Department of Biology, University of Mississippi, University, Mississippi, United States of America.
Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, United States of America.
PLoS One. 2019 Nov 13;14(11):e0224796. doi: 10.1371/journal.pone.0224796. eCollection 2019.
Freshwater mussels are a species-rich group of aquatic invertebrates that are among the most endangered groups of fauna worldwide. As filter-feeders that are constantly exposed to new microbial inoculants, mussels represent an ideal system to investigate the effects of species or the environment on gut microbiome composition. In this study, we examined if host species or site exerts a greater influence on microbiome composition. Individuals of four co-occurring freshwater mussel species, Cyclonaias asperata, Fusconaia cerina, Lampsilis ornata, and Obovaria unicolor were collected from six sites along a 50 km stretch of the Sipsey River in Alabama, USA. High throughput 16S rRNA gene sequencing revealed that mussel gut bacterial microbiota were distinct from bacteria on seston suspended in the water column, and that the composition of the gut microbiota was influenced by both host species and site. Despite species and environmental variation, the most frequently detected sequences within the mussel microbiota were identified as members of the Clostridiales. Sequences identified as the nitrogen-fixing taxon Methylocystis sp. were also abundant in all mussel species, and sequences of both bacterial taxa were more abundant in mussels than in water. Site physicochemical conditions explained almost 45% of variation in seston bacterial communities but less than 8% of variation in the mussel bacterial microbiome. Together, these findings suggest selective retention of bacterial taxa by the freshwater mussel host, and that both species and the environment are important in determining mussel gut microbiome composition.
淡水贻贝是水生无脊椎动物中物种丰富的一个群体，它们是全球最濒危的动物群之一。作为不断暴露于新微生物接种物的滤食者，贻贝是研究物种或环境对肠道微生物组组成影响的理想系统。在这项研究中，我们研究了宿主物种或地点是否对微生物组组成有更大的影响。我们从美国阿拉巴马州锡皮河 50 公里长的一段的六个地点收集了四种共存的淡水贻贝（Cyclonaias asperata、Fusconaia cerina、Lampsilis ornata 和 Obovaria unicolor）的个体。高通量 16S rRNA 基因测序显示，贻贝肠道细菌微生物群与悬浮在水柱中的悬浮物中的细菌不同，并且肠道微生物群的组成受到宿主物种和地点的影响。尽管存在物种和环境变化，但贻贝微生物群中最常检测到的序列被鉴定为梭菌目（Clostridiales）的成员。在所有贻贝物种中也大量存在被鉴定为固氮分类群 Methylocystis sp. 的序列，并且这两个细菌类群的序列在贻贝中的丰度高于水中。地点理化条件解释了悬浮物细菌群落变异的近 45%，但只解释了贻贝细菌微生物组变异的不到 8%。这些发现表明，淡水贻贝宿主对细菌类群具有选择性保留，并且物种和环境对于确定贻贝肠道微生物组组成都很重要。
