was demonstrated that the cessation of growth of L. lactis MG1363 in milk was due to deprivation of leucine and methionine.

Juillard, Vincent; Guillot, Alain; Le Bars, Dominique; Gripon, Jean-Claude

1998-01-01

151

Autolysis of Lactococcus lactis Is Influenced by Proteolysis  

PubMed Central

The autolysin AcmA of Lactococcus lactis was shown to be degraded by the extracellular lactococcal proteinase PrtP. Autolysis, as evidenced by reduction in optical density of a stationary-phase culture and concomitant release of intracellular proteins, was greatly reduced when L. lactis MG1363 cells expressed the cell wall-anchored lactococcal proteinase PrtP of the PI-type caseinolytic specificity (PI). On the other hand, lactococcal strains that did not produce the proteinase showed a high level of autolysis, which was also observed when the cells produced the secreted form of PI or a cell wall-anchored proteinase with PIII-type specificity. Autolysis was also increased when MG1363 expressed the cell wall-anchored hybrid PI/PIII-type proteinase PIac. Zymographic analysis of AcmA activity during stationary phase showed that AcmA was quickly degraded by PI and much more slowly by PrtP proteinases with PIII-type and intermediate specificities. Autolysis of L. lactis by AcmA was influenced by the specificity, amount, and location of the lactococcal proteinase. No autolysis was observed when the various proteinases were expressed in an L. lactis acmA deletion mutant, indicating that PrtP itself did not cause lysis of cells. The chain length of a strain was significantly shortened when the strain expressed a cell wall-anchored active proteinase.

Buist, Girbe; Venema, Gerard; Kok, Jan

1998-01-01

152

KPC-2 carbapenemase and DHA-1 AmpC determinants carried on the same plasmid in Enterobacter aerogenes.  

PubMed

This study was conducted to analyse the presence of a plasmid-mediated carbapenem resistance mechanism in a clinical Enterobacter aerogenes isolate from a patient from Jiangsu province, People's Republic of China. PCR and sequencing confirmed that the isolate harboured Klebsiella pneumoniae carbapenemase (KPC)-2, DHA-1 and TEM-1 ?-lactamase genes. Both the KPC-2 and DHA-1 genes were transferred to Escherichia coli C600 by transconjugation, and Southern blotting confirmed that these two genes were located on the same plasmid, which was of approximately 56 kb in size. The Enterobacter aerogenes isolate was resistant to carbapenems and other tested antimicrobial agents. The Escherichia coli transconjugant showed reduced susceptibility but not resistance to carbapenems and other ?-lactams, indicating the presence of another, possibly permeability-related, resistance mechanism in the clinical isolate. PMID:24173427

Kuai, Shougang; Shao, Haifeng; Huang, Lihua; Pei, Hao; Lu, Zhonghua; Wang, Weiping; Liu, Jun

2014-03-01

153

Detection of Extended-Spectrum b-Lactamases in Clinical Isolates of Enterobacter cloacae and Enterobacter aerogenes  

Microsoft Academic Search

The aim of the present study was to investigate the frequency of extended-spectrum b-lactamases (ESBLs) in a consecutive collection of clinical isolates of Enterobacter spp. The abilities of various screening methods to detect ESBLs in enterobacters were simultaneously tested. Among the 68 consecutive isolates (56 Enterobacter cloacae and 12 Enterobacter aerogenes isolates) that were analyzed for b-lactamase content, 21 (25

EVA TZELEPI; PANAGIOTA GIAKKOUPI; DANAI SOFIANOU; VENETA LOUKOVA; ANASTASSIA KEMEROGLOU; ATHANASSIOS TSAKRIS

2000-01-01

154

2,3Butanediol production by Enterobacter aerogenes : selection of the optimal conditions and application to food industry residues  

Microsoft Academic Search

Optimum values of temperature, pH, and starting substrate concentration are experimentally determined for 2,3-butanediol production by Enterobacter aerogenes through three set of batch fermentations of synthetic glucose solutions. The results of tests carried out at variable temperature show an optimum of 39 °C and are used to estimate, for both fermentation and thermal inactivation, the activation enthalpies (7.19 and 23.6

P. Perego; A. Converti; A. Del Borghi; P. Canepa

2000-01-01

155

Isolation of Enterobacter aerogenes susceptible to beta-lactam antibiotics despite high level beta-lactamase production  

Microsoft Academic Search

This report describes a patient with nosocomial meningitis from whom four distinct isolates ofEnterobacter aerogenes were recovered over a complicated course of chemotherapy. The initial isolate was susceptible to expanded spectrum ?-lactams despite constitutive production of high levels of ?-lactamase. Resistant isolates recovered during antibiotic therapy had lost a 42,000 outer membrane protein. These data suggest that b-lactam susceptibility in

M. A. Mellencamp; J. S. Roccaforte; L. C. Preheim; C. C. Sanders; C. A. Anene; M. J. Bittner

1990-01-01

156

Successive Emergence of Extended-Spectrum  -Lactamase-Producing and Carbapenemase-Producing Enterobacter aerogenes Isolates in a University Hospital  

Microsoft Academic Search

Sixty-two clinical isolates of Enterobacter aerogenes resistant to expanded-spectrum cephalosporins were collected between July 2003 and May 2005. Among these isolates, 23 (37.1%) were imipenem (IPM) susceptible, and 39 (62.9%) were IPM insusceptible, of which 89.7% (35\\/39) were resistant and 10.3% (4\\/39) were inter- mediate. Isolate genotypes were compared by pulsed-field gel electrophoresis. Of 62 isolates, 48 belonged to epidemic

M. Biendo; B. Canarelli; D. Thomas; F. Rousseau; F. Hamdad; C. Adjide; G. Laurans; F. Eb

2008-01-01

157

Co-fermentation of carbon sources by Enterobacter aerogenes ATCC 29007 to enhance the production of bioethanol.  

PubMed

We investigated the enhancement of bioethanol production in Enterobacter aerogenes ATCC 29007 by co-fermentation of carbon sources such as glycerol, glucose, galactose, sucrose, fructose, xylose, starch, mannitol and citric acid. Biofuel production increases with increasing growth rate of microorganisms; that is why we investigated the optimal growth rate of E. aerogenes ATCC 29007, using mixtures of different carbon sources with glycerol. E. aerogenes ATCC 29007 was incubated in media containing each carbon source and glycerol; growth rate and bioethanol production improved in all cases compared to those in medium containing glycerol alone. The growth rate and bioethanol production were highest with mannitol. Fermentation was carried out at 37 °C for 18 h, pH 7, using 50 mL defined production medium in 100 mL serum bottles at 200 rpm. Bioethanol production under optimized conditions in medium containing 16 g/L mannitol and 20 g/L glycerol increased sixfold (32.10 g/L) than that containing glycerol alone (5.23 g/L) as the carbon source in anaerobic conditions. Similarly, bioethanol production using free cells in continuous co-fermentation also improved (27.28 g/L) when 90.37 % of 16 g/L mannitol and 67.15 % of 20 g/L glycerol were used. Although naturally existing or engineered microorganisms can ferment mixed sugars sequentially, the preferential utilization of glucose to non-glucose sugars often results in lower overall yield and productivity of ethanol. Here, we present new findings in E. aerogenes ATCC 29007 that can be used to improve bioethanol production by simultaneous co-fermentation of glycerol and mannitol. PMID:24185706

Thapa, Laxmi Prasad; Lee, Sang Jun; Yang, Xiao Guang; Yoo, Hah Young; Kim, Sung Bong; Park, Chulhwan; Kim, Seung Wook

2014-06-01

158

The AcrAB-TolC efflux pump contributes to multidrug resistance in the nosocomial pathogen Enterobacter aerogenes.  

PubMed

We identified the genes encoding the AcrA-AcrB-TolC efflux pump in Enterobacter aerogenes and constructed acrAB and tolC mutants from a multidrug-resistant isolate. Both derivatives were more susceptible to antibiotics than the parental strain. Sequence analysis and complementation experiments revealed that the multidrug-resistant isolate is an acrR mutant. PMID:12121946

Pradel, Elizabeth; Pagès, Jean-Marie

2002-08-01

159

Hydrophobic membrane thickness and lipid-protein interactions of the leucine transport system of Lactococcus lactis  

Microsoft Academic Search

The effect of the phospholipid acyl chain carbon number on the activity of the branched-chain amino acid transport system of Lactococcus lactis has been investigated. Major fatty acids identified in a total lipid extract of L. lactis membranes are palmitic acid (16:0), oleic acid (18:1) and the cyclopropane-ring containing lactobacillic acid (19?). L. lactis membrane vesicles were fused with liposomes

Jos A. F. op den Kamp; Arnold J. M. Driessen; Gerda in't Veld; Wil N. Konings

1991-01-01

160

Cloning in Streptococcus lactis of plasmid-mediated UV resistance and effect on prophage stability.  

PubMed Central

Plasmid pIL7 (33 kilobases) from Streptococcus lactis enhances UV resistance and prophage stability. A 5.4-kilobase pIL7 fragment carrying genes coding for both characters was cloned into S. lactis, using plasmid pHV1301 as the cloning vector. The recombinant plasmid was subsequently transferred to three other S. lactis strains by transformation or protoplast fusion. Cloned genes were expressed in all tested strains. Images

Chopin, M C; Chopin, A; Rouault, A; Simon, D

1986-01-01

161

Uptake of galactose and lactose by Kluyveromyces lactis: biochemical characteristics and attempted genetical analysis.  

PubMed

Study of the lactose and galactose transport systems in Kluyveromyces lactis has shown that lactose uptake is by active transport. The transport system is under monogenic control and is inducible. Galactose uptake is also by active transport but the system is controlled by two genes which, in the four strains we studied, are present only in K. lactis CBS 2359. Galactose uptake in the other K. lactis strains is by a simple diffusion process. PMID:3655722

Boze, H; Moulin, G; Galzy, P

1987-01-01

162

Cholate Resistance in Lactococcus lactis Is Mediated by an ATP-Dependent Multispecific Organic Anion Transporter  

Microsoft Academic Search

The cholate-resistant Lactococcus lactis strain C41-2, derived from wild-type L. lactis MG1363 through selection for growth on cholate-containing medium, displayed a reduced accumulation of cholate due to an enhanced active efflux. However, L. lactis C41-2 was not cross resistant to deoxycholate or cationic drugs, such as ethidium and rhodamine 6G, which are typical substrates of the multidrug transporters LmrP and

ATSUSHI YOKOTA; MARLOES VEENSTRA; PETER KURDI; HENDRIK W. VAN VEEN; WIL N. KONINGS

2000-01-01

163

Hydrogen peroxide-producing NADH oxidase (nox-1) from Lactococcus lactis  

Microsoft Academic Search

We have successfully applied the sequence comparison-based approach to develop a novel hydrogen peroxide-forming NADH oxidase (nox-1) from Lactococcus lactis (L. lactis) that reduces oxygen to hydrogen peroxide. The nox-1 gene (AhpF) was isolated from genomic L. lactis DNA by PCR and cloned into the expression vector pET32. The His-tagged protein was overexpressed at 20°C after induction with 167?M IPTG,

Rongrong Jiang; Andreas S. Bommarius

2004-01-01

164

Hydrogen peroxide-producing NADH oxidase (nox-1) from Lactococcus lactis  

Microsoft Academic Search

We have successfully applied the sequence comparison-based approach to develop a novel hydrogen peroxide-forming NADH oxidase (nox-1) from Lactococcus lactis (L. lactis) that reduces oxygen to hydrogen peroxide. The nox-1 gene (AhpF) was isolated from genomic L. lactis DNA by PCR and cloned into the expression vector pET32. The His-tagged protein was over- expressed at 20C after induction with167 lM

Rongrong Jiang; Andreas S. Bommarius

2004-01-01

165

Characterization of a Wild, Novel Nisin A-Producing Lactococcus Strain with an L. lactis subsp. cremoris Genotype and an L. lactis subsp. lactis Phenotype, Isolated from Greek Raw Milk  

PubMed Central

Several molecular taxonomic studies have revealed that many natural (wild) Lactococcus lactis strains of dairy origin which are phenotypically representative of the L. lactis subspecies lactis cluster genotypically within subspecies cremoris and vice versa. Recently, we isolated two wild nisin-producing (Nis+) L. lactis strains, M78 and M104, of the lactis phenotype from Greek raw milk (J. Samelis, A. Lianou, A. Kakouri, C. Delbès, I. Rogelj, B. B. Matijašic, and M. C. Montel, J. Food Prot. 72:783–790, 2009); strain M78 possess a novel nisin A sequence (GenBank accession number HM219853). In this study, the actual subspecies identity of M78 and M104 isolates was elucidated, using 16S rRNA and acmA (encoding lactococcal N-acetylmuramidase) gene and histidine biosynthesis operon polymorphisms and 16S rRNA and ldh (encoding lactate dehydrogenase) gene phylogenies. Except the acmA gene analysis, molecular tools revealed that isolates M78 and M104 clustered with strains of the cremoris genotype, including the LMG 6897T strain, while they were distant from strains of the lactis genotype, including the LMG 6890T strain. The two wild isolates had identical repetitive sequence-based PCR (rep-PCR), randomly amplified polymorphic DNA (RAPD), plasmid, and whole-cell protein profiles and shared high 16S rRNA (99.9%) and ldh (100%) gene sequence homologies. In contrast, they exhibited identical sugar fermentation and enzymatic patterns which were similar to those of the subspecies lactis LMG 6890T strain. To our knowledge, this is the first complete identification report on a wild L. lactis subsp. cremoris genotype of the lactis phenotype which is capable of nisin A production and, thus, has strong potential for use as a novel dairy starter and/or protective culture.

Parapouli, Maria; Delbes-Paus, Celine; Kakouri, Athanasia; Koukkou, Anna-Irini; Montel, Marie-Christine

2013-01-01

166

Cloning of a chromosomal gene required for phage infection of Lactococcus lactis subsp. lactis C2.  

PubMed Central

A phage-resistant mutant with a defect in a membrane component required for phage infections in Lactococcus lactis subsp. lactis C2 was transformed with a chromosomal library of the wild-type, phage-sensitive strain. Of the 4,200 transformants screened for phage sensitivity, three were positively identified as phage sensitive. A cause-and-effect relationship between the cloned chromosomal fragments and the phage-sensitive phenotype was established on the basis of the following two criteria: (i) the frequency of loss of the cloned fragments in the absence of antibiotic selection pressure correlated with the frequency of loss of phage sensitivity; and (ii) phage sensitivity was transferred to 100% of recipient, phage-resistant cells transformed with the cloned fragment. The cloned chromosomal DNA from the three independent isolates was physically mapped with restriction endonucleases. The sizes of the cloned fragments were 9.6, 11.8, and 9.5 kb. Each fragment contained an identical stretch of DNA common to all three, which was 9.4 kb. The gene that conferred phage sensitivity was localized by subcloning to a 4.5-kb region. Further subcloning indicated that a single EcoRI site within the 4.5-kb region must lie within the gene or its promoter. The required 4.5-kb region was sequenced and found to code for one partial and two complete open reading frames. The gene required for complementation was functionally mapped by Tn5 mutagenesis and localized to one of the two complete open reading frames, which was designated pip (an acronym for phage infection protein). pip is 2,703 bases in length. Potential promoters start 206 and 212 bases upstream of the open reading frame. A ribosome binding site and a seven-base spacer precede the GTG (Val) translation initiation codon. The amino acid sequence deduced from the gene has 901 residues and an M(r) of 99,426. Hydropathy analysis revealed four to six potential membrane-spanning regions, one near the amino terminus and the others at the extreme carboxyl terminus. The amino terminus has characteristics of a signal sequence. The putative protein would have a 650-residue, central polar domain. Images

Geller, B L; Ivey, R G; Trempy, J E; Hettinger-Smith, B

1993-01-01

167

Optimization of cultural conditions for conversion of glycerol to ethanol by Enterobacter aerogenes S012.  

PubMed

The aim of this research is to optimize the cultural conditions for the conversion of glycerol to ethanol by Enterobacter aerogenes S012. Taguchi method was used to screen the cultural conditions based on their signal to noise ratio (SN). Temperature (°C), agitation speed (rpm) and time (h) were found to have the highest influence on both glycerol utilization and ethanol production by the organism while pH had the lowest. Full factorial design, statistical analysis, and regression model equation were used to optimize the selected cultural parameters for maximum ethanol production. The result showed that fermentation at 38°C and 200 rpm for 48 h would be ideal for the bacteria to produce maximum amount of ethanol from glycerol. At these optimum conditions, ethanol production, yield and productivity were 25.4 g/l, 0.53 g/l/h, and 1.12 mol/mol-glycerol, repectively. Ethanol production increased to 26.5 g/l while yield and productivity decreased to 1.04 mol/mol-glycerol and 0.37 g/l/h, respectively, after 72 h. Analysis of the fermentation products was performed using HPLC, while anaerobic condition was created by purging the fermentation vessel with nitrogen gas. PMID:23388539

Nwachukwu, Raymond E S; Shahbazi, Abolghasem; Wang, Lijun; Worku, Mulumebet; Ibrahim, Salam; Schimmel, Keith

2013-01-01

168

Effect of Growth Rate on Histidine Catabolism and Histidase Synthesis in Aerobacter aerogenes1  

PubMed Central

A study was made of how the catabolism of a carbon and energy source is affected by the biosynthetic demands of growing bacterial cells. Cultures of Aerobacter aerogenes in l-histidine medium were grown in a chemostat at rates determined by the supply of either sulfate or a required amino acid, l-arginine. It was discovered that the rate at which these cells grow under a biosynthetic restriction determines both the rate and the pattern of histidine degradation. (i) Histidine catabolism is partially coupled to the growth rate. This coupling is achieved by catabolite repression of histidase (histidine ammonia lyase; EC 4.3.1.3.), and also by a slightly decreased in vivo function of this enzyme at low growth rates. (ii) The looseness of the coupling results in a direct relationship between growth rate and growth yield, and possibly is correlated with an altered pattern of carbon flow from histidine. (iii) Sudden decreases in growth rate cause total repression of histidase synthesis for substantial periods of time. (iv) Sudden release of biosynthetic restriction leads rapidly to an increase in the functioning of the cells' complement of histidase, an increase in the rate of synthesis of this enzyme, and an increase in the growth yield from histidine.

Jensen, Donald E.; Neidhardt, Frederick C.

1969-01-01

169

Purification, characterization, and in vivo reconstitution of Klebsiella aerogenes urease apoenzyme.  

PubMed Central

Urease was purified from recombinant Klebsiella aerogenes which was grown in the absence of nickel. The protein was inactive and contained no transition metals, yet it possessed the same heteropolymeric structure as native enzyme, demonstrating that Ni is not required for intersubunit association. Ni did, however, substantially increase the stability of the intact metalloprotein (Tm = 79 degrees C) compared with apoenzyme (Tm = 62 degrees C), as revealed by differential scanning calorimetric analysis. An increased number of histidine residues were accessible to diethyl pyrocarbonate in apourease compared with holoenzyme, consistent with possible Ni ligation by histidinyl residues. Addition of Ni to purified apourease did not yield active enzyme; however, urease apoenzyme was very slowly activated in vivo by addition of Ni ions to Ni-free cell cultures, even after treatment of the cells with spectinomycin to inhibit protein synthesis. In contrast, sonicated cells and cells treated with dinitrophenol or dicyclohexylcarbodiimide were incapable of activating apourease. These results indicate that apourease activation is an energy-dependent process that is destroyed by cell disruption.

Lee, M H; Mulrooney, S B; Hausinger, R P

1990-01-01

170

Biodegradation of acrylamide by Enterobacter aerogenes isolated from wastewater in Thailand.  

PubMed

A widespread use of acrylamide, probably a neurotoxicant and carcinogen, in various industrial processes has led to environmental contamination. Fortunately, some microorganisms are able to derive energy from acrylamide. In the present work, we reported the isolation and characterization of a novel acrylamide-degrading bacterium from domestic wastewater in Chonburi, Thailand. The strain grew well in the presence of acrylamide as 0.5% (W/V), at pH 6.0 to 9.0 and 25 degrees C. Identification based on biochemical characteristics and 16S rRNA gene sequence identified the strain as Enterobacter aerogenes. Degradation of acrylamide to acrylic acid started in the late logarithmic growth phase as a biomass-dependent pattern. Specificity of cell-free supernatant towards amides completely degraded butyramide and urea and 86% of lactamide. Moderate degradation took place in other amides with that by formamide > benzamide > acetamide > cyanoacetamide > propionamide. No degradation was detected in the reactions of N,N-methylene bisacrylamide, sodium azide, thioacetamide, and iodoacetamide. These results highlighted the potential of this bacterium in the cleanup of acrylamide/amide in the environment. PMID:21520808

Buranasilp, Kanokhathai; Charoenpanich, Jittima

2011-01-01

171

Antimicrobial susceptibilities of Lactococcus lactis and Lactococcus garvieae and a proposed method to discriminate between them.  

PubMed

The MICs of antimicrobial agents contained in the SCEPTOR Streptococcus MIC panels (Becton Dickinson Microbiology Systems) were determined for Lactococcus lactis, L. garvieae, and unknown Lactococcus species. Several isolates had reduced susceptibilities to many of the antimicrobial agents contained in the panel. For L. garvieae, the MICs of penicillin and, possibly, cephalothin were higher than for L. lactis, and unlike L. lactis, L. garvieae was resistant to clindamycin, indicating that knowledge of the Lactococcus species causing an infection might influence the choice of antimicrobial therapy. Susceptibility to clindamycin can also be used to differentiate between L. lactis and L. garvieae. PMID:8727924

Elliott, J A; Facklam, R R

1996-05-01

172

Yoghurt consumption and damaged colonic mucosa: a case of Lactococcus lactis liver abscess in an immunocompetent patient.  

PubMed

Lactococcus lactis is an uncommon cause of invasive disease in humans. We present a case of L. lactis liver abscess in an immunocompetent adult, apparently related to consumption of live culture yoghurt. PMID:16857633

Denholm, Justin; Horne, Kylie; McMahon, James; Grayson, M Lindsay; Johnson, Paul

2006-01-01

173

Transcriptional Regulation of Fatty Acid Biosynthesis in Lactococcus lactis  

PubMed Central

Here we study the influence of the putative fatty acid biosynthesis (FAB) regulator FabT (originally called RmaG [Llmg_1788]) on gene transcription in Lactococcus lactis MG1363. A strain with a knockout mutation of the putative regulator was constructed, and its transcriptome was compared to that of the wild-type strain. Almost all FAB genes were significantly upregulated in the knockout. Using electrophoretic mobility shift assays (EMSAs) and DNase I footprinting, the binding motif of the regulator and the binding locations in the genome were characterized. Fatty acid composition analysis revealed that a strain lacking FabT contained significantly more saturated acyl chains in its phospholipids. This observation demonstrates that the vital pathway of FAB in L. lactis is regulated by the repressor FabT.

Eckhardt, Tom H.; Skotnicka, Dorota; Kok, Jan

2013-01-01

174

Continuous nisin production with bioengineered Lactococcus lactis strains  

Microsoft Academic Search

Nisin production in continuous cultures of bioengineered Lactococcus lactis strains that incorporate additional immunity and regulation genes was studied. Highest nisin activities were observed at\\u000a 0.2 h–1 dilution rate and 12.5 g l–1 fructose concentration for all strains. Recombinant strains were able to produce greater amounts of nisin at dilution rates\\u000a below 0.3 h?1 compared to the control strain. However, this significant difference

Ö. ?im?ek; N. Akkoç; A. H. Çon; F. Özçelik; P. E. J. Saris; Mustafa Akçelik

2009-01-01

175

Nisin-controlled extracellular production of apidaecin in Lactococcus lactis  

Microsoft Academic Search

Apidaecins are heat-stable, nonhelical antibacterial peptides isolated from lymph fluid of the honeybee (Apis mellifera). These peptides are active against a wide range of gram-negative bacteria and they are the most prominent components of\\u000a the honeybee humoral defense against microbial invasion. In the present study, one isoform of apidaecin, apidaecin Ho, was\\u000a expressed extracellularly in the food-grade bacterium Lactococcus lactis.

Xu-xia Zhou; Yan-bo Wang; Yuan-jiang Pan; Wei-fen Li

2008-01-01

176

Structure-function analysis of multidrug transporters in Lactococcus lactis  

Microsoft Academic Search

The active extrusion of cytotoxic compounds from the cell by multidrug transporters is one of the major causes of failure of chemotherapeutic treatment of tumor cells and of infections by pathogenic microorganisms. A multidrug transporter in Lactococcus lactis, LmrA, is a member of the ATP-binding cassette (ABC) superfamily and a bacterial homolog of the human multidrug resistance P-glycoprotein. Another multidrug

Hendrik W van Veen; Monique Putman; Abelardo Margolles; Kanta Sakamoto; Wil N Konings

1999-01-01

177

Molecular pharmacological characterization of two multidrug transporters in Lactococcus lactis  

Microsoft Academic Search

The active extrusion of cytotoxic compounds from the cell by multidrug transporters is one of the major causes of failure of chemotherapeutic treatment of tumor cells and of infections by pathogenic microorganisms. A multidrug transporter in Lactococcus lactis, LmrA, is a member of the ATP-binding cassette superfamily and a bacterial homolog of the human multidrug resistance P-glycoprotein. Another multidrug transporter

Hendrik W van Veen; Monique Putman; Abelardo Margolles; Kanta Sakamoto; Wil N Konings

2000-01-01

178

Genes but Not Genomes Reveal Bacterial Domestication of Lactococcus Lactis  

PubMed Central

Background The population structure and diversity of Lactococcus lactis subsp. lactis, a major industrial bacterium involved in milk fermentation, was determined at both gene and genome level. Seventy-six lactococcal isolates of various origins were studied by different genotyping methods and thirty-six strains displaying unique macrorestriction fingerprints were analyzed by a new multilocus sequence typing (MLST) scheme. This gene-based analysis was compared to genomic characteristics determined by pulsed-field gel electrophoresis (PFGE). Methodology/Principal Findings The MLST analysis revealed that L. lactis subsp. lactis is essentially clonal with infrequent intra- and intergenic recombination; also, despite its taxonomical classification as a subspecies, it displays a genetic diversity as substantial as that within several other bacterial species. Genome-based analysis revealed a genome size variability of 20%, a value typical of bacteria inhabiting different ecological niches, and that suggests a large pan-genome for this subspecies. However, the genomic characteristics (macrorestriction pattern, genome or chromosome size, plasmid content) did not correlate to the MLST-based phylogeny, with strains from the same sequence type (ST) differing by up to 230 kb in genome size. Conclusion/Significance The gene-based phylogeny was not fully consistent with the traditional classification into dairy and non-dairy strains but supported a new classification based on ecological separation between “environmental” strains, the main contributors to the genetic diversity within the subspecies, and “domesticated” strains, subject to recent genetic bottlenecks. Comparison between gene- and genome-based analyses revealed little relationship between core and dispensable genome phylogenies, indicating that clonal diversification and phenotypic variability of the “domesticated” strains essentially arose through substantial genomic flux within the dispensable genome.

Passerini, Delphine; Beltramo, Charlotte; Coddeville, Michele; Quentin, Yves; Ritzenthaler, Paul

2010-01-01

179

Recombinant expression of Laceyella sacchari thermitase in Lactococcus lactis.  

PubMed

Thermitase (EC 3.4.21.66) is a thermostable endo-protease with the ability to convert various food relevant substrates into low-molecular weight peptides. A thermitase produced by Laceyella sacchari strain DSM43353 was found to have a mature amino acid sequence nearly identical to that of the original thermitase isolated from Thermoactinomyces vulgaris. The DSM43353 thermitase gene sequence contains a pro-peptide including parts of an I9 inhibitor motif. Expression of the thermitase gene in the Lactococcus lactis P170 expression system allowed secretion of stable thermitase in an auto-induced fermentation setup at 30°C. Thermitase accumulated in the culture supernatant during batch fermentations and was easily activated at 50°C or by prolonged dialysis. The activation step resulted in an almost complete degradation of endogenous L. lactis host proteins present in the supernatant. Mature activated product was stable at 50°C and functional at pH values between pH 6 and pH 11, suggesting that substrate hydrolysis can be performed over a broad range of pH values. The L. lactis based P170 expression system is a simple and safe system for obtaining food compatible thermitase in the range of 100 mg/L. PMID:24084004

Jørgensen, Casper M; Madsen, Søren M; Vrang, Astrid; Hansen, Ole C; Johnsen, Mads G

2013-12-01

180

RAG4 gene encodes a glucose sensor in Kluyveromyces lactis.  

PubMed Central

The rag4 mutant of Kluyveromyces lactis was previously isolated as a fermentation-deficient mutant, in which transcription of the major glucose transporter gene RAG1 was affected. The wild-type RAG4 was cloned by complementation of the rag4 mutation and found to encode a protein homologous to Snf3 and Rgt2 of Saccharomyces cerevisiae. These two proteins are thought to be sensors of low and high concentrations of glucose, respectively. Rag4, like Snf3 and Rgt2, is predicted to have the transmembrane structure of sugar transporter family proteins as well as a long C-terminal cytoplasmic tail possessing a characteristic 25-amino-acid sequence. Rag4 may therefore be expected to have a glucose-sensing function. However, the rag4 mutation was fully complemented by one copy of either SNF3 or RGT2. Since K. lactis appears to have no other genes of the SNF3/RGT2 type, we suggest that Rag4 of K. lactis may have a dual function of signaling high and low concentrations of glucose. In rag4 mutants, glucose repression of several inducible enzymes is abolished.

Betina, S; Goffrini, P; Ferrero, I; Wesolowski-Louvel, M

2001-01-01

181

Influence of Lipoteichoic Acid D-Alanylation on Protein Secretion in Lactococcus lactis as Revealed by Random Mutagenesis  

Microsoft Academic Search

Lactococcus lactis, a food-grade nonpathogenic lactic acid bacterium, is a good candidate for the production of heterologous proteins of therapeutic interest. We examined host factors that affect secretion of heterologous proteins in L. lactis. Random insertional mutagenesis was performed with L. lactis strain MG1363 carrying a staphylococcal nuclease (Nuc) reporter cassette in its chromosome. This cassette encodes a fusion protein

S. Nouaille; J. Commissaire; J. J. Gratadoux; P. Ravn; A. Bolotin; A. Gruss; Y. Le Loir; P. Langella

2004-01-01

182

Production, active staining and gas chromatography assay analysis of recombinant aminopeptidase P from Lactococcus lactis ssp. lactis DSM 20481.  

PubMed

The aminopeptidase P (PepP, EC 3.4.11.9) gene from Lactococcus lactis ssp. lactis DSM 20481 was cloned, sequenced and expressed recombinantly in E. coli BL21 (DE3) for the first time. PepP is involved in the hydrolysis of proline-rich proteins and, thus, is important for the debittering of protein hydrolysates. For accurate determination of PepP activity, a novel gas chromatographic assay was established. The release of L-leucine during the hydrolysis of L-leucine-L-proline-L-proline (LPP) was examined for determination of PepP activity. Sufficient recombinant PepP production was achieved via bioreactor cultivation at 16?°C, resulting in PepP activity of 90 ?katLPP Lculture-1. After automated chromatographic purification by His-tag affinity chromatography followed by desalting, PepP activity of 73.8 ?katLPP Lculture-1 was achieved. This was approximately 700-fold higher compared to the purified native PepP produced by Lactococcus lactis ssp. lactis NCDO 763 as described in literature. The molecular weight of PepP was estimated to be?~?40?kDa via native-PAGE together with a newly developed activity staining method and by SDS-PAGE. Furthermore, the kinetic parameters Km and Vmax were determined for PepP using three different tripeptide substrates. The purified enzyme showed a pH optimum between 7.0 and 7.5, was most active between 50°C and 60°C and exhibited reasonable stability at 0°C, 20°C and 37°C over 15?days. PepP activity could be increased 6-fold using 8.92?mM MnCl2 and was inhibited by 1,10-phenanthroline and EDTA. PMID:22853547

Stressler, Timo; Eisele, Thomas; Schlayer, Michael; Fischer, Lutz

2012-01-01

183

Identification of the Minimal Replicon of Lactococcus lactis subsp. lactis UC317 Plasmid pCI305  

PubMed Central

Replication functions of the stable, cryptic 8.7-kilobase (kb) plasmid pCI305 from multi-plasmid-containing Lactococcus lactis subsp. lactis UC317 were studied. Analysis of this replicon was facilitated by the construction of replication probe vectors that consisted of the pBR322 replication region, a pUC18-derived multiple cloning site, and either the cat gene of pC194 (pCI341; 3.1 kb) or the erm gene of pAM?1 (pCI3330; 4.0 kb). Plasmid pCI305 was introduced into plasmid-free L. lactis subsp. lactis MG1363Sm, a streptomycin-resistant derivative of MG1363, by a transformation procedure with the 75-kb lactose-proteinase plasmid pCI301 of UC317 as a marker plasmid. A combination of transposon Tn5 mutagenesis and subcloning in pCI341 and pCI3330 with individual Tn5 insertions around the replication region facilitated the identification of a 1.6-kb minimal replicon on pCI305. This region was separable into two domains: (i) a 1.3-kb region (repB) encoding a trans-acting function (in vitro transcription-translation studies suggested the involvement of a 48-kilodalton protein); and (ii) a 0.3-kb region (repA) sufficient to direct replication when provided with repB in trans and thus probably containing the origin of replication. Lactococcus-Escherichia coli shuttle vectors based on the pCI305 replication region were constructed. Images

Hayes, Finbarr; Daly, Charles; Fitzgerald, Gerald F.

1990-01-01

184

Immunogenicity of an aerogenic BCG vaccine in T-cell-depleted and normal mice.  

PubMed Central

Aerogenic infection of adult thymectomized, lethally irradiated, bone marrow-reconstituted (THXB) C57B1 times C3H F1 hybrid mice with 1 to 3,000 viable BCG Montreal was followed by an extended period of logarithmic growth to a maximum population of 5 times 10-6 bacilli by day 35. The infection spread to the liver, spleen, and bone marrow with extensive multiplication in all test organs before the growth curves abruptly entered a stationary phase. Up to 30% of the THXB mice eventually died as a result of the ongoing BCG infection. There was no sign of an antimicrobial immune response in the THXB mice analogous to that seen in the control animals beginning about day 30. The THXB mice developed considerable immediate but no delayed hypersensitivity to PPD. Intravenous challenge of the BCG-vaccinated THXB mice with 105 virulent Mycobacterium tuberculosis Erdman indicated that they were as susceptible to the tuberculous challenge as a group of unvaccinated controls. Visible surface lesions developed on the lung 90 days postinfection in the T-cell-depleted host with a sharp rise in counts to 175 per lobe on day 120 followed by a plateau for the remainder of the study. Control mice developed visible lesions about day 50, with 225 lesions per lobe by day 70 and a sharp decline to undetectable levels by day 90. The histopathology of these changes was examined carefully, together with the rate of cellular proliferation (tritiated thymidine uptake) by lung and spleen cells as the BCG infection progressed in the THXB mice. Peak uptake by both organs was depressed during the early stages of the BCG infection in the T-cell-depleted mice, but later the incorporation rates were significantly elevated above control values as the infection progressed. Images

Morrison, N E; Collins, F M

1975-01-01

185

Old mice are able to control low-dose aerogenic infections with Mycobacterium tuberculosis.  

PubMed Central

Previous work in this laboratory has led to the development of the hypothesis that the increased susceptibility of old mice to tuberculosis infection reflects a limited ability by immune CD4 mediator cells to accumulate at sites of bacterial implantation. To test this hypothesis with very low dose infections, the present study documented the course of a low-dose aerogenic infection with virulent Mycobacterium tuberculosis Erdman against time in the target organs of young (3-month-old) and old (24-month-old) B6D2F1 hybrid mice. The results of the study indicated that the infection was controlled by the two groups of mice at similar rates, although the bacterial load in the old mice was eventually somewhat higher. Despite these similarities, some subtle differences between the young and old mice were also evident and included evidence of increased hematogenous spread of the infection from the lungs to other organs in the old mice. Interestingly, very poor expression of the cytokine interleukin-12 was observed in the lungs of infected old mice, leading to the hypothesis that the poor CD4 response in such animals could be partially attributed to the lack of this Th1-type, CD4 T-cell-enhancing cytokine. In this regard, treatment of old mice with exogenous interleukin-12 increased resistance and promoted gamma interferon secretion by CD4 T cells from these mice, although the effects were generally modest. These data suggest that old mice possess CD4-independent compensatory mechanisms by which to deal with low-dose pulmonary tuberculosis infections, although such mechanisms are less efficient than those seen in young animals.

Cooper, A M; Callahan, J E; Griffin, J P; Roberts, A D; Orme, I M

1995-01-01

186

Impact of Lactococcus lactis spp. lactis Bio Adhesion on Pathogenic Bacillus cereus Biofilm on Silicone Flowing System.  

PubMed

Bacillus cereus is a food pathogen that can attach on most of the surfaces and form biofilms, which facilitate the persistence and resistance toward antimicrobials. The aims of this study were (i) to characterize the structural dynamics of B. cereus sessile growth in two nutritional environments (with or without a nutrient flow), and (ii) to evaluate the impact of bio adhesion of Lactococcus lactis on B. cereus biofilm. Significantly greater biofilm volume and thickness were observed under dynamic conditions than under static conditions after 48 h and B. cereus biofilm was highly organized. The variation of physico-chemical characteristics of silicone by B. cereus bio adhesion favours the adhesion of hydrophilic Lc. lactis on the surface adhered by biofilm. Lc. lactis was able to adhere to silicone surface and produce biofilm obviously exhibited a significant reduction of B. cereus adhered cells up to nine orders of magnitude after 48 h of contact with competitive activity for nutrient and oxygen. This study constitutes a step ahead in developing strategies to prevent microbial colonization of silicone with lactococcal protective biofilm. PMID:24426121

Ksontini, Hamida; Kachouri, Faten; Hamdi, Moktar

2013-09-01

187

Roles of Glutamate Synthase, gltBD, and gltF in Nitrogen Metabolism of Escherichia coli and Klebsiella aerogenes  

PubMed Central

Mutants of Escherichia coli and Klebsiella aerogenes that are deficient in glutamate synthase (glutamate-oxoglutarate amidotransferase [GOGAT]) activity have difficulty growing with nitrogen sources other than ammonia. Two models have been proposed to account for this inability to grow. One model postulated an imbalance between glutamine synthesis and glutamine degradation that led to a repression of the Ntr system and the subsequent failure to activate transcription of genes required for the use of alternative nitrogen sources. The other model postulated that mutations in gltB or gltD (which encode the subunits of GOGAT) were polar on a downstream gene, gltF, which is necessary for proper activation of gene expression by the Ntr system. The data reported here show that the gltF model is incorrect for three reasons: first, a nonpolar gltB and a polar gltD mutation of K. aerogenes both show the same phenotype; second, K. aerogenes and several other enteric bacteria lack a gene homologous to gltF; and third, mutants of E. coli whose gltF gene has been deleted show no defect in nitrogen metabolism. The argument that accumulated glutamine represses the Ntr system in gltB or gltD mutants is also incorrect, because these mutants can derepress the Ntr system normally so long as sufficient glutamate is supplied. Thus, we conclude that gltB or gltD mutants grow slowly on many poor nitrogen sources because they are starved for glutamate. Much of the glutamate formed by catabolism of alternative nitrogen sources is converted to glutamine, which cannot be efficiently converted to glutamate in the absence of GOGAT activity. Finally, GOGAT-deficient E. coli cells growing with glutamine as the sole nitrogen source increase their synthesis of the other glutamate-forming enzyme, glutamate dehydrogenase, severalfold, but this is still insufficient to allow rapid growth under these conditions.

Goss, Thomas J.; Perez-Matos, Ana; Bender, Robert A.

2001-01-01

188

Improved Production of Heterologous Proteins by a Glucose Repression-Defective Mutant of Kluyveromyces lactis  

Microsoft Academic Search

The secreted production of heterologous proteins in Kluyveromyces lactis was studied. A glucoamylase (GAA) from the yeast Arxula adeninivorans was used as a reporter protein for the study of the secretion efficiencies of several wild-type and mutant strains of K. lactis. The expression of the reporter protein was placed under the control of the strong promoter of the glyceraldehyde-3-phosphate dehydrogenase

Claudia Donnini; Francesca Farina; Barbara Neglia; Maria Concetta Compagno; Daniela Uccelletti; Paola Goffrini; Claudio Palleschi

2004-01-01

189

Immunological analysis of a Lactococcus lactis-based DNA vaccine expressing HIV gp120  

Microsoft Academic Search

For reasons of efficiency Escherichia coli is used today as the microbial factory for production of plasmid DNA vaccines. To avoid hazardous antibiotic resistance genes and endotoxins from plasmid systems used nowadays, we have developed a system based on the food-grade Lactococcus lactis and a plasmid without antibiotic resistance genes. We compared the L. lactis system to a traditional one

Gregers J Gram; Anders Fomsgaard; Mette Thorn; Søren M Madsen; Jacob Glenting

2007-01-01

190

Antihypertensive and hypolipidemic effect of milk fermented by specific Lactococcus lactis strains.  

