Mechanistic insights into the efficient degradation and detoxification of chloramphenicol by Clostridium pasteurianum DSM 525.

Chloramphenicol (CAP), a chlorinated nitroaromatic antibiotic, posed significant ecological and human health risks due to its persistence and toxicity. Although microbial degradation represented a promising remediation strategy, its practical application was often constrained by slow degradation kinetics and incomplete biotransformation. In this study, rapid and efficient CAP degradation by the Gram-positive anaerobe Clostridium pasteurianum DSM 525 was demonstrated. The strain achieved 83.6 % removal of 400 mg L-1 CAP within 8 h, and the degradation kinetics followed a first-order model (R2 ≥ 0.91). Metabolite analysis revealed a nitroreduction pathway, with CAP initially transformed into 4-aminophenyl allyl alcohol and subsequently converted into a dichlorinated aromatic amine (AMCl2). Integrated transcriptomic analysis uncovered a coordinated cellular response underlying the high degradation efficiency. Genes involved in the pentose phosphate pathway were significantly up-regulated, indicating enhanced NADPH supply. In parallel, a nitroreductase gene (log2FC = 2.43) responsible for antibiotic reduction and an EamA family transporter potentially involved in CAP uptake (log2FC = 2.07) were markedly induced, together with the up-regulation of genes encoding F0F1-ATP synthase, which was likely involved in ATP-dependent proton translocation and maintenance of transmembrane electrochemical gradients to support substrate transport. Concurrently, global stress-response mechanisms were activated to alleviate CAP-induced cellular stress. Collectively, this study elucidated the metabolic coordination underlying efficient CAP biodegradation and highlighted the potential of anaerobic Gram-positive bacteria for the bioremediation of nitroaromatic antibiotics.