Chaetosphaeridium globosum

Chaetosphaeridium globosum
Scientific classification
Kingdom:	Plantae
Division:	Streptophyta
Order:	Coleochaetales
Family:	Chaetosphaeridiaceae
Genus:	Chaetosphaeridium
Species:	C. globosum
Binomial name
Chaetosphaeridium globosum (Nordstedt) Klebahn 1893[1][2][3]

Chaetosphaeridium globosum is a one-celled algae which is thought to represent an ancient lineage of the green plants. This organism exists in a filamentous form with one flagella per cell. It is a freshwater species. The flagellum is covered in scales in a 3-prong irregular shape called ‘maple leafs’. The cells are usually 11 to 18μm in diameter and with one pyrenoid. Each cell bears long bristle.^[4]

Researchers have found that the mitochondrial DNA of Chaetosphaeridium is markedly different than that of land plants, suggesting that the mitochondria of land plants evolved significantly after the common ancestor between them and living green algae.^[5] A very slight similarity exists between liverwort mtDNA and Chaetosphaeridium. The chloroplast DNA is markedly similar, however, indicating that a close relationship had existed between the Viridiplantae and the clade that includes Chaetosphaeridium. This seems to argue that chloroplasts in green plants originated in prehistoric green algae; the family which includes Chaetosphaeridium globosum.

Chloroplasts are known to be captured (symbiotic) cyanobacteria with their own genome. Part of this genome has been transferred to the nucleus and part has been retained in the chloroplast for the continuation of metabolic processes. This symbiosis, now proven by modern genomics, has shown us how Chaetosphaeridium globosum links ancient cyanobacteria with modern green plants like those in our garden.

References

1. ^ ITIS Standard Report Page: Chaetosphaeridium globosum
2. ^ http://www.europe.gbif.net/portal/ecat_browser.jsp?taxonKey=7240
3. ^ Algaebase :: Species Detail
4. ^ Guiry, M.D., John, D.M., Rindi, F. and McCarthy, T.K. (Edited) 2007. New Survey of Clare Island. Volume 6: The Freshwater and Terrestrial Algae. Royal Irish Academy. ISBN 978-1-904890-31-7
5. ^ Turmel, Monique. Otis, Christian. Lemieux, Claude (August 20, 2002), "The Chloroplast and Mitochondrial Genome Sequences of the Charophyte Chaetosphaeridium globosum: Insights into the Timing of the Events That Restructured Organelle DNAs Within the Green Algal Lineage That Led to Land Plants", PNAS 99 (17): 11275–11280, doi:10.1073/pnas.162203299, PMC 123247, PMID 12161560, http://www.pnas.org/content/99/17/11275.full 

• Hausmann, Klaus. Hülsmann, Norbert. Radek, Renate. Protistology. E.Schweizerbart’sche Verlagsbuchhandlung. Third edition. 2003
• Turmel, M. Otis, C. Lemieux, C. The Complete Chloroplast DNA Sequences of the Charophycean Green Algae Staurastrum and Zygnema Reveal that the Chloroplast Genome Underwent Extensive Changes During the Evolution of the Zygnemateles. BMC Biol 2005 Oct 20; 3:22.
• Raven, John. Allen, John. Genomics and Chloroplast Evolution: What did Cyanobacteria Do For Plants? Genome Biol. 2003; 4(3): 209