Heliobacteria

Heliobacteria are a unique subset of prokaryotic bacteria that process light for energy. Distinguishable from other phototrophic bacteria, they utilize a unique photosynthetic pigment, bacteriochlorophyll g and are the only known Gram-positive phototroph.[2] They are a key player in symbiotic nitrogen fixation alongside plants, and share a reaction center with green-sulfur bacteria.[3][4]

Heliobacteria
Scientific classification
Domain: Bacteria
Phylum: Bacillota
Class: Clostridia
Order: Eubacteriales
Family: Heliobacteriaceae
Madigan & Asao 2010
Genera[1]
  • Heliobacillus
  • Heliobacterium
  • "Ca. Helioclostridium"
  • Heliomicrobium
  • "Ca. Heliomonas"
  • Heliophilum
  • Heliorestis

RNA trees place the heliobacteria among the Bacillota.[5] They have no outer membrane and like certain other Bacillota (Clostridia), they form heat-resistant endospores, which contain high levels of calcium and dipicolinic acid. Heliobacteria are the only Bacillota known to be phototrophic.

Metabolism

The heliobacteria are phototrophic: they convert light energy into chemical energy using a type I reaction center.[6][7] 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.[5] Phototrophic processes take place at the cell membrane, which does not form folds or compartments as it does in purple bacteria. Though heliobacteria are phototrophic, they can create energy without light using pyruvate fermentation, which generates significantly less energy than it could with light.[8]

Heliobacteria are photoheterotrophic, requiring organic carbon sources, and they are exclusively anaerobic.[5] Bacteriochlorophyll g is inactivated by the presence of oxygen, making them obligate anaerobes (they cannot survive in aerobic conditions). Heliobacteria have been found in soils,[9] hot springs,[10] soda lakes[11][12] and are common in the waterlogged soils of paddy fields.[9] They are avid nitrogen fixers, so are probably important in the fertility of paddy fields.[9] Heliobacteria are mainly terrestrial phototrophs, contrary to the multitudes of others that are aquatic, and often form mutualistic relationships with the plants near them.[13]

Taxonomy

Heliobacteria should not be confused with Helicobacter, which is a genus of bacteria with quite different characteristics.

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[14] and National Center for Biotechnology Information (NCBI)[15]

16S rRNA based LTP_01_2022[16][17][18] and 120 marker proteins based GTDB 07-RS207[19][20][21]
 
 

Heliorestis Bryantseva et al. 2000

 
 
 

Heliophilum Ormerod et al. 1996

 
 
 
 

Heliobacillus Beer-Romero and Gest 1998

 
 

Heliobacterium Gest and Favinger 1985

 
 
 

Heliomicrobium Kyndt et al. 2021

 
 
 
 

See also

References
  1. [Madigan M T, Martinko J M, Dunlap P V, Clark D P. (2009). Brock Biology of Microorganisms 12th edition, p. 453-454].
  2. Sattley, W. Matthew; Swingley, Wesley D. (2013-01-01). "Properties and Evolutionary Implications of the Heliobacterial Genome". Advances in Botanical Research. 66: 67–97. doi:10.1016/B978-0-12-397923-0.00003-5. ISBN 9780123979230. ISSN 0065-2296.
  3. Jagannathan, B.; Golbeck, J.H. (2013-01-01). "FX, FA, and FB Iron–Sulfur Clusters in Type I Photosynthetic Reaction Centers". Encyclopedia of Biological Chemistry. pp. 335–342. doi:10.1016/B978-0-12-378630-2.00184-5. ISBN 9780123786319.
  4. Jagannathan, B.; Golbeck, J.H. (2009-01-01). "Photosynthesis: Microbial". Encyclopedia of Microbiology. pp. 325–341. doi:10.1016/B978-012373944-5.00352-7. ISBN 9780123739445.
  5. Blankenship, Robert (2014). Molecular Mechanisms of Photosynthesis. Wiley-Blackwell. p. 19. ISBN 978-1405189750.
  6. Heinickel and Golbeck 2007
  7. Gisriel, Christopher; Sarrou, Iosifina; Ferlez, Bryan; Golbeck, John H.; Redding, Kevin E.; Fromme, Raimund (2017-07-27). "Structure of a symmetric photosynthetic reaction center–photosystem". Science. 357 (6355): 1021–1025. Bibcode:2017Sci...357.1021G. doi:10.1126/science.aan5611. ISSN 0036-8075. PMID 28751471.
  8. "Fermentation, mitochondria and regulation | Biological Principles". bioprinciples.biosci.gatech.edu. Retrieved 2021-04-26.
  9. Madigan, Michael T.; Ormerod, John G. (1995), Blankenship, Robert E.; Madigan, Michael T.; Bauer, Carl E. (eds.), "Taxonomy, Physiology and Ecology of Heliobacteria", Anoxygenic Photosynthetic Bacteria, Advances in Photosynthesis and Respiration, Springer Netherlands, pp. 17–30, doi:10.1007/0-306-47954-0_2, ISBN 9780306479540
  10. Kimble, Linda K.; Mandelco, Linda; Woese, Carl R.; Madigan, Michael T. (1995-04-01). "Heliobacterium modesticaldum, sp. nov., a thermophilic heliobacterium of hot springs and volcanic soils". Archives of Microbiology. 163 (4): 259–267. doi:10.1007/BF00393378. ISSN 1432-072X. S2CID 5551453.
  11. Asao, Marie; Jung, Deborah O.; Achenbach, Laurie A.; Madigan, Michael T. (2006-10-01). "Heliorestis convoluta sp. nov., a coiled, alkaliphilic heliobacterium from the Wadi El Natroun, Egypt". Extremophiles. 10 (5): 403–410. doi:10.1007/s00792-006-0513-4. ISSN 1433-4909. PMID 16628377. S2CID 6885589.
  12. Bryantseva, Irina A.; Gorlenko, Vladimir M.; Kompantseva, Elena I.; Achenbach, Laurie A.; Madigan, M. T. (1999-08-01). "Heliorestis daurensis, gen. nov. sp. nov., an alkaliphilic rod-to-coiled-shaped phototrophic heliobacterium from a Siberian soda lake". Archives of Microbiology. 172 (3): 167–174. doi:10.1007/s002030050756. ISSN 1432-072X. PMID 10460887. S2CID 22557416.
  13. Asao, Marie; Madigan, Michael T. (June 2010). "Taxonomy, phylogeny, and ecology of the heliobacteria". Photosynthesis Research. 104 (2–3): 103–111. doi:10.1007/s11120-009-9516-1. ISSN 1573-5079. PMID 20094790. S2CID 10052124.
  14. J.P. Euzéby. "Heliobacteriaceae". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2022-09-09.
  15. Sayers; et al. "Heliobacteriaceae". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2022-09-09.
  16. "The LTP". Retrieved 23 February 2022.
  17. "LTP_all tree in newick format". Retrieved 23 February 2022.
  18. "LTP_01_2022 Release Notes" (PDF). Retrieved 23 February 2022.
  19. "GTDB release 07-RS207". Genome Taxonomy Database. Retrieved 20 June 2022.
  20. "bac120_r207.sp_labels". Genome Taxonomy Database. Retrieved 20 June 2022.
  21. "Taxon History". Genome Taxonomy Database. Retrieved 20 June 2022.

Further reading
  • 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 12th edition, p. 453-454
  • Heinnickel M & Golbeck J H (2007) Photosynthesis Research 92:35-53
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