Bacillus thuringiensis peptidoglycan hydrolase SleB171 involved in daughter cell separation during cell division

Whole-genome analyses have revealed a putative cell wall hydrolase gene （sleB171） that constitutes an operon with two other genes （ypeB and yhcN） of unknown function in Bacillus thuringiensis BMB171. The putative SleB171 protein consists of 259 amino acids and has a molecular weight of 28.3 kDa. Gene disruption of sleB171 in the BMB171 genome causes the formation of long cell chains during the vegetative growth phase and delays spore formation and spore release, although it has no significant effect on cell growth and the ultimate release of the spores. The inseparable vegetative cells were nearly restored through the complementation of sleB171 expression. Real-time quantita- tive polymerase chain reaction analysis revealed that sleB171 is mainly active in the vegetative growth phase, with a maximum activity at the early stationary growth phase. Western blot analysis also confirmed that sleB171 is preferentially expressed during the vegetative growth phase. These results demonstrated that SleB171 plays an essential role in the daughter cell separation during cell division.