小柴旦盐湖脱硫棒状菌属的环境适应性机制分析

The environmental adaptation mechanism of Desulfotignum in Xiaochaidan Lake

摘要:

【目的】青藏高原小柴旦盐湖富含硫酸盐卤水，宏基因组学分析揭示该生境蕴藏着丰富的具有耐盐、固碳和脱硫功能的微生物。本研究拟通过生物信息学分析揭示潜在的固碳脱硫微生物脱硫棒状菌(Desulfotignum)的代谢多样性和环境适应性机制。【方法】利用宏基因组分箱分析和公共数据库下载获得小柴旦盐湖脱硫棒状菌属的基因组，通过文献跟踪和16S rRNA基因数据库检索揭示脱硫棒状菌的全球生境分布，基于基因组分类数据库(genome taxonomy database, GTDB)中120个细菌标记蛋白的系统发育树对脱硫棒状菌属的亚群进行分类，通过重构脱硫棒状菌属不同亚群的生理代谢潜能以及基因组比较分析来解析其环境适应机制和代谢多样性。【结果】脱硫棒状菌属全球分布广泛且主要栖息在高盐生境。小柴旦盐湖沉积物中共得到了9个脱硫棒状菌基因组，结合公共数据库中2个基因组，根据基因组系统发育分析、平均核苷酸一致性(average nucleotide identity, ANI)和平均氨基酸一致性(average amino acid identity, AAI)分析将这11个脱硫棒状菌基因组分为了2个亚群(G1和G2)。脱硫棒状菌属的代谢通路重构显示其存在Wood-Ljungdahl (WL)途径和还原甘氨酸(reductive rglycine, rGly)途径2条潜在固碳途径，其中G1亚群可利用亚硝酸盐、硫酸盐、氧气作为电子受体，还可进行乳酸发酵、硫代硫酸盐歧化以及通过鞭毛进行趋化运动；而G2亚群参与部分硝化作用，可利用硫酸盐和氧气作为电子受体，或进行硫代硫酸盐歧化以及通过菌毛扭动方式来运动。这代表脱硫棒状菌属可能是混合营养型微生物，同时利用有机碳和无机碳作为碳源来生长。G1和G2亚群均通过Trk系统摄入K⁺来对抗高盐环境。【结论】本研究扩展了脱硫棒状菌属的物种多样性，率先揭示了该属的生理代谢潜能和潜在的环境适应机制。

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.