Endodermal epithelial cells of Hydra viridissima A99 showing intracellular Chlorella sp. A99 cells. Image under CC-BY 4.0 from Hamada, Mayuko, et al. "Metabolic co-dependence drives the evolutionarily ancient Hydra-Chlorella symbiosis." Elife 7 (2018): e35122.

The Chlorella sp. A99 genome assembly and gene models have not been determined by the JGI, but were downloaded from Okinawa Institute of Science and Technology on October 31, 2019.Please note that this copy of the genome is not maintained by OIST and is therefore not automatically updated. In order to allow comparative analyses with other algal genomes sequenced by the JGI, a copy of this genome is incorporated into PhycoCosm. The JGI Annotation Pipeline was used to add functional annotation to this genome.

Chlorella sp. A99 is an obligate endosymbiont of the cnidarian model system Hydra viridissima. The algal partner provides its host with the disaccharide maltose, while in turn receives nitrogen in the form of the amino acid glutamine (Hamada et al. 2018). The Hydra-Chlorella model system is widely used to investigate the evolution of the metazoan immune system and the phenomenon of photosymbiosis (Galliot 2012; Bosch 2013, 2014). Aside from being a model system for animal-algal symbiosis, algae from the genus Chlorella are widely used for biofuel production and multiple biotechnology applications (Krauss and Shihira 1965; Guccione et al. 2014). The ability to compare and contrast across multiple genomes from the genus Chlorella spanning many different lifestyles (free-living to symbiotic) would allow scientists to better understand the different genomic features related to successful utilization of this microalga.