There are 638 species-level targets recognizing 538 species. In addition, there are 129 genus-level targets.


For some taxa such as Streptococcus, identification is limited to a group of several closely related species rather than an individual species. 16S rDNA sequences for the genus Streptococcus are highly conserved and many species cannot be differentiated in the targeted region (E. coli positions ~341 to 806). Thus, genus or higher taxa probes have been developed to account for those taxa that cannot be differentiated at the species level.


Each species has an Oral Taxon designation as defined in the Human Oral Microbiome Database (HOMD), which provides the scientific community with comprehensive information on the approximate 700 predominant prokaryote species that are present in the human oral cavity.