Heliobacteriaceae

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Heliobacteriaceae
Systematics
Domain : Bacteria (bacteria)
Department : Firmicutes
Class : Clostridia
Order : Clostridiales
Family : Heliobacteriaceae
Scientific name
Heliobacteriaceae
Madigan & Asao 2010
Genera
  • Heliobacillus Beer-Romero & Gest 1998
  • Heliobacterium Gest & Favinger 1985
  • Heliophilum Ormerod et al. 1996
  • Heliorestis Bryantseva et al. 2000

The Heliobacteriaceae family includes bacteria that are exclusively anaerobic and anoxygenic photoheterotroph (see photosynthesis ) and whose cell wall structure is similar to that of Gram-positive bacteria, although they are not positively stained according to Gram . Their bacteriochlorophyll g is characteristic with a main absorption maximum at 790 nm.

The cell wall of the Heliobacteriaceae consists of multilayered peptidoglycan without an outer membrane . Some species form heat-resistant endospores with a high content of calcium and dipicolinic acid like the endospores of the other Clostridia . The bacteria are cylindrical, curved or helical, some swim by means of peritrich flagella , some move by sliding.

physiology

The bacteria have a type (1) membrane electron transport system with an RC-1 photosystem with bacteriochlorophyll g (P798), bound cytochromes , a cytochrome bc 1 complex and an iron-sulfur protein . The photosystem is located in the cell membrane , membrane systems inside the cytoplasm are not present. The bacteria are photoheterotrophic , so they need organic substances (they have neither a Calvin cycle nor a reverse citric acid cycle ). Even in the dark they can grow with organic substances ( chemotrophy ). You can assimilate elemental , molecular nitrogen ( N 2 fixer ).

ecology

Heliobacteriaceae occur in anoxic soils , especially in soils that are periodically or permanently flooded with water, for example in rice fields . They can grow under mats made of cyanobacteria , as they can use the light that falls through and is not absorbed by the cyanobacteria due to the special absorption spectrum based on chlorophyll g .

Significance for the evolution of photosynthesis

A comparison of the amino acid sequences of proteins from different bacteria suggests that Heliobacteriaceae were the first phototrophic creatures. For their phototrophy they use an iron-sulfur reaction center of the type RC-1. Phototrophic bacteria that appear later, the green non-sulfur bacteria (e.g. Chloroflexus ), have a phaeophytin - quinone reaction center of the type RC-2. Only later did the cyanobacteria develop. Using both reaction centers , they were able to carry out oxygenic photosynthesis for the first time with two-stage use of light energy and water as an electron donor .

Genera, species

literature

  • George Garrity (ed.): Bergey's manual of systematic bacteriology , Volume 3: The low G + C Gram Positives . 2nd Edition. Springer-Verlag, New York et al. O. 2008, ISBN 978-0-387-95041-9 .
  • Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer, Erko Stackebrandt: The prokaryotes , 3rd edition, Volume 3: Archaea, Bacteria: Firmicutes, Actinomycetes . Springer-Verlag, New York et al. O. 2006, ISBN 978-0-387-25493-7 (print), ISBN 978-0-387-30747-3 (online), doi : 10.1007 / 0-387-30743-5
  • Robert E. Blankenship, MT Madigan, C. Bauer (Eds.): Anoxygenic photosynthetic bacteria . Kluwer Acad. Publ., Dordrecht, Boston 1995, ISBN 0-7923-3681-X

Web links

Individual evidence

  1. ↑ Radhey S. Gupta, Tariq Mukhtar, Bhag Singh: `` Evolutionary relationship among photosynthetic prokaryotes (Heliobacterium chlorum, Chloroflexus aurantiacus, cyanobacteria, Chlorobium tepidum and proteobacteria): impications regarding the origin of photosynthesis. '' In: Molecular Microbiology. Vol. 32, 1999, pp. 893-906. ISSN  0950-382X