Scientists have found that bacteria, like E. coli, possess an unexpected trait: the ability to form and pass on “memories.” This discovery sheds light on how bacteria adapt and survive, especially in developing infections and antibiotic resistance.

Iron-clad memory

At The University of Texas at Austin, researchers discovered that E. coli uses iron levels to store environmental information. This storage system enables bacteria to modify behaviors, such as resisting antibiotics or forming swarms (large groups of bacteria migrating together over a surface), based on past conditions.

Bacteria don’t have brains or even neurons. Instead, they store ‘memories’ similar to data saved on a computer. Previous experiences, such as moving in swarms, can enhance their future performance. This memory of previous behaviour, tied to the internal iron levels of the bacteria, is inherited by future generations through epigenetic cues, lasting for at least four generations and fading by the seventh, experiments showed.

“If they have encountered that environment frequently, they can store that information and quickly access it later for their benefit,” said Souvik Bhattacharyya, the study’s lead author. This means the organism functionally ‘remembers’ what to do when its internal environment changes.

The central theme here is iron. This abundant element varies among bacteria. The researchers learned that low iron levels among free-floating bacteria lead to better swarming behaviour, while high levels are found in bacteria that form biofilms — dense clusters of bacteria on surfaces that often become difficult to move or remove. Think of the slimy goo that forms on shower tiles or even dental plaque — both are examples of biofilms. Meanwhile, a balanced iron level seems to contribute to antibiotic tolerance.

“Before there was oxygen in the Earth’s atmosphere, early cellular life was utilizing iron for a lot of cellular processes. Iron is not only critical in the origin of life on Earth, but also in the evolution of life,” Bhattacharyya said. “It makes sense that cells would utilize it in this way.”

Based on what they learned, the researchers have a hunch that when iron is scarce, bacteria remember to aggressively swarm to improve their odds of finding more. High iron signals a suitable environment to settle and form biofilms. This could be used against them when pathogens threaten people with disease.

“Iron levels are definitely a target for therapeutics because iron is an important factor in virulence,” Bhattacharyya said. “Ultimately, the more we know about bacterial behavior, the easier it is to combat them.”

The findings were published in the Proceedings of the National Academy of Sciences.