Electrophoretic Patterns of Proteins in the Genus Bifidobacterium and Proposal of Four New Species

Abstract

The polyacrylamide gel electrophoretic patterns of soluble cellular proteins from 1, 094 strains of bifidobacteria were compared with available deoxyribonucleic acid (DNA)-DNA homology data and with the phenotypic and biochemical reactions of these strains. There was excellent correlation between the 25 distinct protein patterns and 24 DNA-DNA homology groups in the genus. Differentiation among species on the basis of common phenotypic properties often was unreliable. Our results demonstrate that the species previously known as “Bifidobacterium eriksonii” is a synonym of Bifidobacterium dentium Scardovi and Crociani; that “Actinomyces parabifidus” is a synonym of Bifidobacterium infantis Reuter; that Bifidobacterium globosum (ex Scardovi, Trovatelli, Crociani, and Sgorbati 1969) sp. nov., nom. rev. (type strain, ATCC 25865) and Bifidobacterium pseudolongum Mitsuoka are closely related but distinct entities; and that Bifidobacterium minimum sp. nov. (type strain, ATCC 27538) and Bifidobacterium subtile sp. nov. (type strain, ATCC 27537) are valid species. Our analyses also indicate that Bifidobacterium coryneforme (ex Scardovi and Trovatelli 1969) sp. nov., nom. rev. (type strain, ATCC 25911) is a valid species. A group of strains intermediate between B. infantis and B. longum, “Bifidobacterium infantislongum,” occurs in calf feces. Identical or nearly identical protein patterns were produced by strains that had 80% or greater DNA homology.