Heat vents create heat gradients, which create chemical gradients.
Being able to stay at a particular place in those gradients
conferred selective advantage. Therefore microbes developed
a way to react to incoming infrared photons; the energy of heat
was information; it was “seen”.
Eventually some of these bacteria through tides or tectonics
find themselves in shallow water; suddenly there is a new, vivid source of photons.
The same molecules used to harvest photons for information are getting enough news to eat.
The information was a source of energy.
Bacteria and archaea gain energy by creating an electrical potential
gradient by pushing protons across their membrane; from this gradient all energy-bearing
molecules are formed. This energy drives metabolic processes that result in molecules that are,
to various extents and by differing methods, assisted across the membrane. Bacteria of the same
and differing strains respond to the presence of these molecules.
Neurons, though their prime energy-generating membrane is in an internal organelle, use electrical
potential across their membranes to transduct a signal to a synaptic gap, where molecules are
transported across the membrane with a high degree of specificity.
How much do these flows of potential and molecule have to do with each other? Gerald Edelman in [A Universe of Consciousness][a] suggests a mechanism for identifying functional clusters in neurons; similar techniques should be applicable to populations of microbes.