Global transcriptional analysis of the stringent response in Enterococcus faecalis.

ABSTRACT: In Enterococcus faecalis, production of guanosine tetraphosphate/guanosine pentaphosphate [(p)ppGpp], the effector molecule of the stringent response, is controlled by the bifunctional synthetase/hydrolase RelA and the monofunctional synthetase RelQ. Previously, the (p)ppGpp profiles of strains lacking relA, relQ or both genes indicated that RelA is the primary enzyme responsible for (p)ppGpp synthesis under stress conditions, while the contributions of RelQ to the stringent response and cell homeostasis remained elusive. Here, survival within the mouse-derived macrophage cell line J774A.1 and killing of Galleria mellonella supported initial evidence that virulence was attenuated in the (p)ppGpp(0) ?relA?relQ strain but not in the ?relA or ?relQ strains. We performed, for the first time to our knowledge, global transcriptome analysis in a documented (p)ppGpp(0) Gram-positive bacterium and provided the first insights into the role of a Gram-positive monofunctional (p)ppGpp synthetase in transcriptional regulation. Transcription profiling after mupirocin treatment confirmed that RelA is the major enzyme responsible for the (p)ppGpp-mediated transcriptional repression of genes associated with macromolecular biosynthesis, but also revealed that RelQ is required for full and timely stringent response induction. The delayed transcriptional response of ?relQ could not be correlated with reduced or slower production of (p)ppGpp, in part because RelA-dependent (p)ppGpp accumulation occurred very rapidly. Comparisons of the transcriptional responses of ?relA or ?relA?relQ strains with the parent strain under starvation conditions revealed upregulation of operons involved in energy metabolism in the (p)ppGpp(0) strain. Thus, while ?relA and ?relA?relQ cannot use (p)ppGpp to sense and respond to stresses, fitness of ?relA?relQ may be further impaired due to an unbalanced metabolism.

SUBMITTER: Gaca AO 

PROVIDER: S-EPMC4811642 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature