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

Mengshuang Liu; Hui Liu; Fangtong Mei; Niping Yang; Dahe Zhao; Guomin Ai; Hua Xiang; Yanning Zheng

doi:10.3389/fmicb.2022.875843

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

Front Microbiol. 2022 Apr 18:13:875843. doi: 10.3389/fmicb.2022.875843. eCollection 2022.

Authors

Mengshuang Liu^{1

2}, Hui Liu³, Fangtong Mei⁴, Niping Yang⁵, Dahe Zhao¹, Guomin Ai¹, Hua Xiang^{1

2}, Yanning Zheng¹

Affiliations

¹ State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
² College of Life Science, University of Chinese Academy of Sciences, Beijing, China.
³ CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
⁴ College of Environment, Hohai University, Nanjing, China.
⁵ School of Life Sciences, Hebei University, Baoding, China.

Abstract

Thioalkalivibrio versutus 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 Thioalkalivibrio species. However, the biosynthetic pathway of glycine betaine in Thioalkalivibrio remained unknown. Here, we found that genes associated with nitrogen metabolism of T. versutus 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 T. versutus D301, with glycine N-methyltransferase (GMT) and sarcosine dimethylglycine N-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 Halorhodospira halochloris. Our results illustrate the glycine betaine biosynthetic pathway in the genus of Thioalkalivibrio for the first time, providing us with a better understanding of the biosynthesis of glycine betaine in haloalkaliphilic Thioalkalivibrio.

Keywords: Thioalkalivibrio versutus; biosynthetic pathway; glycine N-methyltransferase; glycine betaine; sarcosine dimethylglycine N-methyltransferase.