Systematic stress adaptation of Bacillus subtilis to tetracycline exposure

To alleviate the harmful effects of antibiotics on the environment and human health, the stress response and molecular network of Bacillus under tetracycline stress were investigated using a proteomics approach. During the exposure process, Bacillus subtilis exhibited a strong adaptation mechanism. Cell membrane and intracellular reactive oxygen species (ROS) level returned to normal after 5 h. A total of 312 upregulated and 65 downregulated proteins were identified, mainly involved in metabolism and the synthesis of ribosomes, DNA, and RNA. After tetracycline exposure, the core metabolism network was accelerated to supply precursors for the synthesis of DNA, RNA, proteins, peptidoglycans, and saturated fatty acids that were involved in ribosome protection, and strengthened the cell wall and cell membrane. The signal transduction pathways involved were analyzed in association with the stress response of B. subtilis at 15 min of exposure to tetracycline. The primary damage to the ribosome by tetracycline activated a series of response proteins. Antitoxin and heat-shock proteins were activated for the global regulation of transcription and metabolism. Trigger factor Tig was upregulated to ensure proper initiation of transcription and aerobic respiration. Temperature-sensor protein VicR from the two-component system was used by the cell to regulate the composition of the cell wall and cell membrane. The over-consumption of metabolites, such as phosphoribosyl diphosphate (PRPP), purine nucleoside triphosphate (GTP), and acetyl-CoA forced the cells to assimilate more sugar for glycolysis. To this end, methyl-accepting chemotaxis proteins (MCPs) and sugar transportation protein PtsG were upregulated, simultaneously. Ultimately, peroxidase was activated to eliminate the redundant ROS, to minimize cell damage. These findings presented a system-level understanding of adaption processes of bacteria to antibiotic stress.