Chemotaxis in Bacillus subtilis requires either of two functionally redundant CheW homologs

We have characterized mutants in a novel gene of Bacillus subtilis, cheV, which encodes a protein homologous to both CheW and CheY. A null mutant in cheV is only slightly defective in capillary and tethered cell assays. However, a double mutant lacking both CheV and CheW has a strong tumble bias, does not respond to addition of attractant, and shows essentially no accumulation in capillary assays. Thus, CheV and CheW appear in part to be functionally redundant. A strain lacking CheW and expressing only the CheW domain of CheV is chemotactic, suggesting that the truncated CheV protein retains in vivo function. We speculate that CheV and CheW function together to couple CheA activation to methyl-accepting chemotaxis protein receptor status and that possible CheA-dependent phosphorylation of CheV contributes to adaptation.