Collectives of bacteria, or biofilms, stimulated with light remembered the exposure hours after the initial stimulus, according to new research. Reported in a paper in the journal Cell Systems, the discovery reveals surprising parallels between bacteria and neurons that process memory in the human brain.
SEM image of Bacillus subtilis biofilm. Image credit: A. Bridier et al, doi: 10.1371/journal.pone.0044506.
“Even just a few years ago people didn’t think bacterial cells and neurons were anything alike because they are such different cells,” said senior author Professor Gürol Süel, a researcher in the Division of Biological Sciences, the San Diego Center for Systems Biology and the Center for Microbiome Innovation at the University of California San Diego.
“This finding in bacteria provides clues and a chance to understand some key features of the brain in a simpler system.”
“If we understand how something as sophisticated as a neuron came to be — its ancient roots — we have a better chance of understanding how and why it works a certain way.”
Following recent discoveries by Professor Süel’s team that bacteria use ion channels to communicate with each other, the new study suggested that bacteria might also have the ability to store information about their past states.
The study authors were able to encode complex memory patterns in bacterial biofilms with light-induced changes in the cell membrane potential of Bacillus subtilis.
The optical imprints, they found, lasted for hours after the initial stimulus, leading to a direct, controllable single-cell resolution depiction of memory.
“When we perturbed these bacteria with light they remembered and responded differently from that point on,” Professor Süel said.
“So for the first time we can directly visualize which cells have the memory. That’s something we can’t visualize in the human brain.”
Yang et al show that single-cell-level memory patterns can be imprinted in bacterial biofilms by light-induced changes in the membrane potential. Image credit: Yang et al, doi: 10.1016/j.cels.2020.04.002.
The ability to encode memory in bacterial communities could enable future biological computation through the imprinting of complex spatial memory patterns in biofilms.
“Bacteria are the dominant form of life on this planet,” Professor Süel said.
“Being able to write memory into a bacterial system and do it in a complex way is one of the first requirements for being able to do computations using bacterial communities.”
“It may thus be possible to imprint synthetic circuits in bacterial biofilms, by activating different kinds of computations in separate areas of the biofilm,” the researchers said.
“Overall, our work is likely to inspire new membrane-potential-based approaches in synthetic biology and provide a bacterial paradigm for memory-capable biological systems.”
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Chih-Yu Yang et al. Encoding Membrane-Potential-Based Memory within a Microbial Community. Cell Systems, published online April 27, 2020; doi: 10.1016/j.cels.2020.04.002
