Functional amyloid BE-AM1 modulates microbial surface properties, biofilm formation, and adaptation to hydrocarbon stress.

Amyloid proteins are mainly known as misfolded aggregates associated with neurodegenerative diseases in humans and other eukaryotes. However, growing evidence shows that in bacteria, amyloids can serve important functional roles. These include facilitating surface attachment, forming amphipathic films, supporting biofilm development, and mediating interactions with the extracellular matrix and cell surfaces. In the present study, the bacterial amyloid bioemulsifier AM1 (BE-AM1), produced by Solibacillus silvestris AM1, was investigated for its effects on the growth of different microorganisms, including bacteria, fungi, and haloarchaea. The findings highlight its potential utility in antimicrobial applications and in broader biotechnological processes. These groups were selected to assess whether amyloid-mediated surface interactions are conserved across different microbial lineages. The addition of amyloid BE-AM1 increased the free-energy of interaction potential, as determined by contact-angle-based surface thermodynamic analysis, indicating reduced cell-surface hydrophobicity in the tested bacterial, haloarchaeal, and fungal strains. Furthermore, the presence of functional amyloids enhanced secreted protease activity in three bacterial strains and amylase activity in S. silvestris, increased tolerance to hydrocarbons, and promoted microbial growth using hydrocarbons as the sole carbon source. The ability of amyloid BE-AM1 to influence biofilm formation was also investigated in other bacterial species that produce their amyloid proteins. This study improves insight into interspecies interactions involving amyloid proteins and offers a foundation for future research of broader relevance to the amyloid field.