Faecal microbiota dynamics in Cornu aspersum during dietary change and antibiotic challenge

ABSTRACT Despite its widespread geographic distribution and applications, the herbivorous land snail Cornu aspersum represents an understudied animal host. In this study, we used a culture-based approach, in combination with a population analysis based on 16S rRNA amplicon sequencing, to describe changes in the faecal microbiota of wild-caught snails that were fed a nonsterile plant diet over a period of 21 days. At the beginning of the experiment, wild-caught snails harboured diverse populations of Gammaproteobacteria. The two most abundant genera of Gammaproteobacteria were soil-associated Pseudomonas and Buttiauxella; the latter is an understudied genus often reported in snails and slugs. During penicillin treatment, the diversity of Gammaproteobacteria in experimental snails bottlenecked, resulting in Pseudomonas takeover. Following penicillin treatment, experimental snails began to recover, with faecal samples containing pre-treatment Gammaproteobacteria groups by day 21. There was a significant difference in the colony-forming units/g across days and across treatments. Additionally, there was a significant interaction between day and treatment. The food source was not sterile and supported its own population of Gammaproteobacteria, primarily Pseudomonas, which would have been taken up by the snails daily. Given that Buttiauxella was not observed on the food source, we hypothesize that it was present and maintained within the digestive tract of C. aspersum, and this is consistent with the idea that C. aspersum maintains an endogenous gut microbiome.