PubMed Health⌕ Search

Biomedical subjects

Jean-Marc Berjeaud

Publications and source records attributed to Jean-Marc Berjeaud.

8 recordsLinked to original sources
PubMed2006

Characterization of new bacteriocinogenic lactic acid bacteria isolated using a medium designed to simulate inhibition of Listeria by Lactobacillus sakei 2512 on meat.

Bacteriocinogenic bacteria have been proposed to protect food products from Listeria contamination as bioprotective cultures. Lactobacillus sakei 2512 was demonstrated to inhibit the growth of Listeria on sliced cooked ham by challenge test. A liquid medium simulating ham, BHI5L200, was designed in order to select bioprotective strains for meat protection. Two strains were selected, from the 201 lactic acid bacteria screened, that produced bacteriocins at pH 5.8 in BHI5L200. The first one, Leuconostoc pseudomesenteroides 2733, produced a new bacteriocin which was purified and partially characterized. The second, Lactobacillus curvatus 2711, produced sakacin X and was shown to contain sakacin T and sakacin P structural genes. Co-culture experiments in BHI5L200 demonstrated that growth of Listeria was inhibited by L. sakei 2512 as well as by L. curvatus 2711.

Animals↗
PubMed2006

Endogenous factors derived from embryonic cortex regulate proliferation and neuronal differentiation of postnatal subventricular zone cell cultures.

In rodents, the subventricular zone (SVZ) harbours neural stem cells that proliferate and produce neurons throughout life. Previous studies showed that factors released by the developing cortex promote neurogenesis in the embryonic ventricular zone. In the present report, we studied in the rat the possible involvement of endogenous factors derived from the embryonic cortex in the regulation of the development of postnatal SVZ cells. To this end, SVZ neurospheres were maintained with explants or conditioned media (CM) prepared from embryonic day (E) 13, E16 or early postnatal cortex. We demonstrate that early postnatal cortex-derived factors have no significant effect on SVZ cell proliferation or differentiation. In contrast, E13 and E16 cortex release diffusible, heat-labile factors that promote SVZ cell expansion through increased proliferation and reduced cell death. In addition, E16 cortex-derived factors stimulate neuronal differentiation in both early postnatal and adult SVZ cultures. Fibroblast growth factor (FGF)-2- but not epidermal growth factor (EGF)-immunodepletion drastically reduces the mitogenic effect of E16 cortex CM, hence suggesting a major role of endogenous FGF-2 released by E16 cortex in the stimulation of SVZ cell proliferation. The evidence we provide here for the regulation of SVZ cell proliferation and neuronal differentiation by endogenous factors released from embryonic cortex may be of major importance for brain repair research.

Age Factors↗
PubMed2005

Isolation and characterization of a Staphylococcus warneri strain producing an anti-Legionella peptide.

Legionella pneumophila is a pathogenic bacterium found in freshwater environments that is responsible for pneumonia. People become infected through inhalation of contaminated droplets from water devices, such as cooling towers and showers. It is important to find new treatments that decrease the development of Legionella. We found a Staphylococcus warneri strain that inhibits Legionella growth. This activity is due to a molecule secreted by S. warneri. This molecule displayed a high heat-stability and its activity was lost after protease treatments, suggesting that it might be a bacteriocin. Its purification led us to conclude that this anti-Legionella molecule is an highly hydrophobic peptide. It has an original and very specific spectrum of activity, directed only toward the Legionella genus. This is the first description of an antibacterial peptide active against Legionella.

Anti-Bacterial Agents↗
PubMed2005

Development of a real-time PCR assay for quantification of Acanthamoeba trophozoites and cysts.

Free-living amoebae have been found to be a reservoir for various pathogenic bacteria in aquatic environments. For example, the Acanthamoeba genus renders possible the intracellular multiplication of Legionella pneumophila, which is responsible for legionellosis. It consequently matters to quantify Acanthamoeba cells and thereby enhance our assessment of the risk of contamination. The classical microbiological method of quantification relies on amoebae growth and most probable number calculation. We have developed a real-time PCR assay based on a TaqMan probe that hybridizes onto 18S rDNA. This probe is specific to the Acanthamoeba genus. The assay was successful with both the trophozoite and the cyst forms of Acanthamoeba. Highly sensitive, it proved to permit detection of fewer than 10 cells, even those that are not easily cultivable, such as the cyst forms.

