Heliobacteria
{{Short description|Family of bacteria}}
{{Distinguish|Helicobacter}}
{{Automatic taxobox
| name = Heliobacteriaceae
| taxon = Heliobacteriaceae
| authority = Madigan & Asao 2010
| subdivision_ranks = Genera
| subdivision_ref = [Madigan M T, Martinko J M, Dunlap P V, Clark D P. (2009). Brock Biology of Microorganisms 12th edition, p. 453-454].
| subdivision =
}}
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.{{Cite journal|date=2013-01-01|title=Properties and Evolutionary Implications of the Heliobacterial Genome|url=https://www.sciencedirect.com/science/article/pii/B9780123979230000035|journal=Advances in Botanical Research|language=en|volume=66|pages=67–97|doi=10.1016/B978-0-12-397923-0.00003-5|issn=0065-2296|last1=Sattley |first1=W. Matthew |last2=Swingley |first2=Wesley D. |isbn=9780123979230 |url-access=subscription}} They are a key player in symbiotic nitrogen fixation alongside plants, and use a type I reaction center like green-sulfur bacteria.{{Cite book|date=2013-01-01|chapter=FX, FA, and FB Iron–Sulfur Clusters in Type I Photosynthetic Reaction Centers|chapter-url=https://www.sciencedirect.com/science/article/pii/B9780123786302001845|language=en|pages=335–342|doi=10.1016/B978-0-12-378630-2.00184-5|title=Encyclopedia of Biological Chemistry |last1=Jagannathan |first1=B. |last2=Golbeck |first2=J.H. |isbn=9780123786319 }}{{Cite book|date=2009-01-01|chapter=Photosynthesis: Microbial|chapter-url=https://www.sciencedirect.com/science/article/pii/B9780123739445003527|language=en|pages=325–341|doi=10.1016/B978-012373944-5.00352-7|title=Encyclopedia of Microbiology |last1=Jagannathan |first1=B. |last2=Golbeck |first2=J.H. |isbn=9780123739445 }}
RNA trees place the heliobacteria among the Bacillota. 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.Heinickel and Golbeck 2007{{Cite journal|last1=Gisriel|first1=Christopher|last2=Sarrou|first2=Iosifina|last3=Ferlez|first3=Bryan|last4=Golbeck|first4=John H.|last5=Redding|first5=Kevin E.|last6=Fromme|first6=Raimund|date=2017-07-27|title=Structure of a symmetric photosynthetic reaction center–photosystem|journal=Science|volume=357|issue=6355|language=en|pages=1021–1025|doi=10.1126/science.aan5611|issn=0036-8075|pmid=28751471|bibcode=2017Sci...357.1021G|doi-access=free}} 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.{{Cite book|title=Molecular Mechanisms of Photosynthesis|author1-link=Robert E. Blankenship|last=Blankenship|first=Robert|publisher=Wiley-Blackwell|year=2014|isbn=978-1405189750|pages=19}} 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.{{Cite web|title=Fermentation, mitochondria and regulation {{!}} Biological Principles|url=https://bioprinciples.biosci.gatech.edu/07-fermentation-mitochondria-and-regulation/|access-date=2021-04-26|website=bioprinciples.biosci.gatech.edu|language=en-US}}
Heliobacteria are photoheterotrophic, requiring organic carbon sources, and they are exclusively anaerobic. 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,{{Citation|last1=Madigan|first1=Michael T.|title=Taxonomy, Physiology and Ecology of Heliobacteria|date=1995|work=Anoxygenic Photosynthetic Bacteria|pages=17–30|editor-last=Blankenship|editor-first=Robert E.|series=Advances in Photosynthesis and Respiration|publisher=Springer Netherlands|language=en|doi=10.1007/0-306-47954-0_2|isbn=9780306479540|last2=Ormerod|first2=John G.|editor2-last=Madigan|editor2-first=Michael T.|editor3-last=Bauer|editor3-first=Carl E.}} hot springs,{{Cite journal|last1=Kimble|first1=Linda K.|last2=Mandelco|first2=Linda|last3=Woese|first3=Carl R.|last4=Madigan|first4=Michael T.|date=1995-04-01|title=Heliobacterium modesticaldum, sp. nov., a thermophilic heliobacterium of hot springs and volcanic soils|journal=Archives of Microbiology|language=en|volume=163|issue=4|pages=259–267|doi=10.1007/BF00393378|s2cid=5551453 |issn=1432-072X}} soda lakes{{Cite journal|last1=Asao|first1=Marie|last2=Jung|first2=Deborah O.|last3=Achenbach|first3=Laurie A.|last4=Madigan|first4=Michael T.|date=2006-10-01|title=Heliorestis convoluta sp. nov., a coiled, alkaliphilic heliobacterium from the Wadi El Natroun, Egypt|journal=Extremophiles|language=en|volume=10|issue=5|pages=403–410|doi=10.1007/s00792-006-0513-4|pmid=16628377|s2cid=6885589 |issn=1433-4909}}{{Cite journal|last1=Bryantseva|first1=Irina A.|last2=Gorlenko|first2=Vladimir M.|last3=Kompantseva|first3=Elena I.|last4=Achenbach|first4=Laurie A.|last5=Madigan|first5=M. T.|date=1999-08-01|title=Heliorestis daurensis, gen. nov. sp. nov., an alkaliphilic rod-to-coiled-shaped phototrophic heliobacterium from a Siberian soda lake|journal=Archives of Microbiology|language=en|volume=172|issue=3|pages=167–174|doi=10.1007/s002030050756|issn=1432-072X|pmid=10460887|s2cid=22557416 }} and are common in the waterlogged soils of paddy fields. They are avid nitrogen fixers, so are probably important in the fertility of paddy fields. Heliobacteria are mainly terrestrial phototrophs, contrary to the multitudes of others that are aquatic, and often form mutualistic relationships with the plants near them.{{Cite journal|last1=Asao|first1=Marie|last2=Madigan|first2=Michael T.|date=June 2010|title=Taxonomy, phylogeny, and ecology of the heliobacteria|url=https://pubmed.ncbi.nlm.nih.gov/20094790/|journal=Photosynthesis Research|volume=104|issue=2–3|pages=103–111|doi=10.1007/s11120-009-9516-1|issn=1573-5079|pmid=20094790|s2cid=10052124 }}
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){{cite web |author=A.C. Parte |url=https://lpsn.dsmz.de/family/heliobacteriaceae |title=Heliobacteriaceae |access-date=2025-02-28 |publisher=List of Prokaryotic names with Standing in Nomenclature (LPSN) |display-authors=et al.}} and National Center for Biotechnology Information (NCBI).{{cite web |author=C.L. Schoch |url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=31984&lvl=3&lin=f&keep=1&srchmode=1&unlock |title=Heliobacteriaceae |access-date=2025-02-28 |publisher=National Center for Biotechnology Information (NCBI) taxonomy database |display-authors=et al.}}
See also
References
{{Reflist}}
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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