Functional amyloid proteins confer defence against predatory bacteria

Area of Science:

• Microbiology
• Bacterial defense mechanisms
• Structural biology

Background:

• Bdellovibrio bacteriovorus is a predatory bacterium that attacks Gram-negative bacteria.
• Bacterial defense strategies against such predators are not well understood.
• Curli fibers are durable amyloid structures produced by Escherichia coli.

Purpose of the Study:

• To investigate bacterial resistance mechanisms against Bdellovibrio bacteriovorus predation.
• To identify specific bacterial components conferring resistance.
• To explore the broader role of functional amyloids in bacterial defense.

Main Methods:

• Screening of diverse Escherichia coli strains for resistance to B. bacteriovorus.
• Genetic analysis and microscopy to study curli fiber function.
• Bioinformatic analysis of bacterial amyloid systems.

Main Results:

• Approximately one-third of E. coli strains exhibited resistance to B. bacteriovorus.
• Curli fiber production was identified as a key defense mechanism.
• Curli fibers formed a protective barrier independent of biofilm genes.
• This amyloid barrier also protected against Myxococcus xanthus and certain bacteriophages.
• A distinct amyloid from Pseudomonas aeruginosa also conferred resistance.

Conclusions:

• Functional amyloids, such as curli fibers, provide robust defense for bacteria against diverse predatory threats.
• Amyloid-based defense systems are widespread in diderm bacteria.
• This study highlights a novel role for functional amyloids in bacterial immunity.