2019 and the Tardigrade. Whether or not a colony now exists on the moon.
To the Troglofauna, in alluvium to subterranean earth. Oxygen reliant and therefore found in promixity to iron reserves.
Which then follows on to the stygafauna. Or even deeper within the sea itself the creatures created through chemosynthesis of surrounds.
The layers of hydrological life.
Compounded with bacterias wants and needs along with hydrochemistry.
Such as say maybe within the human body, Staphlococcus which likes all your blood near vital organs and Streplococcus which inflames the joints of a humans bone structure.
As an anaerobic bacteria dominanting flow paths may divert action to feed itself. So what might the tiny microfauna do?