Bacterial electrophysiology
What is bacterial electrophysiology?
Bacterial electrophysiology studies the electrical dynamics of bacterial cells. It connects ion transport and membrane voltage with questions about energy, growth and communication.
Bioelectricity is the broader study of electrical phenomena in living systems. Nerve and muscle activity are familiar examples, but membrane potential is Ubiquitous in cells without these specialised functions. Bacteria help us test how general physical principles operate in a different cellular setting.
Membrane potential: voltage across a membrane
We define membrane potential as Δψ = ψinside − ψoutside. A negative value means that the interior is electrically negative relative to the exterior. Selective ion permeability and active transport help generate and maintain this difference.
Membrane potential and the proton motive force
The proton motive force is the sum of membrane potential and chemical potential (pH difference). This drives ATP synthesis, molecular transport and many other cellular processes.
Here ΔpH = pHinside − pHoutside; R is the gas constant, T the absolute temperature and F the Faraday constant.
How do bacteria communicate?
Bacteria influence one another through chemicals, metabolites, direct contact and changes in their shared environment. Quorum sensing is one form of chemical signalling, but it does not encompass all microbial interactions.
Electrical interactions can occur when ion release changes the local environment of neighbouring cells. In studied B. subtilis biofilms, potassium-channel activity is linked to signal propagation across a community.
Shared ion physics does not imply that bacteria have neurons or brains. It provides testable questions about how cells affect one another.
What remains to be understood?
We still do not understand the mechanism of bacterial electrical signalling. Which ions carry a response? What changes in a receiving cell? How do cells generate and maintain membrane voltage? Answering these questions needs perturbations, independent measurements and models that make distinct predictions.