Bacterial and viral diversity of sea squirts(Halocynthia roretzi) and sea urchins(Anthocidaris crassispina)

Abstract

Many studies for microbial diversities in marine environment have been performed so far, but bacterial and viral diversity in marine invertebrates has not been understood much. In this study, phylogenetic diversity of bacteria and genetic diversities of viruses in the intestines of sea squirts and sea urchins were investigated through metagenomics. DNA purified from intestines was amplified using barcoded primers (27F and 518R). PCR products were subjected to 454 pyrosequencing and the sequences were analyzed using QIIME. As a result, sea squirts are dominated by Faecalibacterium and Trichococcus. However, sea urchins are different each of the samples ; SU1 is dominant Crocinitomix, SU2 is dominant Desulfotalea, SU3 is dominant Pleurocapsa and Parvularcula. Viruses were collected through sequential filtration and their abundance ranged from 107 to 108 per gram of intestinal content. Viral DNA was extracted and amplified with multiple displacement amplification method using the phi29 DNA polymerase and was analyzed by pyrosequencing. Results showed that three double stranded DNA viral families including Podoviridae (35%, 44%), Siphoviridae (22%, 18%), Myoviridae (18%, 22%), and four single stranded DNA viral families including Microviridae (5%, 65%), Circoviridae (3%, 2%), Nanoviridae (0.3%, 0.07%), Geminiviridae (0.5%, 0.1%) dominated in sea squirts and urchins. Many sequences of the viromes were novel and distantly related to the previously known viruses.