[ODP-200] Analysis of cell death in Bacillus subtilis caused by essential oils
Plant extracts such as the essential oils (EOs) have been used in various cases including medicine and incense to date. The EOs such as Vetiver and Sandalwood are composed mainly of sesquiterpenes; khusimol and santalol, respectively. We found that they had antimicrobial activity against Bacillus subtilis, but not Escherichia coli. To investigate how these compounds attacked the cells, we have been tried to isolate resistant mutants against these, but not achieved yet. The sensitivity to the compounds of the B. subtilis cells, in which the transcriptional regulators of ECF (extracytoplasmic function) σ factors, especially σM, were inactivate, increased, compared to that of wild type. It is suggested that σM regulon genes involved in tolerance to the compounds by maintaining cell surface integrity. By simultaneous inactivation of multi-ECF sigma factors (ΔsigM, ΔsigW, ΔsigX, and ΔsigV), the suppressor strains, which restored resistance to the bactericidal activity of Vetiver extract, emerged. Whole genome resequencing of the suppressor strains and genetic analysis revealed inactivation of xseB or pnpA, which code for exodeoxyribonuclease or polynucleotide phosphorylase, respectively. This suggested that sesquiterpenes also induce cell death, which is regulated with these genes, in addition to turbulence of cell surface.