Chlorosome

A Chlorosome is a photosynthetic antenna complex found in green sulfur bacteria (GSB) and some green filamentous anoxygenic phototrophs (FAP) (Chloroflexaceae, Oscillochloridaceae). They differ from other antenna complexes by their large size and lack of protein matrix supporting the photosynthetic pigments. Chlorosomes are ellipsoidal bodies, in GSB their length varies from 100 to 200 nm, width of 50-100 nm and height of 15 - 30 nm ^[1], in FAP the chlorosomes are somewhat smaller.

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Inside the bacteria, GSB chlorosomes are thought to be attached to the reaction centers in the cell membrane via FMO-proteins and a chlorosome baseplate composed of csmA proteins. Chlorosomes from FAP lack the FMO complex. The composition of the chlorosomes is mostly bacteriochlorophyll with small amounts of carotenoids and quinones surrounded by a galactolipid monolayer with ten different proteins attached to it.

Current models of the structure of bacterichlorophyll and carotenoids (the main constituents) inside the chlorosomes put them in a lamellar organization, where the long farnesol tails of the bacteriochlorophyll intermix with carotenoids and each other, forming a structure resembling a lipid multilayer ^[2].

List of bacterial species containing chlorosomes

• Chlorobiaceae
  • Chlorobium limicola
  • Chlorobium phaeobacteroides
  • Chlorobium phaeovibrioides
  • Chlorobium vibrioforme
  • Chlorobium tepidum
  • Pelodictyon lutoleum
  • Prostecochloris aestuarii
• Chloroflexaceae
  • Chloroflexus aurantiacus
  • Chloroflexus aggregans
• Oscillochloridaceae
  • Oscillochloris trichoides
  • Chloronema giganteum
• Acidobacteriaceae
  • Chloracidobacterium thermophilum^[3]

Notes

1. ^ A Martinez-Planells et al.: Determination of the topography and biometry of chlorosomes by atomic force microscopy, Photosynthesis Research 71, 2002, p. 83-90 [1]
2. ^ J. Pšenčík et al.: Lamellar Organization of Pigments in Chlorosomes, the Light Harvesting Complexes of Green Photosynthetic Bacteria, Biophys J. 87(2), 2004, p. 1165–1172. [2]
3. ^ Bryant, Donald A. et al. (2007-07-27), " ", Science 317 (5837): 523-526,