(IMAGE) Tokyo Medical and Dental University Caption Each bacterial species and co-occurrence relationship are indicated by a node and an edge, respectively. Bacterial species with significant-high activity are indicated with bold circles, and interactions with significant co-occurrence are indicated with bold lines. Core bacterial species that are shown significant-high activity and significant co-occurrence interactions with other bacteria are indicated in red letters. The gingivitis co-occurrence network appeared to comprise three subnetworks. Subgroup 1 included the species mainly exhibited co-occurrence relationships with red complex bacteria; these species were detected in both gingivitis and periodontitis sites. Subgroup 2 included the species detected mainly in gingivitis sites. Subgroup 3 included mainly the species detected mainly in both healthy and gingivitis sites. Credit Department of Periodontology, TMDU Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.