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Have you ever caught a whiff of something and wondered, “What in the world is responsible for this?” Well, the world of microbes might hold the answer. These tiny organisms, invisible to the naked eye, have the remarkable ability to produce smells that range from delightful to downright repulsive. It’s a world where the nose becomes a gateway to a range of odors, each telling a microbial story.
As a curious microbiologist, I couldn’t resist asking my fellow scientists about their favorite microbial smells. So, I took to Twitter, and the responses were intriguing, with an array of aromas ranging from delicious to disgusting.
One thing that makes these microbial scents so interesting is that they often capture the essence of the environments in which the microbes thrive. Even when grown in the sterile confines of a laboratory petri dish, these microbial fragrances transport us to far-off places, evoking associations we never thought possible.
In this article, we journey into the aromatic world of microbes. Get ready to discover smells that scientists encounter in their quest to understand the hidden wonders of microbial life. At the end, you can find a table of these microbial smells, along with a few extras for good measure. So, take a deep breath because we’re about to dive headfirst into a symphony of microbial scents.
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The Scented Earth: Microbes and the Aroma of Soil and Rain
When it comes to the enchanting scent of soil, we have microbes to thank, and the Streptomyces species are one group particularly known for this role, though others are involved in creating the earthy aroma. But what exactly is it about Streptomyces that makes soil smell the way it does?
One of the key culprits behind the distinctive scent of soil is a chemical compound known as geosmin. Geosmin, derived from the Greek words for “earth” and “smell,” is produced by Streptomyces species and a few other soil microbes and is responsible for the characteristic, intoxicating fragrance of soil, particularly after rainfall. This natural compound has the uncanny ability to evoke feelings of nostalgia and connect us to the wonders of nature.
To illustrate the association between Streptomyces and the scent of soil, here’s an anecdote from Dr. Stephan Cameron.
Streptomyces smells like garden soil in the spring 🙂 Fun when the incubator is full of plates in the middle of winter. — Steph Cameron (@StephanMCameron)
Dr. Cameron’s words beautifully encapsulate the magic of Streptomyces and its ability to transport us to a garden brimming with life, even in the coldest months of winter. It’s a testament to the ability of microbial smells to invoke joy and a sense of wonder, even in the confines of a laboratory.
Among the many responses I received on Twitter, the mention of geosmin and its association with soil emerged as a favorite among many. The allure of this microbial aroma is undeniable, captivating the hearts and noses of scientists and enthusiasts alike.
Learn more about geosmin in this article.
Microbial Culinary Delights: Surprising Food-Like Aromas
While the world of microbes may seem far removed from the aromas of grapes, corn tortillas, caramel, and beef sandwiches, it turns out that these seemingly unrelated words can indeed be associated with microbial smells. It’s a phenomenon that highlights the diverse range of fragrances microbes can produce, often defying our preconceived notions.
One microbe with smells that caught the attention of many scientists is the pathogenic bacterium Pseudomonas aeruginosa. This bacterium has the intriguing ability to produce a variety of odors. Dr. Jesus Romo described the smell of Pseudomonas aeruginosa as reminiscent of “corn tortillas,” while Amy Cannan characterized it as having a distinct “fake grape flavor.”
I have several. Alcaligens faecalis smells like a flower, P. aeruginosa like corn tortillas, Candia like bread, and C. difficile….welll 😵 — J. A. Romo, Ph.D. (@CandidaScience)
Mmmmm… Pseudomonas aeruginosa… an obvious one but a goodie. Yummy grape (fake grape flavor) scent. As long as it’s only a day or so incubation. After that, 🤢. — Amy Cannan (@AmyCannan1)
The scent of corn tortillas and “fake grape” might seem unusual associations when discussing microbial smells, but it exemplifies the complex and unexpected nature of these olfactory encounters. Dr. Romo’s tweet also captures the essence of microbial diversity, as he reveals that in addition to the corn tortilla smell of Pseudomonas aeruginosa, Alcaligens faecalis smells like a flower, Candida like bread, and C. difficile…well, perhaps best left to the stinky section below.