Acanthamoeba↗
PubMed2004

Differences in mesentericin secretion systems from two Leuconostoc strains.

Leuconostoc mesenteroides Y105 and L. mesenteroides FR52 produce both mesentericin Y105 and B105, in equal amounts. The mesentericin operons of L. mesenteroides FR52 and Y105 which are involved in mesentericin Y105 and B105 production, were both sequenced and compared. Differences were limited to the two genes, mesD and mesE, which encode the dedicated transport system of mesentericin Y105. Analysis of mesentericin non-producing mutants and complementation experiments demonstrated that the major role of the membrane fusion protein, MesE, was in bacteriocin secretion for both strains. Moreover, the secretion machinery MesDE was demonstrated to be capable of transportation and maturation of the two pre-bacteriocins, mesentericin Y105 and B105. We also demonstrate that although MesDEs from strains Y105 and FR52 have significant sequence differences, both transporters were capable of assuring secretion of either bacteriocin.

ATP-Binding Cassette Transporters↗
PubMed2004

Mutational analysis of mesentericin y105, an anti-Listeria bacteriocin, for determination of impact on bactericidal activity, in vitro secondary structure, and membrane interaction.

Mesentericin Y105 is a 37-residue bacteriocin produced by Leuconostoc mesenteroides Y105 that displays antagonistic activity against gram-positive bacteria such as Enterococcus faecalis and Listeria monocytogenes. It is closely related to leucocin A, an antimicrobial peptide containing beta-sheet and alpha-helical structures. To analyze structure-function relationships and the mode of action of this bacteriocin, we generated a collection of mesentericin derivatives. Mutations were obtained mostly by PCR random mutagenesis, and the peptides were produced by an original system of heterologous expression recently described. Ten derivatives were obtained displaying modifications at eight different positions in the mesentericin Y105 sequence. Purified peptides were incorporated into lysophosphatidylcholine micelles and analyzed by circular dichroism. The alpha-helical contents of these peptides were compared and related to their respective bactericidal activities. Moreover, studies of the intrinsic fluorescence of tryptophan residues naturally occurring at positions 18 and 37 revealed information about insertion of the peptides in micelles. A model for the mode of action of mesentericin Y105 and related bacteriocins is proposed.

Amino Acid Sequence↗
PubMed2004

Purification of antilisterial bacteriocins.

In recent years, numerous contamination outbreaks, involving various pathogens (i.e., Listeria and Salmonella), have increased concern over food preservation. Research efforts have focused on the discovery of new molecules targeting such foodborne pathogens and therefore able to inhibit and or kill them. Lactic acid bacteria (LAB) extensively used in fermented foods for thousands of years not only improve their flavor and texture but also inhibit pathogenic and spoilage microorganisms. LAB inhibitory activity is primarily owing to pH decrease and competition for substrates. Antagonistic activity of LAB also depends on secreted antimicrobial compounds with a poor selectivity, such as metabolic compounds (i.e., hydrogen peroxide, acetoin, and others) or more specific ones like bacteriocins. The latter are proteinaceous compounds, ribosomally synthesized and subsequently secreted by Gram-positive as well as Gram-negative bacteria. Their antimicrobial activity is generally restricted to strains phylogenetically related to the producers.A classification of bacteriocins produced by LAB was first proposed by Klaenhammer in 1993 and was modified by Nes et al. in 1996; class I and class II bacteriocins are the most abundant and thoroughly studied. Bacteriocins from both classes exhibit antilisterial activity. Class I bacteriocins, namely, lantibiotics, have been widely studied, and among them, nisin is used in many countries as a preservative in food products. These bacteriocins are characterized by the presence, in their primary structure, of post-translationally modified amino acid residues (i.e., lanthionine and methylanthionine) that are formed. Class II bacteriocins, containing three subclasses, consist of small peptides that do not bear any modified amino acid residue. The most studied subclass corresponds to class IIa, also termed anti-Listeria bacteriocins. These peptides share strong structural homologies in their N-terminal domain, with the presence of one disulfide bond and a net positive charge. Their C-terminal domain is more variable but appears quite hydrophobic. Moreover, some of these bacteriocins, namely, sakacin G, pediocin PA-1, enterocin A, coagulin, and divercin V41, are characterized by the presence of a second disulfide bond in the C-terminal region.

Amino Acid Sequence↗