Cell death dependent on holins LrgAB repressed by a novel ArsR family regulator CdsR.

The cell death and survival paradox in various biological processes requires clarification. While spore development causes maternal cell death in Bacillus species, the involvement of other cell death pathways in sporulation remains unknown. Here, we identified a novel ArsR family transcriptional regulator, CdsR, and found that the deletion of its encoding gene cdsR causes cell lysis and inhibits sporulation. To our knowledge, this is the first report of an ArsR family transcriptional regulator governing cell death. We found that CdsR directly repressed lrgAB expression. Furthermore, lrgAB overexpression resulted in cell lysis without sporulation, akin to the cdsR mutant, suggesting that LrgAB, a holin-like protein, induces cell death in Bacillus spp. The lrgAB mutation increases abnormal cell numbers during spore development. In conclusion, we propose that a novel repressor is vital for inhibiting LrgAB-dependent cell lysis.

A Novel Regulator PepR Regulates the Expression of Dipeptidase Gene pepV in Bacillus thuringiensis.

Bacillus thuringiensis produces insecticidal crystal proteins encoded by cry or cyt genes and targets a variety of insect pests. We previously found that a strong promoter of a DeoR family transcriptional regulator (HD73_5014) can efficiently drive cry1Ac expression in B. thuringiensis HD73. Here, we investigated the regulation of neighbor genes by HD73_5014. The HD73_5014 homologs are widely distributed in Gram-positive bacterial species. Its neighbor genes include pepV, rsuA, and ytgP, which encode dipeptidase, rRNA pseudouridine synthase and polysaccharide biosynthesis protein, respectively. The four open reading frames (ORFs) are organized to be a pepR gene cluster in HD73. RT-PCR analysis revealed that the rsuA and ytgP genes formed a transcriptional unit (rsuA-ytgP operon), while pepV formed a transcriptional unit in HD73. Promoter-lacZ fusion assays showed that the pepV and rsuA-ytgP promoters are regulated by HD73_5014. EMSA experiments showed that HD73_5014 directly binds to the pepV promoter region but not to the rusA-ytgP promoter region. Thus, the HD73_5014 transcriptional regulator, which controls the expression of the dipeptidase pepV, was named PepR (dipeptidase regulator). We also confirmed the direct regulation between PepR and PepV by the increased sensitivity to vancomycin in ΔpepV and ΔpepR mutants compared to HD73.