The (p)ppGpp synthetase RelA contributes to stress adaptation and virulence in Enterococcus faecalis V583

• Published in: Microbiology (Society for General Microbiology) 2009-10, Vol.155 (10), p.3226-3237
• Main Authors: Yan, Xue, Zhao, Chen, Budin-Verneuil, Aurelie, Hartke, Axel, Rince, Alain, Gilmore, Michael S, Auffray, Yanick, Pichereau, Vianney
• Format: Article
• Language: English
• Subjects: Acids; Acids - pharmacology; Adaptation, Physiological; Animals; Anti-Bacterial Agents; Anti-Bacterial Agents - pharmacology; Bacteriology; Bile Acids and Salts; Bile Acids and Salts - pharmacology; Biochemistry, Molecular Biology; Biological and medical sciences; Enterococcus faecalis; Enterococcus faecalis - pathogenicity; Enterococcus faecalis - physiology; Ethanol; Ethanol - pharmacology; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gram-Positive Bacterial Infections; Gram-Positive Bacterial Infections - microbiology; Humans; Hydrogen Peroxide; Hydrogen Peroxide - pharmacology; Lepidoptera; Lepidoptera - microbiology; Life Sciences; Ligases; Ligases - genetics; Ligases - physiology; Metabolism. Enzymes; Microbial Sensitivity Tests; Microbiology; Microbiology and Parasitology; Miscellaneous; Molecular Networks; Sequence Deletion; Stress, Physiological; Virulence
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.026146-0

1 Laboratoire Microbiologie de l'Environnement, EA956 – USC INRA 2017 – IFR146 ICORE, Université de Caen, 14032 Caen Cedex, France 2 Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA Guanosine penta- and tetraphosphate [(p)ppGpp] are two unusual nucleotides implied in the bacterial stringent response. In many pathogenic bacteria, mutants unable to synthesize these molecules lose their virulence. In Gram-positive bacteria such as Enterococcus faecalis , the synthesis and degradation of (p)ppGpp mainly depend on the activity of a bifunctional enzyme, encoded by the relA gene. By analysing relA and relQ (which encodes a protein harbouring a ppGpp synthetase activity) deletion mutants, we showed that RelA is by far the main system leading to (p)ppGpp production under our experimental conditions, and during the development of a stringent response induced by mupirocin. We also constructed a mutant ( relAsp ) in which a small part of the relA gene (about 0.7 kbp) encoding the carboxy-terminal domain of the RelA protein was deleted. Both relA mutants were more resistant than the wild-type strain to 0.3 % bile salts, 25 % ethanol and acid (pH 2.3) challenges. Interestingly, the relAsp mutant grew better than the two other strains in the presence of 1 mM H 2 O 2 , but did not display increased tolerance when subjected to lethal doses of H 2 O 2 (45 mM). By contrast, the relA mutant was highly sensitive to 45 mM H 2 O 2 and displayed reduced growth in a medium containing 1 M NaCl. The two mutants also displayed contrasting virulence phenotypes towards larvae of the Greater Wax Moth infection model Galleria mellonella . Indeed, although the relA mutant did not display any phenotype, the relAsp mutant was more virulent than the wild-type strain. This virulent phenotype should stem from its increased ability to proliferate under oxidative environments. Correspondence Vianney Pichereau vianney.pichereau{at}univ-brest.fr Abbreviations: RT qPCR, real-time quantitative PCR Present address: Laboratoire des Sciences de l'Environnement Marin, UMR CNRS 6539, Institut Universitaire Européen de la Mer, Technopole Brest Iroise, 29280 Plouzané, France.