110th Anniversary: High-order interactions can eclipse pairwise interactions in shaping the structure of microbial communities: the case of a synthetic oral microbial community containing Actinomyces viscosus

Microbial species exhibit sophisticated interdependencies as strategies to coexist in communities. Human health and disease are critically dependent on the compositions and structures of these communities. Unraveling the underlying interdependencies would help engineer natural and synthetic microbial communities, central to modern food and healthcare applications. Here, we constructed a synthetic microbial community of 7 naturally co-occurring oral bacteria and employed a bottom-up approach to understand the role of interspecies interactions in deciding the structure of this community. In particular, we focused on the abundance of the species Actinomyces viscosus, implicated in the virulence of oral microbial biofilms and dental caries. The community showed strong evidence of 5th order interactions. The abundance of A. viscosus was high in monoculture, low in the presence of some but not all of the other species, and high again in the 7-species community. To understand these interactions, we investigated ...