Rhodocyclaceae

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Rhodocyclaceae
Systematics
Domain : Bacteria (bacteria)
Department : Proteobacteria
Class : Betaproteobacteria
Order : Rhodocyclales
Family : Rhodocyclaceae
Scientific name of the  order
Rhodocyclales
Garrity et al. 2006
Scientific name of the  family
Rhodocyclaceae
Garrity et al. 2006

The Rhodocyclaceae are a family of gram-negative bacteria. So far this is the only one of the order Rhodocyclales from the class of beta-proteobacteria . Many genera belong to this family that were previously classified as Pseudomonadaceae , but were classified as unrelated to the classical Pseudomonas species according to the findings of molecular phylogeny (e.g. 16S rRNA sequences).

Features and ecology

The Rhodocyclaceae mainly comprise aerobic (dependent on oxygen) rod-shaped bacteria, which are characterized by versatile metabolic activities. Strictly anaerobic bacteria, which can only live in the absence of oxygen and use fermentation (colloquially known as fermentation) as metabolism , can also be found in this family, such as Propionibacter . The different species of the Rhodocyclaceae are usually motile by flagella and occur in fresh water or in the ground. Some, like Zoogloea , are also found in wastewater and play an important role in biological wastewater treatment in sewage treatment plants.

Nitrogen-fixing bacteria are also represented in this family. They can absorb the free, molecular nitrogen (N 2 , dinitrogen) from the environment and utilize it further in the metabolism, an ability that is relatively widespread among bacteria, but is lacking in the plant and animal kingdoms. Some of the nitrogen-fixing species form associations with different plant species, such as rice and kallar grass ( Leptochloa fusca ) and supply them with nitrogen, others occur freely in the soil. The nitrogen-fixing species usually need microaerobic conditions (low oxygen content in the environment) to fix the nitrogen.

The possibility of using Azoarcus to improve rice cultivation is currently being investigated .

The eponymous genus Rhodocyclus is rather untypical for the group, as it is capable of anoxygenic photosynthesis under anaerobic conditions and belongs to the physiological group of non-sulfur purple bacteria . In addition, the species Rhodocyclus purpureus is characterized by unusual, U-shaped to ring-shaped cells.

Nitrogen fixation

The nitrogen fixers of the Rhodocyclaceae include various species of Azoarcus , Azospira , Azovibrio and Azonexus that occur in the soil . The prefix “azo-” is derived from the French “azote” (nitrogen). Several of these species are associated with plants and occur on the root surface or within the root tissue (endophytic). However, there is no formation of special symbiotic structures as is the case with rhizobia and various legumes (root nodules). The species of Azoarcus are ecologically strongly tied to the plants, because they have not yet been found free in the ground, outside of rhizospheres. However, free cultivation in the laboratory after isolation from the plants is possible. The endophytic species include, for example, Azospira oryzae and Azoarcus indigens . They colonize the space between the individual plant cells of the root tissue, the so-called apoplast , so they do not occur within the plant cells. Other species occur on the root surface (epiphytic). These include, for example, Azoarcus evansii and A. buckelii . The different species of Azoarcus , Azovibrio and Azospira were found in roots of kallar grass, a flood-adapted and salt-tolerant C4 plant . Species are also found in the root tissue of rice ( Oryza sativa ).

Other representatives of the nitrogen-fixing Rhodocyclaceae can only be found outside the root sphere, completely independent of plants, in the soil. These include, for example, different types of Azoarcus , such as Azoarcus evansii and A. buckelii . They have not yet been found in or on plants.

Systematics

The following is a list of some genera and species in this family:

  • 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 Reinhold-Hurek and Hurek 2000
    • Azonexus caeni Quan et al. 2006
    • Azonexus hydrophilus Chou et al. 2008
    • Azonexus fungiphilus Reinhold-Hurek and Hurek 2000
  • Azospira Reinhold-Hurek and Hurek 2000
    • Azospira oryzae Reinhold-Hurek and Hurek 2000
    • Azospira restricta Bae et al. 2007
  • Azovibrio Reinhold-Hurek and Hurek 2000
    • Azovibrio restrictus Reinhold-Hurek and Hurek 2000
  • Crabtreella Xie and Yokota 2006
    • Crabtreella saccharophila Xie and Yokota 2006
  • Dechloromonas Achenbach et al. 2001
    • Dechloromonas agitata Achenbach et al. 2001
    • Dechloromonas denitrificans Horn et al. 2005
  • Ferribacterium Cummings et al. 2000
    • Ferribacterium limneticum Cummings et al. 2000
  • Georg fuchsia Weelink et al. 2011
  • Niveibacterium Chun et al. 2016
  • Oryzomicrobium Liu et al. 2017
  • Propionivibrio Tanaka et al. 1991
    • Propionivibrio dicarboxylicus Tanaka et al. 1991
    • Propionivibrio limicola Brune et al. 2002
    • Propionivibrio pelophilus (Meijer et al. 1999) Brune et al. 2002
  • Quatrionicoccus Tindall and Euzéby 2006
    • Quadricoccus australiensis (Maszenan et al. 2002) Tindall and Euzéby 2006
  • Rhodocyclus Pfennig 1978
    • Rhodocyclus purpureus pfennig 1978
    • Rhodocyclus tenuis (Pfennig 1969) Imhoff et al. 1984
  • Sterolibacterium Tarlera and Denner 2003
    • Sterolibacterium denitrificans Tarlera and Denner 2003
  • Thauera Macy et al. 1993
    • 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
  • Uliginosibacterium Weon et al. 2008
  • Zoogloea Itzigsohn 1868
    • Zoogloea caeni Shao et al. 2009
    • Zoogloea oryzae Xie and Yokota 2006
    • Zoogloea ramigera Itzigsohn 1868
    • Zoogloea resiniphila Mohn et al. 1999

swell

  1. ↑ JP Euzéby: List of Prokaryotic names with Standing in Nomenclature - Family Rhodocyclaceae (as of December 1, 2018)

literature

  • Michael T. Madigan, John M. Martinko, Jack Parker: Brock - Microbiology . 11th edition. Pearson Studium, Munich 2006, ISBN 3-8274-0566-1 .
  • George M. Garrity: Bergey's manual of systematic bacteriology . 2nd Edition. Springer, New York 2005, Vol. 2: The Proteobacteria Part C: The Alpha-, Beta-, Delta-, and Epsilonproteabacteria ISBN 0-387-24145-0 .
  • Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer , Erko Stackebrandt (Eds.): The Prokaryotes, A Handbook of the Biology of Bacteria . Volume 5: Proteobacteria: Alpha and Beta Subclasses , 3rd edition, Springer-Verlag, New York et al. O., 2006, ISBN 978-0-387-25495-1 .

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