Pseudomonadaceae

Overview
The Pseudomonadaceae is a family of bacteria that includes the genera Azomonas, Azomonotrichon, Azorhizophilus, Azotobacter, Cellvibrio, Mesophilobacter, Pseudomonas (the type genus), Rhizobacter, Rugamonas, and Serpens. The Azotobacteriaceae were recently published as belonging in this family as well.

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-flagella bacteria. Soon afterwards, a very large number of species was assigned to the genus. Pseudomonads were isolated from many natural niches and a large number of species names was originally assigned to the genus. New methodology and the inclusion of approaches based on the studies of conservative macromolecules have reclassified many strains.

Pseudomonas aeruginosa is increasingly recognized as an emerging opportunistic pathogen of clinical relevance. Several different epidemiological studies indicate that antibiotic resistance in increasing in clinical isolates.

In the year 2000, the complete genome sequence of a Pseudomonas species was determined; more recently the sequence of other strains have been determined including P. aeruginosa strains 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).

Distinguishing characteristics

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

The presence of oxidase, polar flagella and inability to carry out fermentation differentiate Pseudomonads from Enterobacteriaceae:.