A Sensory Pathway Controls Motile Microcolony Formation and Spatial Organization in Gliding Bacteria

How motile bacteria navigating external surfaces convert environmental cues into transitions from dispersed states to cohesive, multicellular assemblies is poorly understood. We identify RgzA, a multi-domain sensory kinase in the gliding bacterium Flavobacterium johnsoniae, that drives the formation of zorbs, which are motile, ball-like three-dimensional microcolonies of gliding cells. A point mutation in RgzA promotes zorb formation, suppresses swarming, and enhances biofilm development, whereas suppressor mutations across its sensory domains restore planktonic behavior. We further show that the response regulator RgzB forms a signaling circuit with RgzA and contributes to the regulation of zorbing. Transcriptomic and perturbation analyses link this transition to iron availability. Phenotypically, RgzAB establish a state in which cells form cohesive, biofilm-like microcolonies that retain motility over external surfaces thus shifting the population from alignment-driven swarming to zorb-based exploration. In mixed populations, RgzA*-derived co-zorbs encapsulate wild-type cells, whose internal organization exhibits a density-dependent percolation-like transition that generates connected cellular networks. Together, these findings show that sensory signaling governs both the formation and spatial organization of motile multicellular assemblies, establishing a link between sensory transduction and different states of collective organization in living systems.