西藏扎布耶盐碱湖细菌的多样性与分离菌株的生长特性

【背景】扎布耶湖位于青藏高原地区，是以水体中富含高浓度CO₃²⁻、HCO₃⁻和Na⁺为显著特性的盐碱湖，因其地理位置高寒、高海拔，人迹罕至，涉及该盐湖微生物的研究相对较少。【目的】系统探究湖水中细菌多样性和菌种资源等，发掘可利用的潜在菌种。【方法】采用Illumina测序16S rRNA基因V3−V4区分析扎布耶湖细菌的群落结构组成、物种多样性特征；采用纯培养筛选分离可培养细菌，明确分离菌株分类学地位、生长特性及产酸能力，同时测定分离菌株四氢嘧啶(ectoine)、吲哚乙酸(3-indoleacetic acid, IAA)和胞外聚合物(extracellular polymeric substances, EPS)的积聚量。【结果】Illumina测序明确分类地位的细菌有21门44纲86目583属，其中优势门类群是变形菌门(Proteobacteria, 25.11%−67.60%)、拟杆菌门(Bacteroidetes, 4.84%−35.02%)和厚壁菌门(Firmicutes, 1.24%−11.01%)，优势属类群是克雷伯氏菌属(Klebsiella, 0.01%−9.53%)、盐单胞菌属(Halomonas, 0.54%−8.75%)、芽单胞菌属(Gemmatimonas, 2.39%−6.00%)和腈基降解菌属(Nitriliruptor, 1.27%−6.26%)。纯培养法筛选获得嗜盐碱菌38株，其中芽孢杆菌属(Bacillus) 23株(60.53%)和盐单胞菌属(Halomonas) 10株(26.32%)，菌株均具有耐盐碱和产酸能力(19.80%−29.68%)。大多数菌株能积聚四氢嘧啶、IAA和EPS，产量范围分别为1.36−175.59、0.27−8.69和0.02−0.22 g/g。【结论】扎布耶湖细菌群落结构与其他地区盐碱湖相似，但存在大量未明确分类学地位的细菌，分离菌株多具有耐盐碱及产酸特性。此外，还发现4株高效生产四氢嘧啶、3株生产吲哚乙酸和3株生产胞外聚合物的潜力菌株，为扎布耶盐湖微生物资源的开发利用奠定了基础。

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

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.