Phylogeny of oral asaccharolytic Eubacterium species determined by 16S ribosomal DNA sequence comparison and proposal of Eubacterium infirmum sp. nov. and Eubacterium tardum sp. nov.

Abstract

16S rRNA gene sequences of Eubacterium brachy, Eubacterium nodatum, Eubacterium saphenum, Eubacterium timidum, and two previously unnamed taxa were determined. The results of a phylogenetic analysis indicated that all of the strains sequenced belonged to a deep branch of the low-G + C-content gram-positive group. The levels of 16S ribosomal DNA sequence similarity between species were low, suggesting that a number of genera may be represented in this group. The representatives of the two unnamed taxa, which were isolated from patients with periodontitis, were clearly distinct from the previously described species, and, therefore, the following two new species are proposed: Eubacterium infirmum (type strain, NCTC 12940) and Eubacterium tardum (type strain, NCTC 12941).