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Y Auffray

Publications and source records attributed to Y Auffray.

At least 37 records · Page 2Linked to original sources

[Enterococci in human environment].

Enterococci, formerly confounded with faecal streptococci, are recognized since the beginning of the century as being faecal in origin and are generally searched for in waste waters and food products; their detection may in fact indicate the presence of enteropathogenic organisms. Although nearly ubiquitous, their preferred ecological niche is the intestine sphere. Rejected in the environment by means of human faeces or animal dejecta, they are scattered afterwards in diverse niches. Once in the external environment, their survival is linked with their exceptional aptitude to resist or grow in hostile environments that are usually detrimental to the development of most mesophilic microorganisms. However, a certain ambiguity exists concerning their relationships with human beings. In fact, certain enterococcus strains or species are used in the elaboration of some milk products. Conversely, others are opportunists and may cause severe infections to people from infants to adults. Moreover, undergoing adaptation perpetually, they present a multiresistance pattern to antibiotics. Thus, the barrier that separates bacteria as nonoffensive contaminants from powerful pathogens appears most fragile, suggesting that people must systematically consider suspect the presence of enterococci in their near environment.

Animals↗

Relationship between stress response toward bile salts, acid and heat treatment in Enterococcus faecalis.

Stress tolerance and cross-protection in Enterococcus faecalis ATCC19433 were examined after exposure to bile salts, acid or heat shock. Bile salts and heat adapted cells demonstrated induced homologous tolerance and cross-resistance. No cross-protection of heat adapted cells against acid stress is observed and pretreatment with bile salts even sensitized the cells to this challenge. Whole-cell protein extract analysis revealed that each treatment induced a battery of stress proteins. Some of these polypeptides are induced by more than one treatment. The greatest overlap is observed between bile salts and heat treatments. Eighteen stress proteins, including DnaK and GroEL, are common between these stresses.

Bile Acids and Salts↗

Molecular analysis of the rpoD gene of Enterococcus faecalis.

The complete nucleotide sequence of the rpoD gene of Enterococcus faecalis ATCC19433 has been determined. This gene encodes a putative 368 amino acids (aa) polypeptide of a predicted Mr of 41842 named sigma 42. Upstream of the rpoD gene and beginning from the end of the cloned chromosomal fragment is an open reading frame encoding a putative 264-aa polypeptide. It is reminiscent of the C-terminal domain of known DNA primase from Gram-positive bacteria indicating that the E. faecalis rpoD gene is included in a macromolecular synthesis (MMS) operon, as it was described for Escherichia coli, Bacillus subtilis and Lactococcus lactis rpoD gene.

Amino Acid Sequence↗

Unusual resistance and acquired tolerance to cadmium chloride in Enterococcus faecalis.

Enterococcus faecalis exhibits an extremely high natural resistance to cadmium which can be even raised by a conditioning treatment at a lower cadmium concentration as well as by a previous exposure to a sublethal temperature. By contrast, thermotolerance is not significantly induced by previous exposure to low cadmium concentration. The synthesis of several proteins is markedly enhanced by a low concentration of the chemical agent.

Adaptation, Biological↗

Defense against lethal treatments and de novo protein synthesis induced by NaCl in Enterococcus faecalis ATCC 19433.

Enterococcus faecalis was strongly resistant to high osmotic pressure in complex medium; however, when it was subjected to a moderate osmotic stress [6.5% (w/v) NaCl or 52% (w/v) sucrose] for 2 h, it showed cross-protection against ethanol (22%), detergents stresses [bile sales (0.3%) and SDS (0.017%)], hydrogen peroxide challenge (45 mM), and to a minor extent against lethal temperature (62 degrees C). In response to salt stress [6.5% (w/v) NaCl], E. faecalis induced a large number of stress proteins. In addition, NaCl strongly induced the synthesis of many proteins more than tenfold. Although the acquired thermotolerance was inhibited markedly by chloramphenicol, the other NaCl-induced cross-tolerances seemed not to be correlated with de novo protein synthesis. The relationship between the stress protein synthesis and the induction of different types of cross-protection is discussed.

Adaptation, Physiological↗

Starvation-induced multiresistance in Enterococcus faecalis JH2-2.

Compared with growing bacteria, carbohydrate-starved cells of Enterococcus faecalis show development of a multiresistance state against heat, H2O2, acid, and ethanol, but not against UV irradiation. The kinetics of acquisition of resistance is different according to the stress. Three hours of starvation provide maximal resistance against ethanol, while the tolerance to heat, H2O2, and acid increases progressively with the duration of starvation. Chloramphenicol treatment does not abolish the ethanol tolerance. Protein synthesis inhibition during the transitional growth phase and the first hours of starvation partially inhibit the acquisition of heat and oxidative resistances. Antibiotic treatment after 3 h of starvation does not affect the increase of these resistances. We suggest that synthesis of specific proteins revealed by 2-D gel analysis in the first 3 h of starvation, followed by a second mechanism related to protein degradation or alteration, is necessary for acquisition of maximal resistance towards heat and oxidative stresses.

