Bacteria Harness Amyloids as Defense Against Predatory Threats

Research from the University of Colorado Boulder has revealed that bacteria use amyloids, often associated with diseases like Alzheimer’s, as a protective mechanism against their own predators. Published in the journal Nature in March 2025, the study highlights how these proteins serve as a molecular armor for bacteria, enabling them to fend off other harmful bacterial species.

Senior author Aaron Whiteley, an assistant professor in the Department of Biochemistry, explained, “We discovered that bacteria all around us are using amyloids as a molecular suit of armor.” This finding not only sheds light on bacterial defense mechanisms but also opens avenues for developing new treatments for infections in settings such as hospitals and food processing facilities. Understanding these defenses can also enhance knowledge of the human immune system, which shares genetic origins with bacteria.

The study focused on the predatory bacterium Bdellovibrio bacteriovorus, commonly known as “Bdello.” This microbe invades other bacteria, consuming their nutrients until they die. Found in diverse environments, from household showers to natural waterways, Bdello poses a significant threat to bacteria like E. coli. Whiteley noted, “They are generally harmless to humans, but they are deadly to the bacteria that make us sick.”

Traditionally, Bdello has been considered nearly invulnerable, with most bacteria unable to resist its predatory behavior. However, Whiteley and postdoctoral fellow Hannah Ledvina sought to determine whether some bacteria could successfully defend themselves against this threat. Their research involved collecting various strains of E. coli from sources worldwide, including animal intestines and environmental samples.

In a surprising discovery, the team found that approximately one-third of the E. coli strains they examined exhibited resistance to Bdello. Using advanced microscopy, they observed that these resistant strains coated themselves in a type of amyloid protein called curli. This protein, while distinct from the amyloids associated with Alzheimer’s disease, shares similar durability traits.

Whiteley stated, “We contend that the same characteristics that make amyloids a problem for humans—the fact that they are durable and hard to break down—make them an ideal suit of armor for bacteria.” This study suggests that amyloids also play a role in forming biofilms, which are layers of bacteria that can adhere to surfaces and contribute to persistent infections.

Current methods to remove biofilms often involve physical scraping, but Whiteley speculates that Bdello and similar predatory bacteria may possess unique enzymes capable of breaking down these resilient structures. He remarked, “Wherever organisms are fighting, there is biochemical innovation happening.” The research team is now exploring the genetic tools these bacteria may have developed to disrupt biofilms.

The implications of this research extend beyond microbial warfare. By understanding how bacteria utilize amyloids and what predatory bacteria do to bypass these defenses, scientists could unlock new strategies for combating antibiotic resistance and diseases related to amyloids, such as Alzheimer’s.

Whiteley concluded, “If we can understand what makes this armor so durable and what some predatory bacteria are doing to circumvent it, it could have all sorts of implications for human health.” As this field of study evolves, the insights gained may lead to groundbreaking advancements in medical science and infection control.