A Note on the Taxonomy of Proteus Hydrophilus

Abstract

Two recent reports (Kulp and Borden, 1942; Guthrie and Hitchner, 1943) have shown that the organism known as Proteus hydrophilus is polarly flagel-lated. Hence this species must be removed from the Enterobacteriaceae and placed in the Pseudomonadaceae. Kulp and Borden have also confirmed the finding of previous workers that P. hydrophilus ferments carbohydrates with vigorous gas production. This is surprising in view of the extreme rarity of true fermentative ability (sensu Pasteur) in the Pseudomonadaceae; in fact, the only previous well-established example is the alcoholic fermentation which was shown by Kluyver and Hoppen-brouwers (1931) to be characteristic of Pseudomonas lindneri. Hence a more detailed study of the action of P. hydrophilus on sugars seemed desirable. An examination of several strains obtained through the kindness of Drs. Kulp and Hitchner has revealed that P. hydrophilus carries out a typical butylene-glycol fermentation substantially identical with that of Aerobacter aerogenes. The outstanding fermentative properties of P. hydrophilus thus clearly call for a generic separation from other polarly flagellated rods. The appropriate genus, Aeromomas, has already been proposed by Kluyver and van Niel (1936) for Beijerinck's (1900) polarly flagellated Aerobacter liquefaciens. Although authentic cultures are not available for comparison, it is highly probable that Aerobacter liquefaciens is identical with P. hydrophilus. Indeed, an extensive synonymy appears to have grown up around P. hydrophilus. Guthrie and Hitchner have suggested its identity with Pseudomonas punctata, originally described by Zim-mermann (1890); it is also indistinguishable culturally and biochemically from Pseudomonas fermentanrs (von Wolzogen Kiihr, 1932). Since these organisms were isolated from water and not tested for pathogenicity, it is readily understandable that their relationships to so vigorous a disease-producer as P. hydrophilus should have been overlooked. The correct name for Proteus hy-drophilus is thus Aeromonas hydrophila, although if its suggested synonymy with Pseudomonas punctata is proved, the latter specific name will have priority. REFERENCES BEIJERINCK, M. W. 1900 Schwefelwasserstoffbildung in den Stadtgriiben und Aufstellung der Gattung Aerobacter. Zentr. Bakt. Parasitenk., II, 6, 193-206. GUTHRIE, R., AND HITCHNBER, E. R. 1943 Studies of microorganisms classified as Proteus hydrophilus.