Table_7_Elevated Seawater Temperatures Decrease Microbial Diversity in the Gut of Mytilus coruscus.XLSX

The gut microbial community is critical for the host immune system, and in recent years, it has been extensively studied in vertebrates using ‘omic’ technologies. In contrast, knowledge about how the interactions between water temperature and diet affect the gut microbiota of marine invertebrates that do not thermoregulate is much less studied. In the present study, the effect of elevated seawater temperature and diet (Isochrysis zhanjiangensis and Platymonas helgolandica var. tsingtaoensis) on the gut microbial community of the commercial mussel, Mytilus coruscus, was investigated. The 16S rRNA gene sequencing was used to characterize the microbial community in M. coruscus gut. The mortality of M. coruscus exposed to a high water temperature (31°C) increased after 3 days and the diversity of the bacterial community in the gut of live M. coruscus was significantly reduced. For example, the abundance of Bacteroides (Bacteroidetes) and norank_Marinilabiaceae (Bacteroidetes) increased in the gut of M. coruscus fed I. zhanjiangensis. In M. coruscus fed P. helgolandica, the abundance of Arcobacter (Proteobacteria) and norank_Marinilabiaceae increased and the abundance of unclassified_Flavobacteriaceae (Bacteroidetes) decreased. The results obtained in the present study suggest that high temperatures favored the proliferation of opportunistic bacteria, including Bacteroides and Arcobacter, which may increase host susceptibility to disease. Microbial community composition of the gut in live M. coruscus was not impacted by the microalgal diet but it was modified in the group of mussels that died. The present study provides insight into the potential effects on the gut microbiome and mussel–bacteria interactions of rising seawater temperatures.

肠道微生物群落对于宿主免疫系统至关重要，近年来，使用‘组学’技术对脊椎动物中的肠道微生物群落进行了广泛的研究。相比之下，关于水温与饮食之间相互作用如何影响不具有体温调节能力的海洋无脊椎动物肠道微生物的研究则相对较少。在本研究中，我们调查了海水温度升高以及饮食（湛江等枝藻和青岛角毛藻）对商业贻贝Mytilus coruscus肠道微生物群落的影响。通过16S rRNA基因测序技术对M. coruscus肠道中的微生物群落进行了表征。M. coruscus在暴露于高温（31°C）后3天死亡率上升，且活体M. coruscus肠道中的细菌群落多样性显著降低。例如，在以湛江等枝藻为食的M. coruscus肠道中，拟杆菌（拟杆菌门）和未分类_Marinilabiaceae（拟杆菌门）的丰度增加。在以青岛角毛藻为食的M. coruscus中，弧菌（变形菌门）和未分类_Marinilabiaceae的丰度增加，而未分类_Flavobacteriaceae（拟杆菌门）的丰度则降低。本研究获得的结果表明，高温有利于条件致病菌，包括拟杆菌和弧菌的增殖，这可能导致宿主对疾病的易感性增加。活体M. coruscus的肠道微生物群落组成并未因微藻饮食而受到影响，但在死亡的贻贝组中发生了改变。本研究揭示了海水温度升高对肠道微生物群和贻贝-细菌相互作用可能产生的影响。