A LysR-like Transcriptional Regulator DsfB Is Required for the Daughter Cell Separation in <i>Bacillus cereus</i> 0–9

<i>Bacillus cereus</i> 0-9 is a biocontrol strain isolated from a healthy wheat root, and studying cell separation after division in this strain will improve our understanding of its growth, environmental adaptation, and spread. In this work, we identified the deletion of <i>dsfB</i> resulted in a chaining phenotype. Four genes, <i>lysM1</i>, <i>lysM2</i>, <i>lysM3</i>, and <i>lysM4</i>, were associated with daughter cell separation in strain 0-9. Furthermore, DsfB bound to the promoter regions of <i>lysM1</i> and <i>lysM2</i> and induced their transcription. The peptidoglycan hydrolase activity of the <i>lysM1</i> and <i>lysM2</i> gene products was confirmed in vitro by site-directed mutagenesis and biochemical analyses. The addition of purified LysM1 or LysM2 proteins in vitro or the overexpression of their coding genes inhibited the chaining phenotype of Δ<i>dsfB</i>. Taken together, our data indicate that DsfB is involved in daughter cell separation via the positive regulation of <i>lysM1</i> and <i>lysM2</i> expression in <i>B. cereus</i> 0-9.