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 CCMP1545 was isolated from temperate coastal waters near Plymouth, England (North Atlantic/English Channel waters). This is in contrast to the environment from which another strain that is being sequenced (MicromonasRCC299) was isolated. RCC299 was isolated from tropical waters (equatorial Pacific). Micromonas strain CCMP1545 was isolated in 1950 and rendered axenic in 1992.
The axenic CCMP1545 culture is available at the Center for Culture of Marine Phytoplankton. For more information on isolation sites, phylogeny, medias and growth conditions for this strain go to PrasinoSite.