Physiological and transcriptional response of Bacillus cereus treated with low-temperature nitrogen gas plasma

This study was conducted to investigate the inactivation kinetics of Bacillus cereus vegetative cells upon exposure to low-temperature nitrogen gas plasma and to reveal the mode of inactivation by transcriptome profiling.

Exponentially growing B. cereus cells were filtered and put on agar plates. The plates, carrying the filters with the vegetative cells, were placed into low-temperature nitrogen gas plasma at atmospheric pressure. After different exposure times, the cells were harvested for RNA extraction and enumeration. The RNA was used to perform whole-transcriptome profiling using DNA microarrays. The transcriptome profile showed a large overlap with profiles obtained from conditions generating reactive oxygen species in B. cereus. However, excess radicals such as peroxynitrite, hydroxyl and superoxide could not be detected using radical-specific fluorescence staining. Lack of UV-specific responses including factors involved in DNA damage repair is in line with the absence of UV-specific emission in the afterglow of the nitrogen gas plasma as analysed using optical emission spectroscopy (OES).

Antibacterial activity of nitrogen gas plasma is not based on UV radiation. Exposure to nitrogen gas plasma leads to oxidative stress and inactivation of targeted cells. A secondary oxidative stress with the indicative formation of reactive oxygen species within cells could not be observed.

This study represents the first investigation of differential gene expression on a genome-wide scale in B. cereus following nitrogen gas plasma exposure. This study may help to design economically feasible, safe and effective plasma decontamination devices.