Overview: Bacteria of the genus Schaalia are abundant in the healthy mouth, particularly on the tongue dorsum, tonsils, and throat where they make up 3 to 6% of the oral microbial community. They were formerly considered to be in genus Actinomyces and were reclassified into genus Schaalia in 2018 (Nouioui et al. 2018).

Ecological role/importance in health and disease: There are 9 species of Schaalia in the mouth, including 5 named species (S. cardiffensis, S. georgiae, S. lingnae [Not Validly Published], S. meyeri, and S. odontolytica, as well as 4 taxa that are currently unnamed (Schaalia spp. HMT 172, 178, 180, and 877). Most of the Schaalia spp. detected in the healthy mouth in Human Microbiome Project data are members of the unnamed taxa S. sp. HMT 172 and S. sp. HMT 180 (Eren et al. 2014). S. odontolytica (formerly A. odontolyticus) is a member of the "purple complex" in subgingival plaque together with Veillonella parvula (Socransky et al. 1998).