AUTHOR=Liu Mengshuang , Liu Hui , Mei Fangtong , Yang Niping , Zhao Dahe , Ai Guomin , Xiang Hua , Zheng Yanning 

TITLE=Identification of the Biosynthetic Pathway of Glycine Betaine That Is Responsible for Salinity Tolerance in Halophilic Thioalkalivibrio versutus D301

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.875843

DOI=10.3389/fmicb.2022.875843

ISSN=1664-302X

ABSTRACT=<p><italic>Thioalkalivibrio versutus</italic> D301 has been widely used in the biodesulfurization process, as it is capable of oxidizing hydrogen sulfide to elemental sulfur under strongly halo-alkaline conditions. Glycine betaine contributes to the increased tolerance to extreme environments in some of <italic>Thioalkalivibrio</italic> species. However, the biosynthetic pathway of glycine betaine in <italic>Thioalkalivibrio</italic> remained unknown. Here, we found that genes associated with nitrogen metabolism of <italic>T. versutus</italic> D301 were significantly upregulated under high-salt conditions, causing the enhanced production of glycine betaine that functions as a main compatible solute in response to the salinity stress. Glycine betaine was synthesized by glycine methylation pathway in <italic>T. versutus</italic> D301, with glycine <italic>N</italic>-methyltransferase (GMT) and sarcosine dimethylglycine <italic>N</italic>-methyltransferase (SDMT) as key enzymes in this pathway. Moreover, substrate specificities of GMT and SDMT were quite different from the well characterized enzymes for glycine methylation in halophilic <italic>Halorhodospira halochloris</italic>. Our results illustrate the glycine betaine biosynthetic pathway in the genus of <italic>Thioalkalivibrio</italic> for the first time, providing us with a better understanding of the biosynthesis of glycine betaine in haloalkaliphilic <italic>Thioalkalivibrio</italic>.</p>