Question

Suppose you leave one agar plate uninoculated, and after the one week incubation period you observe bacterial colonies growing on it. What would you conclude?

Answer 1

This scenario represents the contamination of agar plate while handling of the experiment. You can actually tell by observing the plate how contamination took place, like, if contaminants are imbedded in the agar , they must be poured with the medium. But if the contamination is on top, contaminants could have been introduced after pouring the medium and before closing the lid or while removing condensation by opening the lid.

So, take appropriate measures to avoid these contamination.