Hey Hyroot! Good to see you back, and commendable, your initiative to start this thread
Seeing one of your goals is accuracy, I hope you don't mind my saying a few words about the microbes:
This is, simply, not correct.
Root exudates feed bacteria
and fungi and in this way promote their population growth.
Depending on the nutrients the plant needs at every moment of its life, the exudates it produces will be composed differently and thus cause different groups of microbes to proliferate, mine whatever is their favorite food more intensely, and store the nutrients in their little bodies.
This in itself will not feed the plant. There need to be predator species that will eat the bacteria and fungi, and excrete excess nutrients in that desired plant available form, just at the right time.
Lots of exciting things are being discovered regarding the fungi, but they do not regulate the uptake of nutrients for the plant, the plant does that.
I don't know in how far this also applies to saprophytes (fungi who sustain themselves from the mineral and organic matter of the soil vs being hosted by a plant as mycos are), but Jeff Loewenfels describes in
Teaming with Fungi how it has been found that at the fungal tip, up to 40% of the fungal DNA is actually bacterial in nature (what they do with that, is yet to be ascertained
)
In other reasearch it has been found that fungi secrete their own exudates to culture bacteria that will assist them enzymatically with their digestion processes. So the fungi have their own little flock of helpers to get their job done.
As far as is known so far! haha
Knowledge in this area is being gained in leaps as we write
Cheers!