NADH dehydrogenase is the primary target for the bactericidal effect of CORM-2 in Shewanella oneidensis

Shewanella oneidensis is a good model for investigating the bactericidal effects of chemical agents. In this study, the effects of tricarbonyldichlororuthenium dimer (CORM-2) on the aerobic and anaerobic growth of S. oneidensis were studied, and its bactericidal mechanisms were elucidated. CORM-2 (5 µM) significantly inhibited aerobic and anaerobic respiration. Growth potential tests showed that mutants ΔkatB, ΔoxyR, ΔccmF, and Δcrp and mutants that deleted each cytochrome c-encoding gene exhibited sensitivity to CORM-2 similar to that of the wild-type strain MR-1. Enzymatic analyses showed that cytochrome oxidase, catalase and cysteine desulfurase were activated by CORM-2, while nitrite reductase, nitrate reductase, sulfite reductase, thiosulfate reductase, peroxidase and NADH dehydrogenase were inhibited by CORM-2, and no significant changes were found in the activities of superoxide dismutase and aconitase. Promoter activity assays showed that cco, cyd, cox, katB, sirA and psrA were repressed by CORM-2. Sulfide alleviated the bactericidal effect of CORM-2 and protected NADH dehydrogenase from CORM-2 inhibition. Thus, oxidative stress and cytochrome oxidase inactivation are not the primary reasons for the bactericidal effect of CORM-2, and NADH dehydrogenase is the main target in S. oneidensis. The bactericidal effect of CORM-2 is caused by the toxicity of Ru2+, not by carbon monoxide.