"I can't interface with a bacteria in any meaningful way"

But you do. There are more bacterias in and on the body, than body cells. We are bacterias forming lasting bonds and we still interact with the free floating ones in various ways. Mainly in the gut and that has many effects, also on the brain, but also in various other ways we are beginning to understand.

https://en.wikipedia.org/wiki/Human_microbiome

So no idea about a microbiome consciousness - but who am I to know.