ABSTRACTThe PhoPR two-component signal transduction system controls one of three responses activated byBacillus subtilisto 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, inB. subtilisand some otherFirmicutesbacteria, 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, anddacA), although none show PhoPR-dependent expression under the conditions of this study. We also show that positive autoregulation ofphoPRexpression and full induction of the PHO response upon phosphate limitation require PhoP∼P binding to the 3′ end of thephoPRoperon.IMPORTANCEThe PhoPR two-component system controls one of three responses mounted byB. subtilisto 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, anddacA), 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 ofphoPRexpression requires PhoP∼P binding to the 3′ end of the operon.
Cell wall metabolism in Bacillus subtilis subsp. niger: accumulation of wall polymers in the supernatant of chemostat cultures.
