Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.
Structural and Molecular Microbiology, Structural Biology Research Center, VIB, Brussels, Belgium.
Nat Commun. 2024 Aug 29;15(1):7514. doi: 10.1038/s41467-024-51804-w.
In pathogenic Bacillota, spores can form an infectious particle and can take up a central role in the environmental persistence and dissemination of disease. A poorly understood aspect of spore-mediated infection is the fibrous structures or 'endospore appendages' (ENAs) that have been seen to decorate the spores of pathogenic Bacilli and Clostridia. Current methodological approaches are opening a window on these long enigmatic structures. Using cryoID, Alphafold modelling and genetic approaches we identify a sub-class of robust ENAs in a Bacillus paranthracis foodborne outbreak strain. We demonstrate that L-ENA are encoded by a rare three-gene cluster (ena3) that contains all components for the self-assembly of ladder-like protein nanofibers of stacked heptameric rings, their anchoring to the exosporium, and their termination in a trimeric 'ruffle' made of a complement C1Q-like BclA paralogue. The role of ENA fibers in spore-spore interaction and the distribution of L-ENA operon as mobile genetic elements in B. cereus s.l. strains suggest that L-ENA fibers may increase the survival, spread and virulence of these strains.
在致病性芽孢杆菌中，孢子可以形成感染性颗粒，并在疾病的环境持久性和传播中发挥核心作用。孢子介导的感染的一个尚未被充分了解的方面是纤维结构或“内生孢子附属物”（ENAs），这些结构已被观察到装饰致病性芽孢杆菌和梭菌的孢子。目前的方法学方法为研究这些长期以来神秘的结构提供了一个窗口。通过 cryoID、AlphaFold 建模和遗传方法，我们在一株食源性爆发的炭疽芽孢杆菌中鉴定出了一类具有鲁棒性的 ENA。我们证明 L-ENA 由一个罕见的三基因簇（ena3）编码，该基因簇包含用于自组装堆叠七聚体环的梯状蛋白纳米纤维、将其锚定在外孢囊上以及在由补体 C1Q 样 BclA 旁系同源物组成的三聚体“皱襞”中的终止所需的所有成分。ENAs 纤维在孢子-孢子相互作用中的作用以及 L-ENA 操纵子作为移动遗传元件在 B. cereus s.l. 菌株中的分布表明，L-ENA 纤维可能增加这些菌株的生存、传播和毒力。
