Pseudomonadaceae
P. aeruginosa colonies on an agar plate
Scientific classification
Domain:	Bacteria
Phylum:	Pseudomonadota
Class:	Gammaproteobacteria
Order:	Pseudomonadales
Family:	Pseudomonadaceae Winslow et al., 1917
Type genus
Pseudomonas Migula 1894 (Approved Lists 1980)
Genera
Atopomonas Rudra and Gupta 2021 Azomonas Winogradsky 1938 (Approved Lists 1980) Azorhizophilus Thompson and Skerman 1981 Azotobacter Beijerinck 1901 (Approved Lists 1980) Denitrificimonas Saati-Santamaría et al. 2021 Entomomonas Wang et al. 2020 Halopseudomonas Rudra and Gupta 2021 Mesophilobacter Nishimura et al. 1989 Oblitimonas Drobish et al. 2016 Permianibacter Wang et al. 2014 Pseudomonas Migula 1894 (Approved Lists 1980) Rhizobacter Goto and Kuwata 1988 Rugamonas Austin and Moss 1987 Thiopseudomonas Tan et al. 2015
Synonyms[1]
Azotobacteraceae Pribram 1933 (Approved Lists 1980)

The Pseudomonadaceae are a family of bacteria which includes the genera Azomonas, Azorhizophilus, Azotobacter, Mesophilobacter, Pseudomonas (the type genus), and Rugamonas.^[2][3] The family Azotobacteraceae was recently reclassified into this family.^[4]

History

Pseudomonad literally means false unit, being derived from the Greek 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. The generic 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 is increasingly recognized as an emerging opportunistic pathogen of clinical relevance. Studies also suggest the emergence of antibiotic resistance in P. aeruginosa.^[5]

In 2000, the complete genome of a Pseudomonas species was sequenced; more recently, the genomes of other species have been sequenced, including P. aeruginosa PAO1 (2000), P. putida KT2440 (2002), P. fluorescens Pf-5 (2005), P. fluorescens PfO-1, and P. entomophila L48. Several pathovars of Pseudomonas syringae have been sequenced, including pathovar tomato DC3000 (2003), pathovar syringae B728a (2005), and pathovar phaseolica 1448A (2005).^[3]

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^[6]

The presence of oxidase and polar flagella and inability to carry out fermentation differentiate pseudomonads from the Enterobacteriaceae.^[7]