Comparative transcriptome and phenotype analysis of Bacillus cereus in response to disinfectant treatments

Antimicrobial chemicals are widely applied to clean and disinfect food-contacting surfaces. However, the cellular response of bacteria, such as Bacillus cereus, to various disinfectants is unclear. In this study, the physiological and genome-wide transcriptional responses of B. cereus ATCC 14579 exposed to four different disinfectants (i.e., benzalkonium chloride, sodium hypochlorite, hydrogen peroxide, and peracetic acid) were analyzed. The physiological response of B. cereus to different concentrations of the disinfectants used was investigated. For each disinfectant, concentrations leading to the attenuation of growth, growth arrest, and cell death were studied in more detail. The simultaneous analysis of the transcriptional responses of B. cereus upon exposure to the different concentrations of disinfectants revealed common responses induced by the four disinfectants. Notably, genes involved in the general and oxidative stress responses were commonly up-regulated. Furthermore, the obtained results indicate that all the disinfectants also induce specific responses. Exposure to benzalkonium chloride, a disinfectant known to induce membrane damage, specifically induced genes involved in the fatty acid metabolism. Benzalkonium chloride induced-membrane damage was confirmed by fluorescence microscopy and fatty acid analysis confirmed that fatty acid composition of cell membrane was affected upon exposure to benzalkonium chloride. Sodium hypochlorite induced genes involved in sulfur and sulfur-containing amino acids metabolism, which correlated with the observed sodium hypochlorite-specific induction of oxidation of sulphydryl groups. Hydrogen peroxide and peracetic acid exposures induced genes involved in DNA damage and the SOS response. Notably, hydrogen peroxide and peracetic acid-treated cells exhibited higher mutation rates corroborating with the induced SOS response. Understanding the mechanisms displayed by microorganisms coping with disinfectants-induced stress may allow for design of more efficient sequential and/or disinfectant combination treatments in food processing environments