Characterization of an efficient chloramphenicol-mineralizing bacterial consortium

Obtaining efficient antibiotic-mineralizing consortium or pure cultures is a central issue for the deep elimination of antibiotic-contaminated environments. However, the antibiotic chloramphenicol (CAP) mineralizing consortium has not yet been reported. In this study, an efficient CAP-mineralizing consortium was successfully obtained with municipal activated sludge as the initial inoculum. This consortium is capable of aerobically subsisting on CAP as the sole carbon, nitrogen and energy sources and completely degrading 50 mg L^-1 CAP within 24 h. After 5 d, 71.50 ± 2.63% of CAP was mineralized and Cl^- recovery efficiency was 90.80 ± 7.34%. Interestingly, the CAP degradation efficiency obviously decreased to 18.22 ± 3.52% within 12 h with co-metabolic carbon source glucose. p-nitrobenzoic acid (p-NBA) was identified as an intermediate product during CAP biodegradation. The consortium is also able to utilize p-NBA as the sole carbon and nitrogen sources and almost completely degrade 25 mg L^-1p-NBA within 24 h. Microbial community analysis indicated that the dominant genera in the CAP-mineralizing consortium all belong to Proteobacteria (especially Sphingobium with the relative abundance over 63%), and most bacteria could degrade aromatics including p-NBA, suggesting these genera involved in the upstream and downstream pathway of CAP degradation. Although the acclimated consortium has been successively passaged 152 times, the microbial community structure and core genera were not obviously changed, which was consistent with the stable CAP degradation efficiency observed under different generations. This is the first report that the acclimated consortium is able to mineralize CAP through an oxidative pathway with p-NBA as an intermediate product.