PubMed

The antihypertensive and hypolipidemic effects of milk fermented by specific Lactococcus lactis strains in spontaneously hypertensive rats (SHR) were investigated. The SHR were fed ad libitum milk fermented by Lc. lactis NRRL B-50571, Lc. lactis NRRL B-50572, Captopril (40mg/kg of body weight, Sigma-Aldrich Co., St. Louis, MO) or purified water for 4 wk. Results suggested that Lc. lactis fermented milks presented a significant blood pressure-lowering effect. No significant difference was noted among milk fermented by Lc. lactis NRRL B-50571 and Captopril by the second and third week of treatment. Additionally, milk fermented by Lc. lactis strains modified SHR lipid profiles. Milk fermented by Lc. lactis NRRL B-50571 and B-50572 were able to reduce plasma low-density lipoprotein cholesterol and triglyceride contents. Thus, milk fermented by Lc. lactis strains may be a coadjuvant in the reduction of hypertension and hyperlipidemia and may be used as a functional food for better cardiovascular health. PMID:23628247

Rodríguez-Figueroa, J C; González-Córdova, A F; Astiazaran-García, H; Hernández-Mendoza, A; Vallejo-Cordoba, B

2013-07-01

191

Inactivation of the panE gene in Lactococcus lactis enhances formation of cheese aroma compounds.  

PubMed

Hydroxyacid dehydrogenases limit the conversion of ?-keto acids into aroma compounds. Here we report that inactivation of the panE gene, encoding the ?-hydroxyacid dehydrogenase activity in Lactococcus lactis, enhanced the formation of 3-methylbutanal and 3-methylbutanol. L. lactis IFPL953?panE was an efficient strain producing volatile compounds related to cheese aroma. PMID:23524675

de Cadiñanos, Luz P Gómez; García-Cayuela, Tomás; Yvon, Mireille; Martinez-Cuesta, M Carmen; Peláez, Carmen; Requena, Teresa

2013-06-01

192

Complete Genome Sequence of Lactococcus lactis IO-1, a Lactic Acid Bacterium That Utilizes Xylose and Produces High Levels of l-Lactic Acid  

PubMed Central

We report the complete genome sequence of Lactococcus lactis IO-1 (= JCM7638). It is a nondairy lactic acid bacterium, produces nisin Z, ferments xylose, and produces predominantly l-lactic acid at high xylose concentrations. From ortholog analysis with other five L. lactis strains, IO-1 was identified as L. lactis subsp. lactis.

Kato, Hiroaki; Shiwa, Yuh; Oshima, Kenshiro; Machii, Miki; Araya-Kojima, Tomoko; Zendo, Takeshi; Shimizu-Kadota, Mariko; Hattori, Masahira; Sonomoto, Kenji

2012-01-01

193

Biohydrogen and polyhydroxyalkanoate co-production by Enterobacter aerogenes and Rhodobacter sphaeroides from Calophyllum inophyllum oil cake.  

PubMed

The feasibility of coupled biohydrogen and polyhydroxyalkanoate production by Enterobacter aerogenes and Rhodobacter sphaeroides using Calophyllum inophyllum oil cake was studied under dark and photo fermentation conditions. The utilization of a non-edible acidic oil cake (C. inophyllum), and exploitation of a modified minimal salt media led to reduction in the cost of media. Cost of fermentation is reduced by implementation of alternate dark-photo fermentative periods and through the use of a co-culture consisting of a dark fermentative (E. aerogenes) and a photo fermentative (R. sphaeroides) bacterium. The biohydrogen and polyhydroxyalkanoate produced were 7.95L H2/L media and 10.73g/L media, respectively, under alternate dark and photo fermentation and were 3.23L H2/L media and 5.6g/L media, respectively under complete dark fermentation. The characteristics of the oil cake and alternate dark (16h) and photo (8h) fermentative conditions were found to be supportive in producing high biohydrogen and polyhydroxyalkanoate (PHA) yield. PMID:24859207

Arumugam, A; Sandhya, M; Ponnusami, V

2014-07-01

194

Rapid Fluorescence Assessment of the Viability of Stressed Lactococcus lactis  

PubMed Central

The aim of this study was to establish the use of the fluorescent probes carboxyfluorescein (cF) and propidium iodide (PI) for rapid assessment of viability, using Lactococcus lactis subsp. lactis ML3 exposed to different stress treatments. The cF labeling indicated the reproductive capacity of mixtures of nontreated cells and cells killed at 70°C very well. However, after treatment up to 60°C the fraction of cF-labeled cells remained high, whereas the survival decreased for cells treated at above 50°C and was completely lost for those treated at 60°C. In an extended series of experiments, cell suspensions were exposed to heating, freezing, low pH, or bile salts, after which the colony counts, acidification capacity, glycolytic activity, PI exclusion, cF labeling, and cF efflux were measured and compared. The acidification capacity corresponded with the number of CFU. The glycolytic activity, which is an indicator of vitality, was more sensitive to the stress conditions than the reproduction, acidification, and fluorescence parameters. The cF labeling depended on membrane integrity, as was confirmed by PI exclusion. The fraction of cF-labeled cells was not a general indicator of reproduction or acidification, nor was PI exclusion or cF labeling capacity (the internal cF concentration). When the cells were labeled by cF, a subsequent lactose-energized efflux assay was needed for decisive viability assessment. This novel assay proved to be a good and rapid indicator of the reproduction and acidification capacities of stressed L. lactis and has potential for physiological research and dairy applications related to lactic acid bacteria.

Bunthof, Christine J.; van den Braak, Sabina; Breeuwer, Pieter; Rombouts, Frank M.; Abee, Tjakko

1999-01-01

195

CTP Limitation Increases Expression of CTP Synthase in Lactococcus lactis  

PubMed Central

CTP synthase is encoded by the pyrG gene and catalyzes the conversion of UTP to CTP. A Lactococcus lactis pyrG mutant with a cytidine requirement was constructed, in which ?-galactosidase activity in a pyrG-lacLM transcriptional fusion was used to monitor gene expression of pyrG. A 10-fold decrease in the CTP pool induced by cytidine limitation was found to immediately increase expression of the L. lactis pyrG gene. The final level of expression of pyrG is 37-fold higher than the uninduced level. CTP limitation has pronounced effects on central cellular metabolism, and both RNA and protein syntheses are inhibited. Expression of pyrG responds only to the cellular level of CTP, since expression of pyrG has no correlation to alterations in UTP, GTP, and ATP pool sizes. In the untranslated pyrG leader sequence a potential terminator structure can be identified, and this structure is required for regulation of the pyrG gene. It is possible to fold the pyrG leader in an alternative structure that would prevent the formation of the terminator. We suggest a model for pyrG regulation in L. lactis, and probably in other gram-positive bacteria as well, in which pyrG expression is directly dependent on the CTP concentration through an attenuator mechanism. At normal CTP concentrations a terminator is preferentially formed in the pyrG leader, thereby reducing expression of CTP synthase. At low CTP concentrations the RNA polymerase pauses at a stretch of C residues in the pyrG leader, thereby allowing an antiterminator to form and transcription to proceed. This model therefore does not include any trans-acting protein for sensing the CTP concentration as previously proposed for Bacillus subtilis.

J?rgensen, Casper M?ller; Hammer, Karin; Martinussen, Jan

2003-01-01

196

Engineering signal peptides for enhanced protein secretion from Lactococcus lactis.  

PubMed

Lactococcus lactis is an attractive vehicle for biotechnological production of proteins and clinical delivery of therapeutics. In many such applications using this host, it is desirable to maximize secretion of recombinant proteins into the extracellular space, which is typically achieved by using the native signal peptide from a major secreted lactococcal protein, Usp45. In order to further increase protein secretion from L. lactis, inherent limitations of the Usp45 signal peptide (Usp45sp) must be elucidated. Here, we performed extensive mutagenesis on Usp45sp to probe the effects of both the mRNA sequence (silent mutations) and the peptide sequence (amino acid substitutions) on secretion. We screened signal peptides based on their resulting secretion levels of Staphylococcus aureus nuclease and further evaluated them for secretion of Bacillus subtilis ?-amylase. Silent mutations alone gave an increase of up to 16% in the secretion of ?-amylase through a mechanism consistent with relaxed mRNA folding around the ribosome binding site and enhanced translation. Targeted amino acid mutagenesis in Usp45sp, combined with additional silent mutations from the best clone in the initial screen, yielded an increase of up to 51% in maximum secretion of ?-amylase while maintaining secretion at lower induction levels. The best sequence from our screen preserves the tripartite structure of the native signal peptide but increases the positive charge of the n-region. Our study presents the first example of an engineered L. lactis signal peptide with a higher secretion yield than Usp45sp and, more generally, provides strategies for further enhancing protein secretion in bacterial hosts. PMID:23124224

Ng, Daphne T W; Sarkar, Casim A

2013-01-01

197

CTP limitation increases expression of CTP synthase in Lactococcus lactis.  

PubMed

CTP synthase is encoded by the pyrG gene and catalyzes the conversion of UTP to CTP. A Lactococcus lactis pyrG mutant with a cytidine requirement was constructed, in which beta-galactosidase activity in a pyrG-lacLM transcriptional fusion was used to monitor gene expression of pyrG. A 10-fold decrease in the CTP pool induced by cytidine limitation was found to immediately increase expression of the L. lactis pyrG gene. The final level of expression of pyrG is 37-fold higher than the uninduced level. CTP limitation has pronounced effects on central cellular metabolism, and both RNA and protein syntheses are inhibited. Expression of pyrG responds only to the cellular level of CTP, since expression of pyrG has no correlation to alterations in UTP, GTP, and ATP pool sizes. In the untranslated pyrG leader sequence a potential terminator structure can be identified, and this structure is required for regulation of the pyrG gene. It is possible to fold the pyrG leader in an alternative structure that would prevent the formation of the terminator. We suggest a model for pyrG regulation in L. lactis, and probably in other gram-positive bacteria as well, in which pyrG expression is directly dependent on the CTP concentration through an attenuator mechanism. At normal CTP concentrations a terminator is preferentially formed in the pyrG leader, thereby reducing expression of CTP synthase. At low CTP concentrations the RNA polymerase pauses at a stretch of C residues in the pyrG leader, thereby allowing an antiterminator to form and transcription to proceed. This model therefore does not include any trans-acting protein for sensing the CTP concentration as previously proposed for Bacillus subtilis. PMID:14594829

Jørgensen, Casper Møller; Hammer, Karin; Martinussen, Jan

2003-11-01

198

Engineering Signal Peptides for Enhanced Protein Secretion from Lactococcus lactis  

PubMed Central

Lactococcus lactis is an attractive vehicle for biotechnological production of proteins and clinical delivery of therapeutics. In many such applications using this host, it is desirable to maximize secretion of recombinant proteins into the extracellular space, which is typically achieved by using the native signal peptide from a major secreted lactococcal protein, Usp45. In order to further increase protein secretion from L. lactis, inherent limitations of the Usp45 signal peptide (Usp45sp) must be elucidated. Here, we performed extensive mutagenesis on Usp45sp to probe the effects of both the mRNA sequence (silent mutations) and the peptide sequence (amino acid substitutions) on secretion. We screened signal peptides based on their resulting secretion levels of Staphylococcus aureus nuclease and further evaluated them for secretion of Bacillus subtilis ?-amylase. Silent mutations alone gave an increase of up to 16% in the secretion of ?-amylase through a mechanism consistent with relaxed mRNA folding around the ribosome binding site and enhanced translation. Targeted amino acid mutagenesis in Usp45sp, combined with additional silent mutations from the best clone in the initial screen, yielded an increase of up to 51% in maximum secretion of ?-amylase while maintaining secretion at lower induction levels. The best sequence from our screen preserves the tripartite structure of the native signal peptide but increases the positive charge of the n-region. Our study presents the first example of an engineered L. lactis signal peptide with a higher secretion yield than Usp45sp and, more generally, provides strategies for further enhancing protein secretion in bacterial hosts.

Ng, Daphne T. W.

2013-01-01

199

Characterization of Leuconostoc lactis strains from human sources.  

PubMed Central

An examination of 23 vancomycin-resistant, streptococcuslike isolates of clinical origin revealed a group of 14 to be related to Leuconostoc lactis (type strain, CIP 102422) on the basis of chemotaxonomic studies. These isolates were initially shown to be atypical by classical biochemical tests. However, they were characterized in particular by their polar lipid patterns by thin-layer chromatography and, additionally, by whole-cell protein patterns by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It is feasible, therefore, that common biochemical tests may continue to serve the purpose of routine identification, even though such isolates were formerly thought to be only of dairy origin. Images

Barreau, C; Wagener, G

1990-01-01

200

Use of carbon and energy balances in the study of the anaerobic metabolism of Enterobacter aerogenes at variable starting glucose concentrations  

Microsoft Academic Search

The anaerobic metabolism of Enterobacter aerogenes was studied in batch culture at increasing initial glucose levels (9.0So -1). The ultimate concentrations of fermentation products were utilized to check a metabolic flux analysis based on simple carbon mass and energy balances that promise to be suitable for the study of different fermentation processes, either under aerobic or anaerobic conditions. The stoichiometric

A. Converti; P. Perego

2002-01-01

201

Sequencing and Transcriptional Analysis of the Biosynthesis Gene Cluster of Putrescine-Producing Lactococcus lactis ? †  

PubMed Central

Lactococcus lactis is a prokaryotic microorganism with great importance as a culture starter and has become the model species among the lactic acid bacteria. The long and safe history of use of L. lactis in dairy fermentations has resulted in the classification of this species as GRAS (General Regarded As Safe) or QPS (Qualified Presumption of Safety). However, our group has identified several strains of L. lactis subsp. lactis and L. lactis subsp. cremoris that are able to produce putrescine from agmatine via the agmatine deiminase (AGDI) pathway. Putrescine is a biogenic amine that confers undesirable flavor characteristics and may even have toxic effects. The AGDI cluster of L. lactis is composed of a putative regulatory gene, aguR, followed by the genes (aguB, aguD, aguA, and aguC) encoding the catabolic enzymes. These genes are transcribed as an operon that is induced in the presence of agmatine. In some strains, an insertion (IS) element interrupts the transcription of the cluster, which results in a non-putrescine-producing phenotype. Based on this knowledge, a PCR-based test was developed in order to differentiate nonproducing L. lactis strains from those with a functional AGDI cluster. The analysis of the AGDI cluster and their flanking regions revealed that the capacity to produce putrescine via the AGDI pathway could be a specific characteristic that was lost during the adaptation to the milk environment by a process of reductive genome evolution.

Ladero, Victor; Rattray, Fergal P.; Mayo, Baltasar; Martin, Maria Cruz; Fernandez, Maria; Alvarez, Miguel A.

2011-01-01

202

Sequencing and transcriptional analysis of the biosynthesis gene cluster of putrescine-producing Lactococcus lactis.  

PubMed

Lactococcus lactis is a prokaryotic microorganism with great importance as a culture starter and has become the model species among the lactic acid bacteria. The long and safe history of use of L. lactis in dairy fermentations has resulted in the classification of this species as GRAS (General Regarded As Safe) or QPS (Qualified Presumption of Safety). However, our group has identified several strains of L. lactis subsp. lactis and L. lactis subsp. cremoris that are able to produce putrescine from agmatine via the agmatine deiminase (AGDI) pathway. Putrescine is a biogenic amine that confers undesirable flavor characteristics and may even have toxic effects. The AGDI cluster of L. lactis is composed of a putative regulatory gene, aguR, followed by the genes (aguB, aguD, aguA, and aguC) encoding the catabolic enzymes. These genes are transcribed as an operon that is induced in the presence of agmatine. In some strains, an insertion (IS) element interrupts the transcription of the cluster, which results in a non-putrescine-producing phenotype. Based on this knowledge, a PCR-based test was developed in order to differentiate nonproducing L. lactis strains from those with a functional AGDI cluster. The analysis of the AGDI cluster and their flanking regions revealed that the capacity to produce putrescine via the AGDI pathway could be a specific characteristic that was lost during the adaptation to the milk environment by a process of reductive genome evolution. PMID:21803900

Ladero, Victor; Rattray, Fergal P; Mayo, Baltasar; Martín, María Cruz; Fernández, María; Alvarez, Miguel A

2011-09-01

203

Cholate-Stimulated Biofilm Formation by Lactococcus lactis Cells ? †  

PubMed Central

Bile acid resistance by Lactococcus lactis depends on the ABC-type multidrug transporter LmrCD. Upon deletion of the lmrCD genes, cells can reacquire bile acid resistance upon prolonged exposure to cholate, yielding the ?lmrCDr strain. The resistance mechanism in this strain is non-transporter based. Instead, cells show a high tendency to flocculate, suggesting cell surface alterations. Contact angle measurements demonstrate that the ?lmrCDr cells are equipped with an increased cell surface hydrophilicity compared to those of the parental and wild-type strains, while the surface hydrophilicity is reduced in the presence of cholate. ?lmrCDr cells are poor in biofilm formation on a hydrophobic polystyrene surface, but in the presence of subinhibitory concentrations of cholate, biofilm formation is strongly stimulated. Biofilm cells show an enhanced extracellular polymeric substance production and are highly resistant to bile acids. These data suggest that non-transporter-based cholate resistance in L. lactis is due to alterations in the cell surface that stimulate cells to form resistant biofilms.

Zaidi, Arsalan Haseeb; Bakkes, Patrick J.; Krom, Bastiaan P.; van der Mei, Henny C.; Driessen, Arnold J. M.

2011-01-01

204

Functional Expression of an Orchid Fragrance Gene in Lactococcus lactis  

PubMed Central

Vanda Mimi Palmer (VMP), an orchid hybrid of Vanda tesselata and Vanda Tan Chay Yan is a highly scented tropical orchid which blooms all year round. Previous studies revealed that VMP produces a variety of isoprenoid volatiles during daylight. Isoprenoids are well known to contribute significantly to the scent of most fragrant plants. They are a large group of secondary metabolites which may possess valuable characteristics such as flavor, fragrance and toxicity and are produced via two pathways, the mevalonate (MVA) pathway or/and the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway. In this study, a sesquiterpene synthase gene denoted VMPSTS, previously isolated from a floral cDNA library of VMP was cloned and expressed in Lactococcus lactis to characterize the functionality of the protein. L. lactis, a food grade bacterium which utilizes the mevalonate pathway for isoprenoid production was found to be a suitable host for the characterization of plant terpene synthases. Through recombinant expression of VMPSTS, it was revealed that VMPSTS produced multiple sesquiterpenes and germacrene D dominates its profile.

Song, Adelene Ai Lian; Abdullah, Janna O.; Abdullah, Mohd Puad; Shafee, Norazizah; Rahim, Raha A.

2012-01-01

205

Prophage induction in Lactococcus lactis by the bacteriocin Lactococcin 972.  

PubMed

Lactococcin 972 (Lcn972) is a non-pore forming bacteriocin with a narrow spectrum of activity restricted to Lactococcus. Lcn972 inhibits the incorporation of cell wall precursors in the septum area, thereby inhibiting cell division. In this work, an additional inhibitory effect is described, namely, the induction of the lytic cycle of resident prophages in the lysogenic strain L. lactis IPLA 513. Lcn972 triggered the release of prophages in a concentration-dependent fashion. The extent of prophage induction was influenced by the physiological status of the cultures, being maximal at the early exponential growth phase. A microtiter based protocol was designed and the induction ability of several antimicrobials was compared. Prophages were activated by all cell wall biosynthesis inhibitors tested, although the levels of induction were lower than those obtained after activation of the SOS response. As far as we know, this is the first report of prophage induction by an antimicrobial peptide. Since Lcn972 is active against L. lactis strains currently used in commercial starters, promising applications for dairy fermentations are discussed. PMID:19056139

Madera, Carmen; García, Pilar; Rodríguez, Ana; Suárez, Juan E; Martínez, Beatriz

2009-01-31

206

Nutritional requirements and media development for Lactococcus lactis IL1403.  

PubMed

Lactic acid bacteria are extensively used in food technology and for the production of various compounds, but they are fastidious in nutrient requirements. In order to elucidate the role of each component precisely, defined multicomponent media are required. This study focuses on determining nutrient auxotrophies and minimizing media components (amino acids, vitamins, metal ions, buffers and additional compounds) for the cultivation of Lactococcus lactis subsp. lactis IL1403, using microtitre plates and test tubes. It was shown that glutamine and asparagine were the most important media components for achieving higher biomass yields while the branched-chain amino acids were necessary to increase specific growth rate. The amino acid and glucose ratio was reduced to achieve minimal residual concentration of amino acids in the medium after the growth of cells, whereas the specific growth rate and biomass yield of cells were not considerably affected. As the percentage of each consumed amino acid compared to initial amount is larger than measurement error, these optimized media are important for achieving more precise data about amino acid utilization and metabolism. PMID:24626960

Aller, Kadri; Adamberg, Kaarel; Timarova, Veronica; Seiman, Andrus; Feštšenko, Darja; Vilu, Raivo

2014-07-01

207

Decarboxylation of ?-Keto Acids by Streptococcus lactis var. maltigenes1  

PubMed Central

Decarboxylation rates for a series of C-3 to C-6 ?-keto acids were determined in the presence of resting cells and cell-free extracts of Streptococcus lactis var. maltigenes. The C-5 and C-6 acids branched at the penultimate carbon atom were converted most rapidly to the respective aldehydes in the manner described for ?-carboxylases. Pyruvate and ?-ketobutyrate did not behave as ?-carboxylase substrates, in that O2 was absorbed when they were reacted with resting cells. The same effect with pyruvate was noted in a nonmalty S. lactis, accounting for CO2 produced by some “homofermentative” streptococci. Mixed substrate reactions indicated that the same enzyme was responsible for decarboxylation of ?-ketoisocaproate and ?-ketoisovalerate, but it appeared unlikely that this enzyme was responsible for the decarboxylation of pyruvate. Ultrasonic disruption of cells of the malty culture resulted in an extract inactive for decarboxylation of pyruvate in the absence of ferricyanide. Dialyzed cell-free extracts were inactive against all keto acids and could not be reactivated.

Tucker, J. S.; Morgan, M. E.

1967-01-01

208

Dechlorination of 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane by Aerobacter aerogenes  

PubMed Central

Whole cells or cell-free extracts of Aerobacter aerogenes catalyze the degradation of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in vitro to at least seven metabolites: 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE); 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD); 1-chloro-2,2-bis(p-chlorophenyl)ethylene (DDMU); 1-chloro-2,2-bis(p-chlorophenyl)ethane (DDMS); unsym-bis(p-chlorophenyl)ethylene (DDNU); 2,2-bis(p-chlorophenyl)acetate (DDA); and 4,4?-dichlorobenzophenone (DBP). The use of metabolic inhibitors together with pH and temperature studies indicated that discrete enzymes are involved. By use of the technique of sequential analysis, the metabolic pathway was shown to be: DDT ? DDD ?DDMU ?DDMS ? DDNU ? DDA ? DBP, or DDT ? DDE. Dechlorination was marginally enhanced by light-activated flavin mononucleotide.

Wedemeyer, Gary

1967-01-01

209

Characterization of ESBL (SHV-12) producing clinical isolate of Enterobacter aerogenes from a tertiary care hospital in Nigeria  

PubMed Central

Background We studied the beta-lactamases of an E. aerogenes isolate recovered from the blood of a two-year-old patient. The isolate demonstrated a disk-diffusion phenotype typical for an AmpC-ESBL co-producer. Methods Microbiology studies were performed according to standard protocols. The resistance gene was identified by transconjugation and cloning experiments. Results By transconjugation only a narrow spectrum beta-lactamase (TEM-1) encoded on a small plasmid was transmitted. The ESBL was cloned and expressed in an E. coli host. Sequence analysis of the recombinant plasmid revealed blaSHV-12 associated to the insertion sequence, IS26. Conclusion This is the first study demonstrated the occurrence of SHV-12 in Nigeria.

2010-01-01

210

21 CFR 184.1985 - Aminopeptidase enzyme preparation derived from lactococcus lactis.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Aminopeptidase enzyme preparation derived from lactococcus...GRAS § 184.1985 Aminopeptidase enzyme preparation derived from lactococcus lactis. (a) Aminopeptidase enzyme preparation is derived from the...

2013-04-01

211

The Transcriptional and Gene Regulatory Network of Lactococcus lactis MG1363 during Growth in Milk  

PubMed Central

In the present study we examine the changes in the expression of genes of Lactococcus lactis subspecies cremoris MG1363 during growth in milk. To reveal which specific classes of genes (pathways, operons, regulons, COGs) are important, we performed a transcriptome time series experiment. Global analysis of gene expression over time showed that L. lactis adapted quickly to the environmental changes. Using upstream sequences of genes with correlated gene expression profiles, we uncovered a substantial number of putative DNA binding motifs that may be relevant for L. lactis fermentative growth in milk. All available novel and literature-derived data were integrated into network reconstruction building blocks, which were used to reconstruct and visualize the L. lactis gene regulatory network. This network enables easy mining in the chrono-transcriptomics data. A freely available website at http://milkts.molgenrug.nl gives full access to all transcriptome data, to the reconstructed network and to the individual network building blocks.

de Jong, Anne; Hansen, Morten E.; Kuipers, Oscar P.; Kilstrup, Mogens; Kok, Jan

2013-01-01

212

Heterologous Leaky Production of Transglutaminase in Lactococcus lactis Significantly Enhances the Growth Performance of the Host  

PubMed Central

This study describes a novel strategy to improve the growth performance of Lactococcus lactis by heterologous production of food-grade transglutaminase. The mtg gene from Streptoverticillium mobaraense that encodes the transglutaminase mature protein was cloned into a nisin-inducible expression vector and transformed into L. lactis subsp. cremoris NZ9000. The leaky expression of the mtg gene from the nisA promoter resulted in ammonia formation and carbon flux redistribution at the pyruvate branch. As a consequence, medium acidification was lessened and energy utilization was improved. This led to significantly higher biomass production under aerobic conditions and particularly under non-pH-controlled conditions (up to a 12-fold increase). The results presented here provide a novel way to enhance the growth yield of L. lactis, which is an important step for the purposes of producing proteins of commercial interest using L. lactis as a host.

Fu, Rui-Yan; Chen, Jian; Li, Yin

2005-01-01

213

Comparative genomics of Bifidobacterium animalis subsp. lactis reveals a strict monophyletic bifidobacterial taxon.  

PubMed

Strains of Bifidobacterium animalis subsp. lactis are extensively exploited by the food industry as health-promoting bacteria, although the genetic variability of members belonging to this taxon has so far not received much scientific attention. In this article, we describe the complete genetic makeup of the B. animalis subsp. lactis Bl12 genome and discuss the genetic relatedness of this strain with other sequenced strains belonging to this taxon. Moreover, a detailed comparative genomic analysis of B. animalis subsp. lactis genomes was performed, which revealed a closely related and isogenic nature of all currently available B. animalis subsp. lactis strains, thus strongly suggesting a closed pan-genome structure of this bacterial group. PMID:23645200

Milani, Christian; Duranti, Sabrina; Lugli, Gabriele Andrea; Bottacini, Francesca; Strati, Francesco; Arioli, Stefania; Foroni, Elena; Turroni, Francesca; van Sinderen, Douwe; Ventura, Marco

2013-07-01

214

Comparative Genomics of Bifidobacterium animalis subsp. lactis Reveals a Strict Monophyletic Bifidobacterial Taxon  

PubMed Central

Strains of Bifidobacterium animalis subsp. lactis are extensively exploited by the food industry as health-promoting bacteria, although the genetic variability of members belonging to this taxon has so far not received much scientific attention. In this article, we describe the complete genetic makeup of the B. animalis subsp. lactis Bl12 genome and discuss the genetic relatedness of this strain with other sequenced strains belonging to this taxon. Moreover, a detailed comparative genomic analysis of B. animalis subsp. lactis genomes was performed, which revealed a closely related and isogenic nature of all currently available B. animalis subsp. lactis strains, thus strongly suggesting a closed pan-genome structure of this bacterial group.

Milani, Christian; Duranti, Sabrina; Lugli, Gabriele Andrea; Bottacini, Francesca; Strati, Francesco; Arioli, Stefania; Foroni, Elena; Turroni, Francesca; van Sinderen, Douwe

2013-01-01

215

Development and application of oligonucleotide probes for identification of Lactococcus lactis subsp. cremoris.  

PubMed Central

Lactococcus lactis subsp. cremoris is of considerable interest to the dairy industry, which relies upon the few available strains for the manufacture of cheddar cheese free of fermented and fruity flavors. The subspecies cremoris differs from related subspecies by the lack of a few phenotypic traits. Our purpose was to identify unique rRNA sequences that could be used to discriminate L. lactis subsp. cremoris from related subspecies. The 16S rRNAs from 13 Lactococcus strains were partially sequenced by using reverse transcriptase to identify domains unique to L. lactis subsp. cremoris. All five strains of the subspecies cremoris had a unique base sequence in a hypervariable region located 70 to 100 bases from the 5' terminus. In this region, all L. lactis subsp. lactis biovar diacetylactis strains examined had a sequence identical to that of L. lactis subsp. lactis 7962, which was different from other strains of the subspecies lactis by only one nucleotide at position 90 (Escherichia coli 16S rRNA structural model) (J. Brosius, J. L. Palmer, J. P. Kennedy, and H. F. Noller, Proc. Natl. Acad. Sci. USA 75:4801-4805, 1978). Oligonucleotide probes specific for the genus Lactococcus (212RLa) and for the subspecies cremoris (68RCa) were synthesized and evaluated by hybridization to known rRNAs as well as fixed whole cells. Efficient and specific hybridization to the genus-specific probe was observed for the 13 Lactococcus strains tested. No hybridization was seen with the control species. All five strains of the subspecies cremoris hybridized to the subspecies-specific probe. Images

Salama, M; Sandine, W; Giovannoni, S

1991-01-01

216

Oral immunization with recombinant Lactococcus lactis confers protection against respiratory pneumococcal infection.  

PubMed

In the present work, we evaluated if oral immunization with the pneumococcal protective protein A (PppA), expressed in the cell wall of Lactococcus lactis (L. lactis PppA+), was able to confer protective immunity against Streptococcus pneumoniae. Mice were immunized orally with L. lactis PppA+ for 5 consecutive days. Vaccination was performed one (nonboosted group) or 2 times with a 2 week interval between each immunization (boosted group). Oral priming with L. lactis PppA+ induced the production of anti-PppA IgM, IgG, and IgA antibodies in serum and in bronchoalveolar (BAL) and intestinal (IF) lavage fluids. Boosting with L. lactis PppA+ increased the levels of mucosal and systemic immunoglobulins. Moreover, the avidity and the opsonophagocytic activity of anti-PppA antibodies were significantly improved in the boosted group. The presence of both IgG1 and IgG2a anti-PppA antibodies in serum and BAL and the production of both interferon gamma and interleukin-4 by spleen cells from immunized mice indicated that L. lactis PppA+ stimulated a mixture of Th1 and Th2 responses. The ability of L. lactis PppA+ to confer cross-protective immunity was evaluated using challenge assays with serotypes 3, 6B, 14, and 23F. Lung bacterial cell counts and hemocultures showed that immunization with L. lactis PppA+ improved resistance against all the serotypes assessed, including serotype 3, which was highly virulent in our experimental animal model. To our knowledge, this is the first demonstration of protection against respiratory pneumococcal infection induced by oral administration of a recombinant lactococcal vaccine. PMID:18923553

Villena, Julio; Medina, Marcela; Raya, Raúl; Alvarez, Susana

2008-10-01

217

Effect of X-Prolyl Dipeptidyl Aminopeptidase Deficiency on Lactococcus lactis  

PubMed Central

The genetic determinant (pepXP) of an X-prolyl dipeptidyl aminopeptidase (PepXP) has recently been cloned and sequenced from both Lactococcus lactis subsp. cremoris (B. Mayo, J. Kok, K. Venema, W. Bockelmann, M. Teuber, H. Reinke, and G. Venema, Appl. Environ. Microbiol. 57:38-44, 1991) and L. lactis subsp. lactis (M. Nardi, M.-C. Chopin, A. Chopin, M.-M. Cals, and J.-C. Gripon, Appl. Environ. Microbiol. 57:45-50, 1991). To examine the possible role of the enzyme in the breakdown of caseins required for lactococci to grow in milk, integration vectors have been constructed and used to specifically inactivate the pepXP gene. After inactivation of the gene in L. lactis subsp. lactis MG1363, which is Lac- and Prt-, the Lac+ Prt+ determinants were transferred by conjugation by using L. lactis subsp. lactis 712 as the donor. Since growth of the transconjugants relative to the PepXP+ strains was not retarded in milk, it was concluded that PepXP is not essential for growth in that medium. It was also demonstrated that the open reading frame ORF1, upstream of pepXP, was not required for PepXP activity in L. lactis. A marked difference between metenkephalin degradation patterns was observed after incubation of this pentapeptide with cell extracts obtained from wild-type lactococci and pepXP mutants. Therefore, altered expression of the pepXP-encoded general dipeptidyl aminopeptidase activity may change the peptide composition of fermented milk products. Images

Mayo, Baltasar; Kok, Jan; Bockelmann, Wilhelm; Haandrikman, Alfred; Leenhouts, Kees J.; Venema, Gerard

1993-01-01

218

Protein Kinases Involved in Mating and Osmotic Stress in the Yeast Kluyveromyces lactis  

Microsoft Academic Search

Systematic disruption of genes encoding kinases and mitogen-activated protein kinases (MAPKs) was performed in Kluyveromyces lactis haploid cells. The mutated strains were assayed by their capacity to mate and to respond to hyperosmotic stress. The K. lactis Ste11p (KlSte11p) MAPK kinase kinase (MAPKKK) was found to act in both mating and osmoresponse pathways while the scaffold KlSte5p and the MAPK

Laura Kawasaki; Marõ ´ a Castaneda-Bueno; Edith Sanchez-Paredes; Nancy Velazquez-Zavala; Francisco Torres-Quiroz; Laura Ongay-Larios; Roberto Coria

2008-01-01

219

Inactivation of the ybdD Gene in Lactococcus lactis Increases the Amounts of Exported Proteins  

PubMed Central

Random insertional mutagenesis performed on a Lactococcus lactis reporter strain led us to identify L. lactis ybdD as a protein-overproducing mutant. In different expression contexts, the ybdD mutant shows increased levels of exported proteins and therefore constitutes a new and attractive heterologous protein production host. This study also highlights the importance of unknown regulatory processes that play a role during protein secretion.

Morello, E.; Nouaille, S.; Cortes-Perez, N. G.; Blugeon, S.; Medina, L. F. C.; Azevedo, V.; Gratadoux, J. J.; Bermudez-Humaran, L. G.; Le Loir, Y.

2012-01-01

220

Lactose metabolism in Streptococcus lactis: studies with a mutant lacking glucokinase and mannose-phosphotransferase activities.  

PubMed

A mutant of Streptococcus lactis 133 has been isolated that lacks both glucokinase and phosphoenolpyruvate-dependent mannose-phosphotransferase (mannose-PTS) activities. The double mutant S. lactis 133 mannose-PTSd GK- is unable to utilize either exogenously supplied or intracellularly generated glucose for growth. Fluorographic analyses of metabolites formed during the metabolism of [14C]lactose labeled specifically in the glucose or galactosyl moiety established that the cells were unable to phosphorylate intracellular glucose. However, cells of S. lactis 133 mannose-PTSd GK- readily metabolized intracellular glucose 6-phosphate, and the growth rates and cell yield of the mutant and parental strains on sucrose were the same. During growth on lactose, S. lactis 133 mannose-PTSd GK- fermented only the galactose moiety of the disaccharide, and 1 mol of glucose was generated per mol of lactose consumed. For an equivalent concentration of lactose, the cell yield of the mutant was 50% that of the wild type. The specific rate of lactose utilization by growing cells of S. lactis 133 mannose-PTSd GK- was ca. 50% greater than that of the wild type, but the cell doubling times were 70 and 47 min, respectively. High-resolution 31P nuclear magnetic resonance studies of lactose transport by starved cells of S. lactis 133 and S. lactis 133 mannose-PTSd GK- showed that the latter cells contained elevated lactose-PTS activity. Throughout exponential growth on lactose, the mutant maintained an intracellular steady-state glucose concentration of 100 mM. We conclude from our data that phosphorylation of glucose by S. lactis 133 can be mediated by only two mechanisms: (i) via ATP-dependent glucokinase, and (ii) by the phosphoenolpyruvate-dependent mannose-PTS system. PMID:3920203

Thompson, J; Chassy, B M; Egan, W

1985-04-01

221

Autolysis of Lactococcus lactis Is Increased upon D-Alanine Depletion of Peptidoglycan and Lipoteichoic Acids  

Microsoft Academic Search

Mutations in the genes encoding enzymes responsible for the incorporation of D-Ala into the cell wall of Lactococcus lactis affect autolysis. An L. lactis alanine racemase (alr) mutant is strictly dependent on an external supply of D-Ala to be able to synthesize peptidoglycan and to incorporate D-Ala in the lipoteichoic acids (LTA). The mutant lyses rapidly when D-Ala is removed

Anton Steen; Emmanuelle Palumbo; Marie Deghorain; Pier Sandro Cocconcelli; Jean Delcour; Oscar P. Kuipers; Jan Kok; Girbe Buist; Pascal Hols

2005-01-01

222

The Kluyveromyces lactis CPY homologous genes — Cloning and characterization of the KlPCL1 gene  

Microsoft Academic Search

A 3.85-kb genomic fragment containing the KlPCL1 gene, with an open reading frame (ORF) of 1359 bp, was isolated from Kluyveromyces lactis genomic library by heterologous colony hybridization using the Saccharomyces cerevisiae PRC1 (ScPRC1) gene as a probe. The KlPCL1 nucleotide sequence was identical to the KLLAOC17490g ORF of K. lactis and showed >55 % identity with S. cerevisiae YBR139w

D. Staneva; D. Uccelletti; P. Venkov; G. Miloshev; C. Palleschi

2008-01-01

223

Genetic Evidence for a Defective Xylan Degradation Pathway in Lactococcus lactis  

PubMed Central

Genetic and biochemical evidence for a defective xylan degradation pathway was found linked to the xylose operon in three lactococcal strains, Lactococcus lactis 210, L. lactis IO-1, and L. lactis NRRL B-4449. Immediately downstream of the xylulose kinase gene (xylB) (K. A. Erlandson, J.-H. Park, W. El Khal, H.-H. Kao, P. Basaran, S. Brydges, and C. A. Batt, Appl. Environ. Microbiol. 66:3974–3980, 1999) are two open reading frames encoding a mutarotase (xylM) and a xyloside transporter (xynT) and a partial open reading frame encoding a ?-xylosidase (xynB). These are functions previously unreported for lactococci or lactobacilli. The mutarotase activity of the putative xylM gene product was confirmed by overexpression of the L. lactis enzyme in Escherichia coli and purification of recombinant XylM. We hypothesize that the mutarotase links xylan degradation to xylose metabolism due to the anomeric preference of xylose isomerase. In addition, Northern hybridization experiments suggested that the xylM and xynTB genes are cotranscribed with the xylRAB genes, responsible for xylose metabolism. Although none of the three strains appeared to metabolize xylan or xylobiose, they exhibited xylosidase activity, and L. lactis IO-1 and L. lactis NRRL B-4449 had functional mutarotases.

Erlandson, Karn A.; Delamarre, Soazig C.; Batt, Carl A.

2001-01-01

224

Fate and efficacy of lacticin 3147-producing Lactococcus lactis in the mammalian gastrointestinal tract.  

