The Pseudomonadaceae are a

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

which includes the genera '' Azomonas'', '' Azorhizophilus'', ''

Azotobacter ''Azotobacter'' is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts (and also has hard crust) and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes that play an impo ...

'', '' Mesophilobacter'', ''

Pseudomonas ''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able t ...

'' (the type genus), and '' Rugamonas''. The family Azotobacteraceae was recently reclassified into this family.

History

Pseudomonad literally means false unit, being derived from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''pseudo'' (ψευδο – false) and ''monas'' (μονος – a single unit). The term "monad" was used in the early history of microbiology to denote single-celled organisms. Because of their widespread occurrence in nature, the pseudomonads were observed early in the history of

microbiology Microbiology () is the scientific study of microorganisms, those being unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virology, bacteriology, ...

. The

generic Generic or generics may refer to: In business * Generic term, a common name used for a range or class of similar things not protected by trademark * Generic brand, a brand for a product that does not have an associated brand or trademark, other ...

name ''Pseudomonas'' created for these organisms was defined in rather vague terms in 1894 as a genus of Gram-negative, rod-shaped, and polar-flagellated bacteria. Soon afterwards, a large number of species was assigned to the genus. Pseudomonads were isolated from many natural niches. New methodology and the inclusion of approaches based on the studies of conservative macromolecules have reclassified many species. ''

Pseudomonas aeruginosa ''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic– facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. a ...

'' is increasingly recognized as an emerging opportunistic pathogen of clinical relevance. Studies also suggest the emergence of

antibiotic resistance Antimicrobial resistance (AMR) occurs when microbes evolve mechanisms that protect them from the effects of antimicrobials. All classes of microbes can evolve resistance. Fungi evolve antifungal resistance. Viruses evolve antiviral resistance. ...

in ''P. aeruginosa''. In 2000, the complete genome of a ''

'' species was sequenced; more recently, the genomes of other species have been sequenced, including ''P. aeruginosa'' PAO1 (2000), '' P. putida'' KT2440 (2002), ''

P. fluorescens ''Pseudomonas fluorescens'' is a common Gram-negative, rod-shaped bacterium. It belongs to the ''Pseudomonas'' genus; 16S rRNA analysis as well as phylogenomic analysis has placed ''P. fluorescens'' in the ''P. fluorescens'' group within the genu ...

'' Pf-5 (2005), ''P. fluorescens'' PfO-1, and ''P. entomophila'' L48. Several

pathovar A pathovar is a bacterial strain or set of strains with the same or similar characteristics, that is differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one o ...

s of ''

Pseudomonas syringae ''Pseudomonas syringae'' is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to researchers from inte ...

'' have been sequenced, including pathovar tomato DC3000 (2003), pathovar ''syringae'' B728a (2005), and pathovar ''phaseolica'' 1448A (2005).

Distinguishing characteristics

* Oxidase positive – due to the presence of the enzyme cytochrome c oxidase. * Nonfermentative * Many metabolise glucose by the Entner Doudoroff pathway mediated by 6-phosphoglyceraldehyde dehydrogenase and aldolase * Polar flagella, enabling motility * Many members produce derivatives of the fluorescent pigment

pyoverdin Pyoverdines (alternatively, and less commonly, spelled as pyoverdins) are fluorescent siderophores produced by certain pseudomonads. Pyoverdines are important virulence factors, and are required for pathogenesis in many biological models of infe ...

The presence of oxidase and polar flagella and inability to carry out fermentation differentiate pseudomonads from the

Enterobacteriaceae Enterobacteriaceae is a large family of Gram-negative bacteria. It was first proposed by Rahn in 1936, and now includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject of debate, but o ...

.Krieg, N.R. (Ed.) (1984) Bergey's Manual of Systematic Bacteriology, Volume 1. Williams & Wilkins.

References

Pseudomonadales {{Pseudomonadales-stub