Plants absorb bacteria and fungi through their roots, consuming some and redespositing others elsewhere in the soil continuing this growth cycle. This is process called rhizophagy. So you are going to finding all these endophytes (things that live at the end of the root hairs) in their plant sap.

You would need to check the sap with a microscope to confirm what's actually there though.

Rhizobia is the most famous one because it's been know the longest. But baker/ale/wine yeast is another endophyte that partners with loads of plants so it probably have that in this sap.