Amy Cannan’s tweet further reinforces the idea that Pseudomonas aeruginosa can indeed emit an alluring aroma akin to a “yummy grape (fake grape flavor) scent.” However, it’s important to note that these odors are often time-dependent, as Amy highlights that the enjoyable scent persists only during the initial stages of incubation, after which it takes an unpleasant turn.
As someone who personally delved into the world of Pseudomonas aeruginosa during my PhD studies, I can attest to the multifaceted smells emitted by this bacterium. It’s fascinating how this pathogenic microbe can exhibit fragrances ranging from grapey to the unexpected resemblance of corn tortillas or corn chips. Such encounters serve as a testament to the richness and complexity of microbial smells, continuously engaging our senses in unexpected ways.
So, as we explore the diverse olfactory tapestry woven by microbes, be prepared to uncover more surprising connections between pleasant aromas and the microscopic world.
Aromatic Encounters: Microbes and Sweet Delights
Among the responses to my tweet about favorite microbial smells, one particularly sweet aroma stood out. According to Dr. Geneviève HéryArnaud, the bacterium Streptococcus anginosus produces a scent reminiscent of caramel or butterscotch, evoking memories of Carambar, a sticky caramel candy from France.
I like the smell of Streptococcus anginosus (ex- milleri group): it smells like Carambar, a French sticky caramel candy. More surprising, I like the smell of Staphylococcus lugdunensis: it smells like Rosette de Lyon (Lugdunum in latin), a famous type of French saucisson. #VOC — Geneviève HéryArnaud (@Genevieve_Hery)
Dr. HéryArnaud’s delightful description further emphasizes the enchanting olfactory experiences that certain microbes can provide. But what exactly is it about this bacterium that imparts such an oddly mouthwatering fragrance?
The secret lies in a compound called diacetyl, known for its buttery aroma. Streptococcus anginosus has the remarkable ability to produce diacetyl, infusing its surroundings with a scent reminiscent of caramel or butterscotch. This compound adds a touch of sweetness to the microbial fragrance tapestry.
Dr. HéryArnaud’s reference to the Carambar candy serves as a reminder that the world of microbes extends beyond the realm of laboratories and into our personal experiences, even triggering thoughts of a delectable treat.
As we delve further into the aromatic world of microbes, we’ll continue to uncover surprising connections between the scents these tiny organisms produce and that of delicious food.
Yogurt and Beef Sandwiches: The Whiff of Lactobacillus
When it comes to the world of microbes and their aromatic surprises, it’s hard to overlook the role of Lactobacillus bacteria. These industrious microorganisms are integral to the production of yogurt, so it’s no surprise that they emit a fragrance reminiscent of the beloved dairy treat. Dr. Jade Passey attests to the sweet and warm yogurt scent associated with Lactobacillus.
Lactobacillus smells like sweet, warm yogurt…@HelenLouBrown thinks it smells like beef sandwiches 🤔 — Jade Passey (@JLPassey)
However, in the world of microbial smells, there’s always room for surprises and intriguing anecdotes. Dr. Passey also shared an interesting tidbit — her colleague detected a whiff of “beef sandwiches” Lactobacillus when working with it. While this might seem unexpected given the association of Lactobacillus with yogurt, it highlights the subjective nature of our olfactory perceptions. One person notices a specific aroma, while another may detect an entirely different aspect of it.
The idea that Lactobacillus can evoke scents resembling both yogurt and beef sandwiches serves as a reminder of the incredible diversity of smells that microbes can produce. These unexpected associations blur the lines between the microbial world and the realm of delicious food, demonstrating that bacteria have the astonishing ability to create the aromas that tantalize our taste buds.
