An overlap between the control of programmed cell death

22 The Staphylococcus aureus cid and lrg operons have been shown to control cell death 23 and lysis in a manner thought to be analogous to programmed cell death (apoptosis) in 24 eukaryotic organisms. Although orthologous operons are present in a wide variety of bacterial 25 species, members of the Bacillus cereus group are unique in that they have a total of four cid-26 /lrg-like operons. Two of these operons are similar to the S. aureus cid and lrg operons while 27 the other two (designated clhAB-1 and clhAB-2) are unique to this group. In the current study, 28 the functions and regulation of these loci were examined. Interestingly, the B. anthracis lrgAB 29 mutant displayed decreased stationary phase survival, whereas the clhAB-2 mutant exhibited 30 increased stationary phase survival compared to the parental and complementation strains. 31 However, neither mutation had a dramatic effect on murein hydrolase activity or autolysis. 32 Furthermore, a quantitative analysis of sporulation efficiency revealed both mutants formed 33 fewer spores compared to the parental strain. Similar to S. aureus, B. anthracis lrgAB 34 transcription was shown to be induced by gramicidin and CCCP, agents known to dissipate the 35 proton motive force, in a lytSR-dependent manner. Northern blot analyses also revealed a 36 positive role of lytSR in the clhAB-2 transcription. Taken together, the results of this study 37 demonstrate that the B. anthracis lrgAB and clhAB-2 play important roles in the control of cell 38 death and lysis and reveal a previously unrecognized role of this system in sporulation. 39 3 INTRODUCTION 40