两株聚球藻伴生细菌分离纯化与促生功能鉴定

Isolation and growth-promoting function identification of two associated bacterial strains of Synechococcus sp.

摘要:

【背景】蓝藻周围存在伴生细菌，伴生细菌与蓝藻具有复杂的作用关系。【目的】研究淡水聚球藻伴生细菌对聚球藻生长的影响。【方法】采用高通量测序分析聚球藻伴生细菌多样性；平板划线法纯化聚球藻伴生细菌，通过形态观察结合16S rRNA基因序列同源性比对，对其种属关系进行确定；通过聚球藻和不同浓度伴生细菌共培养测定其叶绿素a浓度，分析伴生细菌对聚球藻生长的影响；采用种子发芽试验验证伴生细菌促生功能。【结果】淡水聚球藻伴生细菌优势菌属为产卟啉杆菌属(Porphyrobacter)、根瘤菌属(Rhizobium)、水单胞菌属(Aquimonas)和中慢生根瘤菌属(Mesorhizobium)，从聚球藻分离获得了两株伴生细菌JQ1和JQ2，基于16S rRNA基因序列鉴定其分别属于Rhizobium和Peribacillus，通过在聚球藻与不同浓度伴生细菌共培养及水稻发芽试验验证，证明伴生细菌JQ1和JQ2在菌藻比例分别为5:1和15:1时具有促生作用，都对增强秧苗素质和根系发育有一定影响但JQ2与JQ1相比能显著提高水稻种子的发芽率。【结论】淡水聚球藻伴生细菌JQ1和JQ2在适宜的浓度均可显著促进聚球藻的生长，并且在水稻中施用伴生细菌能促进水稻的生长，提高其发芽率。

关键词:聚球藻;伴生细菌;藻际环境;促生;发芽

Abstract:

[Background] The associated bacteria have complex interactions with cyanobacteria.[Objective] To study the effect of associated bacteria on the growth of freshwater Synechococcus. [Methods] The diversity of the bacteria associated with Synechococcus was analyzed by high-throughput sequencing. The associated bacteria were isolated by plate streaking and identified based on morphological characteristics and 16S rRNA gene sequence. The impact of associated bacteria on the growth of Synechococcus FACHB-7942 was analyzed by determining the concentration of chlorophyll-a by co-culturing Synechococcus and their associated bacteria of different concentrations. Rice seed germination test was carried out to verify the growth-promoting function of the associated bacteria. [Results] The dominant genera of the associated bacteria of freshwater Synechococcus were Porphyrobacter, Rhizobium, Aquimonas, and Mesorhizobium. Two associated bacterial strains, JQ1 and JQ2, were isolated and identified as species of Rhizobium and Peribacillus, respectively. Through co-cultivation Synechococcus with different concentrations of associated bacteria and rice seed germination test, it was confirmed that JQ1 and JQ2 exerted growth-promoting effect when the ratios of bacteria to cyanobacteria were 5:1 and 15:1, respectively. JQ1 significantly improved the germination rate of rice seeds compared with JQ2, and both strains played a role in improving the seedling quality and root development. [Conclusion] The associated bacterial strains JQ1 and JQ2 at appropriate concentrations can significantly promote the growth of Synechococcus, and the application of associated bacteria in rice can improve the germination and promote the growth of rice.

Key words:Synechococcus;associated bacteria;phycosphere;growth-promoting;germination