Cannibalism stress response in Bacillus subtilis

When faced with carbon source limitation, the Gram-positive soil organism Bacillus subtilis initiates a survival strategy called sporulation, which leads to the formation ofhighly resistant endospores that allow B. subtilis to survive even long periods ofstarvation. In order to avoid commitment to this energy-demanding and irreversibleprocess, B. subtilis employs another strategy called cannibalism to delay sporulationas long as possible. Cannibalism involves the production and secretion of twocannibalism toxins, the sporulation delaying protein, SDP, and the sporulation killingfactor, SKF, which are able to lyse sensitive siblings. The lysed cells are thought tothen provide nutrients for the cannibals to slow down or even prevent them fromentering sporulation. In this study, we uncovered the role of the cell envelope stressresponse (CESR), especially the Bce-like antimicrobial peptide detoxification modules,in cannibalism stress response during stationary phase. SDP and SKF specificallyinduce Bce-like systems and some ECF σ factors in stationary phase cultures, but onlythe latter provide some degree of protection. A full Bce response is only triggered bymature toxins, but not by toxin precursors. Our study provides insights into the closerelationship between stationary phase survival and the CESR of B. subtilis.