Two Novel Sets of Genes Essential for Nicotine Degradation by TY.

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.