Endospore Appendages: a novel pilus superfamily from the endospores of pathogenic Bacilli |
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Authors: | Brajabandhu Pradhan Janine Liedtke Mike Sleutel Toril Lindbck Ephrem Debebe Zegeye Kristin OSullivan AnnKatrin Llarena Ola Brynildsrud Marina Aspholm Han Remaut |
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Institution: | 1. Structural and Molecular Microbiology, VIB‐VUB Center for Structural Biology, VIB, Brussels Belgium ; 2. Department of Bioengineering Sciences, Structural Biology Brussels, Vrije Universiteit Brussel, Brussels Belgium ; 3. Department of Paraclinical Sciences, Faculty of Veterinary Medicine, The Norwegian University of Life Sciences, Ås Norway ; 4. Division of Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo Norway |
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Abstract: | Bacillus cereus sensu lato is a group of Gram‐positive endospore‐forming bacteria with high ecological diversity. Their endospores are decorated with micrometer‐long appendages of unknown identity and function. Here, we isolate endospore appendages (Enas) from the food poisoning outbreak strain B. cereus NVH 0075‐95 and find proteinaceous fibers of two main morphologies: S‐ and L‐Ena. By using cryoEM and 3D helical reconstruction of S‐Enas, we show these to represent a novel class of Gram‐positive pili. S‐Enas consist of single domain subunits with jellyroll topology that are laterally stacked by β‐sheet augmentation. S‐Enas are longitudinally stabilized by disulfide bonding through N‐terminal connector peptides that bridge the helical turns. Together, this results in flexible pili that are highly resistant to heat, drought, and chemical damage. Phylogenomic analysis reveals a ubiquitous presence of the ena‐gene cluster in the B. cereus group, which include species of clinical, environmental, and food importance. We propose Enas to represent a new class of pili specifically adapted to the harsh conditions encountered by bacterial spores. |
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Keywords: | Bacillus Endospore pilus protein nanofiber self‐ assembly |
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