Based on 16S rRNA gene sequence comparison, an isolate that was detected in sterile-filtered vegetable broth was classified as a novel member of the Erysipelothrix line of descent of the Firmicutes. Strain MF-EP02 T resembles members of the two species of Erysipelothrix with validly published names, Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum, in morphology, fatty acid composition, lack of menaquinones in aerobically and anaerobically grown cultures, DNA G+C content and peptidoglycan amino acid composition. Distinct differences in physiological characteristics, however, support the allocation of this isolate to a novel species of the genus Erysipelothrix, for which the name Erysipelothrix inopinata sp. nov. (type strain, MF-EP02 T =DSM 15511 T =CIP 107935 T ) is proposed. Members of the Erysipelothrix line of descent are included in the family Erysipelotrichaceae fam. nov.