**Yoshiaki Nomura 1,\*, Erika Kakuta 2, Ayako Okada 1, Ryoko Otsuka 1, Mieko Shimada 3, Yasuko Tomizawa 4, Chieko Taguchi 5, Kazumune Arikawa 5, Hideki Daikoku 6, Tamotsu Sato <sup>6</sup> and Nobuhiro Hanada <sup>1</sup>**


Received: 29 June 2020; Accepted: 29 July 2020; Published: 31 July 2020

**Abstract:** The oral microbiome of healthy older adults has valuable information about a healthy microbiome. In this study, we collected and analyzed the oral microbiome of denture plaque and tongue coating samples from four female centenarians. After DNA extraction and purification, pyrosequencing of the V3–V4 hypervariable regions of the 16S rRNA was carried out. The bacterial taxonomy for each lead was assigned based on a search of the EzBioCloud 16S database. We obtained a total of 199,723 valid, quality-controlled reads for denture plaque and 210,750 reads for tongue coating. The reads were assigned 407 operational taxonomic units with a 97% identity cutoff. Twenty-nine species were detected in both denture plaque and tongue coatings from all subjects. *Firmicutes* was the most abundant phylum; the *Streptococcus salivarius* group was the most abundant species in both the denture plaque and tongue coatings; and the *Fusobacterium nucleatum* group was detected in all subjects. In the bacterial profile, species formed clusters composed of bacteria with a wide range of prevalence and abundance, not dependent on phyla; each cluster may have specific species that could be candidates for a core microbiome. *Firmicutes* and *Veillonella* were abundant phyla on both plaque and tongue coatings of centenarians.

**Keywords:** oral microbiome; core microbiome; centenarian; next-generation sequencing
