What does the biology do for the soil
The macro- and micro nutrients that plants need are generally abundant in soil particles. However, without the microbes that solubilise these minerals, the plants will not be able to utilise these.
Bacteria and fungi are the little helpers that mine the minerals from soil particles, integrate them into their biomass or release the excess back into the soil.
A large amount of these minerals is released back to the soil in their plant-available forms within the soil food web, i.e. when they are being consumed by the next trophic levels such as protozoa and nematodes.