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Functional amyloid proteins confer defence against predatory bacteria.

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Curli fibers, a type of bacterial amyloid, protect Escherichia coli against predatory bacteria like Bdellovibrio bacteriovorus. This defense mechanism is independent of biofilm formation and effective against various bacterial threats.

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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.