Floyd Dewhirst, DDS, PhD

Floyd Dewhirst was deciphering the oral microbiome before the term microbiome was created.  Dewhirst’s primary research focus has been to define the diversity, genetic capability and pathogenic potential of organisms present in the human oral cavity.

Dewhirst has used sequencing of the 16S rRNA genes directly from cultivated oral bacteria and also sequencing of cloned genes derived from oral plaque DNA to identify all the bacteria that can live in our oral cavities, both cultivated and previously uncultivated.  This effort has resulted in the identification of approximately 700 species or phylotypes of human oral bacteria that are described in the Human Oral Microbiome Database (HOMD - http://www.homd.org). This database contains important phylogenetic, genomic and bibliographic information for each species, as well as bioinformatics tools to examine their genomes.  Many of the strains that the Forsyth team identified and made available to the scientific community were previously unnamed and uncultured species. The availability of these strains and their genome information has allowed scientists worldwide to study them for the first time.

“Prior to this work, there was no reliable way to identify the bacteria that could not be grown,” said Dewhirst. “We now have molecular tools to easily identify currently uncultivated bacteria and investigators can now study their associations with health and disease.”

Dewhirst, along with his colleagues in the Department of Microbiology, have led the way in deciphering the complex oral microbiome. Today, 65% of the species in the HOMD can be grown.  In the next phase of his research, Dewhirst is working to develop innovative new methods to cultivate the remaining uncultivated species.  His ultimate goal is to have full genomic information for all species that comprise the oral microbiome. 


University of California at Santa Barbara, BS, 1969, Chemistry
University of California at Santa Barbara, MA, 1971, Biology
University of California at San Francisco, DDS, 1973, Dentistry
University of Rochester, PhD, 1979, Pharmacology