Biomedical subjects

P Boutibonnes

Publications and source records attributed to P Boutibonnes.

At least 19 recordsLinked to original sources

PubMed1998

Cold stress responses in mesophilic bacteria.

The diversity of the prokaryotes that have been studied, combined with the many different effects of low temperature, has led to an extensive literature concerning cold stress responses in mesophilic bacteria. The aim of this review is to discuss the effects of cold on the behavior of bacteria. The following three responses will be described: (i) biochemical modifications consisting first of membrane fatty acid desaturation and second of the synthesis of cold stress proteins, (ii) physiological responses of the cells to permit growth at low temperatures above 0 degrees C and cryotolerance at lower temperatures, and (iii) control of the cold shock response at a transcriptional and/or translational level. This paper reviews knowledge, most of which has been acquired in the last 10 years, in the field of cold stress responses. It is hoped that these data will help to focus attention on the metabolic responses associated with environmental disturbance.

Bacterial Physiological Phenomena↗

PubMed1997

Relationship between the thermotolerance and the increase of DnaK and GroEL synthesis in Enterococcus faecalis ATCC19433.

Relationship between intrinsic thermal resistance, thermotolerance and heat shock proteins (hsp) synthesis is studied in Enterococcus faecalis. We showed that an impressive phenotypic heat resistance was induced by mild heat and a slight thermotolerance was developed by various sublethal pretreatments such as NaCl, SDS and bile salts. Hydrogen peroxide, acid and alkaline shifts or "thermomimetic" agent such as ethanol, did not enhance the survival of adapted cells against the lethal thermal shock (62 degrees C). The inhibition of protein synthesis by chloramphenicol or rifampin abolished thermotolerance. The immunological identification of the DnaK and GroEL proteins in E. faecalis allowed to study induction of these molecular chaperones under various conditions. Heat was the most efficient inductor of DnaK and GroEL synthesis. However, it was surprising that ethanol did not strongly induce these proteins. We also show that amplification of these hsp is not correlated to acquired thermotolerance with a linear relationship. A weak thermotolerance is not coupled from increased synthesis of DnaK and GroEL. So, we postulate that the high synthesis of the major hsp is not obligatory in the thermal cross-protection but that de novo protein synthesis is an absolute necessity in E. faecalis. Activation of preformed hsp or other factors depending or not on protein synthesis may be also necessary to enhance thermal resistance.

Chaperonin 60↗

PubMed1997

Differential induction of the chaperonin GroEL and the Co-chaperonin GroES by heat, acid, and UV-irradiation in Lactococcus lactis subsp. lactis.

Microsequencing of a polypeptide with MW of 14.5 and pI of 5.0 induced by heat treatment at 42 degrees C and 50 degrees C in Lactococcus lactis subsp. lactis revealed that it corresponds to the co-chaperonin GroES. Quantitative analysis of analytical 2-D gels showed a relative induction of 12- and 11-fold after 30 min of heat adaptation at 42 degrees C and 50 degrees C, respectively. GroES is also induced by an acid shift from pH 7 to pH 5.5 and by UV254 nm-irradiation, with relative induction factors of 3.8 and 2.3, respectively. To our knowledge this is the first report showing induction of GroES by mild acid treatment. Contrasting to the relative induction of the groEL gene product, the second protein encoded by the groESL operon, GroES shows significantly higher induction under all stress situations.

Amino Acid Sequence↗

PubMed1997

Sodium hypochlorite stress in Enterococcus faecalis: influence of antecedent growth conditions and induced proteins.

Compared with exponential growing bacteria, carbohydrate-starved cells of Enterococcus faecalis exhibit a high level of resistance to sodium hypochlorite with maximal resistance observed in cultures entering stationary phase. Chloramphenicol treatment, at various stages of growing phase, does not abolish the hypochlorite resistance of starved cells. However, Enterococcus faecalis conditioned by low sodium hypochlorite concentrations does not develop tolerance towards a lethal dose of the disinfectant. Two-dimensional gel analysis shows that protein synthesis is drastically turned off by hypochlorite treatment, whereas synthesis of a few proteins is enhanced by a low concentration of this chemical agent.

Bacterial Proteins↗

PubMed1997

Glucose starvation response in Enterococcus faecalis JH2-2: survival and protein analysis.

We investigated the survival of Enterococcus faecalis following starvation provoked by energy source glucose exhaustion. Inhibition of protein synthesis by chloramphenicol before 3 h of starvation resulted in a dramatic decrease in viable bacteria. Antibiotic treatment of cells after 3 or 6 h of starvation had a progressively lesser influence on bacterial survival. During the first 24 h of deprivation, a total of 42 proteins were identified as glucose-starvation-inducible; 4 temporal classes of proteins (A, B, C and D) were defined in relation to their enhanced synthesis after glucose exhaustion. Our results show that proteins from the two early classes (A and B) seem to be the most important for long-term survival in E. faecalis. One protein of each of these classes was analysed at the molecular level. The N-terminal sequence of one of them, belonging to class A, showed strong homology with the N-terminal sequence of carbamate kinase from Streptococcus faecium. This enzyme could be implicated in the development of alternative metabolic pathways of energy production and could be compared to the Cst proteins of Escherichia coli.

Bacterial Proteins↗

PubMed1997

Differentiation between cold shock proteins and cold acclimation proteins in a mesophilic gram-positive bacterium, Enterococcus faecalis JH2-2.

Transfer of Enterococcus faecalis to a cold temperature (8 degrees C for 4 to 30 h) led to increased expression of 11 cold shock proteins (CSPs). Furthermore, this mesophilic prokaryote synthesized 10 cold acclimation proteins, five of them distinct from CSPs, during continuous growth (4 days) at the same temperature (8 degrees C).

Bacterial Proteins↗

PubMed1997

[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↗

PubMed1996

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↗

PubMed1996

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↗

PubMed1996

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↗

PubMed1996

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↗

PubMed1996

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↗

PubMed1996

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↗

PubMed1996

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↗

PubMed1995

Segregational stability and copy number of the theta-type lactococcal replicon Rep22 in Lactococcus.

Rep22 is the replication region of the lactococcal theta replicating pUCL22 plasmid. The copy number of Rep22-based plasmids in Lactococcus was determined by using a chromosomal DNA fragment from Lactococcus lactis subsp. lactis MMS368 as reference. Segregational behavior appeared to be linked to copy number and therefore indicated random distribution of copies to daughter cells. Nevertheless, an active partitioning system was detected in the parental plasmid pUCL22. A pUCL22 138-bp DNA restriction fragment bearing a perfect 18-bp inverted repeat was involved in the improvement of Rep22-based plasmid segregational stability during discontinuous exponential growth.

Base Sequence↗

PubMed1995

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↗

PubMed1995

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↗

PubMed1993

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↗