紫金牛叶杆菌RC6b及其诱变菌株对二苯砷酸的降解特征

Diphenylarsinic acid degradation by Phyllobacterium myrsinacearum RC6b and its mutants

摘要:

【目的】阐明紫金牛叶杆菌Phyllobacterium myrsinacearum RC6b及其诱变菌株对二苯砷酸(Diphenylarsinic acid，DPAA)的降解特征与代谢产物。【方法】以紫金牛叶杆菌RC6b为出发菌株，分别以蔗糖、葡萄糖和乙酸钠为外加碳源，优化共代谢降解条件；采用亚硝基胍(N-methyl-N′-nitro-N-nitrosoguanidine，NTG)对出发菌株进行化学诱变，比较诱变前后菌株对DPAA降解能力的变化，鉴定诱变菌株对DPAA的降解代谢产物。【结果】以DPAA为唯一碳源时，培养28 d后RC6b菌株对DPAA的降解率低于2%；分别添加蔗糖、葡萄糖和乙酸钠为外加碳源培养28 d后，DPAA的降解率显著提高，分别达到14.08%、15.21%和15.05%；采用250 μg/mL的NTG诱变后获得3株诱变菌，在以DPAA为唯一碳源培养28 d后，3株诱变菌对DPAA的降解率与出发菌株相比均显著提高，其中N-RC6b2对DPAA的降解率最高，达36.71%；代谢产物鉴定结果表明，诱变菌株N-RC6b2对DPAA的代谢产物中有单羟基化DPAA的生成。【结论】RC6b出发菌株难以直接利用DPAA为唯一碳源生长，外加蔗糖、葡萄糖和乙酸钠等共代谢碳源可显著提高菌株RC6b对DPAA的降解率；NTG化学诱变可进一步提高RC6b菌株对DPAA的降解效果，代谢产物为单羟基化DPAA。

Abstract:

[Objective] To clarify the ability of Phyllobacterium myrsinacearum RC6b and its mutant strains to degrade diphenylarsinic acid (DPAA). [Methods] The conditions for the co-metabolic degradation of DPAA were optimized with P. myrsinacearum RC6b as the original strain and with sucrose, glucose and sodium acetate as different external carbon sources. Strain RC6b was chemically mutated using treatment with N-methyl-N′-nitro-N-nitrosoguanidine (NTG). The DPAA degradation rate was compared before and after chemical mutagenesis, and the metabolite of DPAA by RC6b mutants was also analyzed. [Results] The DPAA degradation rate was <2% after 28 days of incubation when using DPAA as the sole carbon source. After addition of sucrose, glucose and sodium acetate as external carbon sources the DPAA degradation rate increased significantly, by 14.08%, 15.21% and 15.05%, respectively. Three mutant strains of strain RC6b were obtained using 250 μg/mL NTG as chemical mutagen. All three RC6b mutants showed significantly higher DPAA degradation rates than did the original strain. Mutant strain N-RC6b2 showed the highest DPAA degradation rate of 36.71% after 28 days of incubation when using DPAA as the sole carbon source. The main degradation metabolite of DPAA by strain N-RC6b2 was identified as monohydroxylated DPAA. [Conclusion] The original RC6b strain grew only sparingly using DPAA as the sole carbon source. Addition of co-metabolic carbon sources such as sucrose, glucose and sodium acetate significantly enhanced the biodegradation of DPAA. The chemical mutagen NTG further enhanced the biodegradation of DPAA, with monohydroxylated DPAA as the main intermediate product.