Micromonas sp. RCC299 v3.0


Photo: Worden lab (A.Z. Worden)

Micromonas is a eukaryotic, photosynthetic microorganism found throughout marine ecosystems - from polar waters to the tropics. It is classified as a member of the picophytoplankton because of its small size (< 2 µm in diameter). Currently, picophytoplankton are known to be important to primary production, but the individual contributions of each of the different groups, or species (with Micromonas being one of those), aren't well known. To date, Micromonas strains have been described as belonging to a single species. Micromonas pusilla was reported as early as 1951 to be highly abundant in marine systems (Knight-Jones & Walne 1951). However, it is likely that the designation Micromonas pusilla harbors several different (cryptic) species (Slapeta et al. 2006, Worden 2006). Genome sequences from different strains of this organism will help to answer such questions.

Micromonas is a common member of marine phytoplankton communities and the genome sequences are aiding our understanding of the environmental success of these picophytoplankton. The genome is also helpful to those working on the evolution of higher plants. Micromonas belongs to the Prasinophyceae which are ancient members of the green lineage, the lineage giving rise to higher plants. Plants of the green lineage currently dominate terrestrial plant biomass. In terms of its biology, Micromonas is a fast swimmer and, unlike many members of the Prasinophyceae, does not have scales on its cell surface.

Micromonas strain RCC299 was isolated in 1998 during a research cruise in the Equatorial Pacific. Subsequently it was rendered clonal and axenic in 2005. RCC299 (also known as NOUM17) was chosen for complete genome sequencing because it was isolated from tropical waters (equatorial Pacific) in contrast to another strain that is being sequenced (CCMP1545) which was isolated from temperate coastal waters, and belongs to a different phylogenetic clade.

The original strain that was prepared for genome sequencing is available from the Roscoff Culture Collection (where it is designated RCC299). The axenic, clonal culture has now been deposited at the Center for Culture of Marine Phytoplankton (where it is designated CCMP2709). For more information on isolation sites, phylogeny, medias and growth conditions for this strain go to PrasinoSite.

Publication: Green Evolution and Dynamic Adaptations Revealed by Genomes of the Marine Picoeukaryotes Micromonas. Science. 2009 April 10;324(5924):268-272

References

Knight-Jones E.W. & P.R. Walne (1951) Chromulina pusilla Butcher, a dominant member of the ultraplankton. Nature. Vol. 167:445-446.

Slapeta J., López-García P. & D. Moreira (2006) Global Dispersal and Ancient Cryptic Species in the Smallest Marine Eukaryotes. Molecular Biology & Evolution. Vol. 23:23-29.

Worden A.Z. (2006) Picoeukaryote diversity in coastal waters of the Pacific Ocean. Aquatic Microbial Ecology. Vol. 43:165-175.