PubMed

Gastrointestinal survival of the bacteriocin-producing strain, Lactococcus lactis DPC6520, was evaluated systematically in vitro and in vivo with a view to using this strain to deliver biologically active lacticin 3147, a broad-spectrum bacteriocin, to the gut. The activity of the lacticin 3147 producer was also evaluated against two clinically relevant pathogens: Clostridium difficile and Listeria monocytogenes. When suspended in an appropriate matrix, the lactococcal strain is capable of surviving simulated gastrointestinal juices similar to the porcine probiotic, Lactobacillus salivarius DPC6005. Upon administration of L. lactis DPC6520 to pigs (n=4), excretion rates of ?10(2) -10(5) CFU g(-1) faeces were observed by day 5. Although passage through the gastrointestinal tract (GIT) did not affect lacticin 3147 production by L. lactis DPC6520 isolates, activity was undetectable in faecal samples by an agar well diffusion assay. Furthermore, L. lactis DPC6520 had no inhibitory effect on C. difficile or other bacterial populations in a human distal colon model, while lactococcal counts declined 10,000-fold over 24 h. The lacticin 3147 producer failed to prevent L. monocytogenes infection in a mouse model, even though a mean L. lactis DPC6520 count of 4.7 × 10(4) CFU g(-1) faeces was obtained over the 5-day administration period. These data demonstrate that L. lactis DPC6520 is capable of surviving transit through the GIT, and yet lacks antimicrobial efficacy in the models of infection used. PMID:21314706

Dobson, Alleson; Crispie, Fiona; Rea, Mary C; O'Sullivan, Orla; Casey, Pat G; Lawlor, Peadar G; Cotter, Paul D; Ross, Paul; Gardiner, Gillian E; Hill, Colin

2011-06-01

225

Variations in bile tolerance among Lactococcus lactis strains derived from different sources.  

PubMed

Lactococcus lactis subsp. lactis has been isolated from the intestines of marine fish and is a candidate probiotic for aquaculture. In order to use the bacterium as a probiotic, properties such as bile tolerance need to be assessed. Here, we compared bile tolerance in L. lactis strains derived from different sources. Three L. lactis subsp. lactis strains from marine fish (MFL), freshwater fish (FFL), and cheese starter (CSL) were used along with an Lactococcus lactis subsp. cremoris strain from cheese starter (CSC). The four strains were grown under various culture conditions: deMan-Rogosa-Sharpe (MRS) broth containing bile salts/acids, MRS agar containing oxgall, and phosphate-buffered saline (PBS) containing fish bile. Survival/growth of the strains in the presence of sodium cholate and sodium deoxycholate varied in the order MFL, CSL > CSC > FFL; in the presence of sodium taurocholate, the order was MFL > CSL > CSC > FFL. In liquid media containing various concentrations of oxgall, survival of the strains was observed in the order MFL > CSL > FFL and CSC. The survival of MFL was not affected by bile collected from the goldfish (Carassius auratus subsp. auratus) or the puffer fish (Takifugu niphobles), although the other strains showed significant inhibition of growth. It is a novel and beneficial finding that MFL has the highest resistance to bile acid. PMID:24395331

Takanashi, Shihori; Miura, Ai; Abe, Koko; Uchida, Junya; Itoi, Shiro; Sugita, Haruo

2014-07-01

226

Nasal Immunization with Lactococcus lactis Expressing the Pneumococcal Protective Protein A Induces Protective Immunity in Mice?  

PubMed Central

Nisin-controlled gene expression was used to develop a recombinant strain of Lactococcus lactis that is able to express the pneumococcal protective protein A (PppA) on its surface. Immunodetection assays confirmed that after the induction with nisin, the PppA antigen was predictably and efficiently displayed on the cell surface of the recombinant strain, which was termed L. lactis PppA. The production of mucosal and systemically specific antibodies in adult and young mice was evaluated after mice were nasally immunized with L. lactis PppA. Immunoglobulin M (IgM), IgG, and IgA anti-PppA antibodies were detected in the serum and bronchoalveolar lavage fluid of adult and young mice, which showed that PppA expressed in L. lactis was able to induce a strong mucosal and systemic immune response. Challenge survival experiments demonstrated that immunization with L. lactis PppA was able to increase resistance to systemic and respiratory infection with different pneumococcal serotypes, and passive immunization assays of naïve young mice demonstrated a direct correlation between anti-PppA antibodies and protection. The results presented in this study demonstrate three major characteristics of the effectiveness of nasal immunization with PppA expressed as a protein anchored to the cell wall of L. lactis: it elicited cross-protective immunity against different pneumococcal serotypes, it afforded protection against both systemic and respiratory challenges, and it induced protective immunity in mice of different ages.

Medina, Marcela; Villena, Julio; Vintini, Elisa; Hebert, Elvira Maria; Raya, Raul; Alvarez, Susana

2008-01-01

227

Comparative In Vitro Activities of Ciprofloxacin, Clinafloxacin, Gatifloxacin, Levofloxacin, Moxifloxacin, and Trovafloxacin against Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, and Enterobacter aerogenes Clinical Isolates with Alterations in GyrA and ParC Proteins  

Microsoft Academic Search

The in vitro activities of ciprofloxacin, clinafloxacin, gatifloxacin, levofloxacin, moxifloxacin, and trovafloxa- cin were tested against 72 ciprofloxacin-resistant and 28 ciprofloxacin-susceptible isolates of Klebsiella pneu- moniae, Klebsiella oxytoca, Enterobacter cloacae, and Enterobacter aerogenes. Irrespective of the alterations in GyrA and ParC proteins, clinafloxacin exhibited greater activity than all other fluoroquinolones tested against K. pneumoniae and E. aerogenes.

SYLVAIN BRISSE; DANA MILATOVIC; AD C. FLUIT; JAN VERHOEF; NELE MARTIN; SYBILLE SCHEURING; KARL KOHRER; FRANZ-JOSEF SCHMITZ

1999-01-01

228

Comparison of sequences from the malB regions of Salmonella typhimurium and Enterobacter aerogenes with Escherichia coli K12: A potential new regulatory site in the interoperonic region  

Microsoft Academic Search

The malE and malK genes from Salmonella typhimurium, and the MalEFG operon and a portion of malK from Enterobacter aerogenes were cloned and sequenced. Plasmid-borne malE genes from both species and the malF and malG genes from E. aerogenes were expressed normally in Escherichia coli, and their products function in maltose transport. This shows that the malB products from the

Michael K. Dahl; Eric Francoz; William Saurin; Winfried Boos; Michael D. Manson; Maurice Hofnung

1989-01-01

229

Multiple Transcriptional Control of the Lactococcus lactis trp Operon  

PubMed Central

The Lactococcus lactis trpEGDCFBA operon is preceded by a noncoding leader region. Transcriptional studies of the trp operon revealed three transcripts with respective sizes of 8 kb (encompassing the entire operon), 290 bases, and 160 bases (corresponding to parts of the leader region). These transcripts most likely result from initiation at the unique Ptrp promoter, transcription termination at either T1 (upstream of the trp operon) or T2 (downstream of the trp operon), and/or processing. Three parameters were shown to differentially affect the amount of these transcripts: (i) following tryptophan depletion, the amount of the 8-kb transcript increases 300- to 500-fold; (ii) depletion in any amino acid increased transcription initiation about fourfold; and (iii) upon entry into stationary phase the amount of the 8-kb transcript decreases abruptly. The tryptophan-dependent transcription control is exerted through transcription antitermination.

Raya, Raul; Bardowski, Jacek; Andersen, Paal S.; Ehrlich, S. Dusko; Chopin, Alain

1998-01-01

230

Combinational variation of restriction modification specificities in Lactococcus lactis.  

PubMed

Three genes coding for a type I R-M system related to the class C enzymes have been identified on the chromosome of Lactococcus lactis strain IL1403. In addition, plasmids were found that encode only the HsdS subunit that directs R-M specificity. The presence of these plasmids in IL1403 conferred a new R-M phenotype on the host, indicating that the plasmid-encoded HsdS is able to interact with the chromosomally encoded HsdR and HsdM subunits. Such combinational variation of type I R-M systems may facilitate the evolution of their specificity and thus reinforce bacterial resistance against invasive foreign unmethylated DNA. PMID:9593305

Schouler, C; Gautier, M; Ehrlich, S D; Chopin, M C

1998-04-01

231

Genome shuffling of Lactococcus lactis subspecies lactis YF11 for improving nisin Z production and comparative analysis.  

PubMed

Nisin has been widely used in the food industry as a safe and natural preservative to increase the shelf time of many foods. In this study, genome shuffling was applied to improve nisin Z production of Lactococcus lactis ssp. lactis YF11 (YF11) via recursive protoplast fusion. Ultraviolet irradiation and diethyl sulfate mutagenesis were used to generate parental strains for genome shuffling. After 4 rounds of genome shuffling, the best-performing strain F44 was obtained, which showed dramatic improvements in tolerance to both glucose (ranging from 8 to 15% (wt/vol) and nisin (ranging from 5,000 to 14,000IU/mL). Fed-batch fermentation showed that the nisin titer of F44 was up to 4,023IU/mL, which was 2.4 times that of the starting strain YF11. Field emission scanning electron microscope micrographs of YF11 and F44 revealed the apparent differences in cell morphology. Whereas YF11 displayed long and thin cell morphology, F44 cells were short and thick and with a raised surface in the middle of the cell. With the increasing glucose and nisin content in the medium, cells of both YF11 and F44 tended to become shrunken; however, alterations in YF11 cells were more pronounced than those of F44 cells, especially when cultured in tolerance medium containing both nisin and glucose. Nuclear magnetic resonance analysis demonstrated that the structure of nisin from YF11 and F44 was the same. Expression profiling of nisin synthesis related genes by real-time quantitative PCR showed that the transcription level of nisin structural gene nisZ and immunity gene nisI of F44 was 48 and 130% higher than that of the starting strain YF11, respectively. These results could provide valuable insights into the molecular basis underlying the nisin overproduction mechanism in L. lactis, thus facilitating the future construction of industrial strains for nisin production. PMID:24612797

Zhang, Y F; Liu, S Y; Du, Y H; Feng, W J; Liu, J H; Qiao, J J

2014-05-01

232

Phage abortive infection mechanism from Lactococcus lactis subsp. lactis, expression of which is mediated by an Iso-ISS1 element.  

PubMed Central

A 5-kb DNA fragment conferring a phage abortive infection phenotype (Abi+) has been cloned from Lactococcus lactis subsp. lactis IL416. The Abi+ determinant was subcloned on a 2-kb fragment which carried an Iso-ISS1 element and an open reading frame of 753 bp designated ORFX. Deletion within ORFX entailed the loss of the Abi+ phenotype, establishing that ORFX is the structural abi-416 gene. The expression of abi-416 was shown to be mediated by the Iso-ISS1 element, which contains a sequence fitting the consensus sequence for gram-positive promoters. Images

Cluzel, P J; Chopin, A; Ehrlich, S D; Chopin, M C

1991-01-01

233

Coexistence of SHV-4- and TEM24-Producing Enterobacter aerogenes Strains before a Large Outbreak of TEM24-Producing Strains in a French Hospital  

Microsoft Academic Search

In 1996, a monitoring program was initiated at the teaching hospital of Amiens, France, and carried out for 3 years. All extended-spectrum b-lactamase (ESBL)-producing Enterobacter aerogenes isolates recovered from clinical specimens were collected for investigation of their epidemiological relatedness by pulsed-field gel electrophoresis and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and determination of the type of ESBL harbored by isoelectric

H. Mammeri; G. Laurans; M. Eveillard; S. Castelain; F. Eb

2001-01-01

234

Effect of pH and acetic acid on growth and 2,3-butanediol production of Enterobacter aerogenes in continuous culture  

Microsoft Academic Search

The effect of pH and acetic acid on growth and 2,3-butanediol production of Enterobacter aerogenes from glucose was investigated in a microaerobic continuous culture. At a dilution rate of 0.20 h-1 and a fixed oxygen uptake rate (OUR) of 31.5 mmol l-1 h-1 the biomass concentration increased with pH ranging from 5.0 to 7.0, while the specific ATP requirement of

An-Ping Zeng; Hanno Biebl; Wolf-Dieter Deckwer

1990-01-01

235

Hydrogen production with high yield and high evolution rate by self-flocculated cells of Enterobacter aerogenes in a packed-bed reactor  

Microsoft Academic Search

Continuous hydrogen gas evolution by self-flocculated cells of Enterobacter aerogenes, a natural isolate HU-101 and its mutant AY-2, was performed in a packed-bed reactor under glucose-limiting conditions in\\u000a a minimal medium. The flocs that formed during the continuous culture were retained even when the dilution rate was increased\\u000a to 0.9?h?1. The H2 production rate increased linearly with increases in the

M. A. Rachman; Y. Nakashimada; T. Kakizono; N. Nishio

1998-01-01

236

Treatment of a meningitis due to an Enterobacter aerogenes producing a derepressed cephalosporinase and a klebsiella pneumoniae producing an extended-spectrum ?-lactamase  

Microsoft Academic Search

Summary A case of nosocomial meningitis due to aKlebsiella pneumoniae producing a CAZ-5 extendedspectrum ß-lactamase and anEnterobacter aerogenes producing a derepressed cephalosporinase is reported. The intrathecal catheter incriminated was removed and a treatment with ceftazidime (4 g\\/24 h) and amikacin (1.5 g\\/24 h) was started. After 24 h ceftazidime was replaced by imipenem (2 then 4 g\\/24 h). This treatment

C. de Champs; D. Sirot; M. Chanal; J. Sirot; D. Guelon; D. Joyon

1991-01-01

237

Short-chain organic acids produced on glucose, lactose, and citrate media by Enterococcus faecalis, Lactobacillus casei, and Enterobacter aerogenes strains  

Microsoft Academic Search

Three strains of Enterococcus faecalis, three of Lactobacillus casei and two of Enterobacter aerogenes, isolated from commercial Palmita-type cheese were cultured in peptone-yeast extract broth with glucose (PYG), lactose (PYL), or citrate (PYC) added as the main carbon sources. The short-chain volatile and non-volatile organic acids were extracted and their concentration determined by GC with a FID detector. The identity

D. Urdaneta; D. Raffe; A. Ferrer; B. Sulbarán de Ferrer; L. Cabrera; M. Pérez

1995-01-01

238

Reactor comparison and scale-up for the microaerobic production of 2,3-butanediol by Enterobacter aerogenes at constant oxygen transfer rate  

Microsoft Academic Search

Stirred tank (STR), bubble column (BCR) and airlift (ALR) bioreactors of 0.05 and 1.5 m3 total volume were compared for the production of 2,3-butanediol using Enterobacter aerogenes under microaerobic conditions. Batch fermentations were carried out at constant oxygen transfer rate (OTR=35 mmol\\/lh). At 0.05 m3 scale, the STR reactor achieved much higher biomass and product concentrations than the BCR and

T.-G. Byun; A.-P. Zeng; W.-D. Deckwer

1994-01-01

239

Bioproduction of a novel sugar 1-deoxy- l-fructose by Enterobacter aerogenes IK7; isomerization of a 6-deoxyhexose to a 1-deoxyhexose  

Microsoft Academic Search

1-Deoxy-l-fructose, a very rare monosaccharide, was produced by hydrogenation of 6-deoxy-l-mannose (l-rhamnose)—the only cheaply available deoxy sugar—to 1-deoxy-l-mannitol (l-rhamnitol) followed by oxidation with Enterobacter aerogenes IK7. The entire procedure was conducted in water and shows the power of green environmentally friendly chemistry combined with biotechnology in the preparation of new monosaccharides with potential for novel bioactive properties or alternative foodstuffs;

Pushpakiran Gullapalli; Takayuki Shiji; Devendar Rao; Akihide Yoshihara; Kenji Morimoto; Goro Takata; George W. J. Fleet; Ken Izumori

2007-01-01

240

Carbapenem Resistance in a Clinical Isolate of Enterobacter aerogenes Is Associated with Decreased Expression of OmpF and OmpC Porin Analogs  

Microsoft Academic Search

We investigated the mechanism of imipenem resistance in Enterobacter aerogenes strain 810, a clinical isolate from the United States for which the imipenem MIC was 16 g\\/ml and the meropenem MIC was 8 g\\/ml. An imipenem-susceptible revertant, strain 810-REV, was obtained after multiple passages of the strain on non- selective media. For the revertant, the imipenem MIC was <1 g\\/ml

Hesna Yigit; Gregory J. Anderson; James W. Biddle; Christine D. Steward; J. Kamile Rasheed; Lourdes L. Valera; John E. McGowan; F. C. Tenover

2002-01-01

241

Interaction between the genomes of Lactococcus lactis and phages of the P335 species  

PubMed Central

Phages of the P335 species infect Lactococcus lactis and have been particularly studied because of their association with strains of L. lactis subsp. cremoris used as dairy starter cultures. Unlike other lactococcal phages, those of the P335 species may have a temperate or lytic lifestyle, and are believed to originate from the starter cultures themselves. We have sequenced the genome of L. lactis subsp. cremoris KW2 isolated from fermented corn and found that it contains an integrated P335 species prophage. This 41 kb prophage (? KW2) has a mosaic structure with functional modules that are highly similar to several other phages of the P335 species associated with dairy starter cultures. Comparison of the genomes of 26 phages of the P335 species, with either a lytic or temperate lifestyle, shows that they can be divided into three groups and that the morphogenesis gene region is the most conserved. Analysis of these phage genomes in conjunction with the genomes of several L. lactis strains shows that prophage insertion is site specific and occurs at seven different chromosomal locations. Exactly how induced or lytic phages of the P335 species interact with carbohydrate cell surface receptors in the host cell envelope remains to be determined. Genes for the biosynthesis of a variable cell surface polysaccharide and for lipoteichoic acids (LTAs) are found in L. lactis and are the main candidates for phage receptors, as the genes for other cell surface carbohydrates have been lost from dairy starter strains. Overall, phages of the P335 species appear to have had only a minor role in the adaptation of L. lactis subsp. cremoris strains to the dairy environment, and instead they appear to be an integral part of the L. lactis chromosome. There remains a great deal to be discovered about their role, and their contribution to the evolution of the bacterial genome.

Kelly, William J.; Altermann, Eric; Lambie, Suzanne C.; Leahy, Sinead C.

2013-01-01

242

Lactose metabolism in Streptococcus lactis: studies with a mutant lacking glucokinase and mannose-phosphotransferase activities  

SciTech Connect

A mutant of Streptococcus lactis 133 has been isolated that lacks both glucokinase and phosphoenolpyruvate-dependent mannose- phosphotransferase (mannose-PTS) activities. The double mutant S. lactis 133 mannose-PTSd GK- is unable to utilize either exogenously supplied or intracellularly generated glucose for growth. Fluorographic analyses of metabolites formed during the metabolism of (/sup 14/C)lactose labeled specifically in the glucose or galactosyl moiety established that the cells were unable to phosphorylate intracellular glucose. However, cells of S. lactis 133 mannose-PTSd GK- readily metabolized intracellular glucose 6-phosphate, and the growth rates and cell yield of the mutant and parental strains on sucrose were the same. During growth on lactose, S. lactis 133 mannose-PTSd GK- fermented only the galactose moiety of the disaccharide, and 1 mol of glucose was generated per mol of lactose consumed. For an equivalent concentration of lactose, the cell yield of the mutant was 50% that of the wild type. The specific rate of lactose utilization by growing cells of S. lactis 133 mannose-PTSd GK- was ca. 50% greater than that of the wild type, but the cell doubling times were 70 and 47 min, respectively. High-resolution /sup 31/P nuclear magnetic resonance studies of lactose transport by starved cells of S. lactis 133 and S. lactis 133 mannose-PTSd GK- showed that the latter cells contained elevated lactose-PTS activity. Throughout exponential growth on lactose, the mutant maintained an intracellular steady-state glucose concentration of 100 mM.

Thompson, J.; Chassy, B.M.; Egan, W.

1985-04-01

243

Synbiotic intervention of Bifidobacterium lactis and resistant starch protects against colorectal cancer development in rats.  

PubMed

This study evaluated the effect of a probiotic bacteria 'Bifidobacterium lactis', the carbohydrate 'resistant starch' (RS) and their combination (synbiotic), on their ability to protect against colorectal cancer (CRC). Bifidobacterium lactis has been shown previously to utilize RS as a substrate and up-regulate the acute apoptotic response to a carcinogen in the colon [Le Leu et al. (2005) J. Nutr., 135, 996-1001]. Sprague-Dawley rats were divided into six equal groups and fed semi-purified diets for 30 weeks. Colonic neoplasms were induced by 2 weekly injections of azoxymethane (15 mg/kg body wt). The experimental groups were as follows: control-no added dietary fibre or RS; RS in two forms-Hi-maize 958 or Hi-maize 260; B.lactis (lyophilized)-added to control and RS diets (six treatment groups in all). Rats fed RS in combination with B.lactis showed significantly lowered incidence and multiplicity of colonic neoplasms (P < 0.01) by >50% compared with the control group. There was a trend for protection by RS alone (P = 0.07), whereas no protection against cancer was seen in the group supplemented with only B.lactis. Fermentation events [short-chain fatty acid (SCFA), pH] were altered by the inclusion of RS into the diet, whereas the inclusion of B.lactis into the diet had no significant effect on the fermentation parameters. The synbiotic combination of RS and B.lactis significantly protects against the development of CRC in the rat-azoxymethane model. Synbiotic combination of prebiotic and probiotic seems likely to be a superior preventive strategy to prebiotic alone. PMID:19696163

Le Leu, Richard K; Hu, Ying; Brown, Ian L; Woodman, Richard J; Young, Graeme P

2010-02-01

244

Interaction between the genomes of Lactococcus lactis and phages of the P335 species.  

PubMed

Phages of the P335 species infect Lactococcus lactis and have been particularly studied because of their association with strains of L. lactis subsp. cremoris used as dairy starter cultures. Unlike other lactococcal phages, those of the P335 species may have a temperate or lytic lifestyle, and are believed to originate from the starter cultures themselves. We have sequenced the genome of L. lactis subsp. cremoris KW2 isolated from fermented corn and found that it contains an integrated P335 species prophage. This 41 kb prophage (? KW2) has a mosaic structure with functional modules that are highly similar to several other phages of the P335 species associated with dairy starter cultures. Comparison of the genomes of 26 phages of the P335 species, with either a lytic or temperate lifestyle, shows that they can be divided into three groups and that the morphogenesis gene region is the most conserved. Analysis of these phage genomes in conjunction with the genomes of several L. lactis strains shows that prophage insertion is site specific and occurs at seven different chromosomal locations. Exactly how induced or lytic phages of the P335 species interact with carbohydrate cell surface receptors in the host cell envelope remains to be determined. Genes for the biosynthesis of a variable cell surface polysaccharide and for lipoteichoic acids (LTAs) are found in L. lactis and are the main candidates for phage receptors, as the genes for other cell surface carbohydrates have been lost from dairy starter strains. Overall, phages of the P335 species appear to have had only a minor role in the adaptation of L. lactis subsp. cremoris strains to the dairy environment, and instead they appear to be an integral part of the L. lactis chromosome. There remains a great deal to be discovered about their role, and their contribution to the evolution of the bacterial genome. PMID:24009606

Kelly, William J; Altermann, Eric; Lambie, Suzanne C; Leahy, Sinead C

2013-01-01

245

Integrated evaluation of aerogenic pollution by air-transported heavy metals (Pb, Cd, Ni, Zn, Mn and Cu) in the analysis of the main deposit media.  

PubMed

The composition of the ambient air is constantly changing; therefore, the monitoring of ambient air quality to detect the changes caused by aerogenic pollutants makes the essential part of general environmental monitoring. To achieve more effective improvement of the ambient air quality, the Directive 2008/50/EC on 'Ambient Air Quality and Cleaner Air for Europe' was adopted by the European Parliament and the European Council. It informed the public and enterprises about a negative effect of pollution on humans, animals and plants, as well as about the need for monitoring aerogenic pollutants not only at the continuous monitoring stations but also by using indicator methods, i.e. by analysing natural deposit media. The problem of determining the relationship between the accumulation level of pollutants by a deposit medium and the level of air pollution and its risks is constantly growing in importance. The paper presents a comprehensive analysis of the response of the main four deposit media, i.e. snow cover, soil, pine bark and epigeic mosses, to the long-term pollution by aerogenic pollutants which can be observed in the area of oil refinery influence. Based on the quantitative expressions of the amounts of the accumulated pollutants in the deposit media, the territory of the oil refinery investigated in this paper has been referred to the areas of mild or moderate pollution. PMID:23933956

Baltr?nait?, Edita; Baltr?nas, Pranas; Lietuvninkas, Arvydas; Serevi?ien?, Vaida; Zuokait?, Egl?

2014-01-01

246

Characterization of plasmid-encoded citrate permease (citP) genes from Leuconostoc species reveals high sequence conservation with the Lactococcus lactis citP gene.  

PubMed Central

The citrate permease determinant (citP) in several Leuconostoc strains was demonstrated to be plasmid encoded by curing experiments and hybridization studies with a DNA fragment containing the citP gene from Lactococcus lactis subsp. lactis biovar diacetylactis NCDO176. Cloning and nucleotide sequence analysis of Leuconostoc lactis NZ6070 citP revealed almost complete identity to lactococcal citP.

Vaughan, E E; David, S; Harrington, A; Daly, C; Fitzgerald, G F; De Vos, W M

1995-01-01

247

Random Mutagenesis Identifies Novel Genes Involved in the Secretion of Antimicrobial, Cell Wall-Lytic Enzymes by Lactococcus lactis  

Microsoft Academic Search

Lactococcus lactis is a gram-positive bacterium that is widely used in the food industry and is therefore desirable as a candidate for the production and secretion of recombinant proteins. Previously, we generated a L. lactis strain that expressed and secreted the antimicrobial cell wall-lytic enzyme lyso- staphin. To identify lactococcal gene products that affect the production of lysostaphin, we isolated

Yu Pei Tan; Philip M. Giffard; Daniel G. Barry; Wilhelmina M. Huston; Mark S. Turner

2008-01-01

248

Draft Genome Sequence of Lactococcus lactis subsp. cremoris HPT, the First Defined-Strain Dairy Starter Culture Bacterium.  

PubMed

Lactococcus lactis subsp. cremoris HP(T) has been widely used in studies of the metabolism of lactococcal dairy starter cultures. A comparison of the draft HP(T) genome with those from other strains of L. lactis subsp. cremoris will aid our understanding of the domestication and evolution of these important industrial cultures. PMID:24604643

Lambie, Suzanne C; Altermann, Eric; Leahy, Sinead C; Kelly, William J

2014-01-01

249

Complete Genome Sequences of Four Novel Lactococcus lactis Phages Distantly Related to the Rare 1706 Phage Species.  

PubMed

Lactoccocus lactis is a Gram-positive bacterium widely used in the dairy industry in the production of an array of cheeses and other fermented milk products. Here, we describe the sequencing and genome annotations of a set of four phages virulent to L. lactis and exhibiting similarities to phage 1706. PMID:25013130

Kot, Witold; Neve, Horst; Vogensen, Finn K; Heller, Knut J; Sørensen, Søren J; Hansen, Lars H

2014-01-01

250

Orally administered L. lactis secreting an anti-TNF Nanobody demonstrate efficacy in chronic colitis.  

PubMed

Inflammatory bowel disease (IBD) is a chronic inflammatory gastrointestinal disorder. Systemic treatment of IBD patients with anti-tumor necrosis factor (TNF)-alpha antibodies has proven to be a highly promising approach, but several drawbacks remain, including side effects related to systemic administration and high cost of treatment. Lactococcus lactis was engineered to secrete monovalent and bivalent murine (m)TNF-neutralizing Nanobodies as therapeutic proteins. These therapeutic proteins are derived from fragments of heavy-chain camelid antibodies and are more stable than conventional antibodies. L. lactis-secreted anti-mTNF Nanobodies neutralized mTNF in vitro. Daily oral administration of Nanobody-secreting L. lactis resulted in local delivery of anti-mTNF Nanobodies at the colon and significantly reduced inflammation in mice with dextran sulfate sodium (DSS)-induced chronic colitis. In addition, this approach was also successful in improving established enterocolitis in interleukin 10 (IL10)(-/-) mice. Finally, L. lactis-secreted anti-mTNF Nanobodies did not interfere with systemic Salmonella infection in colitic IL10(-/-) mice.In conclusion, this report details a new therapeutic approach for treatment of chronic colitis, involving in situ secretion of anti-mTNF Nanobodies by orally administered L. lactis bacteria. Therapeutic application of these engineered bacteria could eventually lead to more effective and safer management of IBD in humans. PMID:19794409

Vandenbroucke, K; de Haard, H; Beirnaert, E; Dreier, T; Lauwereys, M; Huyck, L; Van Huysse, J; Demetter, P; Steidler, L; Remaut, E; Cuvelier, C; Rottiers, P

2010-01-01

251

Role of lactose on the production of D-arabitol by Kluyveromyces lactis grown on lactose.  

PubMed

There are remarkably few reports on D-arabitol production from lactose. Previous studies in our laboratory have shown that the osmophilic yeast Kluyveromyces lactis NBRC 1903 convert lactose to extracellular D-arabitol. The present study was undertaken to determine the participation of osmotic stress caused by lactose on D-arabitol production by K. lactis NBRC 1903 and to provide the information on the kinetics of D-arabitol production from lactose by K. lactis NBRC 1903. It was confirmed that D-arabitol production was triggered when an initial lactose concentration was above 278 mmol L(-1). D-Arabitol yield increased with an increase in initial lactose concentration. The highest D-arabitol concentration of 79.5 mmol L(-1) was achieved in the cultivation of K. lactis NBRC 1903 in a medium containing 555 mmol L(-1) lactose and 40 g L(-1) yeast extract. Lactose was found to play two important roles in D-arabitol production by K. lactis NBRC 1903 grown on lactose. First, lactose was assimilated as the substrate both for cell growth and D-arabitol production. Second, a high lactose concentration induced cellular response to high osmotic stress and up-regulated the flow from D-glucose-6-phosphate to D-arabitol. The arrest of cell growth triggered D-arabitol production. PMID:20358191

Toyoda, Tomoyuki; Ohtaguchi, Kazuhisa

2010-06-01

252

Immunomodulatory effect of Lactococcus lactis JCM5805 on human plasmacytoid dendritic cells.  

PubMed

Plasmacytoid dendritic cells (pDCs) play a crucial role in anti-viral immunity through production of large amounts of interferons (IFNs). A previous study revealed the existence of lactic acid bacteria that directly stimulate pDCs in mice. In this study, we demonstrated that Lactococcus lactis JCM5805 activates human pDCs and induces IFN production in vitro. In addition, our randomized, placebo-controlled, double blind test showed that yogurt fermented with L. lactis JCM5805 activated pDC activity in vivo. This effect was greater in low pDC subjects, and their ability to produce IFNs was increased from the beginning. Furthermore, the risk of morbidity from the common cold was suppressed in the L. lactis JCM5805 group compared with the placebo group. In conclusion, intake of L. lactis JCM5805 can directly activate pDCs and increase the ability to produce IFNs in vivo. Therefore, L. lactis JCM5805 may be a beneficial tool to enhance anti-viral immunity in humans. PMID:24239838

Sugimura, Tetsu; Jounai, Kenta; Ohshio, Konomi; Tanaka, Takaaki; Suwa, Masahiro; Fujiwara, Daisuke

2013-12-01

253

Factors Affecting Phosphate Uptake by Aerobacter aerogenes in a System Relating Cell Numbers to 32P Uptake 1  

PubMed Central

The uptake of phosphate, from media limited in this ion, by resting cells of Aerobacter aerogenes has been investigated and shown to be dependent upon several factors. An incubation medium composed of 10?2m K+, 5 × 10?3m Mg2+, 1 mg of glucose per ml, and 1 ?Ci of 32PO43? per ml, buffered at pH 6.55 with 0.05 mN-2-hydroxyethyl-piperazine-N?-2-ethanesulfonic acid (HEPES), was found to stimulate optimum accumulation of 32P-orthophosphate. The temperature of incubation, incubation time, the concentration of unlabeled orthophosphate, as well as arsenate, and several metabolic inhibitors were found to affect the accumulation. The labeled cells were collected on a membrane filter, which had been previously boiled in glass-distilled water, for measurement of the radioactivity accumulated. Under optimum conditions, as few as 20,000 cells were capable of accumulating detectable amounts of 32P-orthophosphate in 1 hr of incubation.

White, Lloyd A.; MacLeod, Robert A.

1971-01-01

254

Continuous nisin production with bioengineered Lactococcus lactis strains.  

PubMed

Nisin production in continuous cultures of bioengineered Lactococcus lactis strains that incorporate additional immunity and regulation genes was studied. Highest nisin activities were observed at 0.2 h(-1) dilution rate and 12.5 g l(-1) fructose concentration for all strains. Recombinant strains were able to produce greater amounts of nisin at dilution rates below 0.3 h(-1) compared to the control strain. However, this significant difference disappeared at dilution rates of 0.4 and 0.5 h(-1). For the strains LL27, LAC338, LAC339, and LAC340, optimum conditions for nisin production were determined to be at 0.29, 0.26, 0.27, and 0.27 h(-1) dilution rates and 11.95, 12.01, 11.63, and 12.50 g l(-1) fructose concentrations, respectively. The highest nisin productivity, 496 IU ml(-1) h(-1), was achieved with LAC339. The results of this study suggest that low dilution rates stabilize the high specific nisin productivity of the bioengineered strains in continuous fermentation. Moreover, response surface methodology analysis showed that regulation genes yielded high nisin productivity at wide ranges of dilution rates and fructose concentrations. PMID:19337764

Sim?ek, O; Akkoç, N; Con, A H; Ozçelik, F; Saris, P E J; Akçelik, Mustafa

2009-06-01

255

Controlled release of protein from viable Lactococcus lactis cells.  

PubMed

Overexpression of the lactococcal CsiA protein affects the cell wall integrity of growing cells and leads to leakage of intracellular material. This property was optimized and exploited for the targeted release of biologically active compounds into the extracellular environment, thereby providing a new delivery system for bacterial proteins and peptides. The effects of different levels of CsiA expression on the leakage of endogenous lactate dehydrogenase and nucleic acids were measured and related to the impact of CsiA expression on Lactococcus lactis cell viability and growth. A leakage phenotype was obtained from cells expressing both recombinant and nonrecombinant forms of CsiA. As proof of principle, we demonstrated that CsiA promotes the efficient release of the heterologous Listeria bacteriophage endolysin LM4 in its active form. Under optimized conditions, native and heterologous active-molecule release is possible without affecting cell viability. The ability of CsiA to release intracellular material by controlled lysis without the requirement for an external lytic agent provides a technology for the control of both the extent of lysis and its timing. Taken together, these results demonstrate the potential of this novel approach for applications including product recovery in industrial fermentations, food processing, and medical therapy. PMID:20228099

Stentz, Régis; Bongaerts, Roy J; Gunning, A Patrick; Gasson, Mike; Shearman, Claire

2010-05-01

256

Dynamic modeling of lactic acid fermentation metabolism with Lactococcus lactis.  

PubMed

A dynamic model of lactic acid fermentation using Lactococcus lactis was constructed, and a metabolic flux analysis (MFA) and metabolic control analysis (MCA) were performed to reveal an intensive metabolic understanding of lactic acid bacteria (LAB). The parameter estimation was conducted with COPASI software to construct a more accurate metabolic model. The experimental data used in the parameter estimation were obtained from an LC-MS/ MS analysis and time-course simulation study. The MFA results were a reasonable explanation of the experimental data. Through the parameter estimation, the metabolic system of lactic acid bacteria can be thoroughly understood through comparisons with the original parameters. The coefficients derived from the MCA indicated that the reaction rate of L-lactate dehydrogenase was activated by fructose 1,6-bisphosphate and pyruvate, and pyruvate appeared to be a stronger activator of L-lactate dehydrogenase than fructose 1,6-bisphosphate. Additionally, pyruvate acted as an inhibitor to pyruvate kinase and the phosphotransferase system. Glucose 6-phosphate and phosphoenolpyruvate showed activation effects on pyruvate kinase. Hexose transporter was the strongest effector on the flux through L-lactate dehydrogenase. The concentration control coefficient (CCC) showed similar results to the flux control coefficient (FCC). PMID:21364298

Oh, Euhlim; Lu, Mingshou; Park, Changhun; Park, Changhun; Oh, Han Bin; Lee, Sang Yup; Lee, Jinwon

2011-02-01

257

Targeting diseases with genetically engineered Lactococcus lactis and its course towards medical translation.  

PubMed

The use of the lactic acid bacterium Lactococcus lactis, primarily used in food fermentations, as therapeutic agent is no longer speculative but an imminent reality. After the successful completion of Phase I and II clinical trials in humans for the treatment of inflammatory bowel disease, an ongoing clinical trial to alleviate oral mucositis as well as the development of a pneumococcal and a flu vaccine using genetically modified L. lactis, many exciting possibilities exist to develop novel therapeutic and prophylactic biopharmaceuticals to alleviate a wide range of diseases. Here, we discuss existing characteristics of the systems currently employed and the nature of the immune responses evoked. We also discuss the criteria that are fundamental to making the systems feasible and efficient which should ultimately translate into human therapies. Finally, we examine the prospects for L. lactis to become a commercially viable therapeutic agent. PMID:21204744

Villatoro-Hernandez, Julio; Montes-de-Oca-Luna, Roberto; Kuipers, Oscar P

2011-03-01

258

Conjugal transfer of nisin plasmid genes from Streptococcus lactis 7962 to Leuconostoc dextranicum 181.  

PubMed Central

Acriflavine-generated mutants of Streptococcus lactis 7962 with various combinations of plasmid molecular masses were screened for nisin production. Nisin was produced by both the wild type and mutants that contained a 17.5-megadalton plasmid, which was obscured by chromosomal fragments. No nisin was produced by plasmid-free mutants. Sucrose fermentation and nisin production were simultaneously expressed. A transconjugant obtained from nisin-producing donor S. lactis 7962 and recipient Leuconostoc dextranicum 181 was a "supernisin" producer. The L. dextranicum Nis+ transconjugant was resistant to S. lactis 7962 phage and vancomycin (greater than 1,000 micrograms/ml), and it contained an extra 17.5-megadalton plasmid. Images

Tsai, H J; Sandine, W E

1987-01-01

259

Nasal administration of Lactococcus lactis improves local and systemic immune responses against Streptococcus pneumoniae.  

PubMed

Lactococcus lactis NZ9000 is a non-pathogenic non-invasive bacterium extensively used for the delivery of antigens and cytokines at the mucosal level. However, there are no reports concerning the per se immunomodulatory capacity of this strain. The aim of the present study was to investigate the intrinsic immunostimulating properties of the nasal administration of L. lactis NZ9000 in a pneumococcal infection model. Mice were preventively treated with L. lactis (2, 5 or 7 days with 10(8) cells/day per mouse) and then challenged with Streptococcus pneumoniae. The local and the systemic immune responses were evaluated. Our results showed that nasal administration of L. lactis for 5 days (LLN5d) increased the clearance rate of S. pneumoniae from lung and prevented the dissemination of pneumococci into blood. This effect coincided with an upregulation of the innate and specific immune responses in both local and systemic compartments. LLN5d increased phagocyte activation in lung, blood and bone marrow, determined by NBT and peroxidase tests. Anti-pneumococcal immunoglobulin (Ig)A in bronchoalveolar lavages (BAL) and IgG in BAL and serum were increased in the LLN5d group. Lung tissue injury was reduced by LLN5d treatment as revealed by histopathological examination and albumin concentration and lactate dehydrogenase activity in BAL. The adjuvant effect of L. lactis in our infection model would be an important advantage for its use as a delivery vehicle of pneumococcal proteins and nasal immunization with recombinant L. lactis emerges as an effective route of vaccination for both systemic and mucosal immunity against pneumococcal infection. PMID:18667039

Medina, Marcela; Villena, Julio; Salva, Susana; Vintiñi, Elisa; Langella, Philippe; Alvarez, Susana

2008-08-01

260

Bifidobacterium animalis subsp. lactis ATCC 27673 Is a Genomically Unique Strain within Its Conserved Subspecies  

PubMed Central

Many strains of Bifidobacterium animalis subsp. lactis are considered health-promoting probiotic microorganisms and are commonly formulated into fermented dairy foods. Analyses of previously sequenced genomes of B. animalis subsp. lactis have revealed little genetic diversity, suggesting that it is a monomorphic subspecies. However, during a multilocus sequence typing survey of Bifidobacterium, it was revealed that B. animalis subsp. lactis ATCC 27673 gave a profile distinct from that of the other strains of the subspecies. As part of an ongoing study designed to understand the genetic diversity of this subspecies, the genome of this strain was sequenced and compared to other sequenced genomes of B. animalis subsp. lactis and B. animalis subsp. animalis. The complete genome of ATCC 27673 was 1,963,012 bp, contained 1,616 genes and 4 rRNA operons, and had a G+C content of 61.55%. Comparative analyses revealed that the genome of ATCC 27673 contained six distinct genomic islands encoding 83 open reading frames not found in other strains of the same subspecies. In four islands, either phage or mobile genetic elements were identified. In island 6, a novel clustered regularly interspaced short palindromic repeat (CRISPR) locus which contained 81 unique spacers was identified. This type I-E CRISPR-cas system differs from the type I-C systems previously identified in this subspecies, representing the first identification of a different system in B. animalis subsp. lactis. This study revealed that ATCC 27673 is a strain of B. animalis subsp. lactis with novel genetic content and suggests that the lack of genetic variability observed is likely due to the repeated sequencing of a limited number of widely distributed commercial strains.

