The environmental adaptation mechanism of Desulfotignum in Xiaochaidan Lake

Abstract:

[Objective] The Xiaochaidan Lake on the Qinghai-Tibetan Plateau is rich in sulfate brine. The metagenomics study has demonstrated that Xiaochaidan Lake harbors abundant microorganisms with salt tolerance and the potential of carbon fixation and desulfurization. This paper aims to reveal the metabolic diversity and environmental adaptation mechanism of Desulfotignum via bioinformatics analysis. [Methods] The genomes of Desulfotignum in Xiaochaidan Lake were obtained via metagenomic analysis and public database. The global habitat distribution of Desulfotignum was revealed through literature tracking and 16S rRNA database retrieval. Desulfotignum subgroups were classified based on the phylogenetic analysis of 120 marker proteins in genome taxonomy database (GTDB). The environmental adaptation mechanism and metabolic diversity of Desulfotignum were analyzed through metabolic reconstruction. [Results] Desulfotignum is widely distributed in the world, and most of its habitats have high salinity. Eleven Desulfotignum genomes (nine from the sediments of Xiaochaidan Lake and two from the public database) were clustered into two groups (G1 and G2) according to the phylogenetic tree, average nucleotide identity (ANI), and average amino acid identity (AAI). Metabolic reconstruction indicated that Desulfotignum may be mixotrophic bacteria (using organic carbon and inorganic carbon as carbon sources) with Wood-Ljungdahl (WL) and reductive glycine (rGly) pathways for carbon fixation. The members in G1 can use nitrite, sulfate, and oxygen as electron receptors and carry out lactate fermentation, thiosulfate disproportionation, and chemotaxis through flagella. The members in G2 can use sulfate and oxygen as electron acceptors, participate in partial nitrification and thiosulfate disproportionation, and move via pilus twisting. Both G1 and G2 can take K⁺ through the Trk system to adapt to the high salt environment. [Conclusion] Our study expands new branches of Desulfotignum and predicts the potential metabolic diversity and environmental adaptation mechanism of Desulfotignum.