Microbial Utilization of Glycine Betain in Hypersaline Soda Lakes

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Abstract

Abstract: Glycine betaine (GB) is a biologically important compound for microbial communities living in saline habitats most commonly employed as an organic osmolyte. At fluctuating salinity, halophilic microbes producing GB excrete it into environment making it available for heterotrophic/methylotrophic community members as a source of carbon, energy and nitrogen. Although many halolalkaliphilic bacteria have a potential for synthesis of GB as the main osmolyte, so far there was no targeted investigation of its microbial mineralization at soda lake conditions. In this work GB was used as substrate to enrich for GB-utilizing bacteria and archaea from sediments of hypersaline soda lakes located in southwestern Siberia. Aerobic enrichments at moderate and soda-saturated conditions (pH 10) resulted in isolation of several gammaproteobacterial strains identical in its 16S RNA gene to each other and to the known species Halomonas alkalicola. These isolates grew equally well with several methylated compounds: methylglycine (sarcosine), dimethylglycine (DMG), GB and choline (trimethylethanolamine). No growth was observed in aerobic hypersaline enrichments in presence of antibiotics indicating that bacteria are the main mineralizers of GB in hypersaline soda lakes at oxic conditions. In contrast, an anaerobic enrichment at 4 M Na + and pH 9.7 targeting GB-utilizing haloalrchea was positive with sulfur as electron acceptor and resulted in isolation of a pure natronarchaeal culture belonging to the previously described genus of sulfur-reducing haloarchaea Halalkaliarchaeum. Anaerobic enrichments with GB at fermentative conditions were positive at salinities 2−4 M total Na + (pH 10) and consisted of a bacterial component forming trimethyamine (TMA) and methylotrophic methanogens consuming the latter. In both cases the bacterial component belonged to the genus Natroniella (Halanaerobiia), while the methanogenic partner at 2 M Na + was identified as Methanosalsum natronophilum and at 4 M Na +/48°C—as members of the methyl-reducing genus Methanonatronarchaeum.

Original languageEnglish
Pages (from-to)569-577
Number of pages9
JournalMicrobiology
Volume90
Issue number5
DOIs
Publication statusPublished - 2021

Keywords

  • dimethylglycine
  • glycine betaine
  • haloalkaliphilic
  • sarcosine
  • soda lakes
  • trimethylamine (TMA)

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