Uncovering the diversity of heterotrophic culturable bacteria within the gut of bay scallop Argopecten purpuratus (Lamarck, 1819) from two geographically distant natural banks

We study the bacterial diversity within the gut of the peruvian bay scallop Argopecten purpuratus (Lamarck, 1819) (Mollusca: Pectinidae) collected from two shellfish growing areas in Independence Bay (IB) and Sechura Bay (SB) in Peru. This work aimed to identify isolates of culturable gut-associated microbiota of A. purpuratus through repetitive sequence-based PCR (rep-PCR) and 16S rRNA gene sequences comparison. A total of 20 healthy adult scallops were collected from each location twice, in spring and autumn, 2015 and 2016, respectively. Fecal pellets from the distal intestinal tract of each individual were extracted, and after pooling, samples were cultivated on general and selective media following standard culture conditions. In order to prevent duplicate sequencing of the ribosomal 16S rRNA gene sequences of the isolates, a pre-screened step by (rep-PCR) amplification utilizing BOXA1R primer was performed, then isolates showing different banding profiles were selected for further sequencing. Taxonomic distribution based on the 16S rRNA gene comparison of selected strains placed isolates from IB and SB into 29 and 27 different genera, representing 50 and 42 species, respectively. The major proportions of bacterial species found in IB corresponded to the division Firmicutes (46%), whereas the Proteobacteria and Firmicutes were almost equally distributed in (SB) with 38 and 43% respectively. Remarkable, (IB) showed a high number (28%) and diversity of species within the division Actinobacteria compared to (SB); while the species Salinimicrobium sp. of the division Flavobacteria was isolated only in (SB). Common species in both areas are mainly related to the genus Bacillus, while strains of species Vibrio alginolyticus and V. parahaemoliticus were common representatives of the Proteobacteria. The intestinal tract of A. purpuratus may represent an uninvestigated niche for analyzing the structure of new complex microbial communities. This study showed that the diversity of culturable microbiota within the gut of two populations of A. purpuratus is significantly different at each location.