Exploring changes in ARGs during chromium reduction by Bacillus cereus SH-1 exposed to chromium-contaminated wastewater: a functional analysis from gene to protease

This study researched the combined effects of hexavalent chromium (Cr(VI)) concentration and antibiotics on the ARGs of Bacillus cereus SH-1. As the Cr(VI) concentration increased, it triggered Reactive Oxygen Species (ROS) oxidative stress in SH-1, increased antioxidant enzyme activity, enhanced plasmid conjugative transfer and reduced the removal efficiency of Cr(VI) by SH-1. Meanwhile, antibiotic resistance varied with TET (Tetracycline) and AMC (Amoxicillin) MICs (minimum inhibitory concentration) rising and AZM (Azithromycin) and CL (Chloramphenicol) MICs decreasing with Cr(VI) induction. Overexpression of eight genes of the HAE-1 family efflux pumps was detected through metagenomics and proteomics. Co-contamination of Cr(VI) and antibiotics led to the emergence and spread of antibiotics resistant bacteria (ARBs).