The idiomatic expression “a petri dish” refers to an environment that is conducive to the rapid spread or growth of something. Here are some examples of how it’s commonly used:
“The college dormitories were like a petri dish for viruses last flu season, with all the students living in close quarters.” This implies it was easy for illnesses to spread amongst the students living together.
“Social media has become a petri dish for the spread of misinformation.” Here it suggests platforms allow false information to proliferate very quickly.
“The political debates were a petri dish for new conspiracy theories.” The heated exchanges and conflicting views created favorable conditions for unsubstantiated claims to multiply.
“Our office was a petri dish for gossip during the restructuring.” Employees closely interacting led to gossip about changes to flourish readily.
So in the idiomatic sense, referring to something as a “petri dish” conveys the notion that environmental or situational factors make that place or circumstance highly conducive for rapid contagion, dissemination, or breeding of a phenomenon, similar to how a real petri dish enables microbial cultures to spread and multiply easily under controlled conditions.
