Fig. 1.

T9SS and its associated rotary motor are functional in gliding bacteria of the human microbiome. (A) The frequency distribution of gliding speeds of a population of C. gingivalis cells peaked around 1 µm/s. (B) The center of mass of a C. gingivalis cell tethered to glass followed a circular trajectory. (C) The frequency distribution of rotation speed of a population of tethered C. gingivalis cells peaked around 1.5 Hz. Experiments in A–C were done at room temperature on glass. (D) A matrix showing the similarity between genes that encode the T9SS and gliding motor proteins of abundant bacteria of the human oral microbiome. The reference gene source was F. johnsoniae. A blue square indicates the presence while a gray square indicates the absence of a gene. BLAST was performed using the Human Oral Microbial Database (26). To eliminate random matches, an e value of e⁻⁵ was used as the threshold. The core gliding and core T9SS genes are in green and red, respectively. Bacteria in magenta have all green and red genes and can glide.