Heliobacteria
- Helio Bacillus Beer- Romero & Gest 1998
- Heliobacterium Gest & Favinger 1985
- Heliophilum Ormerod et al. 1996
- Heliorestis Bryantseva et al. 2000
Heliobacteriaceae bacteria in the family are summarized exclusively anaerobic and anoxygen photoheterotroph (see photosynthesis) and whose cell wall structure similar to that of Gram-positive bacteria, although they are not stained by Gram positive. Characteristic her bacteriochlorophyll g with a main absorption maximum at 790 nm
The cell wall of Heliobacteriaceae consists of an outer membrane without any multi-layered peptidoglycan. Some species form heat-resistant endospores with a high content of calcium and dipicolinic acid as the endospores of the other clostridia. The bacteria are cylindrical, curved or helically, some swim by means of peritrichous flagella, and some moves by sliding.
Physiology
The bacteria possess a type - ( 1) - membrane electron transport system with an RC -1 Photosystem with bacteriochlorophyll g ( P798 ), bound cytochromes, cytochrome bc1 complex and an iron-sulfur protein. Photosystem located in the cell membrane, membrane systems inside the cytoplasm are not present. The bacteria are photoheterotroph, that rely on organic materials ( they have neither one nor the Calvin cycle a reverse citric acid cycle ). Even in the dark they can grow with organic substances ( Chemotrophie ). You can elemental, molecular nitrogen assimilation (N2 - fixer).
Ecology
Heliobacteriaceae occur in anoxic soils, especially in periodically or continuously over impounded with water trays, for example in rice fields. You can grow under mats of cyanobacteria, as they can use the pass -catching, not absorbed by the cyanobacterial light because of the special chlorophyll g based absorption spectrum.
Importance for the evolution of photosynthesis
The comparison of amino acid sequences of the proteins of different bacteria suggests that Heliobacteriaceae were the first phototrophic organisms. Use for their phototrophy an iron -sulfur reaction center of the type RC -1. Probably later emerging phototrophic bacteria, the Greens Not sulfur bacteria (eg Chloroflexus ), have a phaeophytin - quinone reaction center of the type RC -2. Still later, only the cyanobacteria, which could operate using two reaction centers for the first time an oxygenic photosynthesis with two-stage light energy use and use of water as an electron donor developed.
Genera, species
- Heliobacterium Heliobacterium Chlorum Gest & Favinger 1985 ( type species )
- Heliobacterium gestii Ormerod et al. 1996
- Heliobacterium modesticaldum Kimble et al. 1996
- Heliobacterium sulfidophilum Bryantseva et al. 2001
- Heliobacterium undosum Bryantseva et al. 2001
- Helio Bacillus mobilis Beer- Romero & Gest 1998
- Heliophilum fasciatum Ormerod et al. 1996
- Heliorestis daurensis Bryantseva et al. 2000
- Heliorestis baculata Bryantseva et al. 2001