Search

Unlabelled: The PhoPR two-component signal transduction system controls one of three responses activated by Bacillus subtilis to adapt to phosphate-limiting conditions (PHO response). The response involves the production of enzymes and transporters that scavenge for phosphate in the environment and assimilate it into the cell. However, in B. subtilis and some other Firmicutes bacteria, cell wall metabolism is also part of the PHO response due to the high phosphate content of the teichoic acids attached either to peptidoglycan (wall teichoic acid) or to the cytoplasmic membrane (lipoteichoic acid). Prompted by our observation that the phosphorylated WalR (WalR∼P) response regulator binds to more chromosomal loci than are revealed by transcriptome analysis, we established the PhoP∼P bindome in phosphate-limited cells. Here, we show that PhoP∼P binds to the chromosome at 25 loci: 12 are within the promoters of previously identified PhoPR regulon genes, while 13 are newly identified. We extend the role of PhoPR in cell wall metabolism showing that PhoP∼P binds to the promoters of four cell wall-associated operons (ggaAB, yqgS, wapA, and dacA), although none show PhoPR-dependent expression under the conditions of this study. We also show that positive autoregulation of phoPR expression and full induction of the PHO response upon phosphate limitation require PhoP∼P binding to the 3' end of the phoPR operon., Importance: The PhoPR two-component system controls one of three responses mounted by B. subtilis to adapt to phosphate limitation (PHO response). Here, establishment of the phosphorylated PhoP (PhoP∼P) bindome enhances our understanding of the PHO response in two important ways. First, PhoPR plays a more extensive role in adaptation to phosphate-limiting conditions than was deduced from transcriptome analyses. Among 13 newly identified binding sites, 4 are cell wall associated (ggaAB, yqgS, wapA, and dacA), revealing that PhoPR has an extended involvement in cell wall metabolism. Second, amplification of the PHO response must occur by a novel mechanism since positive autoregulation of phoPR expression requires PhoP∼P binding to the 3' end of the operon., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

The Bacillus subtilis cell wall is a dynamic structure, composed of peptidoglycan and teichoic acid, that is continually remodeled during growth. Remodeling is effected by the combined activities of penicillin binding proteins and autolysins that participate in the synthesis and turnover of peptidoglycan, respectively. It has been established that one or the other of the CwlO and LytE D,L-endopeptidase-type autolysins is essential for cell viability, a requirement that is fulfilled by coordinate control of their expression by WalRK and SigI RsgI. Here we report on the regulation of cwlO expression. The cwlO transcript is very unstable, with its degradation initiated by RNase Y cleavage within the 187-nucleotide leader sequence. An antisense cwlO transcript of heterogeneous length is expressed from a SigB promoter that has the potential to control cellular levels of cwlO RNA and protein under stress conditions. We discuss how a multiplicity of regulatory mechanisms makes CwlO expression and activity responsive to the prevailing growth conditions.

The CssRS two-component system responds to heat and secretion stresses in Bacillus subtilis by controlling expression of HtrA and HtrB chaperone-type proteases and positively autoregulating its own expression. Here we report on the features of the CssS extracellular loop domain that are involved in signal perception and on CssS subcellular localization. Individual regions of the CssS extracellular loop domain contribute differently to signal perception and activation. The conserved hydrophilic 26-amino-acid segment juxtaposed to transmembrane helix 1 is involved in the switch between the deactivated and activated states, while the conserved 19-amino-acid hydrophobic segment juxtaposed to transmembrane 2 is required for signal perception and/or transduction. Perturbing the size of the extracellular loop domain increases CssS kinase activity and makes it unresponsive to secretion stress. CssS is localized primarily at the septum but is also found in a punctate pattern with lower intensity throughout the cell cylinder. Moreover, the CssRS-controlled HtrA and HtrB proteases are randomly distributed in foci throughout the cell surface, with more HtrB than HtrA foci in unstressed cells.