Revealing the biological significance of multiple metabolic pathways of chloramphenicol by Sphingobium sp. WTD-1

Chloramphenicol (CAP) is an antibiotic that commonly pollutes the environment, and microorganisms primarily drive its degradation and transformation. Although several pathways for CAP degradation have been documented in different bacteria, multiple metabolic pathways in the same strain and their potential biological significance have not been revealed. In this study, Sphingobium WTD-1, which was isolated from activated sludge, can completely degrade 100 mg/L CAP within 60 h as the sole energy source. UPLC-HRMS and HPLC analyses showed that three different pathways, including acetylation, hydroxyl oxidation, and oxidation (C1-C2 bond cleavage), are responsible for the metabolism of CAP. Importantly, acetylation and C3 hydroxyl oxidation reduced the cytotoxicity of the substrate to strain WTD-1, and the C1-C2 bond fracture of CAP generated the metabolite p-nitrobenzoic acid (PNBA) to provide energy for its growth. This indicated that the synergistic action of three metabolic pathways caused WTD-1 to be adaptable and able to degrade high concentrations of CAP in the environment. This study deepens our understanding of the microbial degradation pathway of CAP and highlights the biological significance of the synergistic metabolism of antibiotic pollutants by multiple pathways in the same strain. Chloramphenicol (CAP) is a typical refractory antibiotic contaminant, that poses serious hazards to human health and ecosystems. Microbial degradation is considered a promising strategy for eliminating CAP contamination. However, the bacteria that completely degrade and mineralize CAP is poorly understood. The co-existence of multiple CAP metabolic pathways in the same strain and their potential biological significance have also not been clarified. In this study, a strain WTD-1 with three metabolic pathways to completely degrade CAP was isolated and the potential biological significance of these pathways was revealed. This study provides a powerful microbial resource for CAP bioremediation applications and assists in deepening our understanding of microbial synergistic metabolic mechanisms via the multi-pathways on organic pollutants.