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Cafeteria roenbergensis is a single-celled flagellate from marine environments. It is D-shaped, and about 5-10 µm and has a volume of about 20 µm 3(where 1 µm, a micron, is one-thousandth of a millimeter). It is a eukaryotic organism, with a nucleus, mitochondria and other subcellular compartments. The posterior flagellum attaches the organism to the substrate while it is feeding. If it detaches, the cell will swim around being pulled forward by the beating of the anterior flagellum. When feeding, the action of the anterior flagellum creates a current of water that moves towards the cell. The current carries bacteria, and these are the primary food of the flagellate. The food is ingested below the base of the flagella – this is referred to as the ventral side. The flagella are anchored by ‘rootlets’ ribbons and subcellular ropes. They act as a skeleton and also support the mouth region. Cafeteria roenbergensis was the first species in the genus to be described, and was described only in 1988. It, like many other smaller members of the ocean communities, had largely been overlooked until the 1980s. At that time, it became increasingly evident that bacteria and the organisms that eat them play a very major role in moving food, nutrients and energy in marine ecosystems. As ocean environments are the only environments in which there is a net burial of carbon, a number of major research projects emerged in the1980s to improve our understanding of marine ecosystems typically within the context of global climate change. Cafeteria roenbergensis occurs in all oceans in which they have been looked for, and can grow to very high concentrations (in excess of 10,000 per ml). They are weeds, growing rapidly when food is available and under a reasonably wide range of conditions. It is usually assumed that this species serves as food for larger protozoa or small invertebrate animals, but recent work suggests that the populations are also ‘controlled’ by viruses. Because they are easy to grow, Cafeteria roenbergensis has been subject to a diversity of more detailed studies, such as genomic and ecological studies. From these studies come useful gems such that the mitochondria of all eukaryotes studied, this species have the most functionally compact DNA – with only 3.4% not being used for coding purposes (Hauth et al. 2005).
The name Cafeteria reflects the importance of this organism in marine microbial food webs.