Rhodocyclaceae

The Rhodocyclaceae form a family of gram-negative bacteria. These heard so far the only one to order Rhodocyclales from the class of beta- proteobacteria. This family includes many species that were formerly classified as Pseudomonadaceae, but according to the findings of the molecular phylogeny (eg, 16S rRNA sequences ) were considered not related to the classical Pseudomonas species.

Characteristics and ecology

The Rhodocyclaceae mainly include aerobic ( dependent on oxygen ) rod-shaped bacteria, which are characterized by versatile metabolic activities. Also, strictly anaerobic bacteria that can live only in the absence of oxygen and the metabolism as fermentation ( colloquially referred to as fermentation) apply, are to be found in this family, such as Propionibacter. The different types of Rhodocyclaceae are mobile mostly by flagella and are found in fresh water or in the soil. Some, like Zoogloea, are also present in wastewater and play an important role in the biological wastewater treatment in sewage treatment plants.

Nitrogen-fixing bacteria are also represented in this family. You can take the free, molecular nitrogen (N2, dinitrogen ) from the environment and further use in metabolism, an ability which is relatively widespread among bacteria, but absent in the plant and animal kingdom. Some of the nitrogen- fixer species form associations with different types of plants, such as rice and Kallargras ( Leptochloa fusca ) and supply it with nitrogen, others come free in the ground. The nitrogen-fixing species usually require microaerobic conditions (low oxygen content in the environment) to bind to the nitrogen.

At present, the possibility is investigated, Azoarcus use to improve rice production.

The eponymous genus Rhodocyclus is not typical for the group, as she is alone capable of anoxygenic photosynthesis under anaerobic conditions and belongs to the physiological group of non- sulfur purple bacteria. In addition, the type Rhodocyclus purpureus is characterized by unusual U-shaped to ring-shaped cells.

Nitrogen fixation

Among the nitrogen fixers Rhodocyclaceae include various types of soil occurring in Azoarcus, Azospira, Azovibrio and Azonexus. The prefix " azo " is of French " azote " (nitrogen) derived. Several of these species are associated with this plant and occur on the root surface, or within the root tissue ( endophytic ). However, it is here for the formation of specific structures as symbiotic with rhizobia, and various leguminous plants ( root nodules ) is the case. The types of Azoarcus are ecologically highly bound to the plants, as free in the soil outside of rhizosphere they have not been found. A free Kultuvierung laboratory after isolation from the plant is possible. Among the endophytic species include, for example Azospira oryzae and Azoarcus indigens. They colonize the space between the plant cells of the root tissue, known as the apoplast, thus do not occur within the plant cells. Other species occur on the root surface before ( epiphytic ). These include, for example Azoarcus evansii and A. buckelii. The different types of Azoarcus, Azovibrio and Azospira were found in roots of Kallargras, which is adapted to flooding and salt-tolerant C4 plant. ( Oryza sativa ) Also in the root tissues of rice species occur.

Other representatives of the nitrogen-fixing Rhodocyclaceae turn are exclusively outside the rhizosphere, regardless of plants to be found in the soil. These include, for example, various types of Azoarcus, Azoarcus as evansii and A. buckelii. In or on plants, they have not been found.

System

Genera and some species of this family are:

  • Azoarcus Reinhold- Hurek et al. 1993 Azoarcus anaerobius Springer et al. 1998
  • Azoarcus buckelii Mechichi et al. 2002
  • Azoarcus communis Reinhold- Hurek et al. 1993
  • Azoarcus evansii Anders et al. 1995
  • Azoarcus indigens Reinhold- Hurek et al. 1993
  • Azoarcus toluclasticus Song et al. 1999
  • Azoarcus tolulyticus Zhou et al. 1995
  • Azoarcus toluvorans Song et al. 1999
  • Azonexus caeni Quan et al. 2006
  • Azonexus hydrophilus Chou et al. 2008
  • Azonexus fungiphilus Reinhold- Hurek and Hurek 2000
  • Azospira oryzae Reinhold- Hurek and Hurek 2000
  • Azospira restricta Bae et al. 2007
  • Azovibrio restrictus Reinhold- Hurek and Hurek 2000
  • Crabtreella saccharophila Xie and Yokota 2006
  • Dechloromonas agitata Achenbach et al. 2001
  • Dechloromonas denitrificans Horn et al. 2005
  • Ferribacterium limneticum Cummings et al. 2000
  • Propionivibrio dicarboxylicus Tanaka et al. 1991
  • Propionivibrio limicola Brune et al. 2002
  • Propionivibrio pelophilus ( Meijer et al. 1999) Brune et al. 2002
  • Quadricoccus australiensis ( Maszenan et al. 2002) Tindall and Euzéby 2006
  • Rhodocyclus purpureus Pfennig 1978
  • Rhodocyclus tenuis ( Pfennig 1969) Imhoff et al. 1984
  • Sterolibacterium denitrificans Tarlera and Denner 2003
  • Thauera aminoaromatica Mechichi et al. 2002
  • Thauera aromatica Anders et al. 1995
  • Thauera chlorobenzoica Song et al. 2001
  • Thauera linaloolentis Foss and Harder 1999
  • Thauera mechernichensis Scholten et al. 1999
  • Thauera phenylacetica Mechichi et al. 2002
  • Thauera selenatis Macy et al. 1993
  • Zoogloea caeni Shao et al. 2009
  • Zoogloea oryzae Xie and Yokota 2006
  • Zoogloea ramigera Itzigsohn 1868
  • Zoogloea resiniphila Mohn et al. 1999
Betaproteobacteria Aerobic organism C4 carbon fixation
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