Isolation and identification of bacterial endosymbionts of the brooding brittle star Amphipholis squamata

• Main Authors: Tedford, Abbey Rose, Lesser, Michael P, Morrow, Kathleen M
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2016
• Subjects: Amphipholis; squamata; brittle; echinoderm; endosymbiotic; bacteria; Biology; Life Sciences; Marine Biology; Microbiology; Northwest Atlantic
• Online Access: https://scholars.unh.edu/urc/3; https://scholars.unh.edu/cgi/viewcontent.cgi?article=1004&context=urc

Symbiotic relationships with subcuticular bacteria (SCB) have been identified and studied in numerous echinoderms, but have not been examined using current sequencing technologies in the brooding brittle star, Amphipholis squamata. Previously, A. squamata SCB were placed in the genus Vibrio (γ-Proteobacteria), but recent evidence suggests the SCB is primarily composed of α-Proteobacteria. The present study clarifies the taxonomic composition of SCB associated with A. squamata from the Northwest Atlantic. Isolated gDNA was amplified using 16S rRNA gene-targeted PCR and sequenced on an Illumina HiSeq at the UNH Genomics Center. Results suggest the presence of a single dominant bacterial type within the family Rhodobacteraceae, which composes 70-80% of the A. squamata microbiome. The majority of sequences within Rhodobacteraceae were identified as members of the genus Octadecabacter (97% similarity). By comparison, adjacent seawater and sediment support significantly more diverse bacterial communities, with members in the phyla Proteobacteria, Bacteroidetes, Cyanobacteria, Verrucomicrobia, and Actinobacteria. Thus, distinct SCB communities are clearly evident in A. squamata. Although metatranscriptomic study is needed to characterize specific functions within the SCB community, we have identified a discrete and potentially beneficial symbiont that may support metabolic requirements and nutrient uptake vital to the reproduction of A. squamata.