Photo: Takashi Yamada, Hiroshima University.

Genomes of two microalgae - the free-living Coccomyxa sp.C-169 and the symbiotic Chlorella sp. NC64A - were sequenced to identify features required for free-living vs. symbiotic lifestyles via comparative genome analysis. Lipids produced by these organisms may be an attractive candidate for biofuels. Novel cellulose degrading enzymes from chlorella may be useful in ethanol production from corn stover and switchgrass. Also C-169 has an enzyme-digestible cell wall, which makes it an attractive research subject over some other strains.

The C-169 genome consists of 16 chromosomes ranging from 980 kb to 4 Mb (Higashiyama & Yamada, 1991). Certain repeat elements may be involved in the repair and maintenance of chromosome breaks and stabilizing telomeres (Higashiyama et al., 1997), since they were found to accumulate at the newly formed telomeric regions in broken chromosomes by irradiation with electron beams (Yamamoto et al., 2003). Thus, C-169 can serve as a model to study chromosome repair from irradiation.

Despite morphological similarities between these organisms, genome analysis suggests that these these 2 chlorellae are evolutionary further apart than it was anticipated initially, and that Chlorella vulgaris clearly belongs to the Coccomyxa genus.