Biomedical subjects

Yves Cenatiempo

Publications and source records attributed to Yves Cenatiempo.

7 recordsLinked to original sources

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

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↗

PubMed2003

Characterization of a unique sigma54-dependent PTS operon of the lactose family in Listeria monocytogenes.

The sigma(54) subunit of the RNA polymerase directs the expression of specific operons in association with cognate activators. Three different activators have been detected in the Listeria monocytogenes genome on the basis of the high conservation of a specific domain. Among them, the LacR activator, of the LevR family, was found just upstream from a newly described sigma(54)-dependent operon, lpo, which presents a classical -24/-12 consensus promoter. The lpo operon encodes proteins similar to subunits of a PTS permease (EII) of the lactose family, namely LpoA (IIA) and LpoB (IIB). It also encodes a third putative protein, LpoO, with an unknown function but sharing high similarity with proteins also encoded within PTS operons from other bacteria and bearing a RGD motif. The expression of lpo was clearly dependent on LacR and sigma(54), and was induced by cellobiose, chitobiose and lactose. It underlies that the lpo operon likely encodes proteins involved in the utilization of these sugars by L. monocytogenes.

Animals↗

PubMed2002

Identification of a replicon from pTXL1, a small cryptic plasmid from Leuconostoc mesenteroides subsp. mesenteroides Y110, and development of a food-grade vector.

A 2,665-bp cryptic plasmid, pTXL1, isolated from Leuconostoc mesenteroides subsp. mesenteroides Y110 was identified. This plasmid harbors a replicon localized on a 1,300-bp fragment. Two observations suggested that pTXL1 does not belong to rolling-circle replication (RCR)-type plasmids and most likely replicates via a theta mechanism. These hypotheses are supported by the observation that no detectable single-stranded intermediate was found for the replicon and that, unlike in RCR-type plasmids, the pTXL1 replicon sequence lacks an open reading frame encoding a replicase. The small-sized pTXL1 plasmid is stable and, according to its origin, can be considered in the "generally recognized as safe" category. Its ability to replicate in several lactic acid bacteria was exploited to develop a vector producing mesentericin Y105, a class II anti-Listeria bacteriocin. With this new vector, a recombinant industrial Leuconostoc cremoris strain able to produce mesentericin Y105 was constructed.

Amino Acid Sequence↗

PubMed2001

Analysis of sigma(54)-dependent genes in Enterococcus faecalis: a mannose PTS permease (EII(Man)) is involved in sensitivity to a bacteriocin, mesentericin Y105.

The sigma(54) RNA polymerase subunit has a prominent role in susceptibility of Listeria monocytogenes and Enterococcus faecalis to mesentericin Y105, a class IIa bacteriocin. Consequently, sigma(54)-dependent genes as well as specific activators also required for expression of these genes were sought. Five putative sigma(54)-associated activators were detected in the genome of E. faecalis V583, and all but one could activate the transcription of permease genes belonging to sugar phosphotransferase systems (PTSs). Interestingly, these activators display a helicase signature not yet reported in this activator family, which could explain the ATP-dependent mechanism of DNA unwinding preceding the start of transcription. To find which activator is linked to susceptibility of E. faecalis to mesentericin Y105, their respective genes were subsequently interrupted. Among them, only mptR gene interruption led to a resistance phenotype. Immediately downstream from mptR, a putative sigma(54)-dependent operon was found to encode a mannose PTS permease, namely EII(t)(Man). Moreover, in liquid culture, glucose and mannose induced the sensitivity of E. faecalis to mesentericin Y105. Since sugars have previously been reported to induce PTS permease expression, it appears that EII(t)(Man) expression, presumably induced in the presence of glucose and mannose, leads to an enhanced sensitivity of E. faecalis to the bacteriocin. Additional information was gained from knockouts within the permease operon. Interruption of the distal mptD gene, which encodes the IID subunit of EII(t)(Man), strikingly led to resistance to mesentericin Y105. Moreover, MptD appears to be a peculiar membrane subunit, bearing an additional domain compared to most known IID subunits. According to these results, EII(t)(Man) is clearly involved in susceptibility to mesentericin Y105 and could even be its receptor at the E. faecalis surface. Finally, it is hypothesized that MptD could be responsible for the targeting specificity, via an interaction between its additional domain and mesentericin Y105.

Amino Acid Sequence↗

PubMed1998

Divercin V41, a new bacteriocin with two disulphide bonds produced by Carnobacterium divergens V41: primary structure and genomic organization.

Divercin V41 is a new bacteriocin produced by Carnobacterium divergens V41, a lactic acid bacterium isolated from fish viscera. The amino acid sequence of divercin V41 showed high homologies with pediocin PA-1 and enterocin A. Two disulphide bonds were present in the hydrophilic N-terminal domain and in the highly variable hydrophobic C-terminal domain, respectively. A DNA probe designed from the N-terminal sequence of the purified peptide was used to locate the structural gene of divercin V41. A 6 kb chromosomal fragment containing the divercin V41 structural gene (dvnA) was cloned and sequenced. The results indicate that divercin V41 is synthesized as a pre-bacteriocin of 66 amino acids. The 23-residue N-terminal extension is cleaved off to yield the mature 43-amino-acid divercin V41. In addition, the fragment encodes putative proteins commonly found within bacteriocin operons, including an ATP-dependent transporter, two immunity-like proteins and the two components of a lantibiotic-type signal-transducing system. The genetic organization of the fragment suggested important gene rearrangements.

Amino Acid Sequence↗

PubMed1998

Heterologous expression of the bacteriocin mesentericin Y105 using the dedicated transport system and the general secretion pathway.

Two different N-terminal extensions have been identified within class II bacteriocin precursors. The first one is a two-glycine-type leader peptide associated with a dedicated ATP-binding cassette transporter. The second is a signal peptide which directs the bacteriocin precursor to the general secretion machinery. Mesentericin Y105 is a class II anti-Listeria bacteriocin produced by Leuconostoc mesenteroides Y105 via a dedicated transport system (DTS). To investigate heterologous expression systems capable of producing mesentericin Y105 in various hosts, two different secretion vectors were constructed. One of them, containing the mesentericin Y105 structural gene fused to the segment encoding the divergicin A signal peptide, was introduced into Escherichia coli, Leuconostoc subsp. and Lactococcus subsp. In E. coli, mesentericin Y105 production was linked to a putative periplasmic toxicity. To take advantage of this secretion system, the mesentericin Y105 precursor was also produced in E. coli. It was demonstrated that this pre-bacteriocin exhibited some antagonistic activity against Listeria. To allow for a comparison between the two different transport systems, mesentericin Y105 production using the vector containing the mesentericin Y105 structural gene and its DTS transporter operon was examined. The production of mesentericin Y105 was monitored by a new fast purification method followed by MS analysis. It was shown that, in Leuconostoc, the production of mesentericin Y105 is enhanced via the DTS compared to the general secretion pathway.

Anti-Bacterial Agents↗