Pseudomonas classification. A new case history in the taxonomy of gram-negative bacteria.

Various criteria that have been used in the development of a system of classification of Pseudomonas species, as well as in the precise circumscription of the genus on phenotypic and molecular bases, are discussed. Pseudomonas taxonomy has transcended its own limits by suggesting a general strategy for the definition of taxonomic hierarchies at and above the genus level. A selection of studies on the biochemical and physiological properties of members of the genus is critically examined in relation to the current taxonomic scheme as a frame of reference.