Quorum sensing control of Vibrio cholerae aggregation

Bacteria coordinate their gene expression through the cell-cell communication process called quorum sensing. Quorum sensing (QS) involves the production, release, and group-wide detection of extracellular signal molecules called autoinducers, which allow cells to coordinate gene expression based on cell density. In Vibrio cholerae, QS controls the formation of biofilms: dynamic surface-adhered communities in which the cells are bound to each other and to the surface by the structural matrix extracellular polymeric substances (EPS). In V. cholerae the canonical biofilm program is upregulated in a low-cell-density (LCD) QS-state and the transition to a high-cell-density QS-state has been presumed to play a role largely in dispersal from biofilms. We find that V. cholerae can, in a HCD QS-state, robustly form aggregates in liquid suspension and known EPS constituents are dispensable for their formation. Unlike in traditional V. cholerae biofilms, cell division is not required for the formation of suspended biofilm communities. Instead, cells rapidly aggregate together during stationary phase. These data reveal new mechanisms by which bacteria control the formation of complex multicellular communities.