Bacterial Proteins↗

The Lactic Acid Stress Response of Lactococcus lactis subsp. lactis

The lactic acid tolerance response (LATR) of the lactic acid bacterium Lactococcus lactis subsp. lactis has been studied. A dramatic increase in survival to a severe acid stress (pH 3.9) was obtained by preexposing the cells for 30 min to a mildly acid shock at pH 5.5. Whole-cell protein extract analysis revealed that during the acid tolerance response 33 polypeptides are induced over the level of naive cells. Among these are the major heat shock proteins DnaK and GroEL. In conjunction with a previous report (Hartke et al. 1994), the results establish that L. lactis can adapt to lactic acid exposure in two different ways: a logarithmic phase LATR, which may be activated by protons, and a stationary-phase LATR, which needs no activation by protons. Both systems are independent of de novo protein synthesis.

Journal Article↗

Physiological response of Enterococcus faecalis JH2-2 to cold shock: growth at low temperatures and freezing/thawing challenge.

Growth at low positive temperatures and induced phenotypic resistance to extreme cold temperature (freezing/thawing cycles) of Enterococcus faecalis were investigated. The effect of low temperatures on the specific growth rates was studied; use of Arrhenius profile and Ratkovsky 'square-root' model allowed determination of the 'temperature characteristic' (mu approximately equal to 13,800 cal mol-1), the critical temperature (Tcrit approximately equal to 17.9 degrees C) and the notional minimum growth temperature (T0 approximately equal to 3.6 degrees C). Preincubation of Ent. faecalis cells at low temperatures (8-16 degrees C) during periods corresponding to their generation time resulted in an increased ability of the bacterial cells to withstand short periods of freezing/thawing (-20 degrees C/+37 degrees C) challenge. Moreover, the increase of the incubation period at low positive temperature led to a higher degree of adaptation.

Cold Temperature↗

Comparison of the bile salts and sodium dodecyl sulfate stress responses in Enterococcus faecalis.

The resistance to detergents and detergent-induced tolerance of a gastrointestinal organism, Enterococcus faecalis ATCC 19433, were examined. The most remarkable observation was the rapid response of cells in contact with bile salts and sodium dodecyl sulfate (SDS). The killing by high concentrations of detergents was nearly instantaneous. A 5-s adaptation with moderate sublethal concentrations of bile salts or SDS (0.08 or 0.01%, respectively) was sufficient to induce significant adaptation against homologous lethal conditions (0.3% bile salts or 0.017% SDS). However, resistance to a subsequent lethal challenge progressively increased further to a maximum reached after 30 min of adaptation. Furthermore, extremely strong cross-resistances were observed with bile salts- and SDS-adapted cells. However, no relationship seems to exist between levels of tolerance and de novo-synthesized proteins, since blockage of protein synthesis during adaptation had no effect on induction of resistance to bile salts and SDS. We conclude that this induced tolerance to detergent stress is independent of protein synthesis. Nevertheless, the stress-induced protein patterns of E. faecalis ATCC 19433 showed significant modifications. The rates of synthesis of 45 and 34 proteins were enhanced after treatments with bile salts and SDS, respectively. In spite of the overlap of 12 polypeptides, the protein profiles induced by the two detergents were different, suggesting that these detergents trigger different responses in E. faecalis. Therefore, bile salts cannot be substituted for SDS in biochemical detergent shock experiments with bacteria.

Adaptation, Physiological↗

Induction of thermotolerance by chemical agents in Lactococcus lactis subsp. lactis IL1403.

Like in other organisms tested to date, adapted cells of Lactococcus lactis subsp. lactis IL1403 pretreated at 42 degrees C for 30 min develop a thermotolerant state, i.e. an increased ability to survive subsequent exposure to a lethal challenge temperature (52 degrees C for 15 or 30 min). In different cellular systems, chemicals as diverse as divalent metal salts, natural or synthetic compounds trigger the development of thermotolerance. Yet, in L. lactis subsp. lactis IL1403, among the 17 chemicals tested, only four induced this transient increased tolerance to heat: cadmium chloride, mercury chloride, sodium azide and beta-mercaptoethanol. Intriguingly, none of these four compounds induced the synthesis of three major heat shock proteins (DnaK, GroEL and hsp104-analogue), which are believed to be responsible for thermotolerance in most organisms. It is suggested that: (i) the lesions produced by these various 'proteotoxic' agents are fundamentally different from those produced by heat; (ii) heat shock protein synthesis and transient induced tolerance to heat are not tightly correlated phenomena in L. lactis subsp. lactis as they are in Escherichia coli and some other organisms.

