Host specificity and uniqueness of shell microbiome in freshwater mollusks

Zifan Zhao¹Zhendu Mao¹Dan He¹Heng Wang¹Qinglong L. Wu^1,2,3*

• ¹Southern Marine Science and Engineering Guangdong Laboratory - Guangzhou, Guangzhou, China
• ²Nanjing Institute of Geography and Limnology Chinese Academy of Sciences, Nanjing, China
• ³University of the Chinese Academy of Sciences, Beijing, China

Shell of mollusks represent a major substrate for colonization of microbial communities and aquatic ecosystem functioning. However, our knowledge about shell microbiome is very limited. Here we select Bellamya aeruginosa and Corbicula fluminea as two types of snail and clam to explore their shell epiphytic bacteria by 16S amplicon sequencing. We found different shell bacterial communities between snail and clam, which are also distinct from surrounding environment. Source tracking analysis indicated that snail shell bacteria was derived mostly from sediment, whereas the clam shell was originated from tissue. There was a site-specific difference on the shell bacteria within the habitat. Temporal variation in clam shell bacteria was observed, but not for snail shell, which correspond to their source dynamic in water column and stable surface sediment bacterial communities respectively. The genus Nitrospira was mostly enriched in shell bacteria particularly in eutrophic lake areas. Taxa related to carbon, nitrogen, and sulfur cycling were recognized as the key stone species in the cooccurrence network associated with the shell surface. Our results demonstrate that mollusk shells represent unique ecological niche for microbiome in aquatic ecosystems and may serve as hotspots for biogeochemical cycling.