Biomedical subjects

A Rincé

Publications and source records attributed to A Rincé.

6 recordsLinked to original sources

PubMed2005

Maltose utilization in Enterococcus faecalis.

AIMS: The aim of this research was to characterize the metabolic pathway for maltose utilization in Enterococcus faecalis. METHODS AND RESULTS: Screening a library of Enterococcus faecalis insertional mutants allowed the isolation of mutants affected in maltose utilization. Genetic analysis of the insertion loci revealed insertions in neighbour genes encoding an EII component of a phosphotransferase system (PTS) transporter (malT) and a maltose phosphorylase homologue (malP). The malP gene forms part of an operon which also includes genes encoding a phosphoglucomutase (malB), a mutarotase (aldose 1-epimerase) (malM) and a transcriptional regulator (malR). Analysis of (14)C-labelled carbohydrates uptake revealed that more than 97% of maltose enters the cells by the PTS transporter MalT. CONCLUSIONS: Both experimental data and genetic organization of the malPBMR operon strongly suggest that in Enterococcus faecalis, maltose enters using a PTS, leaving maltose-6-phosphate inside the cells which is hydrolysed by a maltose phosphate phosphorylase (MalP). SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes a new pathway for maltose utilization in lactic acid bacteria.

Base Sequence↗

PubMed2001

The stress proteome of Enterococcus faecalis.

Enterococcus faecalis is a resident bacterium of the intestinal tract of humans and animals. This bacterium can be responsible for serious diseases and is one of the largest causes of hospital-based infections. This hardy organism resists many kinds of stresses and is used as a major indicator of the hygienic quality of food, milk, and drinking water. On the other side, enterococci seem to have beneficial role in the development of cheese aroma and are added in certain starter cultures. Since ten years, our laboratory has used the two-dimensional electrophoresis (2-DE) technique to study the response of E. faecalis to physical or chemical stresses as well as to glucose and total starvation. Twenty-seven protein spots on 2-D gels have been identified by N-terminal sequencing or Western blotting which make up the first proteome database of this species. The proteins were classified in four different groups according to their function and their regulation. The first group comprises well-characterized proteins with known protective functions towards stresses. The second group contains enzymes of catabolic pathways. Their implication in stress resistance seems not obvious. A third group are proteins induced in glucose-starved cells belonging to the CcpA regulon. Induction of these enzymes under starvation may serve to increase the scavenging capacity of the cells for nutrients or may be important to mobilize endogenous energetic reserves. Lastly, nine N-terminal amino acid sequences or open reading frames (ORF) showed no homologies with sequences in databases. A comprehensive description of stress proteins of E. faecalis and analysis of their patterns of expression under different environmental conditions would greatly increase our understanding of the molecular mechanisms underlying the extraordinary capacity of this bacterium to survive under hostile conditions.

Acids↗

PubMed2001

Identification and characterization of gsp65, an organic hydroperoxide resistance (ohr) gene encoding a general stress protein in Enterococcus faecalis.

The Enterococcus faecalis general stress protein Gsp65 has been purified from two-dimensional gel electrophoresis. Determination of its N-terminal sequence and characterization of the corresponding gene revealed that the gsp65 product is a 133-amino-acid protein sharing homologies with organic hydroperoxide resistance (Ohr) proteins. Transcriptional analysis of gsp65 gave evidence for a monocistronic mRNA initiated 52 nucleotides upstream of the ATG start codon and for an induction in response to hydrogen peroxide, heat shock, acid pH, detergents, ethanol, sodium chloride, and tert-butylhydroperoxide (tBOOH). A gsp65 mutant showed increased sensitivity to the organic hydroperoxide tBOOH and to ethanol.

Amino Acid Sequence↗

PubMed2000

Identification of a DNA region from lactococcal phage sk1 protecting phage 712 from the abortive infection mechanism AbiF.

Bacteriophage 712 is a small isometric-headed phage which is sensitive to the lactococcal abortive infection mechanism AbiF. Its 29.6-kb DNA genome was characterized by restriction mapping and transcriptional analysis. Construction of a gene bank of lactococcal phage sk1, which is insensitive to the action of AbiF, in Lactococcus lactis containing AbiF resulted in the identification of a 324-bp DNA fragment which reduced the effect of the abortive infection mechanism on phage 712. Analysis of this region provided evidence that the action of AbiF is related to the cos ends of small isometric-headed phages. Sequence analysis of a 3.2-kb segment containing the middle operon and the cos ends of phage 712 genome allowed comparison of this part of the phage 712 genome with the equivalent sequences of four other small isometric-headed phages.

Cloning, Molecular↗

PubMed2000

IS1675, a novel lactococcal insertion element, forms a transposon-like structure including the lacticin 481 lantibiotic operon.

Two copies of IS1675, a novel lactococcal insertion element from the IS4 family, are present on a 70-kb plasmid, where they frame the lantibiotic lacticin 481 operon. The whole structure could be a composite transposon designated Tn5721. This study shows that the lacticin 481 operon does not include any regulatory gene and provides a new example of a transposon-associated bacteriocin determinant. We identified five other IS1675 copies not associated with the lacticin 481 operon. The conservation of IS1675 flanking sequences suggested a 24-bp target site.

Amino Acid Sequence↗

PubMed1997

Characterization of the lacticin 481 operon: the Lactococcus lactis genes lctF, lctE, and lctG encode a putative ABC transporter involved in bacteriocin immunity.

The lantibiotic lacticin 481 is a bacteriocin produced by Lactococcus lactis strains. The genetic determinants of lacticin 481 production are organized as an operon encoded by a 70-kb plasmid. We previously reported the first three genes of this operon, lctA, lctM, and lctT, which are involved in the bacteriocin biosynthesis and export (A. Rincé, A. Dufour, S. Le Pogam, D. Thuault, C. M. Bourgeois, and J.-P. Le Pennec, Appl. Environ. Microbiol. 60:1652-1657, 1994). The operon contains three additional open reading frames: lctF, lctE, and lctG. The hydrophobicity profiles and sequence similarities strongly suggest that the three gene products associate to form an ABC transporter. When the three genes were coexpressed into a lacticin 481-sensitive L. lactis strain, the strain became resistant to the bacteriocin. This protection could not be obtained when any of the three genes was deleted, confirming that lctF, lctE, and lctG are all necessary to provide immunity to lacticin 481. The quantification of the levels of immunity showed that lctF, lctE, and lctG could account for at least 6% and up to 100% of the immunity of the wild-type lacticin 481 producer strain, depending on the gene expression regulation. The lacticin 481 biosynthesis and immunity systems are discussed and compared to other lantibiotic systems.

ATP-Binding Cassette Transporters↗