The Serology of Pseudomonas pyocyanea

SUMMARY: Three main antigens were found to be variously distributed amongst strains of Pseudomonas p yocyanea. The serological behaviour of the strains studied depended on the presence and quantity of these antigens. It was not possible to ‘ distinguish between flagellar and somatic antigens, but those found were probably somatic. Amongst the peculiarities of serological behaviour of bacteria _in this species the most striking was a complete loss of agglutinability on moderate heating, which left the antigenic activity unimpaired. The classification of the genus Pseudomonas is, like most bacteriological classifications, one of contradictions. The species Ps. pyocyanea is not clearly delimited and most observers have found strains which, though most con-veniently placed in that species, had one or more atypical characteristics. Within the species, classification has been attempted, but without conspicuous success. Gessard (1919, 1920), who made the first extensive study of the organism, based his classification entirely on pigment production. On this basi