Loquasto, Joseph R.; Barrangou, Rodolphe; Dudley, Edward G.; Stahl, Buffy; Chen, Chun

2013-01-01

261

Gene inactivation in Lactococcus lactis: branched-chain amino acid biosynthesis.  

PubMed Central

The Lactococcus lactis subsp. lactis strains isolated from dairy products are auxotrophs for branched-chain amino acids (leucine, isoleucine, and valine), while most strains isolated from nondairy media are prototrophs. We have cloned and sequenced the leu genes from one auxotroph, IL1403. The sequence is 99% homologous to that of the prototroph NCDO2118, which was determined previously. Two nonsense mutations and two small deletions were found in the auxotroph sequence, which might explain the branched-chain amino acid auxotrophy. Nevertheless, the leu genes from the auxotroph appear to be transcribed and regulated similarly to those from the prototroph. Images

Godon, J J; Delorme, C; Bardowski, J; Chopin, M C; Ehrlich, S D; Renault, P

1993-01-01

262

Modulation of gut-associated lymphoid tissue functions with genetically modified Lactococcus lactis.  

PubMed

Lactic acid bacteria are a group of taxonomically diverse, Gram-positive food-grade bacteria that have been safely consumed throughout history. The lactic acid bacterium Lactococcus lactis, well-known for its use in the manufacture of cheese, can be genetically engineered and orally formulated to deliver therapeutic proteins in the gastrointestinal tract. This review focuses on the genetic engineering of Lactococcus lactis to secrete high-quality, correctly processed bioactive molecules derived from a eukaryotic background. The therapeutic applications of these genetically modified strains are discussed, with special regards to immunomodulation. PMID:19954359

Rottiers, Pieter; De Smedt, Tim; Steidler, Lothar

2009-01-01

263

Conjugative Transfer of the Lactococcus lactis Chromosomal Sex Factor Promotes Dissemination of the Ll.LtrB Group II Intron  

PubMed Central

The Ll.LtrB group II intron from the low-G+C gram-positive bacterium Lactococcus lactis was the first bacterial group II intron shown to splice and mobilize in vivo. This retroelement interrupts the relaxase gene (ltrB) of three L. lactis conjugative elements: plasmids pRS01 and pAH90 and the chromosomal sex factor. Conjugative transfer of a plasmid harboring a segment of the pRS01 conjugative plasmid including the Ll.LtrB intron allows dissemination of Ll.LtrB among L. lactis strains and lateral transfer of this retroelement from L. lactis to Enterococcus faecalis. Here we report the dissemination of the Ll.LtrB group II intron among L. lactis strains following conjugative transfer of the native chromosomally embedded L. lactis sex factor. We demonstrated that Ll.LtrB dissemination is highly variable and often more efficient from this integrative and conjugative element than from an engineered conjugative plasmid. Cotransfer among L. lactis strains of both Ll.LtrB-containing elements, the conjugative plasmid and the sex factor, was detected and shown to be synergistic. Moreover, following their concurrent transfer, both mobilizable elements supported the spread of their respective copies of the Ll.LtrB intron. Our findings explain the unusually high efficiency of Ll.LtrB mobility observed following conjugation of intron-containing plasmids.

Belhocine, Kamila; Yam, Karen K.; Cousineau, Benoit

2005-01-01

264

Conjugative transfer of the Lactococcus lactis chromosomal sex factor promotes dissemination of the Ll.LtrB group II intron.  

PubMed

The Ll.LtrB group II intron from the low-G+C gram-positive bacterium Lactococcus lactis was the first bacterial group II intron shown to splice and mobilize in vivo. This retroelement interrupts the relaxase gene (ltrB) of three L. lactis conjugative elements: plasmids pRS01 and pAH90 and the chromosomal sex factor. Conjugative transfer of a plasmid harboring a segment of the pRS01 conjugative plasmid including the Ll.LtrB intron allows dissemination of Ll.LtrB among L. lactis strains and lateral transfer of this retroelement from L. lactis to Enterococcus faecalis. Here we report the dissemination of the Ll.LtrB group II intron among L. lactis strains following conjugative transfer of the native chromosomally embedded L. lactis sex factor. We demonstrated that Ll.LtrB dissemination is highly variable and often more efficient from this integrative and conjugative element than from an engineered conjugative plasmid. Cotransfer among L. lactis strains of both Ll.LtrB-containing elements, the conjugative plasmid and the sex factor, was detected and shown to be synergistic. Moreover, following their concurrent transfer, both mobilizable elements supported the spread of their respective copies of the Ll.LtrB intron. Our findings explain the unusually high efficiency of Ll.LtrB mobility observed following conjugation of intron-containing plasmids. PMID:15659671

Belhocine, Kamila; Yam, Karen K; Cousineau, Benoit

2005-02-01

265

Construction of a Bacteriophage-Resistant Derivative of Lactococcus lactis subsp. lactis 425A by Using the Conjugal Plasmid pNP40  

PubMed Central

Lactococcus lactis subsp. lactis 425A is an atypical strain which excretes a high concentration of ?-acetolactate when grown in milk. The conjugative lactococcal plasmid pNP40, which encodes phage and nisin resistance, was introduced to strain 425A by conjugation, using resistance to phage and nisin as a selection. No phage-nisin resistance mutants were encountered. Transconjugants display complete resistance at both 21 and 39°C to those phage previously identified as lytic for 425A. Transconjugants lose their resistance characteristics when spontaneously cured of pNP40. The commercially important property of 425A—production of high levels of ?-acetolactic acid—is unaffected by the presence of pNP40. Images

Harrington, Aidan; Hill, Colin

1991-01-01

266

Use of a Genetically Enhanced, Pediocin-Producing Starter Culture, Lactococcus lactis subsp. lactis MM217, To Control Listeria monocytogenes in Cheddar Cheese  

PubMed Central

Cheddar cheese was prepared with Lactococcus lactis subsp. lactis MM217, a starter culture which contains pMC117 coding for pediocin PA-1. About 75 liters of pasteurized milk (containing ca. 3.6% fat) was inoculated with strain MM217 (ca. 106 CFU per ml) and a mixture of three Listeria monocytogenes strains (ca. 103 CFU per ml). The viability of the pathogen and the activity of pediocin in the cheese were monitored at appropriate intervals throughout the manufacturing process and during ripening at 8°C for 6 months. In control cheese made with the isogenic, non-pediocin-producing starter culture L. lactis subsp. lactis MM210, the counts of the pathogen increased to about 107 CFU per g after 2 weeks of ripening and then gradually decreased to about 103 CFU per g after 6 months. In the experimental cheese made with strain MM217, the counts of L. monocytogenes decreased to 102 CFU per g within 1 week of ripening and then decreased to about 10 CFU per g within 3 months. The average titer of pediocin in the experimental cheese decreased from approximately 64,000 arbitrary units (AU) per g after 1 day to 2,000 AU per g after 6 months. No pediocin activity (<200 AU per g) was detected in the control cheese. Also, the presence of pMC117 in strain MM217 did not alter the cheese-making quality of the starter culture, as the rates of acid production, the pH values, and the levels of moisture, NaCl, and fat of the control cheese and the experimental cheese were similar. Our data revealed that pediocin-producing starter cultures have significant potential for protecting natural cheese against L. monocytogenes.

Buyong, Nurliza; Kok, Jan; Luchansky, John B.

1998-01-01

267

Prevalence and diversity of qnr alleles in AmpC-producing Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii and Serratia marcescens: a multicentre study from Korea  

Microsoft Academic Search

Methods: A total of 644 consecutive, non-duplicate isolates of Enterobacter cloacae (186), Enterobacter aerogenes (154), Citrobacter freundii (138) and Serratia marcescens (166) were examined. We performed antimicrobial susceptibility testing and PCR for qnr determinants (qnrA, qnrB and qnrS), extended-spectrum b-lactamase (ESBL) (blaTEM, blaSHV and blaCTX-M), orf513, orf1005 and blaDHA-1. To differentiate qnr subtypes, restriction enzyme analysis and sequencing was performed.

Yeon-Joon Park; Jin Kyung Yu; Seungok Lee; Eun-Jee Oh; Gun-Jo Woo

2007-01-01

268

Regulation of Exopolysaccharide Production by Lactococcus lactis subsp. cremoris by the Sugar Source  

Microsoft Academic Search

Lactococcus lactis produced more exopolysaccharide (EPS) on glucose than on fructose as the sugar sub- strate, although the transcription level of the eps gene cluster was independent of the sugar source. A major difference between cells grown on the two substrates was the capacity to produce sugar nucleotides, the EPS precursors. However, the activities of the enzymes required for the

PETRONELLA J. LOOIJESTEIJN; INGEBORG C. BOELS; MICHIEL KLEEREBEZEM; JEROEN HUGENHOLTZ

1999-01-01

269

Exopolysaccharides produced by Lactococcus lactis: from genetic engineering to improved rheological properties?  

Microsoft Academic Search

Over the last years, important advances have been made in the study of the production of exopolysaccharides (EPS) by several lactic acid bacteria, including Lactococcus lactis. From different EPS-producing lactococcal strains the specific eps gene clusters have been characterised. They contain eps genes, which are involved in EPS repeating unit synthesis, export, polymerisation, and chain length determination. The function of

Michiel Kleerebezem; Richard van Kranenburg; Remco Tuinier; Ingeborg C. Boels; Pieternella Zoon; Ellen Looijesteijn; Jeroen Hugenholtz; Willem M. de Vos

1999-01-01

270

Genome Sequence of the Cheese-Starter Strain Lactobacillus delbrueckii subsp. lactis CRL 581.  

PubMed

We report the genome sequence of Lactobacillus delbrueckii subsp. lactis CRL 581 (1,911,137 bp, GC 49.7%), a proteolytic strain isolated from a homemade Argentinian hard cheese which has a key role in bacterial nutrition and releases bioactive health-beneficial peptides from milk proteins. PMID:23929489

Hebert, Elvira María; Raya, Raúl R; Brown, Lucía; Font de Valdez, Graciela; Savoy de Giori, Graciela; Taranto, María Pía

2013-01-01

271

The Plasmid Complement of Lactococcus lactis UC509.9 Encodes Multiple Bacteriophage Resistance Systems.  

PubMed

Lactococcus lactis subsp. cremoris strains are used globally for the production of fermented dairy products, particularly hard cheeses. Believed to be of plant origin, L. lactis strains that are used as starter cultures have undergone extensive adaptation to the dairy environment, partially through the acquisition of extrachromosomal DNA in the form of plasmids that specify technologically important phenotypic traits. Here, we present a detailed analysis of the eight plasmids of L. lactis UC509.9, an Irish dairy starter strain. Key industrial phenotypes were mapped, and genes that are typically associated with lactococcal plasmids were identified. Four distinct, plasmid-borne bacteriophage resistance systems were identified, including two abortive infection systems, AbiB and AbiD1, thereby supporting the observed phage resistance of L. lactis UC509.9. AbiB escape mutants were generated for phage sk1, which were found to carry mutations in orf6, which encodes the major capsid protein of this phage. PMID:24814781

Ainsworth, Stuart; Mahony, Jennifer; van Sinderen, Douwe

2014-07-15

272

Two-tiered biological containment strategy for Lactococcus lactis-based vaccine or immunotherapy vectors.  

PubMed

The concept of biological containment was developed as a strategy to prevent environmental dissemination of engineered live vaccine or drug delivery vehicles. A mutation in the gene encoding thymidylate synthase (thyA), a key enzyme in the pyrimidine biosynthetic pathway, has previously been shown to limit growth of L. lactis vectors under restrictive conditions. We hypothesized that further mutations in the pyrimidine biosynthetic pathway might enhance the stability and safety of live L. lactis vectors. We show that a double mutation in the genes encoding ThyA and CTP synthase (PyrG) in L. lactis confers double auxotrophy for both thymidine and cytidine. However, the combination of two mutations failed to enhance the biological containment phenotype of the engineered strain. In the absence of thymine/thymidine, the thyA mutant exhibited a strong bactericidal phenotype. However, creation of the double mutant caused the loss of this phenotype, though survival in the mouse GI tract was enhanced. The implications for biological containment of live L. lactis based delivery vectors are discussed. PMID:24196273

Hanin, Aurelie; Culligan, Eamonn P; Casey, Pat G; Bahey-El-Din, Mohammed; Hill, Colin; Gahan, Cormac Gm

2014-02-01

273

Characterization of Lactococcus lactis phage 949 and comparison with other lactococcal phages.  

PubMed

The virulent Lactococcus lactis phage 949 was isolated in 1975 from cheese whey in New Zealand. This phage is a member of the Siphoviridae family and of a rare lactococcal phage group that bears its name (949 group). It has an icosahedral capsid (79-nm diameter) and a very long noncontractile tail (length, 500 nm; width, 12 nm). It infected 7 of 59 tested L. lactis strains, a somewhat expanded host range for a rare lactococcal phage. The abortive phage infection defense mechanisms AbiQ and AbiT strongly inhibited the multiplication of phage 949, but AbiK and AbiV did not. Its double-stranded DNA (dsDNA) genome of 114,768 bp is, to date, the largest among lactococcal phages. Its GC content was calculated at 32.7%, which is the lowest reported for a lactococcal phage. Its 154 open reading frames (ORFs) share limited identity with database sequences. In addition, terminal redundancy was observed as well as the presence of six tRNAs, one group I intron, and putative recombinases. SDS-PAGE coupled with mass spectrometry identified 13 structural proteins. The genomes of the members of the 10 currently known L. lactis phage groups were used to construct a proteomic tree. Each L. lactis phage group separated into distinct genetic clusters, validating the current classification scheme. Of note, members of the polythetic P335 groups were clearly separated into subgroups. PMID:20802084

Samson, Julie E; Moineau, Sylvain

2010-10-01

274

Kluyveromyces lactis zymocin and other plasmid-encoded yeast killer toxins  

Microsoft Academic Search

Supported by an endogenous killer plasmid DNA system that codes for an anti-proliferative zymocin toxin, the dairy yeast Kluyveromyces lactis has attracted research into inter-yeast pathogenesis. Molecularly, gene disruption and shuffle techniques have proven powerful means to study components essentially required for the maintenance of the killer plasmid system, namely, autonomously operating replication and transcription apparatuses. Moreover, by studying zymocin

Raffael Schaffrath; Friedhelm Meinhardt

275

Sugar metabolism, redox balance and oxidative stress response in the respiratory yeast Kluyveromyces lactis  

PubMed Central

A lot of studies have been carried out on Saccharomyces cerevisiae, an yeast with a predominant fermentative metabolism under aerobic conditions, which allows exploring the complex response induced by oxidative stress. S. cerevisiae is considered a eukaryote model for these studies. We propose Kluyveromyces lactis as a good alternative model to analyse variants in the oxidative stress response, since the respiratory metabolism in this yeast is predominant under aerobic conditions and it shows other important differences with S. cerevisiae in catabolic repression and carbohydrate utilization. The knowledge of oxidative stress response in K. lactis is still a developing field. In this article, we summarize the state of the art derived from experimental approaches and we provide a global vision on the characteristics of the putative K. lactis components of the oxidative stress response pathway, inferred from their sequence homology with the S. cerevisiae counterparts. Since K. lactis is also a well-established alternative host for industrial production of native enzymes and heterologous proteins, relevant differences in the oxidative stress response pathway and their potential in biotechnological uses of this yeast are also reviewed.

Gonzalez-Siso, M Isabel; Garcia-Leiro, Ana; Tarrio, Nuria; Cerdan, M Esperanza

2009-01-01

276

Sulfur Amino Acid Metabolism and Its Control in Lactococcus lactis IL1403  

Microsoft Academic Search

Cysteine and methionine availability influences many processes in the cell. In bacteria, transcription of the specific genes involved in the synthesis of these two amino acids is usually regulated by different mechanisms or regulators. Pathways for the synthesis of cysteine and methionine and their interconversion were experi- mentally determined for Lactococcus lactis, a lactic acid bacterium commonly found in food.

Brice Sperandio; Patrice Polard; Dusko S. Ehrlich; Pierre Renault; Eric Guedon

2005-01-01

277

Kinetics and regulation of lactose transport and metabolism in Kluyveromyces lactis JA6.  

PubMed

Kluyveromyces lactis strains are able to assimilate lactose. They have been used industrially to eliminate this sugar from cheese whey and in other industrial products. In this study, we investigated specific features and the kinetic parameters of the lactose transport system in K. lactis JA6. In lactose grown cells, lactose was transported by a system transport with a half-saturation constant (K s) of 1.49 ± 0.38 mM and a maximum velocity (V max) of 0.96 ± 0.12 mmol. (g dry weight)(-1) h(-1) for lactose. The transport system was constitutive and energy-dependent. Results obtained by different approaches showed that the lactose transport system was regulated by glucose at the transcriptional level and by glucose and other sugars at a post-translational level. In K. lactis JA6, galactose metabolization was under glucose control. These findings indicated that the regulation of lactose-galactose regulon in K. lactis was similar to the regulation of galactose regulon in Saccharomyces cerevisiae. PMID:24504708

Santos, A M; Silveira, W B; Fietto, L G; Brandão, R L; Castro, I M

2014-07-01

278

Allergy Therapy by Intranasal Administration with Recombinant Lactococcus lactis Producing Bovine ?-Lactoglobulin  

Microsoft Academic Search

Background: In the last years, the use of probiotics such as lactic acid bacteria (LAB) has been proposed as an attractive alternative for the management of allergic diseases. A partial prevention from sensitization to bovine ?-lactoglobulin (BLG), one of the major cows’ milk allergens, could be achieved in mice after intranasal administration with a recombinant LAB strain, Lactococcus lactis, producing

Naima G. Cortes-Perez; Sandrine Ah-Leung; Luis G. Bermúdez-Humarán; Gérard Corthier; Philippe Langella; Jean-Michel Wal; Karine Adel-Patient

2009-01-01

279

Mucosal delivery of a pneumococcal vaccine using lactococcus lactis affords protection against respiratory infection  

Microsoft Academic Search

Background - Economical and effective vaccines against Streptococcus pneumoniae (pneumococcus) are needed for implementation in poorer countries where the disease burden is highest. Here, we evaluated Lactococcus lactis intracellularly producing the pneumococcal surface protein A (PspA) as a mucosal vaccine in conferring protection against pneumococcal disease. Methods - Mice were intranasally (inl) immunized with the lactococcal vaccine. Control groups were

S. B. Hanniffy; A. T. Carter; E. Hitchin; J. M. Wells

2007-01-01

280

Heterologous expression of Brucella abortus GroEL heat-shock protein in Lactococcus lactis  

Microsoft Academic Search

BACKGROUND: Brucella abortus is a facultative intracellular pathogen that mainly infects cattle and humans. Current vaccines rely on live attenuated strains of B. abortus, which can revert to their pathogenic status and thus are not totally safe for use in humans. Therefore, the development of mucosal live vaccines using the food-grade lactic acid bacterium, Lactococcus lactis, as an antigen delivery

Anderson Miyoshi; Luis G Bermúdez-Humarán; Luciana A Ribeiro; Yves Le Loir; Sérgio C Oliveira; Philippe Langella; Vasco Azevedo

2006-01-01

281

Deep neck infection due to Lactococcus lactis cremoris: a case report.  

PubMed

This report describes the first case of deep neck infection resulting from Lactococcus lactis subsp. cremoris. The case is associated with the consumption of unpasteurized milk and occurred in a patient with a buccal mucosa tumor. Anti-infective therapy with ceftriaxone and metronidazole resulted in complete resolution. PMID:15756569

Koyuncu, M; Acuner, I C; Uyar, M

2005-09-01

282

Effect of composite yogurt enriched with acacia fiber and Bifidobacterium lactis  

PubMed Central

AIM: To investigate whether composite yogurt with acacia dietary fiber and Bifidobacterium lactis (B. lactis) has additive effects in irritable bowel syndrome (IBS). METHODS: A total of 130 patients were randomly allocated to consume, twice daily for 8 wk, either the composite yogurt or the control product. The composite yogurt contained acacia dietary fiber and high-dose B. lactis together with two classic yogurt starter cultures. Patients were evaluated using the visual analog scale via a structured questionnaire administered at baseline and after treatment. RESULTS: Improvements in bowel habit satisfaction and overall IBS symptoms from baseline were significantly higher in the test group than in the control group (27.16 vs 15.51, P = 0.010, 64.2 ± 17.0 vs 50.4 ± 20.5, P < 0.001; respectively). In constipation-predominant IBS, improvement in overall IBS symptoms was significantly higher in the test group than in the control group (72.4 ± 18.4 vs 50.0 ± 21.8, P < 0.001). In patients with diarrhea-predominant IBS, improvement in bowel habit satisfaction from baseline was significantly higher in the test group than in the control group (32.90 vs 7.81, P = 0.006). CONCLUSION: Our data suggest that composite yogurt enriched with acacia fiber and B. lactis has greater therapeutic effects in patients with IBS than standard yogurt.

Min, Yang Won; Park, Sang Un; Jang, Yeon Sil; Kim, Young-Ho; Rhee, Poong-Lyul; Ko, Seo Hyun; Joo, Nami; Kim, Sun Im; Kim, Cheol-Hyun; Chang, Dong Kyung

2012-01-01

283

Progress in the development of mucosal vaccines based on Lactococcus lactis  

Microsoft Academic Search

This paper reviews recent work on the construction and characterisation of recombinant strains of Lactococcus lactis which are able to express immunogens derived from e.g. Clostridium tetani, H.I.V. — 1 and Schistosoma mansoni. The immunogenicity of these constructs has been tested in mice. In some instances it has been possible to elicit protective level systemic immune responses as well as

Jeremy M. Wells; Pamela M. Norton; Richard W. F. Le Page

1995-01-01

284

Genome Sequence of the Cheese-Starter Strain Lactobacillus delbrueckii subsp. lactis CRL 581  

PubMed Central

We report the genome sequence of Lactobacillus delbrueckii subsp. lactis CRL 581 (1,911,137 bp, GC 49.7%), a proteolytic strain isolated from a homemade Argentinian hard cheese which has a key role in bacterial nutrition and releases bioactive health-beneficial peptides from milk proteins.

Raya, Raul R.; Brown, Lucia; Font de Valdez, Graciela; Savoy de Giori, Graciela; Taranto, Maria Pia

2013-01-01

285

Diversity in robustness of Lactococcus lactis strains during heat stress, oxidative stress, and spray drying stress.  

PubMed

In this study we tested 39 Lactococcus lactis strains isolated from diverse habitats for their robustness under heat and oxidative stress, demonstrating high diversity in survival (up to 4 log units). Strains with an L. lactis subsp. lactis phenotype generally displayed more-robust phenotypes than strains with an L. lactis subsp. cremoris phenotype, whereas the habitat from which the strains had been isolated did not appear to influence stress survival. Comparison of the stress survival phenotypes with already available comparative genomic data sets revealed that the absence or presence of specific genes, including genes encoding a GntR family transcriptional regulator, a manganese ABC transporter permease, a cellobiose phosphotransferase system (PTS) component, the FtsY protein, and hypothetical proteins, was associated with heat or oxidative stress survival. Finally, 14 selected strains also displayed diversity in survival after spray drying, ranging from 20% survival for the most robust strains, which appears acceptable for industrial application, to 0.1% survival for the least-tolerant strains. The high and low levels of survival upon spray drying correlated clearly with the combined robustness under heat and oxidative stress. These results demonstrate the relevance of screening culture collections for robustness under heat and oxidative stress on top of the typical screening for acidifying and flavor-forming properties. PMID:24212574

Dijkstra, Annereinou R; Setyawati, Meily C; Bayjanov, Jumamurat R; Alkema, Wynand; van Hijum, Sacha A F T; Bron, Peter A; Hugenholtz, Jeroen

2014-01-01

286

Development of microparticulate systems for intestinal delivery of Lactobacillus acidophilus and Bifidobacterium lactis  

Microsoft Academic Search

In the present study intestinal delivery systems resistant to gastric juice, loaded with the probiotic bacteria Lactobacillus acidophilus LA14 and Bifidobacterium lactis BI07, were produced by the polyelectrolyte complexation. First, beads were prepared by the traditional extrusion method and nine formulations were developed using alginate as main carrier and the biopolymer, xanthan gum (XG), as hydrophilic retardant polymer or the

Beatrice Albertini; Beatrice Vitali; Nadia Passerini; Federica Cruciani; Marcello Di Sabatino; Lorenzo Rodriguez; Patrizia Brigidi

2010-01-01

287

Diversity in Robustness of Lactococcus lactis Strains during Heat Stress, Oxidative Stress, and Spray Drying Stress  

PubMed Central

In this study we tested 39 Lactococcus lactis strains isolated from diverse habitats for their robustness under heat and oxidative stress, demonstrating high diversity in survival (up to 4 log units). Strains with an L. lactis subsp. lactis phenotype generally displayed more-robust phenotypes than strains with an L. lactis subsp. cremoris phenotype, whereas the habitat from which the strains had been isolated did not appear to influence stress survival. Comparison of the stress survival phenotypes with already available comparative genomic data sets revealed that the absence or presence of specific genes, including genes encoding a GntR family transcriptional regulator, a manganese ABC transporter permease, a cellobiose phosphotransferase system (PTS) component, the FtsY protein, and hypothetical proteins, was associated with heat or oxidative stress survival. Finally, 14 selected strains also displayed diversity in survival after spray drying, ranging from 20% survival for the most robust strains, which appears acceptable for industrial application, to 0.1% survival for the least-tolerant strains. The high and low levels of survival upon spray drying correlated clearly with the combined robustness under heat and oxidative stress. These results demonstrate the relevance of screening culture collections for robustness under heat and oxidative stress on top of the typical screening for acidifying and flavor-forming properties.

Dijkstra, Annereinou R.; Setyawati, Meily C.; Bayjanov, Jumamurat R.; Alkema, Wynand; van Hijum, Sacha A. F. T.; Hugenholtz, Jeroen

2014-01-01

288

Development, molecular characterization and exploitation of the nisin controlled expression system in Lactococcus lactis  

Microsoft Academic Search

Lactic acid bacteria are gram-positive bacteria that are widely used in a variety of dairy fermentation processes. Notably, strains of the lactic acid starter bacterium Lactococcus lactis are of great economic importance because of their world-wide use in cheese making. The characteristic aroma, flavor and texture of cheese develops during ripening of the cheese curd through the action of numerous

Ruyter de P. G. G. A

1998-01-01

289

Bifidobacterium animalis ssp. lactis 420 Protects against Indomethacin-Induced Gastric Permeability in Rats  

PubMed Central

Gastrointestinal (GI) adverse effects such as erosion and increased permeability are common during the use of nonsteroidal anti-inflammatory drugs (NSAIDs). Our objective was to assess whether Bifidobacterium animalis ssp. lactis 420 protects against NSAID-induced GI side effects in a rat model. A total of 120 male Wistar rats were allocated into groups designated as control, NSAID, and probiotic. The NSAID and probiotic groups were challenged with indomethacin (10?mg/kg?1; single dose). The probiotic group was also supplemented daily with 1010?CFU of B. lactis 420 for seven days prior to the indomethacin administration. The control group rats received no indomethacin or probiotic. The permeability of the rat intestine was analysed using carbohydrate probes and the visual damage of the rat stomach mucosa was graded according to severity. B. lactis 420 significantly reduced the indomethacin-induced increase in stomach permeability. However, the protective effect on the visual mucosal damage was not significant. The incidence of severe NSAID-induced lesions was, nevertheless, reduced from 50% to 33% with the probiotic treatment. To conclude, the B. lactis 420 supplementation protected the rats from an NSAID-induced increase in stomach permeability and may reduce the formation of more serious GI mucosal damage and/or enhance the recovery rate of the stomach mucosa.

Lyra, Anna; Saarinen, Markku; Putaala, Heli; Olli, Kaisa; Lahtinen, Sampo J.; Ouwehand, Arthur C.; Madetoja, Mari; Tiihonen, Kirsti

2012-01-01

290

Internalin-expressing Lactococcus lactis is able to invade small intestine of guinea pigs and deliver DNA into mammalian epithelial cells.  

PubMed

The use of the food-grade bacterium Lactococcus lactis as antigen delivery vehicle at the mucosal level is an attractive vaccination strategy intensively explored during the last decade. In this study, we developed L. lactis strains which could be used as a DNA delivery vector to combine both advantages of mucosal delivery and of DNA vaccination. To render lactococci capable of invading epithelial cells, the Listeria monocytogenes inlA gene was cloned and expressed in L. lactis under transcriptional control of the native promoter. Western blot and immunofluorescence assays revealed that recombinant lactococci efficiently displayed the cell wall anchored form of InlA. We demonstrated that this expression promotes internalization of L. lactis inlA+ into the human epithelial cell line Caco-2. Gentamicin assay showed that invasiveness of L. lactis in these cells is approximately 100-fold higher for L. lactis inlA+ than for wild type (wt) L. lactis strains. Moreover, we showed that L. lactis inlA+ is able to enter intestinal cells in vivo, after oral inoculation of guinea pigs. After internalization, L. lactis inlA+ was able to deliver a functional eukaryotic gfp gene into epithelial Caco-2 cells; GFP was detected in 1% of internalized cells. The L. lactis inlA+ strain will be a useful bacterial vector for the development of new live oral DNA vaccines. It also constitutes an interesting new model to study the role of internalin in bacterial localization in the animal host. PMID:15878681

Guimarães, Valeria Dellaretti; Gabriel, Jane Eyre; Lefèvre, François; Cabanes, Didier; Gruss, Alexandra; Cossart, Pascale; Azevedo, Vasco; Langella, Philippe

2005-05-01

291

Cell surface display system for Lactococcus lactis: a novel development for oral vaccine.  

PubMed

The food-grade Lactococcus lactis is a potential vector to be used as a live vehicle for the delivery of heterologous proteins for vaccine and pharmaceutical purposes. We constructed a plasmid vector pSVac that harbors a 255-bp single-repeat sequence of the cell wall-binding protein region of the AcmA protein. The recombinant plasmid was transformed into Escherichia coli and expression of the gene fragment was driven by the T7 promoter of the plasmid. SDS-PAGE showed the presence of the putative AcmA' fragment and this was confirmed by Western blot analysis. The protein was isolated and purified using a His-tag affinity column. When mixed with a culture of L. lactis MG1363, ELISA and immunofluorescence assays showed that the cell wall-binding fragment was anchored onto the outer surface of the bacteria. This indicated that the AcmA' repeat unit retained the active site for binding onto the cell wall surface of the L. lactis cells. Stability assays showed that the fusion proteins (AcmA/A1, AcmA/A3) were stably docked onto the surface for at least 5 days. The AcmA' fragment was also shown to be able to strongly bind onto the cell surface of naturally occurring lactococcal strains and Lactobacillus and, with less strength, the cell surface of Bacillus sphericus. The new system designed for cell surface display of recombinant proteins on L. lactis was evaluated for the expression and display of A1 and A3 regions of the VP1 protein of enterovirus 71 (EV71). The A1 and A3 regions of the VP1 protein of EV71 were cloned upstream to the cell wall-binding domains of AcmA protein and successfully expressed as AcmA/A1 and AcmA/A3. Whole-cell ELISA showed the successful display of VP1 protein epitopes of EV71 on the surface of L. lactis. The success of the anchoring system developed in this study for docking the A1 and A3 epitopes of VP1 onto the surface of L. lactis cells opens up the possibilities of peptide and protein display for not only Lactococcus but also for other gram-positive bacteria. This novel way of displaying epitopes on the cell surface of L. lactis and other related organisms should be very useful in the delivery of vaccines and other useful proteins. PMID:15635459

Raha, A R; Varma, N R S; Yusoff, K; Ross, E; Foo, H L

2005-07-01

292

Adaptative Potential of the Lactococcus Lactis IL594 Strain Encoded in Its 7 Plasmids  

PubMed Central

The extrachromosomal gene pool plays a significant role both in evolution and in the environmental adaptation of bacteria. The L. lactis subsp. lactis IL594 strain contains seven plasmids, named pIL1 to pIL7, and is the parental strain of the plasmid-free L. lactis IL1403, which is one of the best characterized lactococcal strains of LAB. Complete nucleotide sequences of pIL1 (6,382 bp), pIL2 (8,277 bp), pIL3 (19,244 bp), pIL4 (48,979), pIL5 (23,395), pIL6 (28,435 bp) and pIL7 (28,546) were established and deposited in the generally accessible database (GeneBank). Nine highly homologous repB-containing replicons, belonging to the lactococcal theta-type replicons, have been identified on the seven plasmids. Moreover, a putative region involved in conjugative plasmid mobilization was found on four plasmids, through identification of the presence of mob genes and/or oriT sequences. Detailed bioinformatic analysis of the plasmid nucleotide sequences provided new insight into the repertoire of plasmid-encoded functions in L. lactis, and indicated that plasmid genes from IL594 strain can be important for L. lactis adaptation to specific environmental conditions (e.g. genes coding for proteins involved in DNA repair or cold shock response) as well as for technological processes (e.g. genes encoding citrate and lactose utilization, oligopeptide transport, restriction-modification system). Moreover, global gene analysis indicated cooperation between plasmid- and chromosome-encoded metabolic pathways.

Golebiewski, Marcin; Zylinska, Joanna; Grynberg, Marcin; Bardowski, Jacek K.

2011-01-01

293

Exopolysaccharide Expression in Lactococcus lactis subsp. cremoris Ropy352: Evidence for Novel Gene Organization?  

PubMed Central

Lactococcus lactis subsp. cremoris Ropy352 produces two distinct heteropolysaccharides, phenotypically described as ropy and mucoid, when cultured in nonfat milk. One exopolysaccharide precipitated with 50% ethanol as a series of elongated threads and was composed of glucose and galactose in a molar ratio of 3:2. The second exopolysaccharide precipitated with 75% ethanol as a fine flocculant and consisted of galactose, glucose, and mannose with a molar ratio of 67:21:12. A mutant strain, L. lactis subsp. cremoris EK240, lacking the ropy phenotype did not produce the exopolysaccharide that precipitated with 50% ethanol; however, it produced the exopolysaccharide that precipitated with 75% ethanol, indicating that the former exopolysaccharide is essential for the ropy phenotype. Cultures of L. lactis subsp. cremoris Ropy352 in 10% nonfat milk reached a viscosity of 25 Pa-s after 24 h, while those of the nonropy L. lactis subsp. cremoris EK240 mutant did not change. A mutation abolishing ropy exopolysaccharide expression mapped to a region on a plasmid containing two open reading frames, epsM and epsN, encoding novel glycosyltransferases bordered by ISS1 elements oriented in the same direction. Sequencing of this plasmid revealed two other regions involved in exopolysaccharide expression, an operon located between partial IS981 and IS982 elements, and an independent gene, epsU. Two and possibly three of these regions are involved in L. lactis subsp. cremoris Ropy352 exopolysaccharide expression and are arranged in a novel fashion different from that of typical lactococcal exopolysaccharide loci, and this provides genetic evidence for exopolysaccharide gene reorganization and evolution in Lactococcus.

Knoshaug, Eric P.; Ahlgren, Jeff A.; Trempy, Janine E.

2007-01-01

294

Vanadium and Experimental Caries. VII. Action of Vanadium on the Development of Lactobacillus Acidophilus and Streptococcus Lactis (Vanadio E Carie Sperimentale. VII. Azione del Vanadio sullo Sviluppo del Lactobacillus Acidophilus e dello Streptococcus Lactis).  

National Technical Information Service (NTIS)

The action of solutions with different contents of vanadium on the development and on the production of lactic acid of cultures of lactobacillus acidophilus and streptococcus lactis was investigated by the authors. The authors have established that there ...

G. Santacatterina G. Grippaudo F. Valfre G. Cecchetti

1972-01-01

295

Sugar Utilization and Acid Production by Free and Entrapped Cells of Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Lactococcus lactis subsp. lactis in a Whey Permeate Medium  

PubMed Central

Cells of Streptococcus salivarius subsp. thermophilus and Lactococcus lactis subsp. lactis entrapped in k-carrageenan-locust bean gum gel performed similarly to free cells in the conversion of lactose to lactic acid. Bead diameter influenced the fermentation rate. Cells entrapped in smaller beads (0.5 to 1.0 mm) showed higher release rates, higher lactose, glucose, and formic acid utilization, higher galactose accumulation, and higher lactic acid production than did cells entrapped in larger beads (1.0 to 2.0 mm). Values for smaller beads were comparable with those for free cells. Immobilization affected the fermentation rate of lactic acid bacteria, especially Lactobacillus delbrueckii subsp. bulgaricus. Entrapped cells of L. delbrueckii subsp. bulgaricus demonstrated a lower lactic acid production than did free cells in batch fermentation. The kinetics of the production of formic and pyruvic acids by L. lactis subsp. lactis and S. salivarius subsp. thermophilus are presented.

Audet, Pascal; Paquin, Celine; Lacroix, Christophe

1989-01-01

296

A comparative study on phosphotransferase activity of acid phosphatases from Raoultella planticola and Enterobacter aerogenes on nucleosides, sugars, and related compounds.  

PubMed

Natural and modified nucleoside-5'-monophosphates and their precursors are valuable compounds widely used in biochemical studies. Bacterial nonspecific acid phosphatases (NSAPs) are a group of enzymes involved in the hydrolysis of phosphoester bonds, and some of them exhibit phosphotransferase activity. NSAP containing Enterobacter aerogenes and Raoultella planticola whole cells were evaluated in the phosphorylation of a wide range of nucleosides and nucleoside precursors using pyrophosphate as phosphate donor. To increase the productivity of the process, we developed two genetically modified strains of Escherichia coli which overexpressed NSAPs of E. aerogenes and R. planticola. These new recombinant microorganisms (E. coli BL21 pET22b-phoEa and E. coli BL21 pET22b-phoRp) showed higher activity than the corresponding wild-type strains. Reductions in the reaction times from 21 h to 60 min, from 4 h to 15 min, and from 24 h to 40 min in cases of dihydroxyacetone, inosine, and fludarabine, respectively, were obtained. PMID:23995227

Médici, Rosario; Garaycoechea, Juan I; Valino, Ana L; Pereira, Claudio A; Lewkowicz, Elizabeth S; Iribarren, Adolfo M

2014-04-01

297

Coexistence of SHV-4- and TEM-24-Producing Enterobacter aerogenes Strains before a Large Outbreak of TEM-24-Producing Strains in a French Hospital  

PubMed Central

In 1996, a monitoring program was initiated at the teaching hospital of Amiens, France, and carried out for 3 years. All extended-spectrum ?-lactamase (ESBL)-producing Enterobacter aerogenes isolates recovered from clinical specimens were collected for investigation of their epidemiological relatedness by pulsed-field gel electrophoresis and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and determination of the type of ESBL harbored by isoelectric focusing and DNA sequencing. Molecular typing revealed the endemic coexistence, during the first 2 years, of two clones expressing, respectively, SHV-4 and TEM-24 ESBLs, while an outbreak of the TEM-24-producing strain raged in the hospital during the third year, causing the infection or colonization of 165 patients. Furthermore, this strain was identified as the prevalent clone responsible for outbreaks in many French hospitals since 1996. This study shows that TEM-24-producing E. aerogenes is an epidemic clone that is well established in the hospital's ecology and able to spread throughout wards. The management of the outbreak at the teaching hospital of Amiens, which included the reinforcement of infection control measures, failed to obtain complete eradication of the clone, which has become an endemic pathogen.

Mammeri, H.; Laurans, G.; Eveillard, M.; Castelain, S.; Eb, F.

2001-01-01

298

Promoter and signal sequence from filamentous fungus can drive recombinant protein production in the yeast Kluyveromyces lactis.  

