Ecological Dynamics and Functional Classification of Nanosynbacter lyticus Strain TM7x in the Human Oral Microbiome: A Literature Review

The TM7x strain is a genetic variant of the bacterium Nanosynbacter lyticus, which belongs to the Saccharibacteria phylum within the Candidate Phyla Radiation (CPR) or Patescibacteria group. Its biology differs significantly from that of other bacterial phyla, and its ecological role in the oral cavity remains largely undefined. Through a organyzed and comprehensive literature review, we aim to define the role this bacterium plays within the oral ecosystem. We identified relevant studies from primary sources, included scientific articles from preclinical and clinical studies obtained from three digital databases. The bacterial strain TM7x is an obligate epibiont that exhibits autonomous energy me-tabolism and utilizes a type IV pili system to adhere to its direct host, Schaalia odontolytica. It interacts with its host in two stages: initially as an epipatobiont and subsequently as an episymbiont. TM7x plays a complex ecological role by modulating the host’s metabolism and structure toward a less virulent phenotype resistant to phage attack, while also in-fluencing the human host through immunomodulation and tissue protection. This organism has transitioned from being considered 'biological dark matter' to a key model for understanding coevolution within the human microbiome. Its ability to protect the host from phages, induce protective biofilms, and suppress destructive inflammatory responses positions it as a vital component of human oral microbiome homeostasis.