Ostreococcus tauri

Ostreococcus tauri was discovered in 1994 in the Thau lagoon, France, in a year-long study of the picoplankton population of the lagoon using flow cytometry. O. tauri was found to be the main component of the picoplankton population in the lagoon, and images of cells produced by transmission electron microscopy revealed the smallest yet described free-living eukaryotic cells. ==Anatomy==

Cells are roughly spherical (coccoid), averaging about 1 μm long by 0.7 μm wide. The cell's ultrastructure is very simple, lacking a cell wall and consisting of a nucleus, a single mitochondrion, a single chloroplast, and a single Golgi apparatus. Cells also lack flagella. Initially described as containing 14 chromosomes, it is now known that the nucleus contains 20 chromosomes, in all about 33 fg of DNA. ==Ecology==

Ostreococcus tauri is the dominant algal species, by cell abundance, in the Thau Lagoon in the south of France. The conditions that are thought to lead to this dominance are firstly that the Lagoon is used for intensive mollusc cultivation, and secondly that copper levels in the Lagoon are high. The first consideration selects for smaller cells (picoplankton); larger eukaryotic species of alga and many predators of smaller algae are preferentially consumed by the molluscs, which are filter feeders. The second consideration selects against cyanobacteria, as O. tauri is thought to cope better with "adverse conditions". The excess copper in the lagoon is thought to originate from agricultural chemicals used by surrounding vineyards. ==Use as a model organism==

As early as 1998, O. tauri was identified as "a good candidate for biological models such as cell division and/or genome sequencing studies". ==Cryptic sex==

When grown in the laboratory, O. tauri cells are haploid. Although no sexual life cycle has been described, the occurrence of cryptic sex is indicated by the expression of core genes for meiosis. Sexual exchanges, as indicated by formation of genetic recombinants, appear to occur, but are infrequent. ==Genomics ==

In 2006, the O. tauri genome was sequenced by Derelle et al. ==References==