Nature Communications (Aug 2024)

Helical ultrastructure of the L-ENA spore aggregation factor of a Bacillus paranthracis foodborne outbreak strain

  • Mike Sleutel,
  • Ephrem Debebe Zegeye,
  • Ann-Katrin Llarena,
  • Brajabandhu Pradhan,
  • Marcus Fislage,
  • Kristin O’Sullivan,
  • Nani Van Gerven,
  • Marina Aspholm,
  • Han Remaut

DOI
https://doi.org/10.1038/s41467-024-51804-w
Journal volume & issue
Vol. 15, no. 1
pp. 1 – 12

Abstract

Read online

Abstract 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.