Bacteria store memories and pass them on for generations: Study

Bacteria can create memories about when to form strategies that can cause dangerous infections in people, such as resistance to antibiotics, a study has found.

Researchers at the University of Texas at Austin (UT) in the US said these strategies also help bacteria to form swarms when millions of these microorganisms come together on a single surface.

The finding, published in the journal Proceedings of the National Academy of Sciences, has potential applications for preventing and combatting bacterial infections and addressing antibiotic-resistant bacteria.

The discovery relates to a common chemical element bacterial cells can use to form and pass along these memories to their progeny over later generations, the researchers said.

They found that E. coli bacteria use iron levels as a way to store information about different behaviours that can then be activated in response to certain stimuli.

"Bacteria don't have brains, but they can gather information from their environment, and if they have encountered that environment frequently, they can store that information and quickly access it later for their benefit," said Souvik Bhattacharyya, the lead author and a provost early career fellow at UT.

The researchers noted that it all comes back to iron, one of the most abundant elements on Earth. Singular and free-floating bacteria have varying levels of iron.

They observed that bacterial cells with lower levels of iron were better swarmers.

In contrast, bacteria that formed biofilms, dense, sticky mats of bacteria on solid surfaces, had high levels of iron in their cells. Bacteria with antibiotic tolerance also had balanced levels of iron.

These iron memories persist for at least four generations and disappear by the seventh generation, according to the researchers.

"Before there was oxygen in the Earth's atmosphere, early cellular life was utilising 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 utilise it in this way," he added.

Researchers theorise that when iron levels are low, bacterial memories are triggered to form a fast-moving migratory swarm to seek out iron in the environment.

When iron levels are high, memories indicate this environment is a good place to stick around and form a biofilm.

"Iron levels are definitely a target for therapeutics because iron is an important factor in virulence. Ultimately, the more we know about bacterial behaviour, the easier it is combat them," Bhattacharyya added.