青海湖嗜盐微生物系统发育与种群多样性

Population diversity and phylogeny of halophiles in the Qinghai Lake

青海湖是我国境内最大的内陆咸水湖泊,水体中嗜盐微生物的生存现状尚不明确。本研究利用OSM培养基(Oesterhelt-Stoeckenius medium),从湖域生境水样中富集和分离获得嗜盐微生物35株,以中度嗜盐菌为主,约占62.9%(22株);轻度嗜盐菌次之,约占22.9%(8株);耐盐菌与非嗜盐菌分别占11.4%(4株)和2.9%(1株)。根据16SrDNA序列的系统发育分析表明,γ-变形菌纲(γ-Proteobacteria)菌株最多,约占68.6%(24株);芽孢杆菌纲次之,约占17.1%(6株);放线菌纲、α-变形菌纲(α-Proteobacteria,1株)和散囊菌亚纲(Eurotiomycetidae,1株)的类群相对较少。这些嗜盐菌属于14个属,其中以海洋螺菌目盐单胞菌属(Halomonas)为优势种群,共计10株;其次为海单胞菌属(Marinomonas),共4株。中度嗜盐菌盐单胞菌属应为青海湖嗜盐菌的优势种群,可能因为相对偏低的盐度环境,为其长期进化和适应性生存提供了必要条件。

Qinghai Lake is the largest inland saline lake in China, but the diversity of halophiles within the lake remains unknown. We isolated 35 bacterial strains from different water samples in Qinghai Lake using an Oesterhelt-Stoeckenius medium （OSM）. The majority of halophiles in this lake were moderate halophiles （grew at 0.4 to 3.5 M NaCl）, accounting for about 62.9% （22 strains） of total bacteria, followed by the slight halophiles （22.9%, 8 strains） which could grow at 0 to 1.0 M NaCl, whereas the halotolerant （grew at 0 to more than 1.0 M NaCl） and nonhalophile （grew at 0 to 1.0 M NaCl） represented 11.4% （4 strains） and 2.9% （1 strain） of total bacteria, respectively. We investigated and analyzed the population diversity and evolutionary relationship based on the 16S rDNA sequences. A total of 35 bacterial strains were sequenced, and homology analysis showed that a majority was affiliated with γ-Proteobacteria and Bacilli, which accounted for 68.6% （24 strains） and 17.1% （6 strains） of total bacteria, respectively, whereas Actinobacteridae （3 strains）, α-Proteobacteria （1 strain） and Eurotiomycetidae （1 strain） represented a small portion of total bacteria. Based on phylogenetics, 35 strains belonged to 14 different genera. Ten strains of Halomonas in the Oceanospirillales were the most dominant species, whereas 4 strains of Marinomonas represented a minor species component. Overall, Halomonas was the dominant group of moderate halophile, which can likely be attributed to its ability to adapt to relatively low salinity environments.