Gene Encoding for Methyltransferase Contributing to Dimethyl Diselenide Synthesis Among Methylated Selenium from Stutzerimonas stutzeri NT-I

Abstract

Selenium (Se) is a rare metal refined from the slime byproduct of copper anodes. Selenium circulates globally in various valence states and forms. Soluble selenooxyanions, such as selenate (SeO₄^2-) and selenite (SeO₃^2-) are converted to volatile dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe) and vaporized. Although some microorganisms synthesize volatile Se compounds, and volatile Se compounds is used for resource recovery and soil remediation, the synthesis pathway of DMDSe has not yet been identified. We hypothesized that a methyltransferase in the Stutzerimonas stutzeri NT-I specific contig is involved in the synthesis of methylated Se in S. stutzeri NT-I and cloned the gene encoding the enzyme. We carried out qualitative analysis of synthesized volatile Se compounds using the transgenic E. coli DH5α pGEM-mdsN. A novel gene involved in DMDSe synthesis was identified and named mdsN and found to encode a class I SAM-dependent methyltransferase. When the mdsN was introduced into E. coli DH5α, the recombinant E. coli DH5α pGEM-mdsN acquired the ability to synthesize DMDSe, which corresponds to 62% of the initial Se concentration. In this paper, we report a novel finding that E. coli DH5α pGEM-mdsN, in which mdsN from S. stutzeri NT-I was transformed into E. coli DH5α, synthesized DMDSe from SeO₃^2- and Bio-Se⁰ from S. stutzeri NT-I.