Chlorosome

As Chlorosomes (χλωρός of ancient Greek, Chloros - bright green, fresh and σῶμα soma - body) are intracellular organelles photosynthesis operator acting green sulfur bacteria and green non-sulfur bacteria called (Chloroflexi).
Chlorosomes are rectangular to ellipsoidal structures with a length of 100 to 200 nm, 50 to 100 nm wide and 15 to 30 nm high. They mainly contain bacteriochlorophylls (c, d or e) as well as smaller amounts of carotenoids and quinones and are surrounded by a non-unit membrane (a galacto-lipid layer with different proteins). Functionally, the chlorosomes form a photosynthetic antenna complex that is used to absorb light. The chlorosomes are connected to the reaction centers in the cell membrane by FMO proteins . Here, the absorbed light energy is converted into chemical energy ( ATP ). Compared to similar structures in other phototrophic organisms, chlorosomes are relatively large and are characterized by the lack of a protein matrix that supports the arrangement of the photosynthetic pigments. Current models that describe the organization of bacteriochlorophyll and carotenoids in the chlorosomes assume that the pigments are arranged in layers, in which the farnesol tails of the bacteriochlorophyll interact with one another and with the carotenoids. This creates a structure that corresponds to a lipid multilayer.

Examples of bacteria that contain chlorosomes:

• Chlorobiaceae
  • Chlorobium tepidum
  • Chlorobium phaeobacteroides
  • Chlorobium phaeovibrioides
  • Chlorobium vibrioforme
  • Chlorobium limicola
  • Pelodictyon lutoleum
  • Prostecochloris aestuarii

• Chloroflexi
  • Chloroflexus aurantiacus
  • Chloroflexus aggregans

• Oscillochloridaceae
  • Oscillochloris trichoides
  • Chloronema giganteum

The absorption of light with the help of chlorosomes is very effective. Green sulfur bacteria therefore get by with little light and can still live in water depths that are no longer suitable for many other phototrophic organisms.