Effects of temperature on composition and stability of bacterial community in colonial <i>Microcystis aeruginosa</i> culture systems

Abstract

微囊藻藻际细菌影响微囊藻的生长及其水华的生消.然而特定微囊藻群体中藻际细菌群落组成对温度变化的响应规律仍不清楚.本文把一株从太湖分离得到的群体铜绿微囊藻，置于不同温度（15、20、25和30℃）下进行培养，分析各培养体系中不同粒径附生或游离细菌群落组成的异同.结果表明：温度显著影响微囊藻群体（>20 μm）附生、单细胞小群体（3~20 μm）附生和游离（0.2~3 μm）细菌群落的组成（PERMANOVA，P<0.01），Sphingomonadales、Pseudomonadales和Cytophagales分别是3组细菌群落中的最优势菌目，相对丰度分别为21.35%、19.74%和33.44%.在3组细菌群落中都存在一些核心优势细菌类群，其丰度相对稳定，对温度变化不敏感.其中在微囊藻群体附生细菌群落中，优势菌属Brevundimonas和OPB56在20~30℃之间培养时其相对丰度较为稳定；单细胞小群体附生细菌群落中的核心优势菌属Mariniradius相对丰度也是在20~30℃之间较为稳定，而Gemmobacter相对丰度在4种温度下均较为一致；游离细菌群落中的核心优势菌属Porphyrobacter相对丰度在20~30℃之间时也相对稳定.另外，在15℃时，单细胞小群体附生和游离细菌群落的多样性都达到最高，总体细菌群落物种相关性网络复杂度最高，但合作性关联最弱.该研究结果对于深入了解微囊藻群体的藻菌关系有重要意义.;Bacteria in phycosphere of Microcystis affect growth, development and decline of Microcystis blooms. In specific Microcystis colony, however, the pattern of bacterial community composition in response to different temperatures are still unclear. In this study, a colonial Microcystis aeruginosa strain isolated from Lake Taihu was cultivated at different temperatures (15, 20, 25 and 30℃) to analyse the similarities and differences in the composition of different particle attached or free living bacterial communities in each culture system. Temperature significantly affected community compositions of bacteria including Microcystis colony (>20 μm) attached bacteria, single cell-small colony (3-20 μm) attached bacteria and free-living (0.2-3 μm) bacteria (PERMANOVA,P<0.01), Sphingomonadales, Pseudomonadales and Cytophagales were the most dominant order in the three groups, accounting for 21.35%, 19.74% and 33.44% of the total relative abundance, respectively. There were some core dominant bacterial species in the three groups of bacterial communities, which were relatively stable in abundance and insensitive to temperature changes. The relative abundance of Brevundimonas and OPB56, the dominant genus among the core bacterial community attached with Microcystis colony, were relatively stable when temperature changed from 20 to 30℃. The relative abundance of Mariniradius, the dominant genus among the core bacteria attached with single cell-small colony, was also relatively stable when temperature changed from 20 to 30℃, and the relative abundance of Gemmobacter, the another dominant genus among the core bacteria attached with single cell-small colony, was relatively stable in response to temperature changes. The relative abundance of Porphyrobacter, the dominant genus among the core bacterial community in free-living bacteria, were also relatively stable when temperature changed from 20 to 30℃. Compared with the situations at other three higher temperatures, the complexity of species correlation network at 15℃ was the highest but the cooperative correlation was the weakest. The results of this study were of great significance for understanding the algal-bacterial relationships in phycosphere of colonial Microcystis.