So, whether Lactobacillus triggers thoughts of creamy yogurt or conjures images of savory beef sandwiches, it’s a testament to the multifaceted nature of microbial smells and their ability to evoke a wide range of sensory experiences. As we continue our olfactory exploration, we’ll encounter some connections between microbes and unpleasant scents that you may have assumed from the outset.
The Dark Side: Unpleasant Microbial Odors
While the world of microbial smells can be delightful and intriguing, it’s true that not all aromas produced by microbes are enjoyable. In fact, some of them can be downright repulsive, evoking scents that remind us of vomit and feces. As we venture into this olfactory territory, prepare for the less enchanting side of microbial fragrances.
It’s no surprise that many of these not-so-delightful-smelling microbes find their home in feces. One such resident is *Escherichia coli* Nissile, a bacterium known for its distinctive odor. Dr. Carla Brown described the smell of Escherichia coli Nissle as reminiscent of its “wee home.” While it might not be the most pleasant scent, it serves as a reminder of the diverse olfactory experiences that microbes can provide.
Nissle 1917 always smelled a little like poop! Gross but I used to like that it smelled like it’s wee home. — Carla Louise, Ph.D (@Sci_Game_Girl)
Another less-than-lovely smell scientists encounter is the putrid scent emanating from certain species of Clostridium. Matilda Berkell, an individual with personal experience, aptly describes the smell as a “crossover of poop and vomit.” It’s an odor that elicits a strong reaction and is indeed unpleasant. This example highlights the role of fecal microbes in contributing to the foul smells commonly associated with bathrooms.
Crossover of poop and vomit 👌 that would be #cdiff growing in BHI… — Matilda Berkell (@MBerkell)
While it may not be the most pleasant topic to explore, acknowledging the less desirable smells bacteria produce is crucial in understanding the complex and multifaceted nature of the microbial world. By uncovering the entire spectrum of microbial aromas, we gain a deeper appreciation for the variety of odors they can produce.
Microbial Smells, the Good and the Bad
The microbial world never fails to astound us with its aromatic wonders. Through this exploration of microbial smells, we have witnessed a symphony of scents, ranging from the delightful to the repulsive and everything in between.
Below is a table of the smells contributed by those who responded to my Twitter post. If you’d like to see all of the responses, you can read them here. Since the original post, I posed this question again on Twitter and got a few more interesting responses, which you can read here.
| Smell | Microorganism |
| Dirt, earthy, rain, geosmin | soil microbes like Streptomyces |
| Fake grape, rotting fruit | Pseudomonas aeruginosa |
| Corn chips, corn tortillas | Pseudomonas aeruginosa |
| Butterscotch | Streptococcus anginosus |
| Yogurt | Lactobacillus |
| Poop | Escherichia coli Nissile |
| Poop and vomit | Clostridium |
| Cream corn or cooked broccoli | Campylobacter |
| Ammonia and alcohol-ey bread | Exophiala dermatitidis (Black yeast) |
| New shoe, rubber | Pseudomonas chlororaphis |
Thanks so much to everyone who participated and shared their unique experiences and perspectives on microbial smells. Your contributions have enriched our understanding of how microbes add to the odors surrounding us. Special thanks to those who allowed me to include their responses in this article.
Delving into the smells of microorganisms shows that the microbial world has the power to evoke memories, spark curiosity, and surprise us with unexpected associations. It’s a reminder that the unseen realm of microbes extends far beyond our initial perceptions, engaging our senses in ways we might never have imagined.
If you want to further explore the intriguing world of microbial smells and their practical applications, I highly recommend getting the book “A Field Guide to Bacteria” by Betsey Dexter Dyer. It’s an invaluable resource for enjoying microbes in our daily lives.
So, next time you smell something and think to yourself, “I wonder what made that…” consider that it may have originated from the microbial realm.
Deepen your exploration of the microbial universe!
My ebook, “Joyful Microbiology Activities,” provides 10 engaging, DIY experiments to ignite your curiosity about the unseen world of microbes. Get your copy today!
Discovering the Microbial World: Create Your Own Agar Plates
