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Life Sciences	75%

Selected Abstracts

The ttgGHI solvent efflux pump operon of Pseudomonas putida DOT-T1E is located on a large self-transmissible plasmid

ENVIRONMENTAL MICROBIOLOGY, Issue 6 2007
José J. Rodríguez-Herva
Summary Pseudomonas putida DOT-T1E is a solvent-tolerant strain able to grow in the presence of > 1% (v/v) toluene in the culture medium. A set of multidrug efflux pumps have been found to play a major role in the tolerance of this bacterium to organic solvents (Rojas et al., J Bacteriol 183: 3967,3973). In the course of studies of the mechanisms underlying solvent tolerance in DOT-T1E, we isolated a spontaneous solvent-sensitive mutant derivative which had lost the genes encoding the TtgGHI efflux pump, the most important extrusion element in quantitative terms. Genomic comparisons between the mutant and its parental strain by microarray analysis revealed that in addition to the ttgVW-ttgGHI gene cluster, another group of genes, highly similar to those found in the Tn4653A and ISPpu12 transposable elements of the TOL plasmid pWW0 from P. putida mt-2, were also absent from this strain. Further analysis demonstrated that strain DOT-T1E harboured a large plasmid (named pGRT1) that was lost from the solvent-sensitive mutant. Mapping analysis revealed that the ttgVW-ttgGHI genes and the Tn4653A -like transposon are borne by the pGRT1 plasmid. Plasmid pGRT1 is highly stable and its frequency of loss is below 10,8 per cell per generation under a variety of growth conditions, including nutritional and physical stresses. The pGRT1 plasmid is self-transmissible, and its acquisition by the toluene-sensitive P. putida KT2440 and Pseudomonas aeruginosa PAO1 increased the recipient's tolerance to toluene up to levels similar to those exhibited by P. putida DOT-T1E. We discuss the importance and potential benefits of this plasmid for the development of bacteria with enhanced solvent tolerance, and its potential impact for bioremediation and whole-cell biotransformations. [source]

Interactions between Saccharomyces cerevisiae and malolactic bacteria: preliminary characterization of a yeast proteinaceous compound(s) active against Oenococcus oeni

JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2005
F. Comitini
Abstract Aims:, To investigate the occurrence and extent of Saccharomyces cerevisiae and Oenococcus oeni interactions. Methods and Results:, Interactions between S. cerevisiae and O. oeni were investigated by double-layer and well-plate assays showing the occurrence of specific interactions for each yeast,malolactic bacteria (MLB) coupling. Heat and protease treatments of synthetic grape juice fermented by the S. cerevisiae strain F63 indicated that the inhibitory activity exerted by this yeast on O. oeni is due to a proteinaceous factor(s) which exerts either bacteriostatic or bactericidal effect depending on concentration and affects malolactic fermentation in natural grape juice and wine. Conclusions:, A proteinaceous factor(s) produced by a S. cerevisiae wine strain able to inhibit O. oeni growth and malic acid fermentation was characterized. Significance and Impact of the Study:, The individuation, characterization and exploitation of yeast proteinaceous factor(s) exerting inhibitory activity on MLB may offer new opportunities for the management of malolactic fermentation. [source]

Use of a PGU1 recombinant Saccharomyces cerevisiae strain in oenological fermentations

JOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2000
M. Vilanova
Aim: The aim of this work was the construction of an oenological Saccharomyces cerevisiae strain able to overexpress the PGU1 gene in order to be used in trial fermentations. Methods and Results: The recombinant strain is able to secrete an active endopolygalacturonase into the medium leaving its fermentation ability essentially unchanged. Wines obtained with the recombinant strain and the untransformed counterpart did not differ in their physicochemical parameters or major sensory characteristics. The time needed for wine filtration was dramatically reduced in wines elaborated with the PGU1 recombinant strain, and was comparable to the filtration time shown by wines elaborated from must supplemented with fungal pectolytic enzymes. Conclusions: The oenological strain constructed in this work secretes an endopolygalacturonase into the wine in an efficient manner, resulting in an improvement in wine filtration but preserving wine typicality and keeping the methanol levels unchanged. Significance and Impact of the Study: The PGU1 recombinant strains could be used in oenological fermentations as an alternative to commercial pectolytic enzymes of fungal origin. [source]

Biofilms in chronic bacterial prostatitis (NIH-II) and in prostatic calcifications

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2010
Sandra Mazzoli
Abstract The prevalence of inflammatory conditions of the prostate gland is increasing. In Italy, there is a high incidence of prostatitis (13.3%), also accompanied by prostatic calcifications. Cat NIH-II chronic bacterial prostatitis (CBPs) are the most frequent. Their aetiology theoretically involves the whole range of bacterial species that are able to form biofilms and infect prostate cells. The aim of our study was to isolate potential biofilm-producing bacteria from CBP patients, to evaluate their ability to produce in vitro biofilms, and to characterize intraprostatic bacteria and prostatic calcifications using scanning electron microscopy. The 150 clinical bacterial strains isolated from chronic prostatitis NIH-II patients were: 50 Enterococcus faecalis; 50 Staphylococcus spp.; 30 Escherichia coli; 20 gram-negative miscellanea. Quantitative assay of biofilm production and adhesion was performed according to the classic Christensen microwell assay. Isolates were classified as nonproducers, weak, moderate or strong producers. The majority of E. coli, gram-negative bacteria, Staphylococci and Enterococci strains were strong or medium producers: 63,30%, 75,15%, 46,36%, and 58,14%, respectively. Prostatic calcifications consisted of bacteria-like forms similar to the species isolated from biological materials and calcifications of patients. Our study proves, for the first time, that bacterial strains able to produce biofilms consistently are present in CBP. Additionally, prostatic calcifications are biofilm-related. [source]