Wasn't there an experiment of farting in a lab and contamination of petri dishes?

Something in the lines that at least wearing one layer (underwear) is enough to prevent contamination.

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Wow, there are plenty of studies, this is the funnies one I found:

https://pmc.ncbi.nlm.nih.gov/articles/PMC1121900/

“Our deduction is that the enteric zone in the second Petri dish was caused by the flatus itself, and the splatter ring around that was caused by the sheer velocity of the fart, which blew skin bacteria from the cheeks and blasted it onto the dish. It seems, therefore, that flatus can cause infection if the emitter is naked, but not if he or she is clothed. But the results of the experiment should not be considered alarming, because neither type of bacterium is harmful. In fact, they're similar to the ‘friendly’ bacteria found in yoghurt."