The ''Rhodocyclaceae'' are a family of

gram-negative bacteria Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the Crystal violet, crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelo ...

.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two: The Proteobacteria, Part C: The Alpha-, Beta-, Delta-, and Epsilonproteobacteria. New York, New York: Springer. . They are given their own order in the beta subgroup of

Pseudomonadota Pseudomonadota (synonym "Proteobacteria") is a major phylum of gram-negative bacteria. Currently, they are considered the predominant phylum within the domain of bacteria. They are naturally found as pathogenic and free-living (non- parasitic) ...

, and include many genera previously assigned to the family ''

Pseudomonadaceae The Pseudomonadaceae are a family of bacteria which includes the genera '' Azomonas'', '' Azorhizophilus'', ''Azotobacter'', '' Mesophilobacter'', ''Pseudomonas'' (the type genus), and '' Rugamonas''. The family Azotobacteraceae was recently re ...

''. The family was revised in 2017 with the creation of other families within the order ''

Rhodocyclales The Rhodocyclales are an order of the class Betaproteobacteria in the phylum Pseudomonadota ("Proteobacteria").Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volum ...

'', and the family now contains the genera: *''

Rhodocyclus ''Rhodocyclus'' is a genus of gram-negative bacteria from the family of Rhodocyclaceae which belongs to the class of Betaproteobacteria ''Betaproteobacteria'' are a class of Gram-negative bacteria, and one of the six classes of the phylum '' ...

'' (type genus) species can grow

photoheterotroph Photoheterotrophs (''Greek language, Gk'': ''photo'' = light, ''hetero'' = (an)other, ''troph'' = nourishment) are heterotrophic phototrophs—that is, they are organisms that use light for energy, but cannot use carbon dioxide as their sole carbon ...

ically or photoautotrophically (using molecular

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

as their

electron donor In chemistry, an electron donor is a chemical entity that transfers electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. An obsolete definition equated an electron dono ...

) under anoxia or

heterotroph A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

ically on

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

s under air. Dominant respiratory

quinone The quinones are a class of organic compounds that are formally "derived from aromatic compounds benzene.html" ;"title="uch as benzene">uch as benzene or naphthalene] by conversion of an even number of –CH= groups into –C(=O)– groups with ...

is wikt:rhodoquinone, rhodoquinone-8. Cells are curved rods or rings. *''

Propionivibrio ''Propionivibrio'' is a genus of gram-negative, chemoorganotrophic, non-spore-forming bacteria from the family of Rhodocyclaceae which belongs to the class of Betaproteobacteria ''Betaproteobacteria'' are a class of Gram-negative bacteria, an ...

'' species grow anaerobically by

fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

s, yielding

s, specifically

propionate Propionic acid (, from the Greek words πρῶτος : ''prōtos'', meaning "first", and πίων : ''píōn'', meaning "fat"; also known as propanoic acid) is a naturally occurring carboxylic acid with chemical formula . It is a liquid with a p ...

. The dominant respiratory quinone is ubiquinone-8. Cells are curved rods. *''

Azospira ''Azospira'' is a genus in the phylum Pseudomonadota (Bacteria). It has two members, namely '' Azospira oryzae'' and '' Azospira restricta''. See also * Bacterial taxonomy * Microbiology Microbiology () is the branches of science, scientifi ...

'' species are

s that can fix molecular nitrogen (i.e. are

diazotroph Diazotrophs are organisms capable of nitrogen fixation, i.e. converting the relatively inert diatomic nitrogen (N2) in Earth's atmosphere into bioavailable compound forms such as ammonia. Diazotrophs are typically microorganisms such as bacteria ...

ic) as their source of nitrogen for growth. Cells are spirillae or curved rods. The dominant respiratory quinone is ubiquinone-8.

References

External links

Rhodocyclaceae
J.P. Euzéby: List of Prokaryotic names with Standing in Nomenclature Rhodocyclales {{Betaproteobacteria-stub