Curli-independent defense against Bdellovibrio bacteriovorus in E. coli

Aaron Whiteley — Mon, 29 Sep 2025 15:00:00 +0000

Curli-independent defense against Bdellovibrio bacteriovorus in E. coli Aaron Whiteley Mon, 09/29/2025 - 09:00

Ryan Sayegh , Hannah Ledvina , Aaron Whiteley

Microbiology Spectrum (2025)

Abstract

Predatory bacteria are a group of organisms that use diverse methods to access nutrients and grow by killing prey bacteria. The predator Bdellovibrio bacteriovorus is capable of preying on a wide range of gram-negative bacteria by invading the periplasmic space, killing, digesting, and ultimately lysing prey cells. B. bacteriovorus, like a phage, replicates at the expense of its host, yet unlike phage defense, there are few characterized mechanisms for bacteria to resist B. bacteriovorus. Previously, we discovered that an extracellular amyloid protein called curli protects Escherichia coli from B. bacteriovorus. Here, we searched for additional modes of B. bacteriovorusresistance and identified a strain within the E. coli Reference (ECOR) collection, ECOR29, that uses a curli-independent mechanism that requires lipopolysaccharide (LPS)-modifying enzymes for defense. Over 30% of the ECOR collection is resistant to B. bacteriovorus. We successfully deleted the gene encoding the major curli subunit in many of these, and only ECOR29 remained resistant. We hypothesized that ECOR29 encoded an alternative resistance mechanism and identified determinants of defense using a forward genetic screen. Our screen revealed critical roles for enzymes that modify LPS, alter the outer membrane, and are homologous to plasmid partitioning systems. Examination of ECOR29 by electron microscopy did not identify overt phenotypes or visible alterations to extracellular structures. We also were unable to identify any secreted factors that impacted B. bacteriovorus viability. Our work demonstrates that E. coli encode curli-independent mechanisms that restrict B. bacteriovorus and expand our understanding of the antipredatory bacteria arm of the bacterial immune system.

Citation

Sayegh R, Ledvina HE, Whiteley AT.Curli-independent defense against Bdellovibrio bacteriovorus in E. coli. Microbiol Spectr. 0:e00342-25. https://doi.org/10.1128/spectrum.00342-25

Sayegh R, Ledvina HE, ➤Whiteley AT | Microbiology Spectrum 2025

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Functional amyloid proteins confer defence against predatory bacteria

Aaron Whiteley — Wed, 02 Jul 2025 15:00:00 +0000

Functional amyloid proteins confer defence against predatory bacteria Aaron Whiteley Wed, 07/02/2025 - 09:00

Hannah Ledvina , Ryan Sayegh , Ricardo Carale , Burroughs AM , Alexa Macklin , Azadeh AL , Layla Borja , Aravind L , Aaron Whiteley

Nature (2025) PubMed PMID: 40604283

Abstract

Bdellovibrio bacteriovorus is a predatory bacterium that non-selectively preys on Gram-negative bacteria by invading the prey-cell periplasm, leaching host nutrients and ultimately lysing the infected cell to exit and find a new host. The predatory life cycle of B. bacteriovorus is, in many ways, comparable to a bacteriophage. However, unlike phage defence, defence against B. bacteriovorus has not been widely investigated. Here we screened a collection of diverse Escherichia coli strains for resistance to B. bacteriovorus and identified that roughly one-third of strains robustly defended against predation by producing curli fibres. Curli fibres are oligomers of the functional amyloid protein CsgA, which is exceptionally durable3. Using genetics and microscopy, we demonstrate that curli fibres provide a barrier that protects susceptible cells independent of genes required for biofilm formation. This barrier further protected E. coli against attack by the predatory bacterium Myxococcus xanthus and select phages. Bioinformatic analysis of bacterial amyloids showed these systems are diverse and widespread in diderm bacteria (those with both inner and outer membranes). One of these, an evolutionarily distinct amyloid encoded by Pseudomonas aeruginosa, also protected against B. bacteriovorus. This work establishes that functional amyloids defend bacteria against a wide range of threats.

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Citation

Ledvina HE, Sayegh R, Carale RO, Burroughs AM, Macklin AR, Azadeh AL, Borja Najera LD, Aravind L, Whiteley AT. Functional amyloid proteins confer defence against predatory bacteria. Nature. 2025 Jul 2. doi: 10.1038/s41586-025-09204-7. Epub ahead of print. PMID: 40604283.

Ledvina HE, Sayegh R, Carale RO, Burroughs AM, Macklin AR, Azadeh AL, Borja Najera LD, Aravind L, ➤Whiteley AT | Nature 2025

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Curli-independent defense against Bdellovibrio bacteriovorus in E. coli

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