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Updated: Jun 14, 2025
Recombinant Protein Expression, Crystallization, and Biophysical Studies of a Bacillus-conserved Nucleotide Pyrophosphorylase, BcMazG
Published on: May 16, 2017
Helical ultrastructure of the L-ENA spore aggregation factor of a Bacillus paranthracis foodborne outbreak strain
Mike Sleutel1,2, Ephrem Debebe Zegeye3, Ann-Katrin Llarena3
1Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium. Mike.Sleutel@vub.be.
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.
Insights
Researchers identified novel ladder-like protein nanofibers, or L-ENAs, on pathogenic Bacillus spores. These endospore appendages (ENAs) may enhance bacterial survival, spread, and virulence, contributing to disease dissemination.
Area of Science:
- Microbiology
- Structural Biology
- Genetics
Background:
- Pathogenic Bacillota spores are crucial for disease persistence and spread.
- Endospore appendages (ENAs) on pathogenic spores are poorly understood structures involved in infection.
Purpose of the Study:
- To investigate the structure and genetic basis of endospore appendages (ENAs) in pathogenic Bacillota.
- To elucidate the assembly and potential function of a specific class of ENAs in Bacillus anthracis.
Main Methods:
- Cryo-electron microscopy (cryoID) for high-resolution imaging.
- AlphaFold protein structure prediction.
- Genetic analysis of gene clusters involved in ENA formation.
Main Results:
- Identification of a robust subclass of ENAs, termed L-ENAs, in a Bacillus anthracis foodborne outbreak strain.
- L-ENAs are encoded by a three-gene cluster (ena3) responsible for self-assembly into ladder-like nanofibers.
- These nanofibers anchor to the exosporium and terminate in a unique structure composed of a BclA paralogue.
Conclusions:
- L-ENAs are self-assembling protein nanofibers with a defined structure and anchoring mechanism.
- The distribution of the L-ENA operon as mobile genetic elements suggests a role in enhancing bacterial survival, spread, and virulence.
