Taxonomy of Corynebacterium diphtheriae and related taxa, with recognition of Corynebacterium ulcerans sp. nov. nom. rev.

Levels of genomic DNA relatedness were determined using a S1 nuclease procedure for reference bacteria identified as biotypes of Corynebacterium diphtheriae, biovars of Corynebacterium pseudotuberculosis, and 'Corynebacterium ulcerans'. These results showed that the three species are separate taxa at the genomospecies level whereas biotypes and biovars are closely related genomically within each species. Phylogenetic analyses of small-subunit rDNA sequences revealed that 'Corynebacterium ulcerans' forms a tight cluster with Corynebacterium pseudotuberculosis within the robust branch that groups all Corynebacterium sequenced to date. Therefore, we propose that the species incertae sedis 'C. ulcerans' should be conclusively recognized as a distinct species within the genus Corynebacterium with strain CCUG 2708 = NCTC 7910 as type strain. This species is characterized by urease production and fermentation of glycogen.