thank you for your reply!! as i was putting my germinated seed with taproot into soil i accidentally dropped it in my floor i picked it up and rinsed with water just to be sureBacteria are everywhere, so it's very possible that they could/can enter the taproot. But plants have evolved with bacteria for millions of years so they can defend themselves. Off course ,as with humans too, sometimes something goes wrong and the weak get culled. But trying to achieve bacteria-less conditions is extremely difficult so I wouldn't worry about it too much.