When Plant Growth Promoting Rhizobacteria feed on your organic nutrients, they convert organic matter into inorganic matter. Look into the nitrogen cycle. What they are doing is making ammonium, nitrite, nitrate out of organic nitrogen sources. Yep they are making all those "evil chemicals" except not in an industrial complex but in a soil complex. Combine one with a nearby element of an opposite charge (potassium(+) and sulfate (-) for example) and you get a "salt" from a chemistry perspective. Plants can only take up inorganic nutrients. They take them up in 3 different ways one of which is why hydro and soil drenches work with inorganics...to an extent. Ammonium "sticks" to soil. They can only feed on it when you add water again until your soil dries....mostly. PGPR are everywhere. They now sell soil based probiotic (code for bacteria) supplements. They perform a similar function in human digestion as in plant nutrient assimilation. They function as probiotics for plants too.
PGPR perform other important functions. Their metabolites contain important plsnt growth hormones (Indole 3, cytokins, gibberellic acid, etc), insecticides, pathogen suppressors, Any soil you buy will have some amount of microbes. Even the pot you plant them in, your hands. So whether you realize it or not, they are doing all of these important things necessary for plants to live. Adding more simply boosts the efficiency of this micro ecosystem. That means fewer nutrient and water requirements because more microbes make the work easier. Plants feed your microbes too. They have a mutually vested interest in survival. Plants and people need rocks to live but plants can't eat them and if people do.....well probably not recommended....it doesn't do anything to improve your health. We don't have a gizzard like chickens do. They can actually get mineral nutrients from rocks....it's their powerhouse bacterial population. Certain microbes can "eat rocks", they pass those nutrients on to the plant and the plant passes those nutrients on to animals when eaten. Plants and animals die and feed the microbes. It's the circle of life.
Does this make sense?