What are the differences between aerobic and anaerobic toxic effects of sulfonamides on Escherichia coli?

•Both the aerobic and anaerobic toxicity of SAs to Escherichia coli were determined.•Besides logDow and Ebinding, the key factors to anaerobic toxicity, ROS was also a key factor to aerobic toxicity.•The different total binding energy led to SAs divided into three groups.•This division of three groups was independent of the structures of SAs.

Bacteria in the environment face the threat of antibiotics. However, most studies investigating the toxicity and toxicity mechanisms of antibiotics have been conducted on microorganisms in aerobic conditions, while studies examining the anaerobic toxicity and toxicity mechanisms of antibiotics are still limited. In this study, we determined the aerobic and anaerobic toxicities of sulfonamides (SAs) on Escherichia coli. Next, a comparison of the aerobic and anaerobic toxicities indicated that the SAs could be divided into three groups: Group I: log(1/EC50-anaerobic) > log(1/EC50-aerobic) (EC50-anaerobic/EC50-aerobic, the median effective concentration under anaerobic/aerobic conditions), Group II: log(1/EC50-anaerobic) ≈ log(1/EC50-aerobic), and Group III: log(1/EC50-anaerobic) < log(1/EC50-aerobic). Furthermore, this division was not based on the reactive oxygen species (ROS) level or the interaction energy (Ebinding) value, which represents the affinity between SAs and dihydropteroate synthase (dhps) but rather on the total binding energy. Furthermore, SAs with greatly similar structures were categorized into different groups. This deep insight into the difference between aerobic and anaerobic toxicities will benefit environmental science, and the results of this study will serve as a reference for the risk assessment of chemicals in the environment.

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