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 behaviors and the formation of higher-order community structures. Herein, we demonstrate that in the social δ-proteobacterium Myxococcus xanthus, the secretion of a novel biosurfactant polysaccharide (BPS) is 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 (T4P)-inhibited acidic polymer built of randomly acetylated β-linked tetrasaccharide repeats. Both BPS and exopolysaccharide (EPS) are produced by dedicated Wzx/Wzy-dependent polysaccharide-assembly pathways distinct from that responsible for spore-coat assembly. While EPS is preferentially produced at the lower-density swarm periphery, BPS production is favored in the higher-density swarm interior; this is consistent with the former being known to stimulate T4P retraction needed for community expansion and a function for the latter in promoting initial cell dispersal. Together, these data reveal the central role of secreted polysaccharides in the intricate behaviors coordinating bacterial multicellularity.

多细胞性的发展是一个关键的进化过渡，可以使整个细胞群体的生理功能分化，从而赋予生存优势；在单细胞细菌中，这可能导致复杂的发育行为并形成更高阶的群落结构。在这里，我们证明了在社会δ-变形杆菌Xanthus，新型生物表面活性剂多糖（BPS）的分泌在社区内受到空间调节，介导群体迁移以及形成多细胞群体生物膜和子实体。BPS是由随机乙酰化的β-连接的四糖重复序列构成的IV型菌毛（T4P）抑制酸性聚合物。BPS和胞外多糖（EPS）都是通过专用的Wzx / Wzy依赖性多糖组装途径产生的，该途径不同于负责孢子被膜组装的途径。优先在低密度群体周围生产EPS，而在高密度群体内部则优先使用BPS。这与已知的前者刺激群落扩展所需的T4P收缩以及后者在促进初始细胞扩散中的功能相一致。一起，