Adaptation, Physiological↗

Characterization and replication mode determination of the minimal replicon of Tetragenococcus halophila ATCC33315 plasmid pUCL287.

pUCL287 is a cryptic plasmid of Tetragenococcus halophila (formerly Pediococcus halophilus) ATCC33315 of relatively small size (8.7 kb). Its minimal replicon was located on a 1235 bp MamI-EcoRI fragment. This minimal replicon contains a non-translated region, followed by a gene encoding a putative 311 amino acid protein. Deletion experiments showed that the non-translated region corresponds to the replication origin. Determination of the replication mode was carried out in Enterococcus faecalis JH2-2 harboring pUCL287 minimal replicon. The replicating intermediates detected revealed that pUCL287 minimal replicon follows a bidirectional theta replicating mode.

Amino Acid Sequence↗

Nucleotide sequence of the Lactococcus lactis NCDO 763 (ML3) rpoD gene.

The complete nucleotide sequence of rpoD gene from Lactococcus lactis has been determined. The nucleotide data have indicated the presence of an open reading frame of 1020 base pairs encoding a polypeptide which shares the framework structure for principal sigma factors of eubacteria strains.

Amino Acid Sequence↗

Characterization of the heat shock response in Enterococcus faecalis.

We have characterized the general properties of the heat shock response of the Gram-positive hardy bacterium Enterococcus faecalis. The heat resistance (60 degrees C or 62.5 degrees C, 30 min) of log phase cells of E. faecalis grown at 37 degrees C was enhanced by exposing cells to a prior heat shock at 45 degrees C or 50 degrees C for 30 min. These conditioning temperatures also induced ethanol (22%, v/v) tolerance. The onset of thermotolerance was accompanied by the synthesis of a number of heat shock proteins. The most prominent bands had molecular weights in the range of 48 to 94kDa. By Western blot analysis two of them were found to be immunologically related to the well known DnaK (72kDa) and GroEL (63kDa) heat shock proteins of Escherichia coli. Four other proteins showing little or no variations after exposure to heat are related to DnaJ, GrpE and Lon (La) E. coli proteins and to the Bacillus subtilis sigma 43 factor. Ethanol (2% or 4%, v/v) treatments elicited a similar response although there was a weaker induction of heat shock proteins than with heat shock.

Antigens, Bacterial↗

Partial characterization of an rpoD-like gene of Lactococcus lactis subsp. lactis ML3 with a polymerase chain reaction-based approach.

With degenerated oligonucleotide primers for conserved regions of bacterial sigma factor proteins, a 117-bp internal DNA fragment of an rpoD-like gene of Lactococcus lactis subsp. lactis ML3 was amplified by the polymerase chain reaction (PCR). The DNA sequence of this PCR product was determined by cycle sequencing, and the deduced amino acid sequence of this internal fragment showed an extensive homology with the known sigma factor sequences from six other microorganisms and present a 13-amino acid region corresponding to the typical "RpoD box" of primary sigma factors. This PCR product was used as a probe to specifically detect sigma homologs in Pediococcus acidilactici, Leuconostoc lactis, Lactobacillus helveticus, Lactobacillus acidophilus, Enterococcus faecalis, Streptococcus thermophilus, and Lactococcus lactis subsp. cremoris. These data are consistent with the existence of a high similarity between the primary sigma factors from diverse Gram-positive microorganisms.

Amino Acid Sequence↗

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

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.

Adaptation, Physiological↗

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

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.

Ethanol↗

Response of Lactococcus (Streptococcus) lactis to N-methyl-N'-nitro-N-nitrosoguanidine: absence of adaptive response.

Pretreatment of cells of Lactococcus lactis subsp. lactis with low levels of N-methyl-N'-nitro-N-nitrosoguanidine does not reduce the cytotoxic and mutagenic effects caused by high concentration of this agent. This observation indicates that there is no efficient inducible error-free repair system for alkylation damage similar to the 'adaptive response' described in detail for Escherichia coli.

Alkylating Agents↗

Mutagenesis in Streptococcus lactis exposed to UV irradiation and alkylating agents.

The lethal and mutagenic effects of various mutagens on three strains of Streptococcus lactis were investigated. Lethality studies demonstrated that S. lactis was relatively sensitive to UV irradiation, methyl methanesulphonate (MMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and, to a lesser extent, to ethyl methanesulphonate (EMS). A spontaneous derivative Lac-, which has lost a 37-Md plasmid, was slightly more resistant and much less mutable than the wild-type after UV irradiation. Although the three strains were strongly mutated by EMS for the genetic marker assayed (Rifr), an increase in the mutation frequency was also observed after MMS and MNNG treatments.

Alkylating Agents↗