Project name: cyanobiont of Ornithocercus magnificus

Description: Pelagic heterotrophic dinoflagellates of the genus Ornithocercus are long-known to host cyanobacteria as symbionts (also known as phaeosomes) within their specialized chambers enclosed by developed theca plates. In spite of the fact that earlier observations of the symbiosis can be traced back to over 100 years ago, the detailed nature of cyanobacteria surviving in the chambers has been remained poorly understood. In this project, we sequenced the genome of the symbiotic cyanobacteria isolated from a dinoflagellate Ornithocercus magnificus to understand the genetic feature of the symbiont. The genome sequence revealed that the cyanobacterium represents an underdescribed lineage within an extensively studied major marine cyanobacterial group. This cyanobacterial lineage was shown to be globally distributed and strictly co-exists with the host dinoflagellates through our metagenomic analyses, suggesting the lineage is specifically inhabiting inside the chambers of the host dinoflagellates. Furthermore, comparative analysis of protein repertoire with its cyanobacterial relatives indicated that this lineage has been independently experienced the reductive genome evolution as the same extent as Prochlorococcus, known to have the most reduced genome among free-living cyanobacteria. Discovery of this cyanobacterial lineage hidden by the symbiotic lifestyle provides crucial insight into diversity, ecology and evolution of the marine cyanobacteria.

Data type: Genome sequencing and assembly

Sample scope: Multiisolate

Relevance: Environmental

Release date: 2019-08-01

Last updated: 2018-12-10