Comparison of epiphytic and intestinal bacterial communities in freshwater snails (Bellamya aeruginosa) living on submerged plants

Abstract

The combination of submerged plants and snails can combat eutrophication of freshwater systems by suppressing algal growth and assimilating nutrients. By consuming epiphytes, snails can benefit the growth of submerged plants. However, the efficiency of this phytoremediation strategy may depend on the microbes associated with the plants and snails. In this study, we compared the epiphytic bacterial communities on submerged plants (Vallisneria natans and Cabomba caroliniana) and intestinal bacterial communities of a snail, Bellamya aeruginosa, found on these plants using 16S rRNA gene sequencing. Epiphytic bacterial communities were similar between the two plant species and snails shared a high proportion of snail intestinal bacterial OTUs (75%) and genera (85%) with plants they grazed on. However, significant variations of Bray-Curtis distances differentiated epiphytic and intestinal bacterial communities. In addition, between the top 50 genera shared by intestinal and epiphytic bacterial communities, more Spearman correlations were detected within bacterial communities associated with snails than between communities associated with plants (190 vs. 143), and the correlations in epiphytic bacterial networks were more concentrated on certain genera, indicating they possessed distinct bacterial networks. This suggests the bacterial communities associated with snails do not depend strongly on the plant they graze on, which may be important for better understanding the role of snails in aquatic eco-restoration.

Host species of freshwater snails within the same freshwater ecosystem shapes the intestinal microbiome

“…For instance, biofilms can improve the host's resistance against pathogen invasion, while the presence of mobile elements can improve the host's tolerance to drug resistance (Palmer et al, 2010;Stokes and Gillings, 2011). Stress tolerance can further improve adaptability to environmental changes, such as temperature, salinity and contaminants (Fahy et al, 2008;Li et al, 2022;Liu et al, 2023). In this study, significant differences were found between the intestinal microbiome phenotypes of the three snail species, as evidenced from the results of BugBase.…”

“…These differences could be attributed to variations in the food composition or water environment. Although Planctomycetota was found to be highly abundant in all three snail species and also found in another study of Planorbidae snails (Van Horn et al, 2012), it has rarely been reported in other freshwater snails (Hu et al, 2018;Hu et al, 2021;Liu and Li, 2022;Zhou et al, 2022). In fact, it was only reported in 1 study on the intestinal microbiota of terrestrial Hydrobiidae (Walters et al, 2022).…”

“…The gut microbiome of animals is influenced by many factors, such as the host species, the water environment or food, and therefore, in the case of freshwater snails, much of the experimental data tend to come from artificially controlled environments (Chalifour and Li, 2021;Hu et al, 2021;Li et al, 2022;Zhou et al, 2022). This is because in natural water bodies, it is difficult to model the effects of host species on the microbiota due to a number of naturally occurring uncontrollable factors.…”

“…For example, the number of OTUs in the intestinal microbiota of herbivorous freshwater snails reduced by 71% after they ate diets without fiber, indicating that the gut microbiome is highly dependent on the presence of cellulose-containing plant nutrients (Hu et al, 2021). Furthermore, a study on the intestinal bacterial communities of Bellamya aeruginosa showed that the microbiome did not strongly depend on the microbiota in food (Liu and Li, 2022). Therefore, when sampling freshwater snails from similar natural water bodies, slight food differences have limited effects on the intestinal microbiota composition.…”