PubMed

Cross-recognition of promoters from filamentous fungi in yeast can have important consequences towards developing fungal expression systems, especially for the rapid evaluation of their efficacy. A truncated 510bp inducible Trichoderma reesei cellobiohydrolase I (cbh1) promoter was tested for the expression of green fluorescent protein (GFP) in Kluyveromyces lactis after disrupting its native ?-galactosidase (lac4) promoter. The efficiency of the CBH1 secretion signal was also evaluated by fusing it to the lac4 promoter of the yeast, which significantly increased the secretion of recombinant protein in K. lactis compared to the native ?-mating factor secretion signal. The fungal promoter is demonstrated to have potential to drive heterologous protein production in K. lactis; and the small sized T. reesei cbh1 secretion signal can mediate the protein secretion in K. lactis with high efficiency. PMID:24661814

Madhavan, Aravind; Sukumaran, Rajeev K

2014-08-01

299

Draft Genome Sequence of Bifidobacterium animalis subsp. lactis Strain CECT 8145, Able To Improve Metabolic Syndrome In Vivo  

PubMed Central

Bifidobacterium animalis subsp. lactis strain CECT 8145 is able to reduce body fat content and improve metabolic syndrome biomarkers. Here, we report the draft genome sequence of this strain, which may provide insights into its safety status and functional role.

Chenoll, E.; Codoner, F. M.; Silva, A.; Martinez-Blanch, J. F.; Martorell, P.; Ramon, D.

2014-01-01

300

Conjugative transfer of the Lactococcus lactis sex factor and pRS01 plasmid to Enterococcus faecalis.  

PubMed

The low G+C gram-positive bacterium Lactococcus lactis harbours two highly similar conjugative elements: an integrative and conjugative element called sex factor and the pRS01 plasmid. Originally, it was believed that the host range of the sex factor was limited to L. lactis subspecies. Here, it is reported that pTRK28 cointegrates of a spectinomycin-marked L. lactis sex factor and of the pRS01 conjugative plasmid can be transferred from L. lactis to Enterococcus faecalis. These results demonstrate the conjugative transfer of these elements to other bacterial species. Furthermore, it is reported that Ll.LtrB, a mobile group II intron carried by both elements, can invade its recognition site upon pRS01 conjugative transfer to E. faecalis. PMID:17263841

Belhocine, Kamila; Mandilaras, Victoria; Yeung, Bonnie; Cousineau, Benoit

2007-04-01

301

Molecular Description and Industrial Potential of Tn6098 Conjugative Transfer Conferring Alpha-Galactoside Metabolism in Lactococcus lactis? †  

PubMed Central

A novel 51-kb conjugative transposon of Lactococcus lactis, designated Tn6098, encoding the capacity to utilize ?-galactosides such as raffinose and stachyose, was identified and characterized. Alpha-galactosides are a dominant carbon source in many plant-derived foods. Most dairy lactococcus strains are unable to use ?-galactosides as a growth substrate, yet many of these strains are known to have beneficial industrial traits. Conjugal transfer of Tn6098 was demonstrated from the plant-derived donor strain L. lactis KF147 to the recipient L. lactis NZ4501, a derivative of the dairy model strain L. lactis MG1363. The integration of Tn6098 into the genome of the recipient strain was confirmed by Illumina sequencing of the transconjugant L. lactis NIZO3921. The molecular structure of the integration site was confirmed by a PCR product spanning the insertion site. A 15-bp direct repeat sequence (TTATACCATAATTAC) is present on either side of Tn6098 in the chromosome of L. lactis KF147. One copy of this sequence is also present in the L. lactis MG1363 chromosome and represents the sole integration site. Phenotypic characterization of all strains showed that the transconjugant has not only acquired the ability to grow well in soy milk, a substrate rich in ?-galactosides, but also has retained the flavor-forming capabilities of the recipient strain L. lactis MG1363. This study demonstrates how (induced) conjugation can be used to exploit the beneficial industrial traits of industrial dairy lactic acid bacteria in fermentation of plant-derived substrates.

Machielsen, Ronnie; Siezen, Roland J.; van Hijum, Sacha A. F. T.; van Hylckama Vlieg, Johan E. T.

2011-01-01

302

Lactobacillus acidophilus 74-2 and Bifidobacterium animalis subsp lactis DGCC 420 modulate unspecific cellular immune response in healthy adults  

Microsoft Academic Search

Objective:It was determined whether a combination of Lactobacillus acidophilus (L. acidophilus) 74-2 and Bifidobacterium animalis subsp lactis DGCC 420 (B. lactis 420) affect the faecal microbiota as well as immunological parameters and blood lipids in healthy adults.Design:A placebo-controlled, double-blinded, randomized crossover trial was conducted.Subjects:Twenty-six healthy volunteers (mean age 25 years) were recruited by advertising in academical buildings. All of them

A Klein; U Friedrich; H Vogelsang; G Jahreis

2008-01-01

303

Enzymatic Ability of Bifidobacterium animalis subsp. lactis To Hydrolyze Milk Proteins: Identification and Characterization of Endopeptidase O  

PubMed Central

The proteolytic system of Bifidobacterium animalis subsp. lactis was analyzed, and an intracellular endopeptidase (PepO) was identified and characterized. This work reports the first complete cloning, purification, and characterization of a proteolytic enzyme in Bifidobacterium spp. Aminopeptidase activities (general aminopeptidases, proline iminopeptidase, X-prolyl dipeptidylaminopeptidase) found in cell extracts of B. animalis subsp. lactis were higher for cells that had been grown in a milk-based medium than for those grown in MRS. A high specific proline iminopeptidase activity was observed in B. animalis subsp. lactis. Whole cells and cell wall-bound protein fractions showed no caseinolytic activity; however, the combined action of intracellular proteolytic enzymes could hydrolyze casein fractions rapidly. The endopeptidase activity of B. animalis subsp. lactis was examined in more detail, and the gene encoding an endopeptidase O in B. animalis subsp. lactis was cloned and overexpressed in Escherichia coli. The deduced amino acid sequence for B. animalis subsp. lactis PepO indicated that it is a member of the M13 peptidase family of zinc metallopeptidases and displays 67.4% sequence homology with the predicted PepO protein from Bifidobacterium longum. The recombinant enzyme was shown to be a 74-kDa monomer. Activity of B. animalis subsp. lactis PepO was found with oligopeptide substrates of at least 5 amino acid residues, such as met-enkephalin, and with larger substrates, such as the 23-amino-acid peptide ?s1-casein(f1-23). The predominant peptide bond cleaved by B. animalis subsp. lactis PepO was on the N-terminal side of phenylalanine residues. The enzyme also showed a post-proline secondary cleavage site.

Janer, C.; Arigoni, F.; Lee, B. H.; Pelaez, C.; Requena, T.

2005-01-01

304

Lactococcus lactis LM0230 contains a single aminotransferase involved in aspartate biosynthesis, which is essential for growth in milk  

Microsoft Academic Search

Amino acid aminotransferases (ATases), which catalyse the last biosynthetic step of many amino acids, may have important physiological functions in Lactococcus lactis during growth in milk. In this study, the aspartate ATase gene (aspC) from L. lactis LM0230 was cloned by complementation into Escherichia coli DL39. One chromosomal fragment putatively encoding aspC was partially sequenced. A 1179 bp ORF was

Edward G. Dudley; James L. Steele

305

The development of Tn Nuc and its use for the isolation of novel secretion signals in Lactococcus lactis  

Microsoft Academic Search

We have previously used Tn917 for the identification and characterization of regulated promoters from Lactococcus lactis [Israelsen et al., Appl. Environ. Microbiol. 61 (1995) 2540–2547]. We describe here the construction of a new Tn917-transposon derivative, termed TnNuc, which includes the Staphylococcus aureus nuclease gene (nuc) as a reporter for secretion. Transposition of TnNuc into the L. lactis chromosome allows the

Peter Ravn; José Arnau; Søren M. Madsen; Astrid Vrang; Hans Israelsen

2000-01-01

306

Identification and functional characterization of the Lactococcus lactis rfb operon, required for dTDP-rhamnose biosynthesis  

Microsoft Academic Search

dTDP-rhamnose is an important precursor of cell wall polysaccharides and rhamnose-containing exopolysaccharides (EPS) in Lactococcus lactis. We cloned the rfbACBD operon from L. lactis MG1363, which comprises four genes involved in dTDP-rhamnose biosynthesis. When expressed in Escherichia coli, the lactococcal rfbACBD genes could sustain heterologous production of the Shigella flexneri O antigen, providing evidence of their functionality. Overproduction of the

Ingeborg C. Boels; Marke M. Beerthuyzen; Marit H. W. Kosters; Kaauwen van M. P. W; M. Kleerebezem; Vos de W. M

2004-01-01

307

Phenotypic and Genetic Characterization of the Bacteriophage Abortive Infection Mechanism AbiK fromLactococcus lactis  

Microsoft Academic Search

The natural plasmid pSRQ800 isolated from Lactococcus lactis subsp. lactis W1 conferred strong phage resistance against small isometric phages of the 936 and P335 species when introduced into phage-sensitiveL. lactisstrains. It had very limited effect on prolate phages of the c2 species. The phage resistance mechanism encoded on pSRQ800 is a temperature-sensitive abortive infection system (Abi). Plasmid pSRQ800 was mapped,

ERIC EMOND; BARBARA J. HOLLER; ISABELLE BOUCHER; PETER A. VANDENBERGH; EBENEZER R. VEDAMUTHU; JEFFREY K. KONDO; ANDSYLVAIN MOINEAU

1997-01-01

308

Identification and Molecular Characterization of the Chromosomal Exopolysaccharide Biosynthesis Gene Cluster from Lactococcus lactis subsp. cremoris SMQ-461  

Microsoft Academic Search

The exopolysaccharide (EPS) capsule-forming strain SMQ-461 of Lactococcus lactis subsp. cremoris, isolated from raw milk, produces EPS with an apparent molecular mass of >1.6 106 Da. The EPS biosynthetic genes are located on the chromosome in a 13.2-kb region consisting of 15 open reading frames. This region is flanked by three IS1077-related tnp genes (L. lactis) at the 5 end

N. Dabour; G. LaPointe

2005-01-01

309

Use of a broad-host-range bacteriocin-producing Lactococcus lactis transconjugant as an alternative starter for salami manufacture  

Microsoft Academic Search

Lactococcus lactis DPC4268 is widely used for Cheddar cheese manufacture in Ireland where it is recognised for its reliable fast acid producing ability in dairy environments. A transconjugant of this strain, L. lactis DPC4275, was generated which produces the broad spectrum, two-component bacteriocin lacticin 3147, which is inhibitory to a variety of undesirable Gram-positive bacteria including Clostridium, Bacillus, Enterococcus, Listeria,

A Coffey; M Ryan; R. P Ross; C Hill; E Arendt; G Schwarz

1998-01-01

310

The ldh phylogeny for environmental isolates of Lactococcus lactis is consistent with rRNA genotypes but not with phenotypes.  

PubMed

Lactate dehydrogenase (ldh) gene sequences, levels of 16S rRNA group-specific probe binding, and phenotypic characteristics were compared for 45 environmental isolates and four commercial starter strains of Lactococcus lactis to identify evolutionary groups best suited to cheddar cheese manufacture, ldh sequences from the environmental isolates showed high similarity to those from two groups of L. lactis used for industrial fermentations, L. lactis subsp. cremoris and subsp. lactis. Within each phylogenetically defined subspecies, ldh sequence similarities were greater than 99.1%. Strains with phenotypic traits formerly diagnostic for both subspecies were found in each ldh similarity group, but only strains belonging to L. lactis subsp. cremoris by both the newer, genetic and the older, superseded phenotypic criteria were judged potentially suitable for the commercial production of cheddar cheese. Identical evolutionary relationships were inferred from ldh sequences and from binding of subspecies-specific, 16S rRNA-directed oligonucleotide probes. However, groups defined according to these chromosomal traits bore no relationship to patterns of arginine deamination, carbon substrate utilization, or bacteriophage sensitivity, which may be encoded by cryptic genes or sexually transmissible genetic elements. Fourteen new L. lactis subsp. cremoris isolates were identified as suitable candidates for cheddar cheese manufacture, and 10 of these were completely resistant to three different batteries of commercial bacteriophages known to reduce starter activity. PMID:9023947

Urbach, E; Daniels, B; Salama, M S; Sandine, W E; Giovannoni, S J

1997-02-01

311

Production of Recombinant Peanut Allergen Ara h 2 using Lactococcus lactis  

PubMed Central

Background Natural allergen sources can supply large quantities of authentic allergen mixtures for use as immunotherapeutics. However, such extracts are complex, difficult to define, vary from batch to batch, which may lead to unpredictable efficacy and/or unacceptable levels of side effects. The use of recombinant expression systems for allergen production can alleviate some of these issues. Several allergens have been tested in high-level expression systems and in most cases show immunereactivity comparable to their natural counterparts. The gram positive lactic acid bacterium Lactococcus lactis is an attractive microorganism for use in the production of protein therapeutics. L. lactis is considered food grade, free of endotoxins, and is able to secrete the heterologous product together with few other native proteins. Hypersensitivity to peanut represents a serious allergic problem. Some of the major allergens in peanut have been described. However, for therapeutic usage more information about the individual allergenic components is needed. In this paper we report recombinant production of the Ara h 2 peanut allergen using L. lactis. Results A synthetic ara h 2 gene was cloned into an L. lactis expression plasmid containing the P170 promoter and the SP310mut2 signal sequence. Flask cultures grown overnight showed secretion of the 17 kDa Ara h 2 protein. A batch fermentation resulted in 40 mg/L recombinant Ara h 2. Purification of Ara h 2 from the culture supernatant was done by hydrophobic exclusion and size separation. Mass spectrometry and N-terminal analysis showed a recombinant Ara h 2 of full length and correctly processed by the signal peptidase. The immunological activity of recombinant Ara h 2 was analysed by ELISA using antibodies specific for native Ara h 2. The recombinant Ara h 2 showed comparable immunereactivity to that of native Ara h 2. Conclusion Recombinant production of Ara h 2 using L. lactis can offer high yields of secreted, full length and immunologically active allergen. The L. lactis expression system can support recombinant allergen material for immunotherapy and component resolved allergen diagnostics.

Glenting, Jacob; Poulsen, Lars K; Kato, Kentaro; Madsen, S?ren M; Fr?kiaer, Hanne; Wendt, Camilla; S?rensen, Helle W

2007-01-01

312

Secretion and properties of a hybrid Kluyveromyces lactis-Aspergillus niger ?-galactosidase  

PubMed Central

Background The ?-galactosidase from Kluyveromyces lactis is a protein of outstanding biotechnological interest in the food industry and milk whey reutilization. However, due to its intracellular nature, its industrial production is limited by the high cost associated to extraction and downstream processing. The yeast-system is an attractive method for producing many heterologous proteins. The addition of a secretory signal in the recombinant protein is the method of choice to sort it out of the cell, although biotechnological success is not guaranteed. The cell wall acting as a molecular sieve to large molecules, culture conditions and structural determinants present in the protein, all have a decisive role in the overall process. Protein engineering, combining domains of related proteins, is an alternative to take into account when the task is difficult. In this work, we have constructed and analyzed two hybrid proteins from the ?-galactosidase of K. lactis, intracellular, and its Aspergillus niger homologue that is extracellular. In both, a heterologous signal peptide for secretion was also included at the N-terminus of the recombinant proteins. One of the hybrid proteins obtained has interesting properties for its biotechnological utilization. Results The highest levels of intracellular and extracellular ?-galactosidase were obtained when the segment corresponding to the five domain of K. lactis ?-galactosidase was replaced by the corresponding five domain of the A. niger ?-galactosidase. Taking into account that this replacement may affect other parameters related to the activity or the stability of the hybrid protein, a thoroughly study was performed. Both pH (6.5) and temperature (40°C) for optimum activity differ from values obtained with the native proteins. The stability was higher than the corresponding to the ?-galactosidase of K. lactis and, unlike this, the activity of the hybrid protein was increased by the presence of Ni2+. The affinity for synthetic (ONPG) or natural (lactose) substrates was higher in the hybrid than in the native K. lactis ?-galactosidase. Finally, a structural-model of the hybrid protein was obtained by homology modelling and the experimentally determined properties of the protein were discussed in relation to it. Conclusion A hybrid protein between K. lactis and A. niger ?-galactosidases was constructed that increases the yield of the protein released to the growth medium. Modifications introduced in the construction, besides to improve secretion, conferred to the protein biochemical characteristics of biotechnological interest.

Rodriguez, Angel Pereira; Leiro, Rafael Fernandez; Trillo, M Cristina; Cerdan, M Esperanza; Siso, M Isabel Gonzalez; Becerra, Manuel

2006-01-01

313

Metabolic engineering of Kluyveromyces lactis for L-ascorbic acid (vitamin C) biosynthesis  

PubMed Central

Background L-ascorbic acid (L-AA) is naturally synthesized in plants from D-glucose by 10 steps pathway. The pathway branch to synthesize L-galactose, the key intermediate for L-ascorbic acid biosynthesis, has been recently elucidated. Budding yeast produces an 5-carbon ascorbic acid analogue Dehydro-D-arabinono 1,4-lactone (D-DAL), which is synthesized from D-arabinose. Yeast is able to synthesize L-ascorbic acid only if it is cultivated in the presence of one of its precursors: L-galactose, L-galactono 1,4-lactone, or L-gulono 1,4-lactone extracted from plants or animals. To avoid feeding the yeast culture with this “L” enantiomer, we engineered Kluyveromyces lactis with L-galactose biosynthesis pathway genes: GDP-mannose 3,5-epimerase (GME), GDP-L-galactose phosphorylase (VTC2) and L-galactose-1-phosphate phosphatase (VTC4) isolated from Arabidopsis thaliana. Results Plasmids were constructed and modified such that the cloned plant genes were targeted to the K. lactis LAC4 Locus by homologous recombination and that the expression was associated to the growth on D-galactose or lactose. Upon K. lactis transformation, GME was under the control of the native LAC4 promoter whereas VTC2 and VTC4 were expressed from the S. cerevisiae promoters GPD1 and ADH1 respectively. The expression in K. lactis, of the L-galactose biosynthesis genes was determined by Reverse Transcriptase-PCR and western blotting. The recombinant yeasts were capable to produce about 30 mg.L-1 of L-ascorbic acid in 48 hours of cultivation when cultured on rich medium with 2% (w/v) D-galactose. We also evaluated the L-AA production culturing recombinant recombinant strains in cheese whey, a waste product during cheese production, as an alternative source of lactose. Conclusions This work is the first attempt to engineer K. lactis cells for L-ascorbic acid biosynthesis by a fermentation process without any trace of “L” isomers precursors in the culture medium. We have engineered K. lactis strains capable of converting lactose and D-galactose into L-galactose, by the integration of the genes from the A. thaliana L-galactose pathway. L-galactose is a rare sugar, which is one of the main precursors for L-AA production.

2013-01-01

314

Autolysis of Lactococcus lactis Is Increased upon d-Alanine Depletion of Peptidoglycan and Lipoteichoic Acids  

PubMed Central

Mutations in the genes encoding enzymes responsible for the incorporation of d-Ala into the cell wall of Lactococcus lactis affect autolysis. An L. lactis alanine racemase (alr) mutant is strictly dependent on an external supply of d-Ala to be able to synthesize peptidoglycan and to incorporate d-Ala in the lipoteichoic acids (LTA). The mutant lyses rapidly when d-Ala is removed at mid-exponential growth. AcmA, the major lactococcal autolysin, is partially involved in the increased lysis since an alr acmA double mutant still lyses, albeit to a lesser extent. To investigate the role of d-Ala on LTA in the increased cell lysis, a dltD mutant of L. lactis was investigated, since this mutant is only affected in the d-alanylation of LTA and not the synthesis of peptidoglycan. Mutation of dltD results in increased lysis, showing that d-alanylation of LTA also influences autolysis. Since a dltD acmA double mutant does not lyse, the lysis of the dltD mutant is totally AcmA dependent. Zymographic analysis shows that no degradation of AcmA takes place in the dltD mutant, whereas AcmA is degraded by the extracellular protease HtrA in the wild-type strain. In L. lactis, LTA has been shown to be involved in controlled (directed) binding of AcmA. LTA lacking d-Ala has been reported in other bacterial species to have an improved capacity for autolysin binding. Mutation of dltD in L. lactis, however, does not affect peptidoglycan binding of AcmA; neither the amount of AcmA binding to the cells nor the binding to specific loci is altered. In conclusion, d-Ala depletion of the cell wall causes lysis by two distinct mechanisms. First, it results in an altered peptidoglycan that is more susceptible to lysis by AcmA and also by other factors, e.g., one or more of the other (putative) cell wall hydrolases expressed by L. lactis. Second, reduced amounts of d-Ala on LTA result in decreased degradation of AcmA by HtrA, which results in increased lytic activity.

Steen, Anton; Palumbo, Emmanuelle; Deghorain, Marie; Cocconcelli, Pier Sandro; Delcour, Jean; Kuipers, Oscar P.; Kok, Jan; Buist, Girbe; Hols, Pascal

2005-01-01

315

Plasmids of Raw Milk Cheese Isolate Lactococcus lactis subsp. lactis Biovar diacetylactis DPC3901 Suggest a Plant-Based Origin for the Strain ? †  

PubMed Central

The four-plasmid complement of the raw milk cheese isolate Lactococcus lactis subsp. lactis biovar diacetylactis DPC3901 was sequenced, and some genetic features were functionally analyzed. The complete sequences of pVF18 (18,977 bp), pVF21 (21,739 bp), pVF22 (22,166 bp), and pVF50 (53,876 bp) were obtained. Each plasmid contained genes not previously described for Lactococcus, in addition to genes associated with plant-derived lactococcal strains. Most of the novel genes were found on pVF18 and encoded functions typical of bacteria associated with plants, such as activities of plant cell wall modification (orf11 and orf25). In addition, a predicted high-affinity regulated system for the uptake of cobalt was identified (orf19 to orf21 [orf19-21]), which has a single database homolog on a plant-derived Leuconostoc plasmid and whose functionality was demonstrated following curing of pVF18. pVF21 and pVF22 encode additional metal transporters, which, along with orf19-21 of pVF18, could enhance host ability to uptake growth-limiting amounts of biologically essential ions within the soil. In addition, vast regions from pVF50 and pVF21 share significant homology with the plant-derived lactococcal plasmid pGdh442, which is indicative of extensive horizontal gene transfer and recombination between these plasmids and suggests a common plant niche for their hosts. Phenotypes associated with these regions include glutamate dehydrogenase activity and Na+ and K+ transport. The presence of numerous plant-associated markers in L. lactis DPC3901 suggests a plant origin for the raw milk cheese isolate and provides for the first time the genetic basis to support the concept of the plant-milk transition for Lactococcus strains.

Fallico, Vincenzo; McAuliffe, Olivia; Fitzgerald, Gerald F.; Ross, R. Paul

2011-01-01

316

Heat shock induces thermotolerance and inhibition of lysis in a lysogenic strain of Lactococcus lactis.  

PubMed

In this preliminary work, the heat shock response of lactic acid bacteria was investigated and characterized. Log-phase Lactococcus lactis cells pre-incubated at 40 degrees C before heat challenge at 52 degrees C for 30 min demonstrated increased thermotolerance as compared with cells pre-incubated at 30 degrees C. The response persisted for at least 60 min. Additionally, we demonstrated that: (i) the physiological expression of the heat shock response is temperature dependent; (ii) ethanol 4.0% (v/v) caused, to a lesser extent, a response similar to the heat shock; and (iii) hydrogen peroxide failed to induce a detectable response. Furthermore, we suggest that the induction of the heat shock response increases the resistance of a lysogenic strain of L. lactis, treated by mitomycin C (1.25 micrograms/ml), to lysis by the bacteriophage. PMID:1742167

Boutibonnes, P; Gillot, B; Auffray, Y; Thammavongs, B

1991-10-01

317

Chemical Nature of Malty Flavor and Aroma Produced by Streptococcus lactis var. maltigenes1  

PubMed Central

Mature skim milk cultures of Streptococcus lactis var. maltigenes were steam distilled at low temperature under reduced pressure. Ethyl ether extracts were prepared from the distillates and analyzed by gas-liquid chromatography and mass spectrometry. Twenty of 31 components detected in the culture distillates were identified positively and 11 tentatively, whereas 10 of 19 components detected in the heated skim milk control were identified positively and 9 tentatively. Among components detected in the culture distillate, but not detected in the heated skim milk distillate, and which have not been previously identified in milk cultures of the organism were phenylacetaldehyde and phenethanol. Quantitative analyses of the volatiles entrained from milk cultures of several strains of S. lactis var. maltigenes revealed a probable relationship between variation in the character of the aroma of the cultures and the alcohol/aldehyde ratio.

Sheldon, R. M.; Lindsay, R. C.; Libbey, L. M.; Morgan, M. E.

1971-01-01

318

Production of a Particulate Hepatitis C Vaccine Candidate by an Engineered Lactococcus lactis Strain?  

PubMed Central

Vaccine delivery systems based on display of antigens on bioengineered bacterial polyester inclusions can stimulate cellular immune responses. The food-grade Gram-positive bacterium Lactococcus lactis was engineered to produce spherical polyhydroxybutyrate (PHB) inclusions which abundantly displayed the hepatitis C virus core (HCc) antigen. In mice, the immune response induced by this antigen delivery system was compared to that induced by vaccination with HCc antigen displayed on PHB beads produced in Escherichia coli, to PHB beads without antigen produced in L. lactis or E. coli, or directly to the recombinant HCc protein. Vaccination site lesions were minimal in all mice vaccinated with HCc PHB beads or recombinant protein, all mixed in the oil-in-water adjuvant Emulsigen, while vaccination with the recombinant protein in complete Freund's adjuvant produced a marked inflammatory reaction at the vaccination site. Vaccination with the PHB beads produced in L. lactis and displaying HCc antigen produced antigen-specific cellular immune responses with significant release of gamma interferon (IFN-?) and interleukin-17A (IL-17A) from splenocyte cultures and no significant antigen-specific serum antibody, while the PHB beads displaying HCc but produced in E. coli released IFN-? and IL-17A as well as the proinflammatory cytokines tumor necrosis factor alpha (TNF-?) and IL-6 and low levels of IgG2c antibody. In contrast, recombinant HCc antigen in Emulsigen produced a diverse cytokine response and a strong IgG1 antibody response. Overall it was shown that L. lactis can be used to produce immunogenic PHB beads displaying viral antigens, making the beads suitable for vaccination against viral infections.

Parlane, Natalie A.; Grage, Katrin; Lee, Jason W.; Buddle, Bryce M.; Denis, Michel; Rehm, Bernd H. A.

2011-01-01

319

Production of nisin Z using Lactococcus lactis IO1 from hydrolyzed sago starch  

Microsoft Academic Search

A membrane bioreactor for production of nisin Z was constructed using Lactococcus lactis IO-1 in continuous culture using hydrolyzed sago starch as carbon source. A strategy used to enhance the productivity of\\u000a nisin Z was to maintain the cells in a continuous growth at high cell concentration. This resulted in a volumetric productivity\\u000a of nisin Z, as 50,000 IU l?1 h?1 using a

Octavio Carvajal-Zarrabal; Cirilo Nolasco-Hipólito; Kopli B. Bujang; Ayaaki Ishizaki

2009-01-01

320

KNQ1 , a Kluyveromyces lactis gene encoding a drug efflux permease  

Microsoft Academic Search

Several transport systems play an important role in conferring multiple drug resistance, presumably due to their catalysis of the energy-dependent extrusion of a large number of structurally and functionally unrelated compounds out of the cells. In the present work, the gene named KNQ1 (encoding Kluyveromyces lactis membrane permease) was cloned by functional complementation of the cycloheximide-hypersensitivity phenotype of the Saccharomyces

Maria Takacova; Denisa Imrichova; Jana Cernicka; Yvetta Gbelska; Julius Subik

2004-01-01

321

Crystallization and preliminary X-ray crystallographic analysis of ?-galactosidase from Kluyveromyces lactis  

PubMed Central

?-Galactosidase from Kluyveromyces lactis catalyses the hydrolysis of the ?-­galactosidic linkage in lactose. Owing to its many industrial applications, the biotechnological potential of this enzyme is substantial. This protein has been expressed in yeast and purified for crystallization trials. However, optimization of the best crystallization conditions yielded crystals with poor diffraction quality that precluded further structural studies. Finally, the crystal quality was improved using the streak-seeding technique and a complete diffraction data set was collected at 2.8?Å resolution.

Pereira-Rodriguez, Angel; Fernandez-Leiro, Rafael; Gonzalez Siso, M. Isabel; Cerdan, M. Esperanza; Becerra, Manuel; Sanz-Aparicio, Julia

2010-01-01

322

Genetic and Biochemical Characterization of theLactobacillus delbrueckiisubsp.lactisBacteriophage LL-H Lysin  

Microsoft Academic Search

LL-H, a virulent phage ofLactobacillus delbrueckiisubsp.lactis, produces a peptidoglycan-degrading enzyme, Mur, that is effective on L. delbrueckii, Lactobacillus acidophilus, Lactobacillus helveticus, and Pediococcus damnosuscell walls. In this study, the LL-H genemurwas cloned intoEscherichia coli, its nucleotide sequence was determined, and the enzyme produced in E. coli was purified and biochemically characterized. Mur was purified 112-fold by means of ammonium sulfate

ANTTI VASALA; MERJA VALKKILA; JAVIER CALDENTEY; ANDTAPANI ALATOSSAVA

1995-01-01

323

High-efficiency transformation of Streptococcus lactis protoplasts by plasmid DNA.  

PubMed Central

Streptococcus lactis IL1403 protoplasts were transformed by plasmid pIL204 (5.5 kilobases), which conferred erythromycin resistance with an average efficiency of 5 X 10(6) transformants per microgram of supercoiled DNA. The procedure used and transformation efficiencies obtained were close to those described for Bacillus subtilis (G. Chang and S. N. Cohen, Mol. Gen. Genet. 168:111-115, 1979).

Simon, D; Rouault, A; Chopin, M C

1986-01-01

324

Exploitation of a chromosomally integrated lactose operon for controlled gene expression in Lactococcus lactis  

Microsoft Academic Search

Lactococcus lactis MG5267 is a plasmid-free strain in which the lactose operon is integrated in the bacterial chromosome. The chromosomal lacG gene which encodes phospho-?-galactosidase was inactivated by a double cross-over integration event. Unexpectedly, the resultant mutant was shown to retain a Lac-positive phenotype. The lysin gene from Listeria monocytogenes bacteriophage LM-4 was subsequently integrated into the chromosome of this

John Payne; Caroline A MacCormick; Hugh G Griffin; Michael J Gasson

1996-01-01

325

Effect of ilvBN -encoded ?-acetolactate synthase expression on diacetyl production in Lactococcus lactis  

Microsoft Academic Search

Conversion of pyruvate to ?-acetolactate, which is broken down to diacetyl and acetoin, can be catalysed by two ?-acetolactate\\u000a synthases in Lactococcus lactis. The enzyme encoded by the als gene (Als) has previously been shown to have a low affinity for pyruvate, which limits the formation of diacetyl. In this\\u000a study we have expressed from a plasmid the ilvBN genes,

K. H. Benson; J.-J. Godon; P. Renault; H. G. Griffin; M. J. Gasson

1996-01-01

326

Orally administered L. lactis secreting an anti-TNF Nanobody demonstrate efficacy in chronic colitis  

Microsoft Academic Search

Inflammatory bowel disease (IBD) is a chronic inflammatory gastrointestinal disorder. Systemic treatment of IBD patients with anti-tumor necrosis factor (TNF)-? antibodies has proven to be a highly promising approach, but several drawbacks remain, including side effects related to systemic administration and high cost of treatment. Lactococcus lactis was engineered to secrete monovalent and bivalent murine (m)TNF-neutralizing Nanobodies as therapeutic proteins.

K Vandenbroucke; H de Haard; E Beirnaert; T Dreier; M Lauwereys; L Huyck; J Van Huysse; P Demetter; L Steidler; E Remaut; C Cuvelier; P Rottiers

2010-01-01

327

Nisin inducible production of listeriolysin O in Lactococcus lactis NZ9000  

Microsoft Academic Search

Background  \\u000a Listeria monocytogenesis a well-characterized food-borne pathogen that infects pregnant women and immunocompromised individuals. Listeriolysin O\\u000a (LLO) is the major virulence factor of the pathogen and is often used as a diagnostic marker for detection of L. monocytogenes. In addition, LLO represents a potent antigen driving T cell-mediated immunity during infection. In the present work, Lactococcus lactisNZ9000 was used as

Mohammed Bahey-El-Din; Brendan T Griffin; Cormac GM Gahan

2008-01-01

328

Epidermal growth factor-expressing Lactococcus lactis enhances intestinal development of early-weaned pigs.  

PubMed

Stress and incomplete gastrointestinal development in early-weaned piglets represent significant challenges in commercial swine farming. Orally ingested recombinant epidermal growth factor (EGF) has been shown to remain biologically active in the gastrointestinal tract as well as stimulate intestinal development, reducing the incidence of pathogen infection and diarrhea. We have previously shown that the food-grade bacterium Lactococcus lactis can be genetically altered to express biologically active EGF when fed to early-weaned mice. In this study, we assigned 8 pigs to each of 4 groups that were given EGF-expressing L. lactis (EGF-LL), empty vector-expressing L. lactis (EV-LL), recombinant human EGF, or unsupplemented bacterial media, all of which were delivered as 50-mL i.g. doses twice per day. All pigs were killed after 14 d to examine intestinal morphology. Pigs in the EGF-LL group had greater jejunal and duodenal villus heights (P < 0.0001) and intestinal length (P = 0.049) than pigs in the control group. Immunohistochemistry with antibodies against proliferating cell nuclear antigen (PCNA) revealed that the proliferation of intestinal cells was significantly greater in the EGF-LL group than in the control group. PCNA expression and intestinal length also were greater in the EV-LL group, which received L. lactis that did not express EGF, than in the control group (P = 0.049), further supporting the use of naturally occurring intestinal microbes as desirable vectors for recombinant protein delivery. Our data demonstrates the feasibility of delivering a growth factor using common probiotic bacteria to farm animals for commercial practice. PMID:20147464

Kang, Ping; Toms, Derek; Yin, Yulong; Cheung, Queenie; Gong, Joshhua; De Lange, Kees; Li, Julang

2010-04-01

329

Genotype-phenotype matching analysis of 38 Lactococcus lactis strains using random forest methods  

PubMed Central

Background Lactococcus lactis is used in dairy food fermentation and for the efficient production of industrially relevant enzymes. The genome content and different phenotypes have been determined for multiple L. lactis strains in order to understand intra-species genotype and phenotype diversity and annotate gene functions. In this study, we identified relations between gene presence and a collection of 207 phenotypes across 38 L. lactis strains of dairy and plant origin. Gene occurrence and phenotype data were used in an iterative gene selection procedure, based on the Random Forest algorithm, to identify genotype-phenotype relations. Results A total of 1388 gene-phenotype relations were found, of which some confirmed known gene-phenotype relations, such as the importance of arabinose utilization genes only for strains of plant origin. We also identified a gene cluster related to growth on melibiose, a plant disaccharide; this cluster is present only in melibiose-positive strains and can be used as a genetic marker in trait improvement. Additionally, several novel gene-phenotype relations were uncovered, for instance, genes related to arsenite resistance or arginine metabolism. Conclusions Our results indicate that genotype-phenotype matching by integrating large data sets provides the possibility to identify gene-phenotype relations, possibly improve gene function annotation and identified relations can be used for screening bacterial culture collections for desired phenotypes. In addition to all gene-phenotype relations, we also provide coherent phenotype data for 38 Lactococcus strains assessed in 207 different phenotyping experiments, which to our knowledge is the largest to date for the Lactococcus lactis species.

2013-01-01

330

S 1 site residues of Lactococcus lactis prolidase affect substrate specificity and allosteric behaviour  

Microsoft Academic Search

Lactococcus lactis prolidase preferably hydrolyzes Xaa-Pro dipeptides where Xaa is a hydrophobic amino acid. Anionic Glu-Pro and Asp-Pro dipeptides cannot be hydrolyzed at any observable rates and the hydrolysis of cationic Arg-Pro and Lys-Pro dipeptides is at about one tenth of the rate of Leu-Pro. It was hypothesized that the hydrophobic residues in the S1 site were responsible for this

Keke Hu; Takuji Tanaka

2009-01-01

331

PepR1, a CcpA-like transcription regulator of Lactobacillus delbrueckii subsp. lactis  

Microsoft Academic Search

The PepR1 protein from Lactobacillus delbrueckii subsp. lactis DSM 7290 shares extensive homology with catabolite-control proteins from various Gram- positive bacteria. Expression of the subcloned pepR1 gene allowed for partial complementation of a ccpA defect in Staphylococcus xylosus. The influence of PepR1 on transcription of the prolidase gene pepQ, which is located adjacent to pepR1, was examined by use of

Joachim Schick; Beate Weber; R. Klein; Bernhard Henrich; Fachbereich Biologie

332

Production of kefir like product from mixed cultures of Saccharomyces cerevisiae, Streptococcus cremoris and Streptococcus lactis  

Microsoft Academic Search

Various ratios of Streptococcus cremoris to Streptococcus lactis, 0.5 : 1.5, 1 : 1 and 1.5 : 0.5% were added to milk supplemented with 5% (w\\/v) sucrose. Fermentation temperature was kept constant at 30oC. For the first 15 h of fermentation, the milk was fermented by 5% (v\\/v) Saccharomyces cerevisiae, followed by lactic acid bacteria. The total fermentation time was

Pongpakorn Kaewprasert; Naiyatat Poosaran

333

Cloning and Expression of the Lactococcus lactis purDEK Genes, Required for Growth in Milk  

Microsoft Academic Search

An operon containing the genes purD and purE and part of the purK gene was cloned from the facultative anaerobic gram-positive bacterium Lactococcus lactis by complementation of the purD mutation in Escherichia coli SØ609. The genes encode enzymes in the de novo pathway of purine nucleotides. The expression of the genes was regulated approximately 35-fold at the transcription level by

DAN NILSSON; MOGENS KILSTRUP

1998-01-01

334

Phosphorus31 NMR studies of maltose and glucose metabolism in Streptococcus lactis  

Microsoft Academic Search

Streptococcus lactis ferments glucose in a homolactic fashion but a heterolactic fermentation pattern is observed when it is grown on maltose. Using in vivo phosphorus-31 and carbon-13 NMR studies of glucose-metabolizing cells we confirmed that fructosediphosphate (FDP) is the major glycolytic intermediate and that the production of lactate causes major changes both in the intra- and extracellular pH values. Starved

Elke M. Lohmeier-Vogel; Bärbel Hahn-Hägerdahl; Hans J. Vogel

1986-01-01

335

Physiological and regulatory effects of controlled overproduction of five cold shock proteins of Lactococcus lactis  

Microsoft Academic Search

The physiological and regulatory effects of overproduction of five cold shock proteins (CSPs) of Lactococcus lactis were studied. CspB, CspD, and CspE could be overproduced at high levels (up to 19?f the total protein), whereas for CspA and CspC limited overproduction (0.3 to 0.5?f the total protein) was obtained. Northern blot analysis revealed low abundance of the cspC transcript, indicating

Jeroen A. Wouters; Marielle Mailhes; Frank M. Rombouts; Willem M. de Vos; Oscar P. Kuipers; Tjakko Abee

2000-01-01

336

Experimental and steady-state analysis of the GAL regulatory system in Kluyveromyces lactis.  

