Which Bacteria Smell Like Tortillas, Flowers, or Delicious Browned Butter?

By Veronique Greenwood | July 5, 2012 12:06 pm

spacing is important

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.

  • Jenna

    I’m a nurse, so I’m smelling things in humans/secretions rather than in culture. I agree that Pseudomonas does have a distinctive, sickly sweet smell, but I wouldn’t describe it as floral; I and my coworkers find it unpleasant. And C. diff does smell heinous–both of these I would say are fairly well known in the medical field for their odors.

  • Mark O. Martin

    Well, actually a chemical made by actinobacteria, geosmin, is indeed responsible for the “potting soil” smell of dirt.  Here are some thoughts:


    I enjoyed your post!

  • Guy Plunkett

    FWIW, I’ve always thought that Pseudomonas aeruginosa smelled like Concord grapes. 

  • Shoelost

    peripheral note:  as a graduate student I discovered that the amino acid lysine smelled like semen. Anyone?? 

  • Hoddyhodson1957

    so, natural smells emenate from bacteria too ???

  • http://twitter.com/Aurametrix Aurametrix, Inc.

    People eating corn chips could smell similar to those infected with pseudomonas: http://aurametrix.com/info/2-Aminoacetophenone
    Vetiver root bacteria (alpha-, beta- and gamma proteobacteria) enhance aroma of Vetiver oil. It is used in men’s colognes. 

  • Kertime

    I remember Alcaligines oderans, probably has been re-assigned a new name: the smell of fresh-cut apples!

  • Guest

    very incompetent author. And spiteful too.

  • Carpen

    Years ago, a boyfriend smelled faintly of Parmesan cheese behind his ears.   Just there – the rest of him was Parmesan-free.   Then he got a sore throat, was given antibiotics, and the Parmesan went away.   I missed it! 

  • Dayjm1

    Pseudomonas always smelled like grape lollipops or some other sort of grape candy to me (not pleasant, though). I worked with Streptomyces in graduate school, and was always reminded of the dirt cellar at my parents house when I grew S. lividans in the incubator in our lab. I now brew beer as a hobby, and certain strains of lager yeast can throw some serious rotten egg smells, which thankfully dissipate as the fermentation slows.

  • http://twitter.com/Aurametrix Aurametrix, Inc.

    Flavobacterium odoratum and Alcaligenes faecalis (formerly Alcaligenes odorans) smell fruity

    Proteobacteria add masculine notes to vetiver oil in men’s fragrance.

    As Jenna said, Pseudomonas can smell sickly too or naphthalene-like, depends on the concentration and the mix of chemicals

  • lu

    what causes the wet dog smell


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