Diversity and Predicted Function of Gut Microbes from Two Species of Viviparid Snails

Abstract

Animal gut bacteria are involved in numerous critical functions. In snails, gut bacteria play crucial roles in organic material digestion and nutrient production and have been implicated in aspects of reproduction. Snail gut microbes are known to differ between species and even between anatomical compartments of the digestive tract; dietary changes are also known to alter snail gut flora. In an effort to better understand their diversity and function, we studied the gut microbial communities from two viviparid snails, Campeloma decisum and Cipangopaludina japonica. We were interested in whether significant differences in bacterial community composition existed between the two species, and whether differences in microbial diversity corresponded to differences in community function. Using next-generation sequencing of the bacterial 16S V4 region, we found no significant differences in alpha and beta diversity between Ca. decisum and Ci. japonica. Firmicutes and Proteobacteria were the most abundant bacterial phyla in both species, while Bacteroidetes had a higher mean abundance in Ci. japonica. Nine taxonomic groups were present in significantly different mean abundances between the snail species. Pseudomonads and Enterobacteriaceae were notably more abundant in Ca. decisum, while Proteobacteria and Chitinophagaceae were more abundant in Ci. japonica. Peptidoglycan synthesis, pyruvate fermentation, and aerobic respiration by cytochrome c were the three most abundant microbial pathways represented in the viviparid gut. Fourteen functional pathways differed significantly between Ca. decisum and Ci. japonica, potentially correlated with differences in bacterial community composition and snail life history. Our data fill in data gaps regarding gut microbes in Viviparidae and highlight future research paths examining the prevalence of Firmicutes and unidentified diversity in both snail species.