PubMed

The galactose uptake mechanism in yeast is a well-studied regulatory network. The regulatory players in the galactose regulatory mechanism (GAL system) are conserved in Saccharomyces cerevisiae and Kluyveromyces lactis, but the molecular mechanisms that occur as a result of the molecular interactions between them are different. The key differences in the GAL system of K. lactis relative to that of S. cerevisiae are: (a) the autoregulation of KlGAL4; (b) the dual role of KlGal1p as a metabolizing enzyme as well as a galactose-sensing protein; (c) the shuttling of KlGal1p between nucleus and cytoplasm; and (d) the nuclear confinement of KlGal80p. A steady-state model was used to elucidate the roles of these molecular mechanisms in the transcriptional response of the GAL system. The steady-state results were validated experimentally using measurements of beta-galactosidase to represent the expression for genes having two binding sites. The results showed that the autoregulation of the synthesis of activator KlGal4p is responsible for the leaky expression of GAL genes, even at high glucose concentrations. Furthermore, GAL gene expression in K. lactis shows low expression levels because of the limiting function of the bifunctional protein KlGal1p towards the induction process in order to cope with the need for the metabolism of lactose/galactose. The steady-state model of the GAL system of K. lactis provides an opportunity to compare with the design prevailing in S. cerevisiae. The comparison indicates that the existence of a protein, Gal3p, dedicated to the sensing of galactose in S. cerevisiae as a result of genome duplication has resulted in a system which metabolizes galactose efficiently. PMID:20528923

Pannala, Venkat R; Bhartiya, Sharad; Venkatesh, Kareenhalli V

2010-07-01

337

Glycolic acid production in the engineered yeasts Saccharomyces cerevisiae and Kluyveromyces lactis  

PubMed Central

Background Glycolic acid is a C2 hydroxy acid that is a widely used chemical compound. It can be polymerised to produce biodegradable polymers with excellent gas barrier properties. Currently, glycolic acid is produced in a chemical process using fossil resources and toxic chemicals. Biotechnological production of glycolic acid using renewable resources is a desirable alternative. Results The yeasts Saccharomyces cerevisiae and Kluyveromyces lactis are suitable organisms for glycolic acid production since they are acid tolerant and can grow in the presence of up to 50 g l-1 glycolic acid. We engineered S. cerevisiae and K. lactis for glycolic acid production using the reactions of the glyoxylate cycle to produce glyoxylic acid and then reducing it to glycolic acid. The expression of a high affinity glyoxylate reductase alone already led to glycolic acid production. The production was further improved by deleting genes encoding malate synthase and the cytosolic form of isocitrate dehydrogenase. The engineered S. cerevisiae strain produced up to about 1 g l-1 of glycolic acid in a medium containing d-xylose and ethanol. Similar modifications in K. lactis resulted in a much higher glycolic acid titer. In a bioreactor cultivation with d-xylose and ethanol up to 15 g l-1 of glycolic acid was obtained. Conclusions This is the first demonstration of engineering yeast to produce glycolic acid. Prior to this work glycolic acid production through the glyoxylate cycle has only been reported in bacteria. The benefit of a yeast host is the possibility for glycolic acid production also at low pH, which was demonstrated in flask cultivations. Production of glycolic acid was first shown in S. cerevisiae. To test whether a Crabtree negative yeast would be better suited for glycolic acid production we engineered K. lactis in the same way and demonstrated it to be a better host for glycolic acid production.

2013-01-01

338

Oxidative stress at high temperatures in Lactococcus lactis due to an insufficient supply of Riboflavin.  

PubMed

Lactococcus lactis MG1363 was found to be unable to grow at temperatures above 37°C in a defined medium without riboflavin, and the cause was identified to be dissolved oxygen introduced during preparation of the medium. At 30°C, growth was unaffected by dissolved oxygen and oxygen was consumed quickly. Raising the temperature to 37°C resulted in severe growth inhibition and only slow removal of dissolved oxygen. Under these conditions, an abnormally low intracellular ratio of [ATP] to [ADP] (1.4) was found (normally around 5), which indicates that the cells are energy limited. By adding riboflavin to the medium, it was possible to improve growth and oxygen consumption at 37°C, and this also normalized the [ATP]-to-[ADP] ratio. A codon-optimized redox-sensitive green fluorescent protein (GFP) was introduced into L. lactis and revealed a more oxidized cytoplasm at 37°C than at 30°C. These results indicate that L. lactis suffers from heat-induced oxidative stress at increased temperatures. A decrease in intracellular flavin adenine dinucleotide (FAD), which is derived from riboflavin, was observed with increasing growth temperature, but the presence of riboflavin made the decrease smaller. The drop was accompanied by a decrease in NADH oxidase and pyruvate dehydrogenase activities, both of which depend on FAD as a cofactor. By overexpressing the riboflavin transporter, it was possible to improve FAD biosynthesis, which resulted in increased NADH oxidase and pyruvate dehydrogenase activities and improved fitness at high temperatures in the presence of oxygen. PMID:23913422

Chen, Jun; Shen, Jing; Solem, Christian; Jensen, Peter Ruhdal

2013-10-01

339

KNQ1, a Kluyveromyces lactis gene encoding a drug efflux permease.  

PubMed

Several transport systems play an important role in conferring multiple drug resistance, presumably due to their catalysis of the energy-dependent extrusion of a large number of structurally and functionally unrelated compounds out of the cells. In the present work, the gene named KNQ1 (encoding Kluyveromyces lactis membrane permease) was cloned by functional complementation of the cycloheximide-hypersensitivity phenotype of the Saccharomyces cerevisiae mutant strain lacking a functional PDR5 gene. The isolated gene exhibited 48.9% identity with the S. cerevisiae ATR1 gene conferring resistance to aminotriazole and 4-nitroquinoline- N-oxide and encoded a protein of 553 amino acids. When present in multicopy, it efficiently complemented the phenotype associated with the Delta pdr5 or Delta pdr1Delta pdr3 mutations in S. cerevisiae. Overexpression of the KNQ1 gene in K. lactis wild-type strains led to resistance against several cytotoxic compounds, like 4-nitroquinoline- N-oxide, 3-aminotriazole, bifonazole and ketoconazole. The gene was assigned to K. lactis chromosome III and its expression was found to be responsive to oxidative stress induced by hydrogen peroxide. Based on the phenotype of homologous and heterologous transformants, we propose that the gene encodes a membrane-associated component of the machinery responsible for decreasing the concentration of several toxic compounds in the cytoplasm of yeast cells. PMID:14595517

Takacova, Maria; Imrichova, Denisa; Cernicka, Jana; Gbelska, Yvetta; Subik, Julius

2004-02-01

340

Mutations in Mgi Genes Convert Kluyveromyces Lactis into a Petite-Positive Yeast  

PubMed Central

Following targeted disruption of the unique CYC1 gene, the petite-negative yeast, Kluyveromyces lactis, was found to grow fermentatively in the absence of cytochrome c-mediated respiration. This observation encouraged us to seek mitochondrial mutants by treatment of K. lactis with ethidium bromide at the highest concentration permitting survival. By this technique, we isolated four mtDNA mutants, three lacking mtDNA and one with a deleted mitochondrial genome. In the three isolates lacking mtDNA, a nuclear mutation is present that permits petite formation. The three mutations occur at two different loci, designated MGI1 and MGI2 (for Mitochondrial Genome Integrity). The mgi mutations convert K. lactis into a petite-positive yeast. Like bakers' yeast, the mgi mutants spontaneously produce petites with deletions in mtDNA and lose this genome at high frequency on treatment with ethidium bromide. We suggest that the MGI gene products are required for maintaining the integrity of the mitochondrial genome and that, petite-positive yeasts may be naturally altered in one or other of these genes.

Chen, X. J.; Clark-Walker, G. D.

1993-01-01

341

Measuring Kinetic Dissociation/Association Constants Between Lactococcus lactis Bacteria and Mucins Using Living Cell Probes  

PubMed Central

In this work we focused on quantifying adhesion between Lactococcus lactis, the model for lactic acid bacteria (LAB) and mucins. Interactions between two strains of L. lactis (IBB477 and MG1820 as control) and pig gastric mucin–based coating were measured and compared with the use of atomic force microscopy. Analysis of retraction force-distance curves shed light on the differential contributions of nonspecific and specific forces. An increased proportion of specific adhesive events was obtained for IBB477 (20% vs. 5% for the control). Blocking assays with free pig gastric mucin and its O-glycan moiety showed that oligosaccharides play a major (but not exclusive) role in L. lactis-mucins interactions. Specific interactions were analyzed in terms of kinetic constants. An increase in the loading rate of atomic force microscope tip led to a higher force between interacting biological entities, which was directly linked to the kinetic dissociation constant (Koff). Enhancing the contact time between the tip and the sample allowed an increase in the interaction probability, which can be related to the kinetic association constant (Kon). Variations in the loading rate and contact time enabled us to determine Kon (3.3 × 102 M?1·s?1) and Koff (0.46 s?1), and the latter was consistent with values given in the literature for sugar-protein interactions.

Le, Doan Thanh Lam; Guerardel, Yann; Loubiere, Pascal; Mercier-Bonin, Muriel; Dague, Etienne

2011-01-01

342

Acid- and multistress-resistant mutants of Lactococcus lactis : identification of intracellular stress signals.  

PubMed

Lactococcus lactis growth is accompanied by lactic acid production, which results in acidification of the medium and arrest of cell multiplication. Despite growth limitation at low pH, there is evidence that lactococci do have inducible responses to an acid pH. In order to characterize the genes involved in acid tolerance responses, we selected acid-resistant insertional mutants of the L. lactis strain MG1363. Twenty-one independent characterized mutants were affected in 18 different loci, some of which are implicated in transport systems or base metabolism. None of these genes was identified previously as involved in lactococcal acid tolerance. The various phenotypes obtained by acid stress selection allowed us to define four classes of mutants, two of which comprise multistress-resistant strains. Our results reveal that L. lactis has several means of protecting itself against low pH, at least one of which results in multiple stress resistance. In particular, intracellular phosphate and guanine nucleotide pools, notably (p)ppGpp, are likely to act as signals that determine the level of lactococcal stress response induction. Our results provide a link between the physiological state of the cell and the level of stress tolerance and establish a role for the stringent response in acid stress response regulation. PMID:10672175

Rallu, F; Gruss, A; Ehrlich, S D; Maguin, E

2000-02-01

343

Biotechnological and safety characterization of Enterococcus lactis, a recently described species of dairy origin.  

PubMed

The biotechnological and safety properties of a recently described enterococcal species, Enterococcus lactis, were investigated. With regard to the technological properties, in milk all the strains tested had weak acidifying and proteolytic activities, generally medium reduction activity over 24 h (-102 mV < Eh < -2 mV) and low lipolytic activity on tributyrin agar. The isolates were tested for resistance against 14 antibiotics and none of the studied strains were classified as resistant to clinically important antibiotics such as ampicillin, erythromycin, penicillin G, tetracycline and vancomycin. Furthermore, PCR-based detection did not identify any of the common genetic determinants for vancomycin, tetracycline and erythromycin resistance. The E. lactis strains showed good survival in simulated in vitro digestion and were able to inhibit the growth of Enterococcus durans, Enterococcus faecalis, Enterococcus faecium, Clostridium sporogenes, Clostridium tyrobutyricum and Pseudomonas syringae. Screening for enterocin structural genes showed that all isolates harboured the entP gene. The presence of nine virulence factor genes (cylA, asa1, gelE, hyl, esp, ace, efaA, hdc and tdc) was investigated by PCR and no virulence determinants were detected. This study highlights that the recently described E. lactis may be a potential source of novel strains with interesting features that could be used for fermented dairy foods. PMID:22961639

Morandi, Stefano; Silvetti, Tiziana; Brasca, Milena

2013-01-01

344

Construction and expression of food-grade ?-galactosidase gene in Lactococcus Lactis.  

PubMed

Recombinant Lactococcus lactis MG1363/pMG36e-lacZ exhibiting high ?-galactosidase activities were constructed by us in the previous study. However, erythromycin resistance present in these recombinants restricted their practical application in food preparation. This study was conducted to delete the gene coding for erythromycin resistance present in recombinant L. lactis, as a result of which these bacteria express food-grade ?-galactosidase. In this study, the recombinant plasmid pMG36e-lacZ was digested with restriction enzymes BclI and HpaI and the food-grade plasmid FGZW was rebuilt. FGZW was transformed into Escherichia coli JM109 and L. lactis MG1363. Erythromycin resistance, enzyme activity determination, gene sequencing and SDS-PAGE analysis indicated that these new recombinant bacteria lost erythromycin resistance and its relevant gene but still expressed ?-galactosidase activities, although a decrease in the expression of ?-galactosidase of these new strains was observed. The ?-galactosidase food-grade expression system was successfully constructed and it could provide a new solution for the management of lactose intolerance. These results might promote the usage of gene-modified microorganisms and related technology in the food sector, which has the highest priority for food safety. PMID:20924584

Zhang, Wen; Wang, Chuan; Huang, Chengyu; Yu, Qian; Liu, Hengchuan; Zhang, Chaowu; Pei, Xiaofang

2011-02-01

345

Evolutionary aspects of a genetic network: studying the lactose/galactose regulon of Kluyveromyces lactis.  

PubMed

The budding yeast Kluyveromyces lactis has diverged from the Saccharomyces lineage before the whole-genome duplication and its genome sequence reveals lower redundancy of many genes. Moreover, it shows lower preference for fermentative carbon metabolism and a broader substrate spectrum making it a particularly rewarding system for comparative and evolutionary studies of carbon-regulated genetic networks. The lactose/galactose regulon of K. lactis, which is regulated by the prototypic transcription activator Gal4 exemplifies important aspects of network evolution when compared with the model GAL regulon of Saccharomyces cerevisiae. Differences in physiology relate to different subcellular compartmentation of regulatory components and, importantly, to quantitative differences in protein-protein interactions rather than major differences in network architecture. Here, we introduce genetic and biochemical tools to study K. lactis in general and the lactose/galactose regulon in particular. We present methods to quantify relevant protein-protein interactions in that network and to visualize such differences in simple plate assays allowing for genetic approaches in further studies. PMID:21468994

Anders, Alexander; Breunig, Karin D

2011-01-01

346

Probiotic assessment of Enterococcus durans 6HL and Lactococcus lactis 2HL isolated from vaginal microflora.  

PubMed

Forty-five lactic acid bacteria (LAB) were isolated from the vaginal specimens of healthy fertile women, and the identities of the bacteria were confirmed by sequencing of their 16S rDNA genes. Among these bacteria, only four isolates were able to resist and survive in low pH, bile salts and simulated in vitro digestion conditions. Lactococcus lactis 2HL, Enterococcus durans 6HL, Lactobacillus acidophilus 36YL and Lactobacillus plantarum 5BL showed the best resistance to these conditions. These strains were evaluated further to assess their ability to adhere to human intestinal Caco-2 cells. Lactococcus lactis 2HL and E. durans 6HL were the most adherent strains. In vitro tests under neutralized pH proved the antimicrobial activity of both strains. Results revealed that the growth of Escherichia coli O26, Staphylococcus aureus and Shigella flexneri was suppressed by both LAB strains. The antibiotic susceptibility tests showed that these strains were sensitive to all nine antibiotics: vancomycin, tetracycline, ampicillin, penicillin, gentamicin, erythromycin, clindamycin, sulfamethoxazole and chloramphenicol. These data suggest that E. durans 6HL and Lactococcus lactis 2HL could be examined further for their useful properties and could be developed as new probiotics. PMID:24913559

Nami, Yousef; Abdullah, Norhafizah; Haghshenas, Babak; Radiah, Dayang; Rosli, Rozita; Khosroushahi, Ahmad Yari

2014-08-01

347

Trans-splicing of the Ll.LtrB group II intron in Lactococcus lactis  

PubMed Central

The Ll.LtrB intron from the Gram-positive bacterium Lactococcus lactis is one of the most studied bacterial group II introns. Ll.LtrB interrupts the relaxase gene of three L. lactis conjugative elements. The relaxase enzyme recognizes the origin of transfer (oriT?) and initiates the intercellular transfer of its conjugative element. The splicing efficiency of Ll.LtrB from the relaxase transcript thus controls the conjugation level of its host element. Here, we used the level of sex factor conjugation as a read-out for Ll.LtrB splicing efficiency. Using this highly sensitive splicing/conjugation assay (107-fold detection range), we demonstrate that Ll.LtrB can trans-splice in L. lactis when fragmented at various positions such as: three different locations within domain IV, within domain I and within domain III. We also demonstrate that the intron-encoded protein, LtrA, is absolutely required for Ll.LtrB trans-splicing. Characteristic Y-branched trans-spliced introns and ligated exons are detected by RT-PCR from total RNA extracts of cells harbouring fragmented Ll.LtrB. The splicing/conjugation assay we developed constitutes the first model system to study group II intron trans-splicing in vivo. Although only previously observed in bacterial-derived organelles, we demonstrate that assembly and trans-splicing of a fragmented group II intron can take place efficiently in bacterial cells.

Belhocine, Kamila; Mak, Anthony B.; Cousineau, Benoit

2007-01-01

348

Trans-splicing of the Ll.LtrB group II intron in Lactococcus lactis.  

PubMed

The Ll.LtrB intron from the Gram-positive bacterium Lactococcus lactis is one of the most studied bacterial group II introns. Ll.LtrB interrupts the relaxase gene of three L. lactis conjugative elements. The relaxase enzyme recognizes the origin of transfer (oriT ) and initiates the intercellular transfer of its conjugative element. The splicing efficiency of Ll.LtrB from the relaxase transcript thus controls the conjugation level of its host element. Here, we used the level of sex factor conjugation as a read-out for Ll.LtrB splicing efficiency. Using this highly sensitive splicing/conjugation assay (10(7)-fold detection range), we demonstrate that Ll.LtrB can trans-splice in L. lactis when fragmented at various positions such as: three different locations within domain IV, within domain I and within domain III. We also demonstrate that the intron-encoded protein, LtrA, is absolutely required for Ll.LtrB trans-splicing. Characteristic Y-branched trans-spliced introns and ligated exons are detected by RT-PCR from total RNA extracts of cells harbouring fragmented Ll.LtrB. The splicing/conjugation assay we developed constitutes the first model system to study group II intron trans-splicing in vivo. Although only previously observed in bacterial-derived organelles, we demonstrate that assembly and trans-splicing of a fragmented group II intron can take place efficiently in bacterial cells. PMID:17389638

Belhocine, Kamila; Mak, Anthony B; Cousineau, Benoit

2007-01-01

349

Effect of wild strains of Lactococcus lactis on the volatile profile and the sensory characteristics of ewes' raw milk cheese.  

PubMed

The production of volatile compounds by wild strains of Lactococcus lactis used as starter cultures and their effect on the sensory characteristics of ewes' raw milk cheese were investigated. Sixteen vats of cheese were manufactured and ripened for 120 d in two experiments, each of them duplicated. In the first experiment, milk was inoculated with different ratios of four wild Lactococcus lactis strains, two producing and two not producing branched-chain volatile compounds, and in the second experiment with different ratios of a commercial starter culture and the two strains producing branched-chain volatile compounds. Cheese pH, proteolysis, and aminopeptidase activity increased when the strains producing branched-chain volatile compounds were inoculated at a higher rate. Fifty volatile compounds were identified in cheeses using a purge and trap system coupled to a gas chromatography-mass spectrometry apparatus. The relative abundances of 30 volatile compounds (8 alcohols, 5 aldehydes, 3 ketones, 12 esters, 1 sulfur compound, and 1 benzenic compound) were influenced by starter culture composition. 2-Methylpropanol, 3-methylbutanol, isobutyl acetate, isoamyl acetate, ethyl butyrate, isobutyl butyrate, and isoamyl butyrate were always more abundant in the cheeses made with a higher level of L. lactis strains producing branched-chain volatile compounds. Flavor intensity was enhanced by a high level of L. lactis strains producing branched-chain volatile compounds in the first experiment, in which four wild L. lactis strains were used as starter culture, but not in the second experiment, in which a combination of two wild L. lactis strains and the commercial starter culture were used. Flavor quality, as judged by trained panelists, was impaired in both experiments by a high level of L. lactis strains producing branched-chain volatile compounds. PMID:12512589

Centeno, J A; Tomillo, F J; Fernández-García, E; Gaya, P; Nuñez, M

2002-12-01

350

The rhizome of the multidrug-resistant Enterobacter aerogenes genome reveals how new "killer bugs" are created because of a sympatric lifestyle.  

PubMed

Here, we sequenced the 5,419,609 bp circular genome of an Enterobacter aerogenes clinical isolate that killed a patient and was resistant to almost all current antibiotics (except gentamicin) commonly used to treat Enterobacterial infections, including colistin. Genomic and phylogenetic analyses explain the discrepancies of this bacterium and show that its core genome originates from another genus, Klebsiella. Atypical characteristics of this bacterium (i.e., motility, presence of ornithine decarboxylase, and lack of urease activity) are attributed to genomic mosaicism, by acquisition of additional genes, such as the complete 60,582 bp flagellar assembly operon acquired "en bloc" from the genus Serratia. The genealogic tree of the 162,202 bp multidrug-resistant conjugative plasmid shows that it is a chimera of transposons and integrative conjugative elements from various bacterial origins, resembling a rhizome. Moreover, we demonstrate biologically that a G53S mutation in the pmrA gene results in colistin resistance. E. aerogenes has a large RNA population comprising 8 rRNA operons and 87 cognate tRNAs that have the ability to translate transferred genes that use different codons, as exemplified by the significantly different codon usage between genes from the core genome and the "mobilome." On the basis of our findings, the evolution of this bacterium to become a "killer bug" with new genomic repertoires was from three criteria that are "opportunity, power, and usage" to indicate a sympatric lifestyle: "opportunity" to meet other bacteria and exchange foreign sequences since this bacteria was similar to sympatric bacteria; "power" to integrate these foreign sequences such as the acquisition of several mobile genetic elements (plasmids, integrative conjugative element, prophages, transposons, flagellar assembly system, etc.) found in his genome; and "usage" to have the ability to translate these sequences including those from rare codons to serve as a translator of foreign languages. PMID:23071100

Diene, Seydina M; Merhej, Vicky; Henry, Mireille; El Filali, Adil; Roux, Véronique; Robert, Catherine; Azza, Saïd; Gavory, Frederick; Barbe, Valérie; La Scola, Bernard; Raoult, Didier; Rolain, Jean-Marc

2013-02-01

351

A bacteriocin gene cluster able to enhance plasmid maintenance in Lactococcus lactis  

PubMed Central

Background Lactococcus lactis is widely used as a dairy starter and has been extensively studied. Based on the acquired knowledge on its physiology and metabolism, new applications have been envisaged and there is an increasing interest of using L. lactis as a cell factory. Plasmids constitute the main toolbox for L. lactis genetic engineering and most rely on antibiotic resistant markers for plasmid selection and maintenance. In this work, we have assessed the ability of the bacteriocin Lactococcin 972 (Lcn972) gene cluster to behave as a food-grade post-segregational killing system to stabilize recombinant plasmids in L. lactis in the absence of antibiotics. Lcn972 is a non-lantibiotic bacteriocin encoded by the 11-kbp plasmid pBL1 with a potent antimicrobial activity against Lactococcus. Results Attempts to clone the full lcn972 operon with its own promoter (P972), the structural gene lcn972 and the immunity genes orf2-orf3 in the unstable plasmid pIL252 failed and only plasmids with a mutated promoter were recovered. Alternatively, cloning under other constitutive promoters was approached and achieved, but bacteriocin production levels were lower than those provided by pBL1. Segregational stability studies revealed that the recombinant plasmids that yielded high bacteriocin titers were maintained for at least 200 generations without antibiotic selection. In the case of expression vectors such as pTRL1, the Lcn972 gene cluster also contributed to plasmid maintenance without compromising the production of the fluorescent mCherry protein. Furthermore, unstable Lcn972 recombinant plasmids became integrated into the chromosome through the activity of insertion sequences, supporting the notion that Lcn972 does apply a strong selective pressure against susceptible cells. Despite of it, the Lcn972 gene cluster was not enough to avoid the use of antibiotics to select plasmid-bearing cells right after transformation. Conclusions Inserting the Lcn972 cluster into segregational unstable plasmids prevents their lost by segregation and probable could be applied as an alternative to the use of antibiotics to support safer and more sustainable biotechnological applications of genetically engineered L. lactis.

2014-01-01

352

Internalin-expressing Lactococcus lactis is able to invade small intestine of guinea pigs and deliver DNA into mammalian epithelial cells  

Microsoft Academic Search

The use of the food-grade bacterium Lactococcus lactis as antigen delivery vehicle at the mucosal level is an attractive vaccination strategy intensively explored during the last decade. In this study, we developed L. lactis strains which could be used as a DNA delivery vector to combine both advantages of mucosal delivery and of DNA vaccination. To render lactococci capable of

Valeria Dellaretti Guimarães; Jane Eyre Gabriel; François Lefèvre; Didier Cabanes; Alexandra Gruss; Pascale Cossart; Vasco Azevedo; Philippe Langella

2005-01-01

353

Mucosal Delivery of Murine Interleukin2 (IL2) and IL6 by Recombinant Strains of Lactococcus lactis Coexpressing Antigen and Cytokine  

Microsoft Academic Search

Lactococcus lactis is a nonpathogenic and noncolonizing bacterium which is being developed as a vaccine delivery vehicle for immunization by mucosal routes. To determine whether lactococci can also deliver cyto- kines to the immune system, we have constructed novel constitutive expression strains of L. lactis which accumulate a test antigen, tetanus toxin fragment C (TTFC), within the cytoplasmic compartment and

LOTHAR STEIDLER; KAREN ROBINSON; LISA CHAMBERLAIN; KARIN M. SCHOFIELD; ERIK REMAUT; RICHARD W. F. LE PAGE; JEREMY M. WELLS

1998-01-01

354

Novel angiotensin I-converting enzyme inhibitory peptides produced in fermented milk by specific wild Lactococcus lactis strains.  

PubMed

The ability of specific wild Lactococcus lactis strains to hydrolyze milk proteins to release angiotensin I-converting enzyme (ACE) inhibitory peptides was evaluated. The peptide profiles were obtained from the <3 kDa water-soluble extract and subsequently fractionated by reversed-phase HPLC. The fractions with the lowest half-maximal inhibitory concentration estimated values (peptide concentration necessary to inhibit ACE activity by 50%) were Lc. lactis NRRL B-50571 fraction (F)1 (0.034 ± 0.002 ?g/mL; mean ± SD) and Lc. lactis NRRL B-50572B F 0005 (0.041 ± 0.003 ?g/mL; mean ± SD). All peptide fractions were analyzed by reversed-phase HPLC tandem mass spectrometry. Twenty-one novel peptide sequences associated with ACE inhibitory (ACEI) activity were identified. Several novel ACEI peptides presented peptides encrypted with proven hypotensive activity. In conclusion, specific wild Lc. lactis strains were able to hydrolyze milk proteins to generate potent ACEI peptides. However, further studies are necessary to find out the relationship between Lc. lactis strain proteolytic systems and their ability to biogenerate hypotensive peptides. PMID:22901481

Rodríguez-Figueroa, J C; González-Córdova, A F; Torres-Llanez, M J; Garcia, H S; Vallejo-Cordoba, B

2012-10-01

355

The crystal structure of pyruvate decarboxylase from Kluyveromyces lactis. Implications for the substrate activation mechanism of this enzyme.  

PubMed

The crystal structure of pyruvate decarboxylase from Kluyveromyces lactis has been determined to 2.26 A resolution. Like other yeast enzymes, Kluyveromyces lactis pyruvate decarboxylase is subject to allosteric substrate activation. Binding of substrate at a regulatory site induces catalytic activity. This process is accompanied by conformational changes and subunit rearrangements. In the nonactivated form of the corresponding enzyme from Saccharomyces cerevisiae, all active sites are solvent accessible due to the high flexibility of loop regions 106-113 and 292-301. The binding of the activator pyruvamide arrests these loops. Consequently, two of four active sites become closed. In Kluyveromyces lactis pyruvate decarboxylase, this half-side closed tetramer is present even without any activator. However, one of the loops (residues 105-113), which are flexible in nonactivated Saccharomyces cerevisiae pyruvate decarboxylase, remains flexible. Even though the tetramer assemblies of both enzyme species are different in the absence of activating agents, their substrate activation kinetics are similar. This implies an equilibrium between the open and the half-side closed state of yeast pyruvate decarboxylase tetramers. The completely open enzyme state is favoured for Saccharomyces cerevisiae pyruvate decarboxylase, whereas the half-side closed form is predominant for Kluyveromyces lactis pyruvate decarboxylase. Consequently, the structuring of the flexible loop region 105-113 seems to be the crucial step during the substrate activation process of Kluyveromyces lactis pyruvate decarboxylase. PMID:16939618

Kutter, Steffen; Wille, Georg; Relle, Sandy; Weiss, Manfred S; Hübner, Gerhard; König, Stephan

2006-09-01

356

Glutamate Dehydrogenase Activity Can Be Transmitted Naturally to Lactococcus lactis Strains To Stimulate Amino Acid Conversion to Aroma Compounds  

PubMed Central

Amino acid conversion to aroma compounds by Lactococcus lactis is limited by the low production of ?-ketoglutarate that is necessary for the first step of conversion. Recently, glutamate dehydrogenase (GDH) activity that catalyzes the reversible glutamate deamination to ?-ketoglutarate was detected in L. lactis strains isolated from a vegetal source, and the gene responsible for the activity in L. lactis NCDO1867 was identified and characterized. The gene is located on a 70-kb plasmid also encoding cadmium resistance. In this study, gdh gene inactivation and overexpression confirmed the direct impact of GDH activity of L. lactis on amino acid catabolism in a reaction medium at pH 5.5, the pH of cheese. By using cadmium resistance as a selectable marker, the plasmid carrying gdh was naturally transmitted to another L. lactis strain by a mating procedure. The transfer conferred to the host strain GDH activity and the ability to catabolize amino acids in the presence of glutamate in the reaction medium. However, the plasmid appeared unstable in a strain also containing the protease lactose plasmid pLP712, indicating an incompatibility between these two plasmids.

Tanous, Catherine; Chambellon, Emilie; Le Bars, Dominique; Delespaul, Gilbert; Yvon, Mireille

2006-01-01

357

Lactococcus lactis NCC 2287 Alleviates Food Allergic Manifestations in Sensitized Mice by Reducing IL-13 Expression Specifically in the Ileum  

PubMed Central

Objective. Utilizing a food allergy murine model, we have investigated the intrinsic antiallergic potential of the Lactococcus lactis NCC 2287 strain. Methods. BALB/c mice were sensitized at weekly intervals with ovalbumin (OVA) plus cholera toxin (CT) by the oral route for 7 weeks. In this model, an oral challenge with a high dose of OVA at the end of the sensitization period leads to clinical symptoms. Lactococcus lactis NCC 2287 was given to mice via the drinking water during sensitization (prevention phase) or after sensitization (management phase). Results. Lactococcus lactis NCC 2287 administration to sensitized mice strikingly reduced allergic manifestations in the management phase upon challenge, when compared to control mice. No preventive effect was observed with the strain. Lactococcus lactis NCC 2287 significantly decreased relative expression levels of the Th-2 cytokine, IL-13, and associated chemokines CCL11 (eotaxin-1) and CCL17 (TARC) in the ileum. No effect was observed in the jejunum. Conclusion/Significance. These results taken together designate Lactococcus lactis NCC 2287 as a candidate probiotic strain appropriate in the management of allergic symptoms.

Zuercher, Adrian W.; Weiss, Marietta; Holvoet, Sebastien; Moser, Mireille; Moussu, Helene; van Overtvelt, Laurence; Horiot, Stephane; Moingeon, Philippe; Nutten, Sophie; Prioult, Guenolee; Singh, Anurag; Mercenier, Annick

2012-01-01

358

Display of the Viral Epitopes on Lactococcus lactis: A Model for Food Grade Vaccine against EV71  

PubMed Central

In this study, we have developed a system for display of antigens of Enterovirus type 71 (EV71) on the cell surface of L. lactis. The viral capsid protein (VP1) gene from a local viral isolate was utilized as the candidate vaccine for the development of oral live vaccines against EV71 using L. lactis as a carrier. We expressed fusion proteins in E. coli and purified fusion proteins were incubated with L. lactis. We confirmed that mice orally fed with L. lactis displaying these fusion proteins on its surface were able to mount an immune response against the epitopes of EV71. This is the first example of an EV71 antigen displayed on the surface of a food grade organism and opens a new perspective for alternative vaccine strategies against the EV71. We believe that the method of protein docking utilized in this study will allow for more flexible presentations of short peptides and proteins on the surface of L. lactis to be useful as a delivery vehicle.

Varma, Nadimpalli Ravi S.; Toosa, Haryanti; Foo, Hooi Ling; Alitheen, Noorjahan Banu Mohamed; Nor Shamsudin, Mariana; Arbab, Ali S.; Yusoff, Khatijah; Abdul Rahim, Raha

2013-01-01

359

Protective Vaccination against Infectious Bursal Disease Virus with Whole Recombinant Kluyveromyces lactis Yeast Expressing the Viral VP2 Subunit  

PubMed Central

Here we report on vaccination approaches against infectious bursal disease (IBD) of poultry that were performed with complete yeast of the species Kluyveromyces lactis (K. lactis). Employing a genetic system that enables the rapid production of stably transfected recombinant K. lactis, we generated yeast strains that expressed defined quantities of the virus capsid forming protein VP2 of infectious bursal disease virus (IBDV). Both, subcutaneous as well as oral vaccination regiments with the heat-inactivated but otherwise untreated yeast induced IBDV-neutralizing antibodies in mice and chickens. A full protection against a subsequent IBDV infection was achieved by subcutaneous inoculation of only milligram amounts of yeast per chicken. Oral vaccination also generated protection: while mortality was observed in control animals after virus challenge, none of the vaccinees died and ca. one-tenth were protected as indicated by the absence of lesions in the bursa of Fabricius. Recombinant K. lactis was thus indicated as a potent tool for the induction of a protective immune response by different applications. Subcutaneously applied K. lactis that expresses the IBDV VP2 was shown to function as an efficacious anti-IBD subunit vaccine.

Arnold, Marina; Durairaj, Vijay; Mundt, Egbert; Schulze, Katja; Breunig, Karin D.; Behrens, Sven-Erik

2012-01-01

360

Heterologous Production of Methionine-?-Lyase from Brevibacterium linens in Lactococcus lactis and Formation of Volatile Sulfur Compounds? †  

PubMed Central

The conversion of methionine to volatile sulfur compounds (VSCs) is of great importance in flavor formation during cheese ripening and is the focus of biotechnological approaches toward flavor improvement. A synthetic mgl gene encoding methionine-?-lyase (MGL) from Brevibacterium linens BL2 was cloned into a Lactococcus lactis expression plasmid under the control of the nisin-inducible promoter PnisA. When expressed in L. lactis and purified as a recombinant protein, MGL was shown to degrade l-methionine as well as other sulfur-containing compounds such as l-cysteine, l-cystathionine, and l-cystine. Overproduction of MGL in recombinant L. lactis also resulted in an increase in the degradation of these compounds compared to the wild-type strain. Importantly, gas chromatography-mass spectrometry analysis identified considerably higher formation of methanethiol (and its oxidized derivatives dimethyl disulfide and dimethyl trisulfide) in reactions containing either purified protein, whole cells, or cell extracts from the heterologous L. lactis strain. This is the first report of production of MGL from B. linens in L. lactis. Given their significance in cheese flavor development, the use of lactic acid bacteria with enhanced VSC-producing abilities could be an efficient way to enhance cheese flavor development.

Hanniffy, Sean B.; Philo, Mark; Pelaez, Carmen; Gasson, Michael J.; Requena, Teresa; Martinez-Cuesta, M. C.

2009-01-01

361

[Construction of a food-grade secretion expression vector and use it for reporter protein expression in Lactococcus lactis].  

PubMed

We constructed a food-grade secretion expression vector and used it for reporter protein expression in live delivery vehicle L lactis MBP71. The p32 fragment, which containing the stronger p32 promoter, was amplified by polymerase chain reaction (PCR) with the plasmid pMG36e as template. After being purified, the p32 fragment was ligated with SPusp45 fragment amplified from genomic DNA of L lactis MG1363. The fusion fragment p32-SPusp45 was inserted into the food-grade vector pSH91 to construct a secretion expression vector, pSQ. The coding sequence of NucA (nucA) was also amplified from Staphylococcus aureus chromosome and inserted into pSQ under the control of p32 promoter to construct a recombinant plasmid pSQ-nucA. Nuclease plate activity assay and zymograme assay demonstrate that NucA was secretion expressed from L lactis harboring the recombinant plasmid pSQ- nucA, and the quantity of NucA secreted into supernamant was about ten times more than which in cell lysate. Results also indicate that expression efficiency of L lactis/pSQ-nucA was higher than that of L lactis/pSQZ-nucA, constructed by us earlier. PMID:18479053

Sun, Qiangzheng; Xiong, Yanwen; Ye, Changyun; Xu, Jianguo

2008-03-01

362

Oral administration of a catalase-producing Lactococcus lactis can prevent a chemically induced colon cancer in mice.  

PubMed

Reactive oxygen species, such as hydrogen peroxide (H2O2), are involved in various aspects of tumour development. Decreasing their levels can therefore be a promising approach for colon cancer prevention. The objective of this study was to evaluate the effect of catalase-producing Lactococcus lactis on the prevention of an experimental murine 1,2-dimethylhydrazine (DMH)-induced colon cancer. DMH-treated BALB/c mice received either a catalase-producing L. lactis strain or the isogenic non-catalase-producing strain as a control, whereas other untreated mice did not receive bacterial supplementation. Catalase activity and H2O2 levels in intestinal fluids and blood samples were measured, and changes in the histology of the large intestines during tumour progression were evaluated. The catalase-producing L. lactis strain used in this study was able to slightly increase catalase activities in DMH-treated mice (1.19+/-0.08 U ml(-1)) and reduce H2O2 levels (3.4+/-1.1 microM) compared to (i) animals that received the non-catalase-producing strain (1.00+/-0.09 U ml(-1), 9.0+/-0.8 microM), and (ii) those that did not receive bacterial supplementation (1.06+/-0.07 U ml(-1), 10.0+/-1.1 microM). Using the histopathological grading scale of chemically induced colorectal cancer, animals that received the catalase-producing L. lactis had a significantly lesser extent of colonic damage and inflammation (2.0+/-0.4) compared to animals that received the non-catalase-producing L. lactis (4.0+/-0.3) or those that did not receive bacterial supplementation (4.7+/-0.5). The catalase-producing L. lactis strain used in this study was able to prevent tumour appearance in an experimental DMH-induced colon cancer model. PMID:18065674

de Moreno de LeBlanc, Alejandra; LeBlanc, Jean Guy; Perdigón, Gabriela; Miyoshi, Anderson; Langella, Philippe; Azevedo, Vasco; Sesma, Fernando

2008-01-01

363

Experimental study on the growth of Salmonella and coli-aerogenes bacteria in pure and mixed cultures, in a fermentor, in two different enrichment media: Sodium selenite and tetrathionate broth  

Microsoft Academic Search

Different serotypes of Salmonella and coli-aerogenes bacteria were grown in a fermentor at +43°C. The Culture media used were composed of two different nutrient broths, one supplemented with sodium selenite, the other with potassium tetrathionate. The growth of both bacteria and the following types of mixed bacteria was studied: Escherichia coli-Salmonella brancaster and Klebsiella pneumoniae-Salmonella brancaster. During the first 10

B. Hugues; M. Plissier; A. Pagliardini; J. L. Plantat; J. Gaissa

1978-01-01

364

A Zn-Dependent Metallopeptidase Is Responsible for Sensitivity to LsbB, a Class II Leaderless Bacteriocin of Lactococcus lactis subsp. lactis BGMN1-5  

PubMed Central

Lactococcus lactis subsp. lactis BGMN1-5 produces a leaderless class II bacteriocin called LsbB. To identify the receptor for LsbB, a cosmid library of the LsbB-sensitive strain BGMN1-596 was constructed. About 150 cosmid clones were individually isolated and transferred to LsbB-resistant mutants of BGMN1-596. Cosmid pAZILcos/MN2, carrying a 40-kb insert, was found to restore LsbB sensitivity in LsbB-resistant mutants. Further subcloning revealed that a 1.9-kb fragment, containing only one open reading frame, was sufficient to restore sensitivity. The fragment contains the gene yvjB coding for a Zn-dependent membrane-bound metallopeptidase, suggesting that this gene may serve as the receptor for LsbB. Further support for this notion derives from several independent experiments: (i) whole-genome sequencing confirmed that all LsbB-resistant mutants contain mutations in yvjB; (ii) disruption of yvjB by direct gene knockout rendered sensitive strains BGMN1-596 and IL1403 resistant to LsbB; and (iii) most compellingly, heterologous expression of yvjB in naturally resistant strains of other species, such as Lactobacillus paracasei and Enterococcus faecalis, also rendered them sensitive to the bacteriocin. To our knowledge, this is the first time a membrane-bound peptidase gene has been shown to be involved in bacteriocin sensitivity in target cells. We also demonstrated a novel successful approach for identifying bacteriocin receptors.

