Wang Haixia, Xie Cuixiao, Zhu Panpan, Zhou Ning-Yi, Lu Zhenmei
Institute of Microbiology, College of Life Sciences, Zhejiang University Hangzhou, China.
State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University Shanghai, China.
Front Microbiol. 2017 Jan 17;7:2060. doi: 10.3389/fmicb.2016.02060. eCollection 2016.
Nicotine is a type of environmental pollutant present in the tobacco waste that is generated during tobacco manufacturing. TY can utilize nicotine as a sole source of carbon, nitrogen and energy via a variant of the pyridine and pyrrolidine pathway (the VPP pathway). In this study, we report the identification of two novel sets of genes, , and , which are crucial for nicotine degradation by strain TY. and exhibit similarity with both nicotine dehydrogenase from and nicotine hydroxylase from sp. SJY1. The transcriptional levels of and in strain TY were significantly upregulated in the presence of nicotine. Furthermore, or knockout resulted in a loss of the ability to degrade nicotine, whereas gene complementation restored the capacity of each mutant to utilize nicotine for growth. Biodegradation assays indicated that the mutant strains retained the ability to degrade the first intermediate in the pathway, 6-hydroxynicotine (6 HN). However, heterologous expression of and did not confer nicotine dehydrogenase activity to DH5α, KT2440 or . These results provide information on the VPP pathway of nicotine degradation in TY, and we conclude that these two sets of genes have essential functions in the conversion of nicotine to 6 HN in strain TY.
尼古丁是烟草制造过程中产生的烟草废料中存在的一种环境污染物。菌株TY可以通过吡啶和吡咯烷途径的变体（VPP途径）将尼古丁作为唯一的碳、氮和能量来源。在本研究中，我们报告了鉴定出两组新的基因，即 和 ，它们对于菌株TY降解尼古丁至关重要。 和 与来自 的尼古丁脱氢酶 以及来自 sp. SJY1的尼古丁羟化酶 均表现出相似性。在尼古丁存在的情况下，菌株TY中 和 的转录水平显著上调。此外， 或 基因敲除导致降解尼古丁的能力丧失，而基因互补恢复了每个突变体利用尼古丁生长的能力。生物降解试验表明，突变菌株保留了降解该途径中第一个中间体6-羟基尼古丁（6-HN）的能力。然而， 和 的异源表达并未赋予 DH5α、 KT2440或 尼古丁脱氢酶活性。这些结果提供了关于菌株TY中尼古丁降解VPP途径的信息，并且我们得出结论，这两组基因在菌株TY中将尼古丁转化为6-HN的过程中具有重要功能。
