CapP mediates the structural formation of biofilm-specific pili in the opportunistic human pathogen Bacillus cereus
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Fibrillary proteins are structural scaffolds that diversify the functionality of the architectural bacterial extracellular matrix. Here, we report a previously uncharacterized bacterial factor called bc1280 that is exclusive to B. cereus group and indispensable for the establishment of a biofilm lifestyle. We propose that BC1280 is an architectural conductor for the assembly of the amyloid platform, leading to the polymerization of heteropili with two functional amyloids, CalY and TasA. From its cellular localization in the cell membrane, aggregates of BC1280 nucleate the polymerization of CalY, which further incorporates TasA into nascent pili. Additionally, BC1280 modulates the expression of EPS via an uncharacterized pathway that is activated by a protease and an ECF-type sigma factor. The pilus biogenesis system described in this work partially mirrors curli system in Escherichia coli , unveiling a new paradigm in the structural biology of gram-positive bacteria and highlighting the complexity of extracellular matrix assembly in B. cereus .
