title: Characterization of CidR-mediated regulation in Bacillus anthracis reveals a previously undetected role of S-layer proteins as murein hydrolases.
abstract: Recent studies have shown that the Staphylococcus aureus cidABC and lrgAB operons are involved in the regulation of cell death and lysis. The transcription of cidABC and lrgAB was shown to be induced by acetic acid and was dependent on the cidR gene encoding a new member of the LysR-type transcription regulator (LTTR) family of proteins. In the study presented here, we examined the phenotypic and regulatory effects of disrupting a cidR homologue in Bacillus anthracis. As in S. aureus, the cidR mutation affected expression of the B. anthracis cid and lrg homologues, murein hydrolase activity and cell viability in stationary phase. Interestingly, the predominant murein hydrolase affected was an 85 kDa protein that was identified as Sap, a primary constituent of the S-layer in B. anthracis. The ability of Sap, as well as its counterpart EA1, to exhibit murein hydrolase activity was confirmed by cloning their respective genes in Escherichia coli and showing that the overexpressed proteins contained this activity. Northern blot analyses revealed that the cidR mutation caused reduced transcription of the genes encoding Sap and EA1, as well as CsaB involved in the attachment of the S-layer proteins to the cell wall. The results of these studies not only establish the existence of the cid and lrg murein hydrolase regulatory network in B. anthracis, but also help to define the function and regulation of the S-layer proteins.
authors.affiliation: Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE 68198-6495, USA.
authors.forename: Jong-Sam
authors.initials: JS
authors.lastname: Ahn
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Chandramohan
authors.forename: Linda E
authors.initials: LE
authors.lastname: Liou
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Bayles
mesh_terms: D001408:Bacillus anthracis / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002262:Carboxy-Lyases / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008562:Membrane Glycoproteins / Q000502:physiology*; D009154:Mutation; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000502:physiology*; D009876:Operon; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; C055764:S-layer proteins; D009238:N-Acetylmuramoyl-L-alanine Amidase; D002262:Carboxy-Lyases; C023746:acetolactate decarboxylase