MclX modulates the process of mother cell lysis by SpoIIID in Bacillus thuringiensis.

UNLABELLED: Cell differentiation is essential for the survival and adaptation of organisms. In Bacillus species, sporulation is a tightly coordinated program that culminates in mother cell lysis, a critical step for spore release. Despite its importance, the mechanisms modulating the process remain poorly understood. Here, we show that MclX regulates mother cell lysis by inhibiting SpoIIID, a sporulation-specific transcription factor that represses cwlC, which encodes a key hydrolase required for lysis. SpoIIID directly binds to the cwlC promoter, and its overexpression during sporulation markedly delays both the onset and progression of mother cell lysis. These findings support a model in which MclX modulates SpoIIID to control cwlC expression and lysis process. Collectively, this work defines a previously unrecognized MclX-SpoIIID-cwlC regulatory axis, providing new insight into the control of late sporulation events and the process of mother cell lysis. IMPORTANCE: Mother cell lysis is a critical step in Bacillus sporulation, yet its regulation remains poorly understood. Here, we identify mclX as an upstream factor that modulates the onset and progression of mother cell lysis in Bacillus thuringiensis. MclX reduces SpoIIID levels, which in turn directly represses cwlC expression. These findings provide new insight into the regulatory network governing lysis process and advance our understanding of bacterial cell differentiation.