title: Transcription of the Staphylococcus aureus cid and lrg murein hydrolase regulators is affected by sigma factor B.
abstract: The Staphylococcus aureus lrg and cid loci are homologous operons that have been shown to regulate murein hydrolase activity and affect sensitivity to penicillin. Although the mode of action of these operons has not been demonstrated, a model based on the similarities of the lrgA and cidA gene products to the bacteriophage holin family of proteins has been proposed. In this study, the transcription organization and regulation of these operons were examined by Northern blot analyses. Unexpectedly, cidB and a gene located immediately downstream, designated cidC, were found to be cotranscribed on a 2.7-kb transcript. Maximal cidBC transcription occurred during early exponential growth, and high-level transcription of cidBC was dependent on the rsbU-mediated activation of the alternative sigma factor B (sigmaB). In contrast, lrgAB transcription in stationary phase was negatively regulated by sigmaB. Although cidABC transcription was not detected by Northern blot analysis, reverse transcriptase PCR revealed that these genes are also cotranscribed as a single RNA message in early exponential growth. Primer extension analysis revealed the presence of two cidBC transcription start sites, but no apparent sigmaB-dependent promoter consensus sequence was identified in these regions. The rsbU gene was also shown to have a positive impact on murein hydrolase activity but a negligible effect on sensitivity to penicillin-induced killing. These results suggest that the lrgAB and cidBC genes may be part of the S. aureus sigmaB-controlled stress regulon.
authors.affiliation: Department of Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow, Idaho 83844-3052, USA.
authors.forename: Kelly C
authors.initials: KC
authors.lastname: Rice
authors.forename: Toni
authors.initials: T
authors.lastname: Patton
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Yang
authors.forename: Alexis
authors.initials: A
authors.lastname: Dumoulin
authors.forename: Markus
authors.initials: M
authors.lastname: Bischoff
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Bayles
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000378:metabolism*; D009876:Operon; D010406:Penicillins / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000502:physiology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; C406202:LrgA protein, Staphylococcus aureus; D008565:Membrane Proteins; D010406:Penicillins; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D009238:N-Acetylmuramoyl-L-alanine Amidase