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Physiological and molecular aspects of bile salt response in Enterococcus faecalis
Alain Rincé1, Yoann Le Breton, Nicolas Verneuil
1Laboratoire de Microbiologie de l'Environnement, EA 956 USC INRA, Institut de Recherche en Biologie Appliquée, Université de Caen, 14032 Caen Cedex, France. rince@ibba.unicaen.fr
International Journal of Food Microbiology
|November 5, 2003
Summary
Enterococcus faecalis rapidly develops tolerance to bile salts, involving general stress proteins and impacting DNA repair and cell division. This study reveals mechanisms of bacterial stress response and cross-protection.
Area of Science:
- Microbiology
- Bacterial Physiology
- Stress Response
Background:
- Enterococcus faecalis exhibits susceptibility to bile salts, necessitating investigation into tolerance mechanisms.
- Bile salt tolerance can involve homologous and cross-protective responses.
- Understanding bacterial stress responses is crucial for antimicrobial strategies.
Purpose of the Study:
- To analyze the susceptibility and tolerance acquisition of Enterococcus faecalis to bile salts.
- To identify proteins involved in bile salt tolerance and general stress response.
- To elucidate the genetic basis of bile salt sensitivity through mutagenesis.
Main Methods:
- Two-dimensional (2-D) electrophoresis to identify protein expression changes.
- Random mutagenesis to generate bile salt-sensitive mutants.
- Characterization of mutant genes and their functions.
Main Results:
- Bile salt exposure caused rapid killing and induced tolerance, with evidence of homologous and cross-protections.
- 45 proteins were amplified in response to bile salts, including seven general stress proteins.
- Ten bile salt-sensitive mutants were isolated, with mutations in genes related to DNA repair, oxidative response, and cell division.
- A sagA gene mutation resulted in morphological changes, cell division defects, and reduced stress resistance.
Conclusions:
- Enterococcus faecalis develops bile salt tolerance through specific protein induction and general stress responses.
- Genes involved in DNA repair, oxidative response, and cell wall synthesis are critical for bile salt resistance.
- The sagA gene plays a role in cell morphology, division, and overall stress resistance in E. faecalis.