Cultivation of new marine Verrucomicrobia subgroups at the ocean surface and Genome Sequence of the Strain IMCC8625

초록

The phylum Verrucomicrobia, one of the primary lineages in the domain Bacteria, inhabits diverse habitats, primarily terrestrial environments. Several recent studies have shown that members of the Verrucomicrobia are present everywhere in marine surface environments albeit their low densities. However, very limited cultured isolates have been reported for the marine Verrucomicrobia group. In this study, we report the isolation and characterization of 65 novel marine strains that are affiliated with the distinct phylogenetic lineages of the order Puniceicoccales in the Verrucomicrobia. Dilution-to-extinction culturing and 16S rRNA gene-pyrosequencing analysis for bacterial community were applied to surface seawater samples that were collected from the East Sea every month of 2009. A majority of the verrucomicrobial strains were isolated in August and September when the abundance of the Verrucomicrobia reached their highest levels as revealed by pyrosequencing. Notably, 38.9% of the pyrosequencing reads classified as the phylum Verrucomicrobia showed more than 99% 16S rRNA gene sequence similarities with the verrucomicrobial strains cultured in this study, demonstrating that abundant groups of the Verrucomicrobia in the East Sea were successfully isolated by the dilution-to-extinction culturing. Phylogenetic analyses showed that most of the isolates formed 3 distinct groups within the Puniceicoccales: MPG (Marine Puniceicoccaceae Group)-1 (31 strains), MPG-2 (17 strains), and MPG-3 (16 strains). Specific growth rates (μ) at different temperatures and varying carbon concentrations were different for the representative strains of three MPGs. Similarly, strains of each MPG showed clear differences in physiological characteristics including colony-forming abilities and fatty acids compositions. Among the verrucomicrobial strains isolated in this study, a draft genome sequence of strain IMCC8625, a member of the MPG-3, was determined by Illumina sequencing. The 2,843,603