The sulfur stress response and protein S-thioallylation caused by allicin and diallyl polysulfanes in Bacillus subtilis as revealed by transcriptomics and proteomics

In this study, we compared the transcriptome signatures under allicin and diallyl tetrasulfane (DAS4) exposure in the Gram-positive bacterium B. subtilis. We further used shotgun proteomics to unravel the overall S-thioallylomes provoked by allicin and DAS4. Allicin and DAS4 caused a similar thiol-specific oxidative and electrophile stress response, protein and DNA damage in the transcriptome. At the proteome level, we identified in total 108 S-thioallylated proteins under allicin and/or DAS4 stress, while allicin appeared to have a stronger thiolation affect on redox-sensitive proteins. The S-thioallylome includes enzymes involved in the biosynthesis of surfactin (SrfAA, SrfAB), amino acids (SerA, MetE, YxjG, YitJ, CysJ, GlnA, YwaA), nucleotides (PurB, PurC, PyrAB, GuaB), translation factors (EF-Tu, EF-Ts, EF-G), antioxidant enzymes (AhpC, MsrB) as well as redox-sensitive MarR/OhrR and DUF24-family regulators (OhrR, HypR, YodB, CatR). Growth phenotype analysis revealed that the LMW thiol bacillithiol, the thiol-redox regulator Spx as well as the HypR and OhrR regulons confer protection against allicin and DAS4 stress. Altogether, we could show here that allicin and DAS4 cause both an oxidative and sulfur stress response in the transcriptome and widespread S-thioallylation of redox-sensitive proteins in B. subtilis.