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Heliobacteria: Wikis

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From Wikipedia, the free encyclopedia

Heliobacteria
Scientific classification
Kingdom: Bacteria
Phylum: Firmicutes
Class: Clostridia
Order: Clostridiales
Family: Heliobacteriaceae
Genera

Heliobacterium
Heliobacillus
Heliophilum
Heliorestis

The heliobacteria are phototrophic, that is to say, they convert light energy into chemical energy by photosynthesis; they use a PSI type reaction center. The primary pigment involved is bacteriochlorophyll g, which is unique to the group and has a unique absorption spectrum; this gives the heliobacteria their own environmental niche. Phototrophy takes place at the cell membrane, which does not form folds or compartments as it does in purple phototrophic bacteria. Even though heliobacteria are phototrophic, they can grow without light by fermentation of pyruvate.

RNA trees place the heliobacteria among the Firmicutes but they do not stain gram-positively. They have no outer membrane and like certain other firmicutes (clostridia) they form heat resistant endospores, which contain high levels of calcium and dipicolinic acid. Heliobacteria are the only firmicutes known to conduct photosynthesis.

Heliobacteria are photoheterotrophic, requiring organic carbon sources, and they are exclusively anaerobic. So far heliobacteria have only been found in soils, and are apparently widespread in the waterlogged soils of paddy fields. They are avid nitrogen fixers and are therefore probably important in the fertility of paddy fields.

References

  • Gest H & Favinger J L (1983) Arch Microbiol 136:11-16.
  • Madigan M T (1992) In Balows et al. (eds) The Prokaryotes pp. 1981-1992 Springer New York.
  • Madigan M T & Ormerod J G (1995) In Blankenship et al. (eds) Anoxygenic Photosynthetic Bacteria pp 17-30. Kluwer Academic Publishers New York.
  • Ormerod J G et al. (1996) Arch Microbiol 165:226-234.
  • Madigan M T, Martinko J M, Dunlap P V, Clark D P. (2009). Brock Biology of Microorganisms 12-th edition p. 453-454

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