From Genomics to Microbial Physiology: Exploring adaptability of Cyclobacterium marinum Atlantic-IS to various C-source in oligotrophic environment

The majority of microbial biodiversity in the ocean lies within the realm of the rare biosphere. These rare microbes contribute to the ecology and carbon cycling that differ substantially from abundant species. Based on their growth patterns they are grouped as copiotrophic or oligotrophic bacteria. Of the phylum Bacteroidetes and the class Flavobacteria, the genus Cyclobacterium gets its name from its members’ circular-like morphology. Cyclobacterium are gram-negative, non-motile heterotrophs that have been isolated from various marine and sediment environments. We have successfully cultured a rare bacterium, Cyclobacterium marinum Atlantic-IS, from the Atlantic slope at the depth of 258 meters and presume it to be a conditional copiotroph. It is capable of growing in hypersaline Artificial Seawater Media supplemented with increasing NaCl up to 12%. The draft genome length is 6,156,343 bps, comprising 136 contigs (N50 = 314,733, L50 = 8), with an average GC content of 38.46%. Based on annotation by NCBI’s Prokaryotic Genome Annotation Pipeline (PGAP), the assembly contains 4,690 complete coding-sequence predictions, 37 tRNAs, and 75 pseudogenes. This large genome is packed into a small <1μm compact coiled shape cell. Cyclobacterium has relatively higher number of sigma factor and anti-factor (~88), which typically range from 12-18, are pivotal for the generation of swift and adapted metabolic response to fluctuating environmental conditions. However, the large genome and a range of regulatory factors potentially provide strategies to utilize a diverse range of C- source for growth and enhance its adaptability.