In a Bacillus subtilis ugtP mutant lacking glucolipids, SigI was activated in the log phase, and the activation of SigI in the mutant was suppressed by expression of native ugtP. By contrast, SigI was inhibited in a yfnI mutant lacking one of the lipoteichoic acid (LTA) synthase genes, and the inhibition was suppressed by expression of yfnI. A series of mutation analyses of the sigI promoter revealed that the two WalR binding sites were involved in the increase of PsigI-lacZ activity in the ugtP mutant and decrease of the lacZ activity in the yfnI mutant. Transcription from the SigI recognition sequence was enhanced in the ugtP mutant, whereas yfnI disruption inhibited the transcription from the SigA recognition sequence in the sigI promoter. We found that not only SigI but also WalKR, the essential two-component system, was activated in the ugtP mutant, and inhibited in the yfnI mutant. The walK mutants with activated WalR exhibited abnormal morphology, but this phenotype was suppressed by addition of MgSO4. We conclude that glucolipids and LTA are key compounds in the maintenance of normal cell surface structure in B. subtilis.