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Keywords:

  • RelA;
  • SpoT;
  • (p)ppGpp;
  • Stringent response;
  • Starvation

Abstract

The bacterial stringent response is a pleiotrophic physiological response that is evoked when bacteria are subjected to nutrient stress and is mediated through the accumulation of hyperphosphorylated guanine nucleotides ((p)ppGpp) which are synthesized by the combined action of the relA and spoT gene products. The relA and spoT genes were cloned from Neisseria gonorrhoeae strain MS11 and various insertional and deletion mutants were constructed. Deletion of the gonococcal relA gene abrogated the production of (p)ppGpp when the organism was starved for the amino acid serine. Also, N. gonorrhoeaeΔrelA null mutants were impaired for growth when propagated on rich medium, a phenotype that could be relieved by deleting the spoT gene. Sequence analysis of the gonococcal SpoT polypeptide indicated a strong similarity to its Escherichia coli counterpart. However, in contrast to studies with E. coli, insertional spoT mutants could be obtained that still accumulated (p)ppGpp when gonococci were starved for nutrients provided that the non-polar insertions were located downstream of the putative phosphohydrolase active site. In time course studies, it is also shown that gonococci rapidly accumulate (p)ppGpp (within 5 min) when encountering nutrient deprivation.