Bacterial diversity and growth characteristics of isolates from Zabuye Lake, Xizang

Abstract:

[Background] Zabuye Lake located in the Qinghai-Xizang Plateau in China is characterized by high concentrations of CO₃²⁻, HCO₃⁻, and Na⁺. Due to the alpine climate, high altitude, and the location off the beaten track, few studies have been conducted on the microorganisms of Zabuye Lake. [Objective] To systematically explore the bacterial diversity and mine valuable strains in Zabuye Lake. [Methods] Illumina sequencing of the 16S rRNA gene V3-V4 region was carried out to analyze the bacterial community structure and diversity in Zabuye Lake. The pure culture method was used to isolate the culturable bacterial strains, and the taxonomic status, growth characteristics, and alkali-degrading capacity of the isolates were determined. Furthermore, the accumulation of ectoine, indole acetic acid (IAA), and extracellular polymeric substances (EPS) was determined for the isolates. [Results] Illumina sequencing yielded 583 genera of bacteria belonging to 86 orders, 44 classes, and 21 phyla. The dominant phyla were Proteobacteria (25.11%-67.60%), Bacteroidetes (4.84%-35.02%), and Firmicutes (1.24%-11.01%), and the dominant genera were Klebsiella (0.01%-9.53%), Halomonas (0.54%-8.75%), Gemmatimonas (2.39%-6.00%), and Nitriliruptor (1.27%-6.26%). A total of 38 strains of haloalkaliphilic bacteria were isolated, including 23 (60.53%) strains of Bacillus and 10 (26.32%) strains of Halomonas. All the strains showed salinity tolerance and alkali-degrading capacity (19.80%-29.68%). Most strains were able to accumulate ectoine, IAA, and EPS with the yields of 1.36-175.59 mg/L, 0.27-8.69 mg/L, and 0.02-0.22 g/g, respectively. [Conclusion] The bacterial community structure of Zabuye Lake is similar to that of other saline lakes, while there are a large number of undefined bacteria taxa. Most of the strains isolated from Zabuye Lake have salinity tolerance and alkali-degrading capacity. In addition, 4, 3, and 3 potential strains for the efficient production of ectoine, IAA, and EPS, respectively, were identified. This study lays a foundation for the development and utilization of microbial resources and saline environment improvement in Zabuye Lake.