Abstract
The human microbiome is an assemblage of diverse bacteria that interact with one another to design a community. Bacteria that form a community are arranged in a three-dimensional matrix with many degrees of freedom. Snapshots of microbial communities display well-defined structures but how a non-ordered community reaches an ordered state is not clear. Bacterial gliding is defined as the motion of cells in a screw-like fashion over an external surface. Genomic analysis suggests that gliding bacteria are abundant in human microbial communities. Gliding bacteria require a functional bacterial Type IX Secretion System, and a motility machinery that propels the mobile cell-surface adhesin SprB. Here we report that cells of abundant non-motile bacteria found in human oral microbial communities attach to single gliding bacterial cells via SprB. The attached non-motile bacteria are propelled as ‘cargo’ along the length of a gliding cell. Multi-color fluorescent spectral imaging of live bacterial cells within a polymicrobial community shows long-range transport of non-motile cargo bacteria by a moving swarm. Tracking of fluorescently labeled single cells and of fluid flow patterns via gas bubbles suggests hierarchy within a swarm. We find that the synchronized public transport of cargo bacteria provides a specific spatial structure to a polymicrobial community, and that some non-motile bacteria use public transport more efficiently than other members of their community.
