My sister, a medical student who has worked in a pathology lab, recently mentioned in passing that specific strains of bacteria, grown in an incubator, can have some pretty unusual smells. When I asked what she meant, she drew me this table (on some handy Discover stationary).
Now, I've grown plenty of yeast in my day, and they just smell like gym socks. Maybe, if you get some wild ones in there, like gym shorts (I've never enjoyed fancy beer made with wild yeast. Too redolent of crotch).
This level of olfactory whimsy, then, was totally new to me: Pseudomonas aeruginosa smells like flowers? Streptococcus milleri smells of browned butter? Clostridium difficule, scourge of elderly intestines, bringer of fecal transplants, smells like horse poo? I'll confess, I never quite thought about what happens when you get millions of a single kind of bacteria all together in one place and take a nice long sniff. I did not think it would ever be pleasant. I was wrong.
I'll be writing much more on this soon---answering questions like: why do they smell like this? what exactly are they producing? is C. difficile what makes horse patties smell, or it is just the same molecules?---but here are just a few quick tidbits from around the web suggesting that bacteria might be responsible for certain day-to-day smells we take for granted. Proteus bacteria, known for their "sweet, corn tortilla smell" (?!), may be responsible for the popcorn scent of your dog's feet. And soil bacteria Actinomycetes may be behind that rich, wet-earth smell that comes after a rain.
Have any of you ever experienced bacterial scents? Let us know in the comments.