Disease-causing bacteria secrete numerous toxins to invade and subjugate their hosts. Unlike many smaller toxins, the secretion machinery of most large toxins remains enigmatic. By combining genomic editing, proteomic profiling and cryo-electron tomography of the insect pathogen Yersinia entomophaga, we demonstrate that a specialized subset of these cells produces a complex toxin cocktail, including the nearly ribosome-sized Tc toxin YenTc, which is subsequently exported by controlled cell lysis using a transcriptionally coupled, pH-dependent type 10 secretion system (T10SS). Our results dissect the Tc toxin export process by a T10SS, identifying that T10SSs operate via a previously unknown lytic mode of action and establishing them as crucial players in the size-insensitive release of cytoplasmically folded toxins. With T10SSs directly embedded in Tc toxin operons of major pathogens, we anticipate that our findings may model an important aspect of pathogenesis in bacteria with substantial impact on agriculture and healthcare.

致病细菌会分泌大量毒素来入侵和征服宿主。与许多较小的毒素不同，大多数大毒素的分泌机制仍然是个谜。通过结合昆虫病原体耶尔森氏菌的基因组编辑、蛋白质组分析和冷冻电子断层扫描，我们证明这些细胞的一个特殊子集会产生复杂的毒素混合物，包括接近核糖体大小的 Tc 毒素 YenTc，随后通过受控的使用转录耦合、pH 依赖性 10 型分泌系统 (T10SS) 裂解细胞。我们的结果剖析了 T10SS 的 Tc 毒素输出过程，确定 T10SS 通过以前未知的裂解作用模式进行操作，并将它们确定为细胞质折叠毒素的大小不敏感释放的关键参与者。由于 T10SS 直接嵌入主要病原体的 Tc 毒素操纵子中，我们预计我们的发现可能会模拟细菌发病机制的一个重要方面，对农业和医疗保健产生重大影响。