A recent study showed that brainless bacteria may have “memory” from previous experiences, and surprisingly, this memory is carried down across a few generations.
While humans accumulate countless memories over the years, bacterial memories are limited to certain factors, such as iron levels. This aids the bacteria’s adaptation to their surroundings.
According to researchers from the University of Texas (UT) in Austin, E. coli has created a natural biological system in which iron levels function as a trigger, resulting in the creation of a type of memory in bacteria that regulates their behavior.
These findings might be useful in reducing bacterial infections and combating the growing problem of antibiotic resistance, as per the press release.
Bacteria memory in the form of iron
Scientists revealed that E. coli bacteria use iron levels to retain information about diverse behaviors. In response to particular stimuli, this stored knowledge can be triggered and activated.
“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 in the Department of Molecular Biosciences at UT.
These iron-based memories may guide bacteria in determining when to adopt strategies that pose risks to human health. These strategies include developing resistance to antibiotics and forming bacterial swarms in which millions of bacteria congregate on a single surface.
Researchers propose a theory that suggests when iron levels are low, bacterial memories are activated, prompting the formation of a rapidly moving migratory swarm to search for iron in the surrounding environment. However, when iron levels are high, the bacteria develop a biofilm because the environment is suitable for staying.
“Iron levels are definitely a target for therapeutics because iron is an important factor in virulence. Ultimately, the more we know about bacterial behavior, the easier it is to combat them,” Bhattacharyya concluded.
The findings were published in the journal Proceedings of the National Academy of Sciences.
Study abstract:
The importance of memory in bacterial decision-making is relatively unexplored. We show here that a prior experience of swarming is remembered when Escherichia coliencounters a new surface, improving its future swarming efficiency. We conducted >10,000 single-cell swarm assays to discover that cells store memory in the form of cellular iron levels. This “iron” memory preexists in planktonic cells, but the act of swarming reinforces it. A cell with low iron initiates swarming early and is a better swarmer, while the opposite is true for a cell with high iron. The swarming potential of a mother cell, which tracks with its iron memory, is passed down to its fourth-generation daughter cells. This memory is naturally lost by the seventh generation, but artificially manipulating iron levels allows it to persist much longer. A mathematical model with a time-delay component faithfully recreates the observed dynamic interconversions between different swarming potentials. We demonstrate that cellular iron levels also track with biofilm formation and antibiotic tolerance, suggesting that iron memory may impact other physiologies.
