Role of the (p)ppGpp synthase RSH, a RelA/SpoT homolog, in stringent response and virulence of Staphylococcus aureus.
In most bacteria, nutrient limitations provoke the stringent control through the rapid synthesis of the alarmones pppGpp and ppGpp. Little is known about the stringent control in the human pathogen Staphylococcus aureus, partly due to the essentiality of the major (p)ppGpp synthase/hydrolase enzyme RSH (RelA/SpoT homolog). Here, we show that mutants defective only in the synthase domain of RSH (rsh(syn)) are not impaired in growth under nutrient-rich conditions. However, these mutants were more sensitive toward mupirocin and were impaired in survival when essential amino acids were depleted from the medium. RSH is the major enzyme responsible for (p)ppGpp synthesis in response to amino acid deprivation (lack of Leu/Val) or mupirocin treatment. Transcriptional analysis showed that the RSH-dependent stringent control in S. aureus is characterized by repression of genes whose products are predicted to be involved in the translation machinery and by upregulation of genes coding for enzymes involved in amino acid metabolism and transport which are controlled by the repressor CodY. Amino acid starvation also provoked stabilization of the RNAs coding for major virulence regulators, such as SaeRS and SarA, independently of RSH. In an animal model, the rsh(syn) mutant was shown to be less virulent than the wild type. Virulence could be restored by the introduction of a codY mutation into the rsh(syn) mutant. These results indicate that stringent conditions are present during infection and that RSH-dependent derepression of CodY-regulated genes is essential for virulence in S. aureus.
Geiger
Tobias
T
Interfaculty Institute of Microbiology and Infection Medicine, Universität Tübingen, Elfriede-Aulhorn-Strasse 6, 72076 Tübingen, Germany.
Goerke
Christiane
C
Fritz
Michaela
M
Schäfer
Tina
T
Ohlsen
Knut
K
Liebeke
Manuel
M
Lalk
Michael
M
Wolz
Christiane
C
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D053898:Biosynthetic Pathways / Q000235:genetics; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry; D005260:Female; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006158:Guanosine Pentaphosphate / Q000378:metabolism; D008025:Ligases / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D016712:Mupirocin / Q000494:pharmacology; D009154:Mutation; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity / Q000502:physiology*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
D000900:Anti-Bacterial Agents; D003470:Culture Media; D037521:Virulence Factors; D006158:Guanosine Pentaphosphate; D016712:Mupirocin; C100969:guanosine pentaphosphate synthetase; D008025:Ligases