Modulation of bacterial multicellularity via spatiotemporal polysaccharide secretion

The development of multicellularity is a key evolutionary transition allowing for differentiation of physiological functions across a cell population that confers survival benefits; among unicellular bacteria, this can lead to complex developmental behaviours and the formation of higher-order community structures. Herein, we demonstrate that in the social δ-proteobacterium Myxococcus xanthus , the secretion of a novel secreted biosurfactant polysaccharide (BPS) is temporally and spatially modulated within communities, mediating swarm migration as well as the formation of multicellular swarm biofilms and fruiting bodies. BPS is a type IV pilus-inhibited acidic polymer built of randomly-acetylated β-linked tetrasaccharide repeats. Both BPS and the “shared good” EPS are produced by dedicated Wzx/Wzy-dependent polysaccharide assembly pathways distinct from that responsible for spore coat assembly. To our knowledge, such pathways have never-before been explicitly shown to synthesize a biosurfactant. Together, these data reveal the central role of secreted polysaccharides in the intricate behaviours coordinating bacterial multicellularity.