Direct from the Genomics and Microbiology lab: A Scented Citizen Science Project!
This post is brought to you by Dr. Sarah Council, postdoctoral fellow for the Center for Science, Math & Technology Education at NC Central University in Durham, NC and in our own Nature Research Center. Thank you Dr. Council!
Who hasn’t smelled themselves after a great run or an intense basketball game? You can thank your microbes for your body odor! We want to learn more about them, so we recently hosted a multi-day sampling event at the Museum to explore the microbes of the human body and enlisted citizen scientists to help.
Microbes (single-celled organisms like bacteria, fungi, and archaea) make up over 90% of the cells on and in your body. They benefit the human body by producing vitamins, breaking down our food, and even making us smell (1, 2). Microbes located on your skin are what give us “body odor.”
The human skin microbiome (the microbial community on our outer surface), in particular the armpit microbiome, is composed of 4 to 5 types of bacteria, though the majority is made up of bacteria called Staphylococcus and Corynebacteria (3). Bacteria colonizing our armpits thrive from nutrients in our sweat and in turn produce the characteristic body odor smell (4). Knowing this important fact lead Dr. Julie Horvath’s team in the NRC Genomics and Microbiology lab to question how these bacteria affect our daily habits.
For the Armpits, Microbes, and Odor project, we convinced 23 citizen scientists to let us sample their armpit microbes. The goal: to better classify the microbes of the human armpit, understand the odor and other compounds the microbes produce, and rate the attractiveness of those odors.
On Day 1, we captured participant armpit microbiomes during a normal day, or the microbiome present as our subjects followed their usual hygiene routines. From our participants, we sampled:
- DNA (Deoxyribonucleic acid, the molecule responsible for coding cellular instructions for life)
- Metabolites (molecules used as nutrients by living cells)
- Volatiles (a type of metabolite that can be an odor)
We then asked participants to go without underarm product (antiperspirant and deodorant) for 3 days. Antiperspirants act to physically block the excretion of sweat from glands under your arm. Deodorant products kill microbes with the use of alcohol-based solutions and mask the odor with fragrance. Both products have a significant impact on the human armpit microbiome (5).
Our citizen scientists were allowed to shower normally, though we gave everyone a plethora of fragrance-free products, including shampoo, body wash, sunscreen, body lotion, and face lotion. Eliminating fragrance was important so we could capture a person’s natural smell. In addition, we gave participants cotton t-shirts laundered in fragrance-free detergent to wear as they slept for 3 nights. These t-shirts would soak up that natural smell.
On Day 4, we repeated the first day’s sampling, and participants turned in their T-shirts in a sealed plastic bag. But we didn’t stop there! Our participants and other citizen scientists then had the opportunity to participate in a “Speed Smelling” event in the NRC Daily Planet. Emceed by our own Brian Malow, participants smelled the shirts worn by project participants as well as two unworn t-shirts washed in fragrance-free detergent. Over the course of an hour, each shirt was rated on overall smell, odor intensity and attractiveness by 20 smellers. We also asked if the T-shirt had a specific smell and if participants could identify their own T-shirt.
Processing over 250 samples of DNA, metabolite and volatile samples will take some time but we do have preliminary results from our Speed Smelling event. We learned that the top 3 most attractive t-shirts were worn by females and smelled floral and sweet. To our surprise only one participant identified their own shirt. One more interesting note was that a participant classified the unworn T-shirt as smelling like Boston Crème Pie!
We’re hard at work processing the samples from our citizen scientists, so stay tuned for further results connecting microbes, odor and attractiveness!
You can keep up-to-date on Dr. Council’s and Dr. Horvath’s work by following them on Twitter with hashtag #skinscent or by following @SarahCouncil and @NRCJulie. You can also learn more about the lab and the armpit microbiome project at http://naturalsciences.org/nature-research-center/genomics-microbiology and http://armpits.yourwildlife.org/.
(1) Turnbaugh PJ, Ley RE, Hamady M, Fraser-Liggett CM, Knight R, Gordon JI. The human microbiome project. Nature 2007 Oct 18;449(7164):804-810.
(2) Leyden JJ, McGinley KJ, Hölzle E, Labows JN, Kligman AM. The microbiology of the human axilla and its relationship to axillary odor. J Invest Dermatol 1981;77(5):413-416.
(3) Council S, Savage A, Urban J, Ehlers M, Dunn R, Horvath J. The Diversity and Evolution of the Primate Skin Microbiome: How different are humans from our closest relatives? (in review).
(4) Shelley WB, Hurley HJ, Nichols AC. Axillary odor: experimental study of the role of bacteria, apocrine sweat, and deodorants. AMA Archives of Dermatology and Syphilology 1953;68(4):430-446.
(5) Urban J, Ehlers M, Fergus D, Menninger H, Dunn R, Horvath J. Deodorants and antiperspirants inhibit growth and modulate species composition in human axilla (in review).