一株氯霉素降解细菌的分离鉴定与代谢特性研究

Isolation, identification and characterization of a chloramphenicol-degrading bacterium

摘要:

微生物是介导环境中氯霉素降解转化的主要驱动者，但高效降解矿化菌株资源匮乏，氧化反应介导的代谢途径不清。为研究微生物介导下氯霉素的环境归趋过程，为氯霉素污染环境强化修复提供菌株资源，文中以受氯霉素污染的活性污泥为接种源，首先富集获得一个由红球菌Rhodococcus主导 (相对丰度>70%) 的氯霉素高效降解菌群，并从中分离获得一株能够高效降解氯霉素的菌株CAP-2，通过16S rRNA基因分析鉴定为红球菌Rhodococcus sp.。菌株CAP-2能在不同营养条件下高效降解氯霉素。基于菌株CAP-2对检测到的代谢产物对硝基苯甲酸和已报道的代谢产物对硝基苯甲醛和原儿茶酸的生物转化特征，提出其降解途径是由氯霉素侧链氧化断裂生成对硝基苯甲醛，进一步氧化为对硝基苯甲酸的新型氧化降解途径。该菌株对于氯霉素分解代谢的分子机制研究以及受氯霉素污染环境的原位生物修复应用具有巨大潜力。

Abstract:

Microorganisms are the dominant players driving the degradation and transformation of chloramphenicol (CAP) in the environment. However, little bacterial strains are able to efficiently degrade and mineralize CAP, and the CAP degrading pathways mediated by oxidative reactions remain unclear. In this study, a highly efficient CAP-degrading microbial consortium, which mainly consists of Rhodococcus (relative abundance >70%), was obtained through an enrichment process using CAP-contaminated activated sludge as the inoculum. A bacterial strain CAP-2 capable of efficiently degrading CAP was isolated from the consortium and identified as Rhodococcus sp. by 16S rRNA gene analysis. Strain CAP-2 can efficiently degrade CAP under different nutrient conditions. Based on the biotransformation characteristics of the detected metabolite p-nitrobenzoic acid and the reported metabolites p-nitrobenzaldehyde and protocatechuate by strain CAP-2, a new oxidative pathway for the degradation of CAP was proposed. The side chain of CAP was oxidized and broken to generate p-nitrobenzaldehyde, which was further oxidized to p-nitrobenzoic acid. Strain CAP-2 can be used to further study the molecular mechanism of CAP catabolism, and has the potential to be used in in situ bioremediation of CAP-contaminated environment.