Streptomyces are a genus of ubiquitous soil bacteria from which the majority of clinically utilized antibiotics derive¹. The production of these antibacterial molecules reflects the relentless competition Streptomyces engage in with other bacteria, including other Streptomyces species^1,2. Here we show that in addition to small-molecule antibiotics, Streptomyces produce and secrete antibacterial protein complexes that feature a large, degenerate repeat-containing polymorphic toxin protein. A cryo-electron microscopy structure of these particles reveals an extended stalk topped by a ringed crown comprising the toxin repeats scaffolding five lectin-tipped spokes, which led us to name them umbrella particles. Streptomyces coelicolor encodes three umbrella particles with distinct toxin and lectin composition. Notably, supernatant containing these toxins specifically and potently inhibits the growth of select Streptomyces species from among a diverse collection of bacteria screened. For one target, Streptomyces griseus, inhibition relies on a single toxin and that intoxication manifests as rapid cessation of vegetative hyphal growth. Our data show that Streptomyces umbrella particles mediate competition among vegetative mycelia of related species, a function distinct from small-molecule antibiotics, which are produced at the onset of reproductive growth and act broadly^3,4. Sequence analyses suggest that this role of umbrella particles extends beyond Streptomyces, as we identified umbrella loci in nearly 1,000 species across Actinobacteria.

链霉菌是一种普遍存在的土壤细菌，临床上使用的大多数抗生素均源自链霉菌¹。这些抗菌分子的产生反映了链霉菌与其他细菌（包括其他链霉菌物种）的无情竞争^1,2。在这里，我们表明，除了小分子抗生素之外，链霉菌还产生并分泌抗菌蛋白复合物，其特征是含有大的、简并重复的多态性毒素蛋白。这些颗粒的冷冻电子显微镜结构显示出一个延伸的茎，顶部有一个环状的冠，其中包含毒素重复支架，五个带有凝集素尖端的辐条，这使我们将它们命名为伞状颗粒。天蓝色链霉菌编码三种具有不同毒素和凝集素成分的伞状颗粒。值得注意的是，含有这些毒素的上清液特异性且有效地抑制从筛选的多种细菌中选择的链霉菌属物种的生长。对于一个目标，灰色链霉菌，抑制依赖于单一毒素，并且中毒表现为营养菌丝生长的快速停止。我们的数据显示，链霉菌伞状颗粒介导相关物种的营养菌丝体之间的竞争，这一功能不同于小分子抗生素，小分子抗生素在生殖生长开始时产生，作用广泛^3,4。序列分析表明，伞状颗粒的这种作用不仅限于链霉菌，因为我们在放线菌的近 1,000 个物种中发现了伞状位点。