Uzelac, Gordana; Lozo, Jelena; Aleksandrzak-Piekarczyk, Tamara; Gabrielsen, Christina; Kristensen, Tom; Nes, Ingolf F.; Diep, Dzung B.; Topisirovic, Ljubisa

2013-01-01

365

Enzymatic synthesis and characterization of hydroquinone galactoside using Kluyveromyces lactis lactase.  

PubMed

Hydroquinone galactoside (HQ-Gal) as a potential skin whitening agent was synthesized by the reaction of lactase (beta-galactosidase) from Kluyveromyces lactis, Aspergillus oryzae, Bacillus circulans, and Thermus sp. with lactose as a donor and HQ as an acceptor. Among these lactases, the acceptor reaction involving HQ and lactose with K. lactis lactase showed a higher conversion ratio to HQ-Gal (60.27%). HQ-Gal was purified using butanol partitioning and silica gel column chromatography. The structure of the purified HQ-Gal was determined by nuclear magnetic resonance, and the ionic product was observed at m/z 295 (C12H16O7Na)+ using matrix assisted laser desorption ionization time-of-flight mass spectrometry. HQ-Gal was identified as 4-hydroxyphenyl-beta-d-galactopyranoside. The optimum conditions for HQ-Gal synthesis by K. lactis determined using response surface methodology were 50 mM HQ, 60 mM lactose, and 20 U mL(-1) lactase. These conditions produced a yield of 2.01 g L(-1) HQ-Gal. The half maximal inhibitory concentration (IC50) of diphenylpicrylhydrazyl scavenging activity was 3.31 mM, indicating a similar antioxidant activity compared to beta-arbutin (IC50=3.95 mM). The Ki value of HQ-Gal (0.75 mM) against tyrosinase was smaller than that of beta-arbutin (Ki=1.97 mM), indicating its superiority as an inhibitor. HQ-Gal inhibited (23%) melanin synthesis without being significantly toxic to the cells, while beta-arbutin exhibited only 8% reduction of melanin synthesis in B16 melanoma cells compared with the control. These results indicate that HQ-Gal may be a suitable functional component in the cosmetics industry. PMID:20687552

Kim, Go-Eun; Lee, Jin-Ha; Jung, Sun-Hwa; Seo, Eun-Seong; Jin, Sheng-De; Kim, Ghahyun J; Cha, Jaeho; Kim, Eui-Joong; Park, Ki-Deok; Kim, Doman

2010-09-01

366

Altered Superoxide Dismutase Activity by Carbohydrate Utilization in a Lactococcus lactis Strain.  

PubMed

Reactive oxygen species, such as superoxide, can damage cellular components, such as proteins, lipids, and DNA. Superoxide dismutase (SOD) enzymes catalyze the conversion of superoxide anions to hydrogen peroxide and dioxygen. SOD is present in most lactococcal bacteria, which are commonly used as starters for manufacturing fermented dairy products and may have health benefits when taken orally. We assessed the effects of carbohydrate use on SOD activity in lactococci. In Lactococcus lactis ssp. lactis G50, the SOD activity of cells grown on lactose and galactose was higher than that on glucose; in Lactococcus lactis ssp. cremoris H61, SOD activity was independent of the type of carbohydrate used. We also investigated the activity of NADH oxidase, which is related to the production of superoxide in strains G50 and H61. Activity was highest in G50 cells grown on lactose, lower on galactose, and lowest on glucose, whereas activity in H61 cells did not differ with the carbohydrate source used. The SOD and NADH oxidase activities of strain G50 in three carbohydrates were linked. Strain G50 fermented lactose and galactose to lactate, acetate, formate, and ethanol (mixed-acid fermentation) and fermented glucose to mainly lactate (homolactic fermentation). Strain H61 fermented glucose, lactose, and galactose to mainly lactate (homolactic fermentation). In strain G50, when growth efficiency was reduced by adding a metabolic inhibitor to the growth medium, SOD activity was higher than in the control; however, the metabolism was homofermentative. Aerobic conditions, but not glucose-limited conditions, increased SOD activity, and mixed-acid fermentation occurred. We conclude that the effect of carbohydrate on SOD activity in lactococci is strain dependent and that the activity of commercial lactococci can be enhanced through carbohydrate selection for mixed-acid fermentation or by changing the energy distribution, thus enhancing the value of the starter and the resulting dairy products. PMID:24988023

Kimoto-Nira, H; Moriya, N; Ohmori, H; Suzuki, C

2014-07-01

367

Mechanism of Citrate Metabolism in Lactococcus lactis: Resistance against Lactate Toxicity at Low pH  

PubMed Central

Measurement of the flux through the citrate fermentation pathway in resting cells of Lactococcus lactis CRL264 grown in a pH-controlled fermentor at different pH values showed that the pathway was constitutively expressed, but its activity was significantly enhanced at low pH. The flux through the citrate-degrading pathway correlated with the magnitude of the membrane potential and pH gradient that were generated when citrate was added to the cells. The citrate degradation rate and proton motive force were significantly higher when glucose was metabolized at the same time, a phenomenon that could be mimicked by the addition of lactate, the end product of glucose metabolism. The results clearly demonstrate that citrate metabolism in L. lactis is a secondary proton motive force-generating pathway. Although the proton motive force generated by citrate in cells grown at low pH was of the same magnitude as that generated by glucose fermentation, citrate metabolism did not affect the growth rate of L. lactis in rich media. However, inhibition of growth by lactate was relieved when citrate also was present in the growth medium. Citrate did not relieve the inhibition by other weak acids, suggesting a specific role of the citrate transporter CitP in the relief of inhibition. The mechanism of citrate metabolism presented here provides an explanation for the resistance to lactate toxicity. It is suggested that the citrate metabolic pathway is induced under the acidic conditions of the late exponential growth phase to make the cells (more) resistant to the inhibitory effects of the fermentation product, lactate, that accumulates under these conditions.

Magni, Christian; de Mendoza, Diego; Konings, Wil N.; Lolkema, Juke S.

1999-01-01

368

Nisin inducible production of listeriolysin O in Lactococcus lactis NZ9000  

PubMed Central

Background Listeria monocytogenes is a well-characterized food-borne pathogen that infects pregnant women and immunocompromised individuals. Listeriolysin O (LLO) is the major virulence factor of the pathogen and is often used as a diagnostic marker for detection of L. monocytogenes. In addition, LLO represents a potent antigen driving T cell-mediated immunity during infection. In the present work, Lactococcus lactis NZ9000 was used as an expression host to hyper-produce LLO under inducible conditions using the NICE (NIsin Controlled Expression) system. We created a modified pNZ8048 vector encoding a six-His-tagged LLO downstream of the strong inducible PnisA promoter. Results The constructed vector (pNZPnisA:CYTO-LLO) was expressed in L. lactis NZ9000 and was best induced at mid-log phase with 0.2% v/v nisin for 4 h statically at 30°C. Purification of the His-tagged LLO was accomplished by Ni-NTA affinity chromatography and functionality was confirmed through haemolytic assays. Total LLO yield (measured as total protein content) was 4.43–5.9 mg per litre culture and the haemolytic activity was still detectable after 8 months of storage at 4°C. Conclusion The LLO production method described in this work provides an approach to efficient LLO production in the Gram-positive Lactococcus bacterium to yield a significant source of the protein for research and diagnostic applications. Expression of LLO in L. lactis has a number of benefits over E. coli which may facilitate both in vivo and in vitro applications of this system.

Bahey-El-Din, Mohammed; Griffin, Brendan T; Gahan, Cormac GM

2008-01-01

369

Restriction for gene insertion within the Lactococcus lactis Ll.LtrB group II intron  

PubMed Central

The Ll.LtrB intron, from the low G+C gram-positive bacterium Lactococcus lactis, was the first bacterial group II intron shown to splice and mobilize in vivo. The detailed retrohoming and retrotransposition pathways of Ll.LtrB were studied in both L. lactis and Escherichia coli. This bacterial retroelement has many features that would make it a good gene delivery vector. Here we report that the mobility efficiency of Ll.LtrB expressing LtrA in trans is only slightly affected by the insertion of fragments <100 nucleotides within the loop region of domain IV. In contrast, Ll.LtrB mobility efficiency is drastically decreased by the insertion of foreign sequences >1 kb. We demonstrate that the inhibitory effect caused by the addition of expression cassettes on Ll.LtrB mobility efficiency is not sequence specific, and not due to the expression, or the toxicity, of the cargo genes. Using genetic screens, we demonstrate that in order to maintain intron mobility, the loop region of domain IV, more specifically domain IVb, is by far the best region to insert foreign sequences within Ll.LtrB. Poisoned primer extension and Northern blot analyses reveal that Ll.LtrB constructs harboring cargo sequences splice less efficiently, and show a significant reduction in lariat accumulation in L. lactis. This suggests that cargo-containing Ll.LtrB variants are less stable. These results reveal the potential, yet limitations, of the Ll.LtrB group II intron to be used as a gene delivery vector, and validate the random insertion approach described in this study to create cargo-containing Ll.LtrB variants that are mobile.

Plante, Isabelle; Cousineau, Benoit

2006-01-01

370

Influence of growth conditions on the nisin production of bioengineered Lactococcus lactis strains  

Microsoft Academic Search

Nisin production of three bioengineered strains, (LAC338, LAC339 and LAC340) with immunity (nisFEG) and\\/or regulation (nisRK) genes of nisin biosynthesis on plasmids in the Lactococcus lactis LL27 nisin producer, was evaluated under pH-controlled and pH-uncontrolled batch fermentations. Optimization studies showed\\u000a that fructose and yeast extract yielded the highest nisin activity. The strains LAC338, LAC339, and LAC340 produced 24, 45,\\u000a and

Ö. ?im?ek; A. H. Çon; N. Akkoç; P. E. J. Saris; Mustafa Akçelik

2009-01-01

371

Physical and genetic characterization of the genome of Lactobacillus lactis bacteriophage LL-H.  

PubMed Central

Bacteriophage LL-H is a virulent phage of Lactobacillus lactis LL23. A restriction map of the phage genome was constructed with various restriction endonucleases. This chromosome has a 34-kilobase size and seems to be circularly permuted. We used a bank of LL-H restriction fragments to study the expression of five of the seven main phage particle proteins. Immunoblotting experiments permitted the mapping on the chromosome of several genes coding for phage particle proteins. We also show that the gene of the main capsid protein is expressed from its own promoter in an Escherichia coli strain.

Trautwetter, A; Ritzenthaler, P; Alatossava, T; Mata-Gilsinger, M

1986-01-01

372

The structure and possible function of the glycolipid from Staphylococcus lactis I3  

PubMed Central

1. The total lipid was extracted from Staphylococcus lactis I3 with chloroform–methanol mixtures and the glycolipid component was isolated by chromatography on silicic acid. 2. Saponification yielded a non-crystalline glycoside for which the structure O-?-d-glucopyranosyl-(1?6)-O-?-d-glucopyranosyl-(1?1)-d-glycerol has been established by chemical degradations and by comparison with synthetic material. 3. The role of the glycosyl diglycerides in bacterial membranes is discussed. ImagesFig. 1.

Brundish, D. E.; Shaw, N.; Baddiley, J.

1967-01-01

373

Genetic Manipulation of the Pathway for Diacetyl Metabolism inLactococcus lactis  

Microsoft Academic Search

Diacetylisanimportantfoodflavorcompoundproducedbycertainstrainsofcitrate-metabolizinglacticacid bacteria.Citrateisconvertedtopyruvate,fromwhichdiacetylisproducedviaintermediate a-acetolactate.This paper reports the cloning and analysis of the gene (aldB) encoding a-acetolactate decarboxylase fromLacto- coccus lactis MG1363. Deletion of the MG1363 chromosomal aldB gene was achieved by double crossover homologous recombination. The mutant strain was found to produce diacetyl; a-acetolactate decarboxylase activity was eliminated. Overexpression of the clonedilvBNgenes (encoding an a-acetolactate synthase) in the aldBdeletion strain produced

SIMON R. SWINDELL; KIM H. BENSON; HUGH G. GRIFFIN; P. RENAULT; S. DUSKO EHRLICH; ANDMICHAEL J. GASSON

1996-01-01

374

Complete Genome Sequence of Bifidobacterium animalis subsp. lactis BB-12, a Widely Consumed Probiotic Strain?  

PubMed Central

Bifidobacterium animalis subsp. lactis BB-12 is a commercially available probiotic strain used throughout the world in a variety of functional foods and dietary supplements. The benefits of BB-12 have been documented in a number of independent clinical trials. Determination of the complete genome sequence reveals a single circular chromosome of 1,942,198 bp with 1,642 predicted protein-encoding genes, 4 rRNA operons, and 52 tRNA genes. Knowledge of this sequence will lead to insight into the specific features which give this strain its probiotic properties.

Garrigues, Christel; Johansen, Eric; Pedersen, Martin B.

2010-01-01

375

In vivo regulation of glycolysis and characterization of sugar: phosphotransferase systems in Streptococcus lactis.  

PubMed Central

Two novel procedures have been used to regulate, in vivo, the formation of phosphoenolpyruvate (PEP) from glycolysis in Streptococcus lactis ML3. In the first procedure, glucose metabolism was specifically inhibited by p-chloromercuribenzoate. Autoradiographic and enzymatic analyses showed that the cells contained glucose 6-phosphate, fructose 6-phosphate, fructose-1,6-diphosphate, and triose phosphates.Dithiothreitol reversed the p-chloromercuribenzoate inhibition, and these intermediates were rapidly and quantitatively transformed into 3- and 2-phosphoglycerates plus PEP. The three intermediates were not further metabolized and constituted the intracellular PEP potential. The second procedure simply involved starvation of the organisms. The starved cells were devoid of glucose 6-phosphate, fructose 6-phosphate, fructose- 1,6-diphosphate, and triose phosphates but contained high levels of 3- and 2-phosphoglycerates and PEP (ca. 40 mM in total). The capacity to regulate PEP formation in vivo permitted the characterization of glucose and lactose phosphotransferase systems in physiologically intact cells. Evidence has been obtained for "feed forward" activation of pyruvate kinase in vivo by phosphorylated intermediates formed before the glyceraldehyde-3-phosphate dehydrogenase reaction in the glycolytic sequence. The data suggest that pyruvate kinase (an allosteric enzyme) plays a key role in the regulation of glycolysis and phosphotransferase system functions in S. lactis ML3. Images

Thompson, J

1978-01-01

376

Influence of growth conditions on the nisin production of bioengineered Lactococcus lactis strains.  

PubMed

Nisin production of three bioengineered strains, (LAC338, LAC339 and LAC340) with immunity (nisFEG) and/or regulation (nisRK) genes of nisin biosynthesis on plasmids in the Lactococcus lactis LL27 nisin producer, was evaluated under pH-controlled and pH-uncontrolled batch fermentations. Optimization studies showed that fructose and yeast extract yielded the highest nisin activity. The strains LAC338, LAC339, and LAC340 produced 24, 45, and 44% more nisin, respectively, than wild-type L. lactis LL27 after 12-h incubation. However, sharp decreases in the yield of nisin were observed at the late phase of fermentation with LAC339 and LL27 in contrast to LAC340 and LAC338 strains for which the high level of nisin could be maintained longer. Obviously, increasing the copy number of the regulation genes together with immunity genes in the nisin producers retarded the loss of nisin in the late phase of the fermentation. PMID:19137338

Sim?ek, O; Con, A H; Akkoç, N; Saris, P E J; Akçelik, Mustafa

2009-04-01

377

[Production and partial characterization of beta-galactosidase from Kluyveromyces lactis grown in deproteinized whey].  

PubMed

The purpose of this work was to optimize the beta-galactosidase production by Kluyveromyces lactis, applying the Surface Response Methodology (SRM) and using deproteinized whey as fermentation medium. An Orthogonal Central Compound Design (OCCD) was used without repetition, with four factors: temperature, pH, agitation speed and fermentation time. Then, enzyme activity (U/ml) as response variable was used. Thirty trials in twenty-five treatments, with six repetitions at the central point, were carried out, in a New Brunswick Bioflo 2000 fermentor with a volume of 2 liters. The deproteinized whey obtained by thermocoagulation was chemically analyzed. The results were: moisture 93.83%, total solids 6.17%, protein 0.44%, lactose 4.85%, acidity 0.43% and pH 4.58. The best conditions in the enzyme production were: temperature 30.3 degrees C, pH 4.68, agitation speed 191 r.p.m. and fermentation time 18.5 h. with an enzyme production of 8.3 U/ml. The degree of purification obtained was 7.4 times and the yield was 50.8%. The purified enzyme had an optimum temperature of 60 degrees C and a pH of 6.2. This work shows that the yeast Kluyveromyces lactis grown in deproteinized whey is able to produce the enzyme beta-galactosidase and SRM can be used in the fermentology processes, specifically in determining the best suitable operation conditions. PMID:14528611

Ramírez Matheus, Alejandra O; Rivas, Nilo

2003-06-01

378

Increasing Acidification of Nonreplicating Lactococcus lactis ?thyA Mutants by Incorporating ATPase Activity  

PubMed Central

Lactococcus lactis MBP71 ?thyA (thymidylate synthase) cannot synthesize dTTP de novo, and DNA replication is dependent on thymidine in the growth medium. In the nonreplicating state acidification by MBP71 was completely insensitive to bacteriophages (M. B. Pedersen, P. R. Jensen, T. Janzen, and D. Nilsson, Appl. Environ. Microbiol. 68:3010-3023, 2002). For nonreplicating MBP71 the biomass increased 3.3-fold over the first 3.5 h, and then the increase stopped. The rate of acidification increased 2.3-fold and then started to decrease. Shortly after inoculation the lactic acid flux was 60% of that of exponentially growing MBP71. However, when nonspecific ATPase activity was incorporated into MBP71, the lactic acid flux was restored to 100% but not above that point, indicating that control over the flux switched from ATP demand to ATP supply (i.e., to sugar transport and glycolysis). As determined by growing nonreplicating cells with high ATPase activity on various sugar sources, it appeared that glycolysis exerted the majority of the control. ATPase activity also stimulated the rate of acidification by nonreplicating MBP71 growing in milk, and pH 5.2 was reached 40% faster than it was without ATPase activity. We concluded that ATPase activity is a functional means of increasing acidification by nonreplicating L. lactis.

Pedersen, Martin B.; Koebmann, Brian J.; Jensen, Peter R.; Nilsson, Dan

2002-01-01

379

Dosage suppression of the Kluyveromyces lactis zymocin by Saccharomyces cerevisiae ISR1 and UGP1.  

PubMed

The Kluyveromyces lactis zymocin complex kills Saccharomyces cerevisiae cells in a process that involves tRNA cleavage by its tRNAse gamma-toxin subunit. In contrast to the gamma-toxin mode of action, the early steps of the zymocin response are less well characterized. Here, we present high-dosage suppressors of zymocin that encode a putative Pkc1-related kinase (ISR1) and UDP-glucose pyrophosphorylase (UGPase) (UGP1). Anti-UGPase Western blots and GAL10 - ISR1 overexpression suggest that zymocin suppression correlates with overproduction of UGPase or Isr1. As judged from protection against exo-zymocin and unaltered sensitivity to endogenous gamma-toxin, high-copy ISR1 and UGP1 operate in early, nontarget steps of the zymocin pathway. Consistent with a recent report on in vitro phosphorylation of Isr1 and UGPase by the CDK Pho85, high-copy ISR1 and UGP1 suppression of zymocin is abolished in a pho85 null mutant lacking CDK activity of Pho85. Moreover, suppression requires UGPase enzyme activity, and ISR1 overexpression also protects against CFW, a chitin-interfering poison. Our data agree with roles for UGPase in cell wall biosynthetic processes and for Isr1 in Pkc1-related cell wall integrity. In sum, high-copy ISR1 and UGP1 cells affect early steps of the zymocin response and potentially prevent the lethal K. lactis killer complex from establishing cell surface recognition and/or contact. PMID:17367514

Mehlgarten, Constance; Zink, Sabrina; Rutter, Jared; Schaffrath, Raffael

2007-08-01

380

The Carbohydrate Metabolism Signature of Lactococcus lactis Strain A12 Reveals Its Sourdough Ecosystem Origin  

PubMed Central

Lactococcus lactis subsp. lactis strain A12 was isolated from sourdough. Combined genomic, transcriptomic, and phenotypic analyses were performed to understand its survival capacity in the complex sourdough ecosystem and its role in the microbial community. The genome sequence comparison of strain A12 with strain IL1403 (a derivative of an industrial dairy strain) revealed 78 strain-specific regions representing 23% of the total genome size. Most of the strain-specific genes were involved in carbohydrate metabolism and are potentially required for its persistence in sourdough. Phenotype microarray, growth tests, and analysis of glycoside hydrolase content showed that strain A12 fermented plant-derived carbohydrates, such as arabinose and ?-galactosides. Strain A12 exhibited specific growth rates on raffinose that were as high as they were on glucose and was able to release sucrose and galactose outside the cell, providing soluble carbohydrates for sourdough microflora. Transcriptomic analysis identified genes specifically induced during growth on raffinose and arabinose and reveals an alternative pathway for raffinose assimilation to that used by other lactococci.

Passerini, Delphine; Coddeville, Michele; Le Bourgeois, Pascal; Loubiere, Pascal; Ritzenthaler, Paul; Fontagne-Faucher, Catherine; Cocaign-Bousquet, Muriel

2013-01-01

381

Characterization of Lactococcus lactis UV-sensitive mutants obtained by ISS1 transposition.  

PubMed

Studies of cellular responses to DNA-damaging agents, mostly in Escherichia coli, have revealed numerous genes and pathways involved in DNA repair. However, other species, particularly those which exist under different environmental conditions than does E. coli, may have rather different responses. Here, we identify and characterize genes involved in DNA repair in a gram-positive plant and dairy bacterium, Lactococcus lactis. Lactococcal strain MG1363 was mutagenized with transposition vector pG+host9::ISS1, and 18 mutants sensitive to mitomycin and UV were isolated at 37 degrees C. DNA sequence analyses allowed the identification of 11 loci and showed that insertions are within genes implicated in DNA metabolism (polA, hexB, and deoB), cell envelope formation (gerC and dltD), various metabolic pathways (arcD, bglA, gidA, hgrP, metB, and proA), and, for seven mutants, nonidentified open reading frames. Seven mutants were chosen for further characterization. They were shown to be UV sensitive at 30 degrees C (the optimal growth temperature of L. lactis); three (gidA, polA, and uvs-75) were affected in their capacity to mediate homologous recombination. Our results indicate that UV resistance of the lactococcal strain can be attributed in part to DNA repair but also suggest that other factors, such as cell envelope composition, may be important in mediating resistance to mutagenic stress. PMID:9226255

Duwat, P; Cochu, A; Ehrlich, S D; Gruss, A

1997-07-01

382

Quantitative physiology of Lactococcus lactis at extreme low-growth rates.  

PubMed

This paper describes the metabolic adaptation of Lactococcus lactis during the transition from a growing to a non-growing state using retentostat cultivation. Under retentostat cultivation, the specific growth rate decreased from 0.025?h(-1) to 0.0001?h(-1) in 42 days, while doubling time increased to more than 260 days. Viability of the overall culture was maintained above 90% but included approximately 20% damaged cells, which had lost their colony forming capacity on solid media. Although culture biomass and viability had reached a steady-state after 14 days of retentostat cultivation, the morphology of the cells changed from coccus-to-rod shape at later stages of retentostat cultivation, by which the cell's surface to volume ratio was estimated to increase 2.4-fold. Furthermore, the metabolic patterns switched between homolactic and mixed-acid fermentation during the retentostat cultivation. Retentostat cultivation enabled the calculation of accurate substrate- and energy-related maintenance coefficients and biomass yields under non-growing conditions, which were in good agreement with those calculated by extrapolation from chemostat cultivations at high dilution rates. In this study, we illustrate how retentostat cultivation allows decoupling of growth and non-growth associated processes in L.?lactis, enabling the analysis of quantitative physiological responses of this bacterium to near zero-specific growth rates. PMID:23461598

Ercan, Onur; Smid, Eddy J; Kleerebezem, Michiel

2013-08-01

383

Controlled Modulation of Folate Polyglutamyl Tail Length by Metabolic Engineering of Lactococcus lactis  

PubMed Central

The dairy starter bacterium Lactococcus lactis is able to synthesize folate and accumulates >90% of the produced folate intracellularly, predominantly in the polyglutamyl form. Approximately 10% of the produced folate is released into the environment. Overexpression of folC in L. lactis led to an increase in the length of the polyglutamyl tail from the predominant 4, 5, and 6 glutamate residues in wild-type cells to a maximum of 12 glutamate residues in the folate synthetase overproducer and resulted in a complete retention of folate in the cells. Overexpression of folKE, encoding the bifunctional protein 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine pyrophosphokinase and GTP-cyclohydrolase I, resulted in reduction of the average polyglutamyl tail length, leading to enhanced excretion of folate. By simultaneous overexpression of folKE and folC, encoding the enzyme folate synthetase or polyglutamyl folate synthetase, the average polyglutamyl tail length was increased, again resulting in normal wild-type distribution of folate. The production of bioavailable monoglutamyl folate and almost complete release of folate from the bacterium was achieved by expressing the gene for ?-glutamyl hydrolase from human or rat origin. These engineering studies clearly establish the role of the polyglutamyl tail length in intracellular retention of the folate produced. Also, the potential application of engineered food microbes producing folates with different tail lengths is discussed.

Sybesma, Wilbert; van den Born, Erwin; Starrenburg, Marjo; Mierau, Igor; Kleerebezem, Michiel; de Vos, Willem M.; Hugenholtz, Jeroen

2003-01-01

384

Development of a LAC4 promoter-based gratuitous induction system in Kluyveromyces lactis.  

PubMed

A gratuitous induction system based on the strong, indigenous LAC4 promoter was developed for Kluyveromyces lactis. To prevent consumption of the inducer galactose, a strain with a gal1-209 mutation was employed; this mutation disables the galactokinase function but retains the regulatory function for induction. The Escherichia coli lacZ gene (encoding beta-galactosidase) is functional in K. lactis and was used as the reporter gene downstream of the LAC4 promoter on a multicopy plasmid. The gal1-209 strain exhibited several unexpected phenomena, including partial consumption of the inducer galactose (although at a much slower rate relative to GAL1 strains) and growth inhibition at high concentrations of galactose. These unusual characteristics, however, did not prevent the successful construction of a strong gratuitous induction system. Due to the low rate of inducer consumption for the gratuitous strain, very low concentrations of galactose (1:20 galactose:glucose) resulted in high-level induction. Under these conditions, beta-galactosidase specific and volumetric activities were 4.2- and 5.5-fold higher, respectively, than those for the "GAL1" nongratuitous strain. This research demonstrated the improved productivity possible via LAC4 promoter-based gratuitous induction (and thus a more stable inducer concentration). The effects of various carbon source concentrations on growth and induction were also determined. PMID:10620756

Hsieh, H B; Da Silva, N A

2000-02-20

385

Identification of Four Phage Resistance Plasmids from Lactococcus lactis subsp. cremoris HO2  

PubMed Central

The bacteriophage-host sensitivity patterns of 16 strains of Lactococcus lactis originally isolated from a mixed strain Cheddar cheese starter culture were determined. Using phages obtained from cheese factory whey, four of the strains were found to be highly phage resistant. One of these isolates, Lactococcus lactis subsp. cremoris HO2, was studied in detail to determine the mechanisms responsible for the phage insensitivity phenotypes. Conjugal transfer of plasmid DNA from strain HO2 allowed a function to be assigned to four of its six plasmids. A 46-kb molecule, designated pCI646, was found to harbor the lactose utilization genes, while this and plasmids of 58 kb (pCI658), 42 kb (pCI642), and 4.5 kb (pCI605) were shown to be responsible for the phage resistance phenotypes observed against the small isometric-headed phage ?712 (936 phage species) and the prolate-headed phage ?c2 (c2 species). pCI658 was found to mediate an adsorption-blocking mechanism and was also responsible for the fluffy pellet phenotype of cells containing the molecule. pCI642 and pCI605 were both shown to be required for the operation of a restriction-modification system.

Forde, Amanda; Daly, Charles; Fitzgerald, Gerald F.

1999-01-01

386

Gene Targeting in the Gram-Positive Bacterium Lactococcus lactis, Using Various Delta Ribozymes  

PubMed Central

The trans-acting antigenomic delta ribozyme, isolated from the human hepatitis delta virus, was shown to be highly stable and active in vitro, as well as in mammalian cell lines. However, the stability and gene-targeting competence of this small ribozyme have not been studied previously in bacterial cells. In this paper we describe the use of two variants of the trans-acting antigenomic delta ribozyme targeting the abundant EF-Tu mRNA in the industrially important gram-positive bacterium Lactococcus lactis. These two delta ribozyme variants were expressed at significant levels and were shown to be highly stable in vivo. The half-life of the EF-Tu mRNA was slightly but consistently reduced in the presence of the classical delta ribozymes (7 to 13%). In contrast, delta ribozymes harboring a specific on/off riboswitch (SOFA-delta ribozymes) targeting the same sites on the EF-Tu mRNA considerably reduced the half-life of this mRNA (22 to 47%). The rates of catalysis of the SOFA-delta ribozymes in L. lactis were similar to the rates determined in vitro, showing that this new generation of delta ribozymes was highly efficient in these bacterial cells. Clearly, SOFA-delta ribozymes appear to be an ideal means for development of gene inactivation systems in bacteria.

Fiola, Karine; Perreault, Jean-Pierre; Cousineau, Benoit

2006-01-01

387

Cloning and verification of the Lactococcus lactis pyrG gene and characterization of the gene product, CTP synthase.  

PubMed

The pyrG gene of Lactococcus lactis subsp. cremoris, encoding CTP synthase, has been cloned and sequenced. It is flanked upstream by an open reading frame showing homology to several aminotransferases and downstream by an open reading frame of unknown function. L. lactis strains harboring disrupted pyrG alleles were constructed. These mutants required cytidine for growth, proving that in L. lactis, the pyrG product is the only enzyme responsible for the amination of UTP to CTP. In contrast to the situation in Escherichia coli, an L. lactis pyrG mutant could be constructed in the presence of a functional cdd gene encoding cytidine deaminase. A characterization of the enzyme revealed similar properties as found for CTP synthases from other organisms. However, unlike the majority of CTP synthases the lactococcal enzyme can convert dUTP to dCTP, although a half saturation concentration of 0.6 mm for dUTP makes it unlikely that this reaction plays a significant physiological role. As for other CTP synthases, the oligomeric structure of the lactococcal enzyme was found to be a tetramer, but unlike most of the other previously characterized enzymes, the tetramer was very stable even at dilute enzyme concentrations. PMID:11500486

Wadskov-Hansen, S L; Willemoës, M; Martinussen, J; Hammer, K; Neuhard, J; Larsen, S

2001-10-12

388

A Klaac null mutant of Kluyveromyces lactis is complemented by a single copy of the Saccharomyces cerevisiae AAC1 gene.  

PubMed

The KlAAC gene, encoding the ADP/ATP carrier in Kluveromyces lactis, has previously been cloned by complementation of the op1(aac2) mutation of Saccharomyces cerevisiae. We examined the effect of a null mutation of this gene on the phenotype of K. lactis. The consequence of this mutation was found to be multiple. The mutant was respiratory deficient, had an undetectable level of cytochrome a-a3 and b and did not grow on glycerol. The mitochondrial D-lactate ferricytochrome c oxidoreductase activity, as well as the lactate-induced transcription of its gene, KlDLD, was severely reduced. Furthermore, the mutant was unable to grow on galactose, maltose and raffinose. Transcript analysis showed that KlAAC was the only ADP/ATP carrier gene present in K. lactis. The Klaac mutation was fully complemented not only by AAC2, the major gene for the ADP/ATP carrier in S. cerevisiae, but also by AAC1, a gene which is poorly expressed in S. cerevisiae. AAC1 introduced in K. lactis was transcribed to a high level consistent with normal growth on glycerol being restored in the transformed mutant. KlAAC was not subject to control by KlHap2, in contrast to AAC2 which is regulated by the Hap2 complex in S. cerevisiae. PMID:10447592

Viola, A M; Lodi, T; Ferrero, I

1999-08-01

389

Food-grade expression of Helicobacter pylori ureB subunit in Lactococcus lactis and its immunoreactivity.  

PubMed

Helicobacter pylori is the principal cause of chronic active gastritis, peptic ulcer, and gastric cancer. To develop an oral vaccine against H. pylori infection, we had expressed the H. pylori ureB gene (Genbank accession no. FJ436980) in nisin-controlled expression vectors using Lactococcus lactis NZ3900 as host. The ureB gene was amplified by PCR from a H.pylori strain MEL-Hp27. Then the ureB gene was fused translationally downstream of the nisin-inducible promoter nisA in a L. lactis plasmid pNZ8149. Lactose utilization based on the complementation of the lacF gene was used as a dominant selection marker for the food-grade expression system employing L. lactis NZ3900. The conditions of UreB expression in this system were optimized by orthogonal experiment. The optimized conditions have been determined as follows: induction of expression was carried out at the cells density of OD(600) ? 0.4 with 25 ng/ml nisin, and harvest after 5 h. The maximum percentage of recombinant UreB was estimated to be 7% of total soluble cellular proteins and the yield was 12.9 ?g/ml. Western blot demonstrated that the UreB protein was expressed in the L. lactis transformant and had favorable immunoreactivity. These results indicated that the lactococci-derived vaccines could be promising candidates as alternative vaccine strategies for preventing H. pylori infection. PMID:21431835

Chen, Shuaiyin; Zhang, Rongguang; Duan, Guangcai; Shi, Jianxiang

2011-06-01

390

Peptide Accumulation and Bitterness in Cheddar Cheese Made Using Single-Strain Lactococcus lactis Starters with Distinct Proteinase Specificities1  

Microsoft Academic Search

This study investigated peptide accumulation and bitterness in reduced- and full-fat Cheddar cheeses that were manufactured with single-strain Lactococ- cus lactis starters that had distinct cell envelope pro- teinase specificities. Micellar electrokinetic capillary electrophoresis of aqueous cheese extracts detected three large peaks, designated O, P, and Q, that eluted with peptide standards and increased in area during cheese maturation in

Jeffery R. Broadbent; Marie Strickland; Bart C. Weimer; Mark E. Johnson; James L. Steele

1998-01-01

391

Multiple-copy integration of the alpha-galactosidase gene from Cyamopsis tetragonoloba into the ribosomal DNA of Kluyveromyces lactis.  

PubMed

We have developed a vector system for high-copy-number integration into the ribosomal DNA of the yeast Kluyveromyces lactis. This system is analogous to the pMIRY-system developed for Saccharomyces cerevisiae. Plasmids containing a portion of K. lactis rDNA for targeted homologous recombination, as well as the S. cerevisiae TRP1 gene with various promoter deletions, were constructed and, after transformation to K. lactis, analyzed for both copy number and stability. These plasmids were found to be present in about 60 copies per cell and were stably maintained during growth under non-selective conditions. Using this vector system, we expressed a fusion construct containing the S. cerevisiae GAL7 promoter, the SUC2 (invertase) signal sequence and the gene coding for alpha-galactosidase from the plant Cyamopsis tetragonoloba. Although the maximum copy number of these integrated plasmids was only about 15, we nevertheless obtained a high level of alpha-galactosidase production (250 mg/l) with a secretion efficiency of about 95%. When compared to extrachromosomal K. lactis vectors containing the same fusion construct, the multicopy integrants showed a much higher alpha-galactosidase production level and a considerably higher stability under non-selective conditions. PMID:1326415

Bergkamp, R J; Kool, I M; Geerse, R H; Planta, R J

1992-04-01

392

Genome Sequence of Lactobacillus delbrueckii subsp. lactis CNRZ327, a Dairy Bacterium with Anti-Inflammatory Properties  

PubMed Central

Lactobacillus delbrueckii subsp. lactis CNRZ327 is a dairy bacterium with anti-inflammatory properties both in vitro and in vivo. Here, we report the genome sequence of this bacterium, which appears to contain no less than 215 insertion sequence (IS) elements, an exceptionally high number regarding the small genome size of the strain.

El Kafsi, Hela; Binesse, Johan; Loux, Valentin; Buratti, Julien; Boudebbouze, Samira; Dervyn, Rozenn; Hammani, Amal; Maguin, Emmanuelle

2014-01-01

393

Genotypic and phenotypic analysis of dairy Lactococcus lactis biodiversity in milk: volatile organic compounds as discriminating markers.  

PubMed

The diversity of nine dairy strains of Lactococcus lactis subsp. lactis in fermented milk was investigated by both genotypic and phenotypic analyses. Pulsed-field gel electrophoresis and multilocus sequence typing were used to establish an integrated genotypic classification. This classification was coherent with discrimination of the L. lactis subsp. lactis bv. diacetylactis lineage and reflected clonal complex phylogeny and the uniqueness of the genomes of these strains. To assess phenotypic diversity, 82 variables were selected as important dairy features; they included physiological descriptors and the production of metabolites and volatile organic compounds (VOCs). Principal-component analysis (PCA) demonstrated the phenotypic uniqueness of each of these genetically closely related strains, allowing strain discrimination. A method of variable selection was developed to reduce the time-consuming experimentation. We therefore identified 20 variables, all associated with VOCs, as phenotypic markers allowing discrimination between strain groups. These markers are representative of the three metabolic pathways involved in flavor: lipolysis, proteolysis, and glycolysis. Despite great phenotypic diversity, the strains could be divided into four robust phenotypic clusters based on their metabolic orientations. Inclusion of genotypic diversity in addition to phenotypic characters in the classification led to five clusters rather than four being defined. However, genotypic characters make a smaller contribution than phenotypic variables (no genetic distances selected among the most contributory variables). This work proposes an original method for the phenotypic differentiation of closely related strains in milk and may be the first step toward a predictive classification for the manufacture of starters. PMID:23709512

Dhaisne, Amandine; Guellerin, Maeva; Laroute, Valérie; Laguerre, Sandrine; Cocaign-Bousquet, Muriel; Le Bourgeois, Pascal; Loubiere, Pascal

2013-08-01

394

Oral Vaccination with the Porcine Rotavirus VP4 Outer Capsid Protein Expressed by Lactococcus lactis Induces Specific Antibody Production  

PubMed Central

The objective of this study to design a delivery system resistant to the gastrointestinal environment for oral vaccine against porcine rotavirus. Lactococcus lactis NZ9000 was transformed with segments of vP4 of the porcine rotavirus inserted into the pNZ8112 surface-expression vector, and a recombinant L. lactis expressing VP4 protein was constructed. An approximately 27?kDa VP4 protein was confirmed by SDS-PAGE , Western blot and immunostaining analysis. BALB/c mice were immunized orally with VP4-expression recombinant L. lactis and cellular, mucosal and systemic humoral immune responses were examined. Specific anti-VP4 secretory IgA and IgG were found in feces, ophthalmic and vaginal washes and in serum. The induced antibodies demonstrated neutralizing effects on porcine rotavirus infection on MA104 cells. Our findings suggest that oral immunization with VP4-expressing L. lactis induced both specific local and systemic humoral and cellular immune responses in mice.

Li, Yi-jing; Ma, Guang-peng; Li, Gui-wei; Qiao, Xin-yuan; Ge, Jun-wei; Tang, Li-jie; Liu, Min; Liu, Li-wei

2010-01-01

395

Microencapsulation of B. lactis (BI 01) and L. acidophilus (LAC 4) by Complex Coacervation Followed by Spouted-Bed Drying  

Microsoft Academic Search

Microcapsules containing B. lactis and L. acidophilus were produced by complex coacervation and spouted bed dehydrated afterwards. The aim of this study was to evaluate the resistance of these microorganisms in face of the dehydration process, shelf life, and in vitro tolerance to acid pH besides microcapsules and particles morphology by optical microscopic and SEM. The processes of complex coacervation,

A. C. Oliveira; T. S. Moretti; C. Boschini; J. C. C. Baliero; L. A. P. Freitas; O. Freitas; C. S. Favaro-Trindade

2007-01-01

396

Hsp65-producing Lactococcus lactis prevents experimental autoimmune encephalomyelitis in mice by inducing CD4+LAP+ regulatory T cells  

PubMed Central

Heat shock proteins (Hsps) participate in the cellular response to stress and they are hiperexpressed in inflammatory conditions. They are also known to play a major role in immune modulation, controlling, for instance, autoimmune responses. In this study, we showed that oral administration of a recombinant Lactococcus lactis strain that produces and releases LPS-free Hsp65 prevented the development of experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice. This was confirmed by the reduced inflammatory cell infiltrate and absence of injury signs in the spinal cord. The effect was associated with reduced IL-17 and increased IL-10 production in mesenteric lymph node and spleen cell cultures. Hsp65-producing-L. lactis-fed mice had a remarkable increase in the number of natural and inducible CD4+Foxp3+ regulatory T (Treg) cells and CD4+LAP+ (Latency-associated peptide) Tregs - which express the membrane-bound TGF-? - in spleen, inguinal and mesenteric lymph nodes as well as in spinal cord. Moreover, many Tregs co-expressed Foxp3 and LAP. In vivo depletion of LAP+ cells abrogated the effect of Hsp65-producing L. lactis in EAE prevention and worsened disease in medium-fed mice. Thus, Hsp65-L.lactis seems to boost this critical regulatory circuit involved in controlling EAE development in mice.

