First Reports on the Bacterial Community of the Digestive System of Endemic Baikal Gastropods Benedictia baicalensis

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Abstract—Diversity and comparative analysis of the microbiota composition of the digestive system of Lake Baikal endemic gastropods Benedictia baicalensis (Caenogastropoda) and of the bottom sediments from their habitat were studied. Strains belonging to 11 genera of heterotrophic bacteria (Pseudomonas, Acinetobacter, Alcaligenes, Flavobacterium, Enterobacter, Escherichia, Citrobacter, Klebsiella, Bacillus, Staphylococcus, Streptococcus, and Micrococcus) were isolated from the stomach and gut content. Molecular genetic analysis of total DNA from the digestive tract revealed the 16S rRNA gene sequences of the genera Pseudomonas, Flavobacterium, Mesorhizobium, Deefgea, and of the phylum Tenericutes. Most isolates were found to utilize various organic substances, including those of animal origin, which was probably due to the pantophagy of these mollusks. The cultured bacterial community of B.baicalensis digestive system was shown to be formed by gram-negative bacteria (95–97% strains), although in the bottom sediments 51% of the isolates were gram-positive coccoid and spore-forming rod-shaped bacteria. Low frequency of occurrence or complete absence of gram-positive bacteria in the mollusk intestine compared to the bottom sediments (fivefold or more) may indicate their use as a nutrient substrate.