Deciphering the enzymatic responses, composition, network complexity, and functional degraders of the marine sediment bacterial community in response to 2-methyl-4-isothiazoline-3-one exposure

2-Methyl-4-isothiazoline-3-one (MIT) is a widely employed antimicrobial agent frequently detected in environments; however, current documentation regarding its impacts on microbial communities and biodegradation processes remains limited. Herein, marine sediment systems were established to investigate the MIT impacts under tiered concentrations (CK, 0 μg/L; LC, 5 μg/L; MC, 50 μg/L; HC 5 mg/L). The extracellular polymeric substance contents increased in the LC and MC groups, but not in the HC group, after one day of exposure. MIT inhibited the protease, dehydrogenase, and catalase activities in the HC group after 14 days of exposure. Bacterial community structure was altered in response to high concentrations of MIT. Lutibacter (44.59 %) and Flavobacterium (7.90 %) were the predominant genera that maintained its stability. Cognatiyoonia and Pseudorhodobacter decreased on Day 1, while Rhodoferax and Pseudorhodobacter increased on Day 14. Network analysis demonstrated reduced bacterial community interactions. Functional prediction indicated that MIT inhibited carbon metabolism and citrate cycle process in the HC group. These results suggested the potential ecotoxicological risks of MIT to marine systems under prolonged exposure conditions. Furthermore, three novel bacterial strains, i.e., Brevibacterium sp., Microbacterium sp., and Epilithonimonas sp., were isolated with demonstrated MIT biodegradation capacity for the first time. This study advances our comprehension of the impacts of MIT on the marine environment and provides valuable bacterial resources for bioremediation.