Rezende, Rafael M.; Oliveira, Rafael P.; Medeiros, Samara R.; Gomes-Santos, Ana C.; Alves, Andrea C.; Loli, Flavia G.; Guimaraes, Mauro A.F.; Amaral, Sylvia S.; da Cunha, Andre P.; Weiner, Howard L.; Azevedo, Vasco; Miyoshi, Anderson; Faria, Ana M.C.

2013-01-01

397

Hsp65-producing Lactococcus lactis prevents experimental autoimmune encephalomyelitis in mice by inducing CD4+LAP+ regulatory T cells.  

PubMed

Heat shock proteins (Hsps) participate in the cellular response to stress and they are hiperexpressed in inflammatory conditions. They are also known to play a major role in immune modulation, controlling, for instance, autoimmune responses. In this study, we showed that oral administration of a recombinant Lactococcus lactis strain that produces and releases LPS-free Hsp65 prevented the development of experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice. This was confirmed by the reduced inflammatory cell infiltrate and absence of injury signs in the spinal cord. The effect was associated with reduced IL-17 and increased IL-10 production in mesenteric lymph node and spleen cell cultures. Hsp65-producing-L. lactis-fed mice had a remarkable increase in the number of natural and inducible CD4+Foxp3+ regulatory T (Treg) cells and CD4+LAP+ (Latency-associated peptide) Tregs - which express the membrane-bound TGF-? - in spleen, inguinal and mesenteric lymph nodes as well as in spinal cord. Moreover, many Tregs co-expressed Foxp3 and LAP. In vivo depletion of LAP+ cells abrogated the effect of Hsp65-producing L. lactis in EAE prevention and worsened disease in medium-fed mice. Thus, Hsp65-L.lactis seems to boost this critical regulatory circuit involved in controlling EAE development in mice. PMID:22939403

Rezende, Rafael M; Oliveira, Rafael P; Medeiros, Samara R; Gomes-Santos, Ana C; Alves, Andrea C; Loli, Flávia G; Guimarães, Mauro A F; Amaral, Sylvia S; da Cunha, André P; Weiner, Howard L; Azevedo, Vasco; Miyoshi, Anderson; Faria, Ana M C

2013-02-01

398

Kluyveromyces lactis and Saccharomyces cerevisiae , two potent deacidifying and volatile-sulphur-aroma-producing microorganisms of the cheese ecosystem  

Microsoft Academic Search

Cheese flavour is the result of complex biochemical transformations attributed to bacteria and yeasts grown on the curd of smear-ripened cheeses. Volatile sulphur compounds (VSCs) are responsible for the characteristic aromatic notes of several cheeses. In the present study, we have assessed the ability of Kluyveromyces lactis, Kluyveromyces marxianus and Saccharomyces cerevisiae strains, which are frequently isolated from smear-ripened cheeses,

Dafni-Maria Kagkli; Roselyne Tâche; Timothy M. Cogan; Colin Hill; Serge Casaregola; Pascal Bonnarme

2006-01-01

399

Transcription profiling of interactions between Lactococcus lactis subsp. cremoris SK11 and Lactobacillus paracasei ATCC 334 during Cheddar cheese simulation.  

PubMed

The starter cultures (Lactococcus sp.) and non-starter lactic acid bacteria (mostly Lactobacillus spp.) are essential to flavor development of Cheddar cheese. The aim of this study was to elucidate the transcriptional interaction between Lactococcus lactis subsp. cremoris SK11 and Lactobacillus paracasei ATCC 334 in mixed cultures during simulated Cheddar cheese manufacture (Pearce activity test) and ripening (slurry). Reverse transcription quantitative PCR (RT-qPCR) was used to quantify the expression of 34 genes common to both bacteria and for eight genes specific to either L. lactis subsp. cremoris SK11 or L. paracasei ATCC 334. The multifactorial analysis (MFA) performed on fold change results for each gene revealed that the genes linked to stress, protein and peptide degradation as well as carbohydrate metabolism of L. paracasei ATCC 334 were especially overexpressed in mixed culture with L. lactis subsp. cremoris SK11 during the ripening simulation. For L. lactis subsp. cremoris SK11, genes coding for amino acid metabolism were more expressed during the cheese manufacture simulation, especially in single culture. These results show how complementary functions of starter and NSLAB contribute to activities useful for flavor development. PMID:24674930

Desfossés-Foucault, Émilie; LaPointe, Gisèle; Roy, Denis

2014-05-16

400

Identification, Cloning, and Characterization of a Lactococcus lactis Branched-Chain ?-Keto Acid Decarboxylase Involved in Flavor Formation  

PubMed Central

The biochemical pathway for formation of branched-chain aldehydes, which are important flavor compounds derived from proteins in fermented dairy products, consists of a protease, peptidases, a transaminase, and a branched-chain ?-keto acid decarboxylase (KdcA). The activity of the latter enzyme has been found only in a limited number of Lactococcus lactis strains. By using a random mutagenesis approach, the gene encoding KdcA in L. lactis B1157 was identified. The gene for this enzyme is highly homologous to the gene annotated ipd, which encodes a putative indole pyruvate decarboxylase, in L. lactis IL1403. Strain IL1403 does not produce KdcA, which could be explained by a 270-nucleotide deletion at the 3? terminus of the ipd gene encoding a truncated nonfunctional decarboxylase. The kdcA gene was overexpressed in L. lactis for further characterization of the decarboxylase enzyme. Of all of the potential substrates tested, the highest activity was observed with branched-chain ?-keto acids. Moreover, the enzyme activity was hardly affected by high salinity, and optimal activity was found at pH 6.3, indicating that the enzyme might be active under cheese ripening conditions.

Smit, Bart A.; van Hylckama Vlieg, Johan E. T.; Engels, Wim J. M.; Meijer, Laura; Wouters, Jan T. M.; Smit, Gerrit

2005-01-01

401

Genome analysis of the obligately lytic bacteriophage 4268 of Lactococcus lactis provides insight into its adaptable nature  

Microsoft Academic Search

Analysis of the complete nucleotide sequence of the lactococcal phage 4268, which is lytic for the cheese starter Lactococcus lactis DPC4268, is presented. Phage 4268 has a linear genome of 36,596 bp, which is modularly organised and encompasses 49 open reading frames. Putative functions were assigned to approximately 45% of the predicted products of these open reading frames based on

Maeve Trotter; Olivia McAuliffe; Michael Callanan; Rob Edwards; Gerald F. Fitzgerald; Aidan Coffey; R. Paul Ross

2006-01-01

402

Analysis of a soluble (UreD:UreF:UreG)2 accessory protein complex and its interactions with Klebsiella aerogenes urease by mass spectrometry.  

PubMed

Maturation of the nickel-containing urease of Klebsiella aerogenes is facilitated by the UreD, UreF, and UreG accessory proteins along with the UreE metallo-chaperone. A fusion of the maltose binding protein and UreD (MBP-UreD) was co-isolated with UreF and UreG in a soluble complex possessing a (MBPUreD: UreF:UreG)2 quaternary structure. Within this complex a UreF:UreF interaction was identified by chemical cross-linking of the amino termini of its two UreF protomers, as shown by mass spectrometry of tryptic peptides. A preactivation complex was formed by the interaction of (MBP-UreD:UreF:UreG)2 and urease. Mass spectrometry of intact protein species revealed a pathway for synthesis of the urease pre-activation complex in which individual hetero-trimer units of the (MBP-UreD:UreF:UreG)2 complex bind to urease. Together, these data provide important new insights into the structures of protein complexes associated with urease activation. PMID:23797863

Farrugia, Mark A; Han, Linjie; Zhong, Yueyang; Boer, Jodi L; Ruotolo, Brandon T; Hausinger, Robert P

2013-09-01

403

Malonate-bound structure of the glycerophosphodiesterase from Enterobacter aerogenes (GpdQ) and characterization of the native Fe[superscript 2+] metal-ion preference  

SciTech Connect

The structure of a malonate-bound form of the glycerophosphodiesterase from Enterobacter aerogenes, GpdQ, has been refined at a resolution of 2.2 {angstrom} to a final R factor of 17.1%. The structure was originally solved to 2.9 {angstrom} resolution using SAD phases from Zn{sup 2+} metal ions introduced into the active site of the apoenzyme [Jackson et al. (2007), J. Mol. Biol. 367, 1047-1062]. However, the 2.9 {angstrom} resolution was insufficient to discern significant details of the architecture of the binuclear metal centre that constitutes the active site. Furthermore, kinetic analysis revealed that the enzyme lost a significant amount of activity in the presence of Zn2+, suggesting that it is unlikely to be a catalytically relevant metal ion. In this communication, a higher resolution structure of GpdQ is presented in which malonate is visibly coordinated in the active site and analysis of the native metal-ion preference is presented using atomic absorption spectroscopy and anomalous scattering. Catalytic implications of the structure and its Fe{sup 2+} metal-ion preference are discussed.

Jackson, Colin J.; Hadler, Kieran S.; Carr, Paul D.; Oakley, Aaron J.; Yip, Sylvia; Schenk, Gerhard; Ollis, David L. (Queensland); (ANU)

2011-09-28

404

Malonate-bound structure of the glycerophosphodiesterase from Enterobacter aerogenes (GpdQ) and characterization of the native Fe[supscript 2+] metal-ion preference  

SciTech Connect

The structure of a malonate-bound form of the glycerophosphodiesterase from Enterobacter aerogenes, GpdQ, has been refined at a resolution of 2.2 {angstrom} to a final R factor of 17.1%. The structure was originally solved to 2.9 {angstrom} resolution using SAD phases from Zn{sup 2+} metal ions introduced into the active site of the apoenzyme [Jackson et al. (2007), J. Mol. Biol. 367, 1047-1062]. However, the 2.9 {angstrom} resolution was insufficient to discern significant details of the architecture of the binuclear metal centre that constitutes the active site. Furthermore, kinetic analysis revealed that the enzyme lost a significant amount of activity in the presence of Zn{sup 2+}, suggesting that it is unlikely to be a catalytically relevant metal ion. In this communication, a higher resolution structure of GpdQ is presented in which malonate is visibly coordinated in the active site and analysis of the native metal-ion preference is presented using atomic absorption spectroscopy and anomalous scattering. Catalytic implications of the structure and its Fe{sup 2+} metal-ion preference are discussed.

Jackson, Colin J.; Hadler, Kieran S.; Carr, Paul D.; Oakley, Aaron J.; Yip, Sylvia; Schenk, Gerhard; Ollis, David L. (Queensland); (ANU)

2010-09-20

405

Analysis of a Soluble (UreD:UreF:UreG)2 Accessory Protein Complex and Its Interactions with Klebsiella aerogenes Urease by Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Maturation of the nickel-containing urease of Klebsiella aerogenes is facilitated by the UreD, UreF, and UreG accessory proteins along with the UreE metallo-chaperone. A fusion of the maltose binding protein and UreD (MBP-UreD) was co-isolated with UreF and UreG in a soluble complex possessing a (MBP-UreD:UreF:UreG)2 quaternary structure. Within this complex a UreF:UreF interaction was identified by chemical cross-linking of the amino termini of its two UreF protomers, as shown by mass spectrometry of tryptic peptides. A pre-activation complex was formed by the interaction of (MBP-UreD:UreF:UreG)2 and urease. Mass spectrometry of intact protein species revealed a pathway for synthesis of the urease pre-activation complex in which individual hetero-trimer units of the (MBP-UreD:UreF:UreG)2 complex bind to urease. Together, these data provide important new insights into the structures of protein complexes associated with urease activation.

Farrugia, Mark A.; Han, Linjie; Zhong, Yueyang; Boer, Jodi L.; Ruotolo, Brandon T.; Hausinger, Robert P.

2013-09-01

406

Intra- and interspecies conjugal transfer of Tn916-like elements from Lactococcus lactis in vitro and in vivo.  

PubMed

Tetracycline-resistant Lactococcus lactis strains originally isolated from Polish raw milk were analyzed for the ability to transfer their antibiotic resistance genes in vitro, using filter mating experiments, and in vivo, using germfree rats. Four of six analyzed L. lactis isolates were able to transfer tetracycline resistance determinants in vitro to L. lactis Bu2-60, at frequencies ranging from 10(-5) to 10(-7) transconjugants per recipient. Three of these four strains could also transfer resistance in vitro to Enterococcus faecalis JH2-2, whereas no transfer to Bacillus subtilis YBE01, Pseudomonas putida KT2442, Agrobacterium tumefaciens UBAPF2, or Escherichia coli JE2571 was observed. Rats were initially inoculated with the recipient E. faecalis strain JH2-2, and after a week, the L. lactis IBB477 and IBB487 donor strains were introduced. The first transconjugants were detected in fecal samples 3 days after introduction of the donors. A subtherapeutic concentration of tetracycline did not have any significant effect on the number of transconjugants, but transconjugants were observed earlier in animals dosed with this antibiotic. Molecular analysis of in vivo transconjugants containing the tet(M) gene showed that this gene was identical to tet(M) localized on the conjugative transposon Tn916. Primer-specific PCR confirmed that the Tn916 transposon was complete in all analyzed transconjugants and donors. This is the first study showing in vivo transfer of a Tn916-like antibiotic resistance transposon from L. lactis to E. faecalis. These data suggest that in certain cases food lactococci might be involved in the spread of antibiotic resistance genes to other lactic acid bacteria. PMID:19666731

Boguslawska, Joanna; Zycka-Krzesinska, Joanna; Wilcks, Andrea; Bardowski, Jacek

2009-10-01

407

Oral immunization with Lactococcus lactis secreting attenuated recombinant staphylococcal enterotoxin B induces a protective immune response in a murine model  

PubMed Central

Background Staphylococcus aureus is unrestrictedly found in humans and in animal species that maintain thermal homeostasis. Inadequate cleaning of processing equipment or inappropriate handling can contaminate processed food and cause severe food poisoning. Staphylococcal enterotoxin B (SEB), a potent superantigenic exotoxin, is produced by 50% of clinical isolates of S. aureus and is associated with massive food poisoning and with the induction of toxic shock syndrome. Results A gene sequence encoding a recombinant SEB (rSEB), devoid of superantigenic activity, was successfully cloned and expressed in a cytoplasmic or a secreted form in the food-grade lactic acid bacterium Lactococcus lactis. The recombinant protein detected in the cytoplasm or in the culture medium exhibited the expected molecular mass and was recognized by a SEB-polyclonal antibody. Oral immunization with the recombinant L. lactis strains induced a protective immune response in a murine model of S. aureus infection. Immunized mice survived intraperitoneal challenge with an S. aureus SEB-producer strain. Counts of S. aureus in the spleen of rSEB-immunized mice were significantly reduced. The rSEB-immunized mice showed significant titers of anti-SEB IgA and IgG in stools and serum, respectively. Both recombinant L. lactis strains were able to elicit cellular or systemic immune responses in mice, with no significant difference if rSEB was produced in its cytoplasmic or secreted form. However, recombinant L. lactis expressing the cytoplasmic rSEB increased the survival rate of the challenged mice by 43%. Conclusions These findings show the vaccine efficacy of L. lactis carrying an attenuated SEB, in a murine model, following lethal S. aureus challenge.

2013-01-01

408

Functional analysis of the Lactococcus lactis galU and galE genes and their impact on sugar nucleotide and exopolysaccharide biosynthesis  

Microsoft Academic Search

We studied the UDP-glucose pyrophosphorylase (galU) and UDP-galactose epimerase (galE) genes of Lactococcus lactis MG1363 to investigate their involvement in biosynthesis of UDP-glucose and UDP-galactose, which are precursors of glucose- and galactose-containing exopolysaccharides (EPS) in L. lactis. The lactococcal galU gene was identified by a PCR approach using degenerate primers and was found by Northern blot analysis to be transcribed

INGEBORG C. BOELS; ANA RAMOS; MICHIEL KLEEREBEZEM; Vos de W. M

2001-01-01

409

Development of an enteric-coated formulation containing freeze-dried, viable recombinant Lactococcus lactis for the ileal mucosal delivery of human interleukin-10  

Microsoft Academic Search

Recombinant hIL-10 producing Lactococcus lactis (Thy12) looks a promising intestinal mucosal delivery system for treatment of Crohn's disease [L. Steidler, W. Hans, L. Schotte, S. Neirynck, F. Obermeirer, W. Falk, W. Fiers, E. Remaut, Treatment of murine colitis by L. lactis secreting interleukin-10, Science 289 (2000) 1352–1355. L. Steidler, S. Neirynck, N. Huyghebaert, V. Snoeck, A. Vermeire, B.M. Goddeeris, E.

Nathalie Huyghebaert; An Vermeire; Sabine Neirynck; Lothar Steidler; Erik Remaut; Jean Paul Remon

2005-01-01

410

Metabolic engineering of Lactococcus lactis: Influence of overproduction of ß-acetolactate synthase in strains deficient in lactate dehydrogenase as a function of culture conditions  

Microsoft Academic Search

under the control of the inducible L. lactis lacA promoter. More than a hundredfold overproduction of a-acetolactate synthase was obtained inL. lactisunder inducing conditions as compared with that of the host strain, which contained a single chromosomal copy of the als gene. The effect of a-acetolactate synthase overproduction on the formation of end products in various L. lactis strains was

CHRIST PLATTEEUW; JEROEN HUGENHOLTZ; MARJO STARRENBURG; Alen-Boerrigter van I; Vos de W. M

1995-01-01

411

Use of the usp45 lactococcal secretion signal sequence to drive the secretion and functional expression of enterococcal bacteriocins in Lactococcus lactis  

Microsoft Academic Search

Replacement of the signal peptide (SP) of the bacteriocins enterocin P (EntP) and hiracin JM79 (HirJM79), produced by Enterococcus faecium P13 and Enterococcus hirae DCH5, respectively, by the signal peptide of Usp45 (SP\\u000a usp45\\u000a ), the major Sec-dependent protein secreted by Lactococcus lactis, permits the production, secretion, and functional expression of EntP and HirJM79 by L. lactis. Chimeric genes encoding

Juan Borrero; Juan J. Jiménez; Loreto Gútiez; Carmen Herranz; Luis M. Cintas; Pablo E. Hernández

2011-01-01

412

Monitoring the cell number of Lactococcus lactis subsp. cremoris FC in human feces by real-time PCR with strain-specific primers designed using the RAPD technique  

Microsoft Academic Search

Strain-specific PCR primers for Lactococcus lactis subsp. cremoris FC were developed using the randomly amplified polymorphic DNA (RAPD) technique. RAPD was used to generate strain-specific markers. A 1164-bp RAPD marker found to be strain-specific was sequenced, and a primer pair specific for L. lactis subsp. cremoris FC was designed. The specificity of this primer pair was tested with 23 L.

Toshinari Maruo; Mitsuo Sakamoto; Toshiya Toda; Yoshimi Benno

2006-01-01

413

Variable Bacteriocin Production in the Commercial Starter Lactococcus lactis DPC4275 Is Linked to the Formation of the Cointegrate Plasmid pMRC02  

Microsoft Academic Search

Lactococcus lactis DPC4275 is a bacteriocin-producing transconjugant of the industrial starter strain DPC4268. Strain DPC4275 was generated through conjugal transfer by mating DPC4268 with L. lactis MG1363 containing the 60-kb plasmid pMRC01, which encodes the genetic determinants for the lantibiotic lacticin 3147 and for a phage resistance mechanism of the abortive infection type. The many significant applications of this strain

Maeve Trotter; Olivia E. McAuliffe; Gerald F. Fitzgerald; Colin Hill; R. Paul Ross; Aidan Coffey

2004-01-01

414

Reduced Lysis upon Growth of Lactococcus lactis on Galactose Is a Consequence of Decreased Binding of the Autolysin AcmA?  

PubMed Central

When Lactococcus lactis subsp. lactis IL1403 or L. lactis subsp. cremoris MG1363 is grown in a medium with galactose as the carbon source, the culture lyses to a lesser extent in stationary phase than when the bacteria are grown in a medium containing glucose. Expression of AcmA, the major autolysin of L. lactis, is not influenced by the carbon source. Binding studies with a fusion protein consisting of the MSA2 protein of Plasmodium falciparum and the C-terminal peptidoglycan-binding domain of AcmA revealed that cell walls of cells from both subspecies grown on galactose bind less AcmA than cell walls of cells grown on glucose. Cells grown on glucose or galactose and treated with trichloroacetic acid prior to AcmA binding bind similar amounts of AcmA. Analysis of the composition of the lipoteichoic acids (LTAs) of L. lactis IL1403 cells grown on glucose or galactose showed that the LTA composition is influenced by the carbon source: cells grown on galactose contain LTA with less galactose than cells grown on glucose. In conclusion, growth of L. lactis on galactose changes the LTA composition in the cell wall in such a way that less AcmA is able to bind to the peptidoglycan, resulting in a decrease in autolysis.

Steen, Anton; Buist, Girbe; Kramer, Naomi E.; Jalving, Ruud; Benus, Germaine F. J. D.; Venema, Gerard; Kuipers, Oscar P.; Kok, Jan

2008-01-01

415

Lactococcus lactis SpOx Spontaneous Mutants: a Family of Oxidative-Stress-Resistant Dairy Strains§  

PubMed Central

Numerous industrial bacteria generate hydrogen peroxide (H2O2), which may inhibit the growth of other bacteria in mixed ecosystems. We isolated spontaneous oxidative-stress-resistant (SpOx) Lactococcus lactis mutants by using a natural selection method with milk-adapted strains on dairy culture medium containing H2O2. Three SpOx mutants displayed greater H2O2 resistance. One of them, SpOx3, demonstrated better behavior in different oxidative-stress situations: (i) higher long-term survival upon aeration in LM17 and milk and (ii) the ability to grow with H2O2-producing Lactobacillus delbrueckii subsp. delbrueckii strains. Furthermore, the transit kinetics of the SpOx3 mutant in the digestive tract of a human flora-associated mouse model was not affected.

Rochat, Tatiana; Gratadoux, Jean-Jacques; Corthier, Gerard; Coqueran, Berard; Nader-Macias, Maria-Elena; Gruss, Alexandra; Langella, Philippe

2005-01-01

416

The effect of Lactococcus lactis starter cultures on the oxidative stability of liquid whey.  

PubMed

The oxidative stability of liquid Cheddar cheese whey was evaluated using 2 Lactococcus lactis starter cultures in combination and alone along with a control, utilizing glucono-delta-lactone for acid development. Fresh and stored whey were evaluated for volatile composition, free fatty acids, and flavor by descriptive sensory analysis. A significant increase in volatile lipid oxidation products, most notably, hexanal, occurred during storage, and a corresponding decline in the free fatty acid linoleic acid was found. The flavor and aroma characteristic, cardboardy, was correlated to the increase in volatile lipid oxidation products and the decline in linoleic acid. Evidence strongly suggested that lipid oxidation was initiated during whey production and escalated during storage and that the starter cultures significantly influenced the level of volatile lipid oxidation products. Further understanding of the impact of starter cultures on whey may allow for the production of higher quality whey ingredients with wider food application. PMID:14762072

Tomaino, R M; Turner, L G; Larick, D K

2004-02-01

417

Inducible Amplification of Gene Copy Number and Heterologous Protein Production in the Yeast Kluyveromyces lactis  

PubMed Central

Heterologous protein production can be doubled by increasing the copy number of the corresponding heterologous gene. We constructed a host-vector system in the yeast Kluyveromyces lactis that was able to induce copy number amplification of pKD1 plasmid-based vectors upon expression of an integrated copy of the plasmid recombinase gene. We increased the production and secretion of two heterologous proteins, glucoamylase from the yeast Arxula adeninivorans and mammalian interleukin-1?, following gene dosage amplification when the heterologous genes were carried by pKD1-based vectors. The choice of the promoters for expression of the integrated recombinase gene and of the episomal heterologous genes are critical for the mitotic stability of the host-vector system.

Morlino, Giovanni B.; Tizzani, Lorenza; Fleer, Reinhard; Frontali, Laura; Bianchi, Michele M.

1999-01-01

418

A Food-Grade Approach for Functional Analysis and Modification of Native Plasmids in Lactococcus lactis  

PubMed Central

While plasmids from lactic acid bacteria possess many traits that are of industrial value, their exploitation is often frustrated by an inability to conduct food-grade engineering of native plasmids or to readily screen for their transfer. Here we describe a system that uses a RepA+ temperature-sensitive helper plasmid and a RepA? cloning vector to overcome these problems while maintaining the food-grade status of the native plasmid. This strategy was used to precisely delete ltnA1 alone, or in conjunction with ltnA2 (encoding the structural proteins of the lantibiotic lacticin 3147), from the native 60.2-kb plasmid pMRC01 and to select for the transfer of pMRC01 between Lactococcus lactis strains.

Cotter, Paul D.; Hill, Colin; Ross, R. Paul

2003-01-01

419

Production of nisin Z using Lactococcus lactis IO-1 from hydrolyzed sago starch.  

PubMed

A membrane bioreactor for production of nisin Z was constructed using Lactococcus lactis IO-1 in continuous culture using hydrolyzed sago starch as carbon source. A strategy used to enhance the productivity of nisin Z was to maintain the cells in a continuous growth at high cell concentration. This resulted in a volumetric productivity of nisin Z, as 50,000 IU l(-1) h(-1) using a cell concentration of 15 g l(-1), 30( degrees )C, pH 5.5 and a dilution rate of 1.24 h(-1). Adding 10 g l(-1) YE and 2 g l(-1) polypeptone, other inducers were unnecessary to maintain production of nisin. The operating conditions of the reactor removed nisin and lactate, thus minimizing their effects which allowed the maintenance of cells in continuous exponential growth phase mode with high metabolic activity. PMID:19137340

Carvajal-Zarrabal, Octavio; Nolasco-Hipólito, Cirilo; Bujang, Kopli B; Ishizaki, Ayaaki

2009-03-01

420

Intracellular production of IFN-alpha 2b in Lactococcus lactis.  

PubMed

Human interferon alpha (IFN-?) was expressed in two strains of Lactococcus lactis by aid of two promoters (P32 and Pnis) giving rise to two recombinant strains: MG:IFN and NZ:IFN, respectively. The expression of IFN was confirmed by ELISA and western blotting. Highest production was achieved using glucose for growth of both recombinant strains with nisin, used for induction of the recombinant strain with Pnis promoter, at 30 ng/ml. The optimum time for MG:IFN was 9 h and for NZ:IFN was 4.5 h. The highest productions by MG:IFN and NZ:IFN were 1.9 and 2.4 ?g IFN/l, respectively. Both of the expressed IFNs showed bioactivities of 1.9 × 10(6) IU/mg that were acceptable for further clinical studies. PMID:24185903

Bayat, Omid; Baradaran, Ali; Ariff, Arbakariya; Mohamad, Rosfarizan; Rahim, Raha Abdul

2014-03-01

421

Heterologous expression of pneumococcal virulence factor PspC on the surface of Lactococcus lactis confers adhesive properties.  

PubMed

Lactococcus lactis is a non-pathogenic bacterium that is used in the food industry but is also used as a heterologous host to reveal protein functions of pathogenic bacteria. The adhesin PspC from Streptococcus pneumoniae is a choline-binding protein that is non-covalently anchored to the bacterial cell wall. To assess the exclusive impact of pneumococcal surface protein C (PspC) on the interplay with its host we generated recombinant L. lactis producing a nisin-inducible and covalently anchored variant of PspC on the lactococcal cell surface. A translational fusion of the 5'-end of pspC3.4 with the 3'-end of hic (pspC11.4) was designed to decorate the surface of L. lactis with a chimeric PspC. The PspC3.4 part comprises the first 281 aa residues of PspC3.4, while the Hic sequence consists of the proline-rich and sortase-anchored domain. The results demonstrated that PspC is sufficient for adhesion and subsequent invasion of host epithelial cells expressing the human polymeric Ig receptor (hpIgR). Moreover, invasion via hpIgR was even more pronounced when the chimeric PspC was produced by lactococci compared with pneumococci. This study shows also for the first time that PspC plays no significant role during phagocytosis by macrophages. In contrast, recruitment of Factor H via the PspC chimer has a dramatic effect on phagocytosis of recombinant but not wild-type lactococci, as Factor H interacts specifically with the amino-terminal part of PspC and mediates the contact with phagocytes. Furthermore, L. lactis expressing PspC increased intracellular calcium levels in pIgR-expressing epithelial cells, thus resembling the effect of pneumococci, which induced release of Ca(2+) from intracellular stores via the PspC-pIgR mechanism. In conclusion, expression of the chimeric PspC confers adhesive properties to L. lactis and indicates the potential of L. lactis as a suitable host to study the impact of individual bacterial factors on their capacity to interfere with the host and manipulate eukaryotic epithelial cells. PMID:22222496

Asmat, Tauseef M; Klingbeil, Katharina; Jensch, Inga; Burchhardt, Gerhard; Hammerschmidt, Sven

2012-03-01

422

Sulfur Amino Acid Metabolism and Its Control in Lactococcus lactis IL1403  

PubMed Central

Cysteine and methionine availability influences many processes in the cell. In bacteria, transcription of the specific genes involved in the synthesis of these two amino acids is usually regulated by different mechanisms or regulators. Pathways for the synthesis of cysteine and methionine and their interconversion were experimentally determined for Lactococcus lactis, a lactic acid bacterium commonly found in food. A new gene, yhcE, was shown to be involved in methionine recycling to cysteine. Surprisingly, 18 genes, representing almost all genes of these pathways, are under the control of a LysR-type activator, FhuR, also named CmbR. DNA microarray experiments showed that FhuR targets are restricted to this set of 18 genes clustered in seven transcriptional units, while cysteine starvation modifies the transcription level of several other genes potentially involved in oxidoreduction processes. Purified FhuR binds a 13-bp box centered 46 to 53 bp upstream of the transcriptional starts from the seven regulated promoters, while a second box with the same consensus is present upstream of the first binding box, separated by 8 to 10 bp. O-Acetyl serine increases FhuR binding affinity to its binding boxes. The overall view of sulfur amino acid metabolism and its regulation in L. lactis indicates that CysE could be a master enzyme controlling the activity of FhuR by providing its effector, while other controls at the enzymatic level appear to be necessary to compensate the absence of differential regulation of the genes involved in the interconversion of methionine and cysteine and other biosynthesis genes.

Sperandio, Brice; Polard, Patrice; Ehrlich, Dusko S.; Renault, Pierre; Guedon, Eric

2005-01-01

423

Lactococcus lactis as an adjuvant and delivery vehicle of antigens against pneumococcal respiratory infections  

PubMed Central

Most studies of Lactococcus lactis as delivery vehicles of pneumococcal antigens are focused on the effectiveness of mucosal recombinant vaccines against Streptococcus pneumoniae in animal models. At present, there are three types of pneumococcal vaccines: capsular polysaccharide pneumococcal vaccines (PPV), protein-polysaccharide conjugate pneumococcal vaccines (PCV) and protein-based pneumococcal vaccines (PBPV). Only PPV and PCV have been licensed. These vaccines, however, do not represent a definitive solution. Novel, safe and inexpensive vaccines are necessary, especially in developing countries. Probiotic microorganisms such as lactic acid bacteria (LAB) are an interesting alternative for their use as vehicles in pneumococcal vaccines due to their GRAS (Generally Recognized As Safe) status. Thus, the adjuvanticity of Lactococcus lactis by itself represents added value over the use of other bacteria, a question dealt with in this review. In addition, the expression of different pneumococcal antigens as well as the use of oral and nasal mucosal routes of administration of lactococcal vaccines is considered. The advantages of nasal live vaccines are evident; nonetheless, oral vaccines can be a good alternative when the adequate dose is used. Another point addressed here is the use of live versus inactivated vaccines. In this sense, few researchers have focused on inactivated strains to be used as vaccines against pneumoccoccus. The immunogenicity of live vaccines is better than the one afforded by inactivated ones; however, the probiotic-inactivated vaccine combination has improved this matter considerably. The progress made so far in the protective immune response induced by recombinant vaccines, the successful trials in animal models and the safety considerations of their application in humans suggest that the use of recombinant vaccines represents a good short-term option in the control of pneumococcal diseases.

Vintini, Elisa; Villena, Julio; Raya, Raul

2010-01-01

424

Transport of Glucose by Bifidobacterium animalis subsp. lactis Occurs via Facilitated Diffusion?  

PubMed Central

Two strains of Bifidobacterium animalis subsp. lactis were indistinguishable by several nucleic acid-based techniques; however, the type strain DSMZ 10140 was glucose utilization positive, while RB 4825, an industrially employed strain, was unable to grow rapidly on glucose as the principal carbon source. This difference was attributed to the presence of a low-affinity facilitated-diffusion glucose transporter identified in DSMZ 10140 but lacking in RB 4825. Uptake of d-[U-14C]glucose in DSMZ 10140 was stimulated by monovalent cations (ammonium, sodium, potassium, and lithium) and inhibited by divalent cations (calcium and magnesium). When competitor carbohydrates were included in the uptake assays, stereospecific inhibition was exhibited, with greater competition by methyl-?-glucoside than methyl-?-glucoside. Significant inhibition (>30%) was observed with phloretin, an inhibitor of facilitated diffusion of glucose, whereas there was no inhibition by sodium fluoride, iodoacetate, sodium arsenate, sodium azide, 2,4-dinitrophenol, monensin, or valinomycin, which typically reduce energy-driven transport. Based on kinetic analyses, the mean values for Kt and Vmax were 14.8 ± 3.4 mM d-glucose and 0.13 ± 0.03 ?mol glucose/min/mg cell protein, respectively. Glucose uptake by several glucose-utilizing commercial strains of B. animalis subsp. lactis was also inhibited by phloretin, indicating the presence of facilitated diffusion glucose transporters in those strains. Since DSMZ 10140 has been previously reported to lack a functional glucose phosphoenolpyruvate phosphotransferase system, the glucose transporter identified here is responsible for much of the organism's glucose uptake.

Briczinski, E. P.; Phillips, A. T.; Roberts, R. F.

2008-01-01

425

Lactococcus lactis as an adjuvant and delivery vehicle of antigens against pneumococcal respiratory infections.  

PubMed

Most studies of Lactococcus lactis as delivery vehicles of pneumococcal antigens are focused on the effectiveness of mucosal recombinant vaccines against Streptococcus pneumoniae in animal models. At present, there are three types of pneumococcal vaccines: capsular polysaccharide pneumococcal vaccines (PPV), protein-polysaccharide conjugate pneumococcal vaccines (PCV) and protein-based pneumococcal vaccines (PBPV). Only PPV and PCV have been licensed. These vaccines, however, do not represent a definitive solution. Novel, safe and inexpensive vaccines are necessary, especially in developing countries. Probiotic microorganisms such as lactic acid bacteria (LAB) are an interesting alternative for their use as vehicles in pneumococcal vaccines due to their GRAS (Generally Recognized As Safe) status. Thus, the adjuvanticity of Lactococcus lactis by itself represents added value over the use of other bacteria, a question dealt with in this review. In addition, the expression of different pneumococcal antigens as well as the use of oral and nasal mucosal routes of administration of lactococcal vaccines is considered. The advantages of nasal live vaccines are evident; nonetheless, oral vaccines can be a good alternative when the adequate dose is used. Another point addressed here is the use of live versus inactivated vaccines. In this sense, few researchers have focused on inactivated strains to be used as vaccines against pneumoccoccus. The immunogenicity of live vaccines is better than the one afforded by inactivated ones; however, the probiotic-inactivated vaccine combination has improved this matter considerably. The progress made so far in the protective immune response induced by recombinant vaccines, the successful trials in animal models and the safety considerations of their application in humans suggest that the use of recombinant vaccines represents a good short-term option in the control of pneumococcal diseases. PMID:21326831

Medina, Marcela; Vintiñi, Elisa; Villena, Julio; Raya, Raul; Alvarez, Susana

2010-01-01

426

How recombinant swollenin from Kluyveromyces lactis affects cellulosic substrates and accelerates their hydrolysis  

PubMed Central

Background In order to generate biofuels, insoluble cellulosic substrates are pretreated and subsequently hydrolyzed with cellulases. One way to pretreat cellulose in a safe and environmentally friendly manner is to apply, under mild conditions, non-hydrolyzing proteins such as swollenin - naturally produced in low yields by the fungus Trichoderma reesei. To yield sufficient swollenin for industrial applications, the first aim of this study is to present a new way of producing recombinant swollenin. The main objective is to show how swollenin quantitatively affects relevant physical properties of cellulosic substrates and how it affects subsequent hydrolysis. Results After expression in the yeast Kluyveromyces lactis, the resulting swollenin was purified. The adsorption parameters of the recombinant swollenin onto cellulose were quantified for the first time and were comparable to those of individual cellulases from T. reesei. Four different insoluble cellulosic substrates were then pretreated with swollenin. At first, it could be qualitatively shown by macroscopic evaluation and microscopy that swollenin caused deagglomeration of bigger cellulose agglomerates as well as dispersion of cellulose microfibrils (amorphogenesis). Afterwards, the effects of swollenin on cellulose particle size, maximum cellulase adsorption and cellulose crystallinity were quantified. The pretreatment with swollenin resulted in a significant decrease in particle size of the cellulosic substrates as well as in their crystallinity, thereby substantially increasing maximum cellulase adsorption onto these substrates. Subsequently, the pretreated cellulosic substrates were hydrolyzed with cellulases. Here, pretreatment of cellulosic substrates with swollenin, even in non-saturating concentrations, significantly accelerated the hydrolysis. By correlating particle size and crystallinity of the cellulosic substrates with initial hydrolysis rates, it could be shown that the swollenin-induced reduction in particle size and crystallinity resulted in high cellulose hydrolysis rates. Conclusions Recombinant swollenin can be easily produced with the robust yeast K. lactis. Moreover, swollenin induces deagglomeration of cellulose agglomerates as well as amorphogenesis (decrystallization). For the first time, this study quantifies and elucidates in detail how swollenin affects different cellulosic substrates and their hydrolysis.

2011-01-01

427

Structural Basis for the Transcriptional Regulation of Heme Homeostasis in Lactococcus lactis*  

PubMed Central

Although heme is a crucial element for many biological processes including respiration, heme homeostasis should be regulated strictly due to the cytotoxicity of free heme molecules. Numerous lactic acid bacteria, including Lactococcus lactis, acquire heme molecules exogenously to establish an aerobic respiratory chain. A heme efflux system plays an important role for heme homeostasis to avoid cytotoxicity of acquired free heme, but its regulatory mechanism is not clear. Here, we report that the transcriptional regulator heme-regulated transporter regulator (HrtR) senses and binds a heme molecule as its physiological effector to regulate the expression of the heme-efflux system responsible for heme homeostasis in L. lactis. To elucidate the molecular mechanisms of how HrtR senses a heme molecule and regulates gene expression for the heme efflux system, we determined the crystal structures of the apo-HrtR·DNA complex, apo-HrtR, and holo-HrtR at a resolution of 2.0, 3.1, and 1.9 ?, respectively. These structures revealed that HrtR is a member of the TetR family of transcriptional regulators. The residue pair Arg-46 and Tyr-50 plays a crucial role for specific DNA binding through hydrogen bonding and a CH-? interaction with the DNA bases. HrtR adopts a unique mechanism for its functional regulation upon heme sensing. Heme binding to HrtR causes a coil-to-helix transition of the ?4 helix in the heme-sensing domain, which triggers a structural change of HrtR, causing it to dissociate from the target DNA for derepression of the genes encoding the heme efflux system. HrtR uses a unique heme-sensing motif with bis-His (His-72 and His-149) ligation to the heme, which is essential for the coil-to-helix transition of the ?4 helix upon heme sensing.

Sawai, Hitomi; Yamanaka, Masaru; Sugimoto, Hiroshi; Shiro, Yoshitsugu; Aono, Shigetoshi

2012-01-01