Bacteria communicate electrically, just like brain neurons with long-range signalling capacity, according to a recent study published in Nature. The previously unclear mechanism occurs through ion channels within biofilm communities and shows bacteria may function like a ‘microbial brain’.
Using a Bacillus subtilis microbial community, researchers monitored long-range electrical fluctuations and investigated changes in membrane potential during metabolic changes or stress to the biofilm.
Previous research in this area showed that when these bacteria, as a biofilm community, grew to a large size, they selectively restricted the unlimited nutrient (glutamate) flow to the bacteria on the outer edge of the biofilm. This inhibited growth and the nutrient uptake by the outer bacteria, providing a nutrient-rich environment for the inner colony centre to grow and survive. This process requires long-range metabolic co-dependence between cells in the biofilm interior and periphery.
Additionally, with the electrically charged glutamate uptake dependent upon trans-membrane electrical potential, this led the researchers to wonder whether metabolic co-ordination amongst distant cells in the biofilm might involve a form of electrical signalling.
The results of this study showed that oscillations in the membrane potential matched the biofilm growth oscillations. Spatially propagating waves of the charged ion potassium through the biofilm produced long-range electrical signalling and co-ordinated the metabolic activity of the bacteria in the inner and outer regions. When the researchers deleted the potassium ion channels, the biofilm could no longer conduct these electrical signals.
Just like the brain, the bacteria used ion channels for membrane potential changes and communication.
In the brain, this specific mechanism is known as ‘cortical spreading depression’, which is thought to be involved in migraines and seizures. Both migraines and electrical signalling in bacteria are triggered by metabolic stress, suggesting drug therapy for migraines and seizures may be effective in attacking bacterial biofilms.
1. Prindle A, Liu J, Asally M, et al. Ion channels enable electrical communication in bacterial communities. Nature 2015;527:59-63. [Abstract]