Scientists have unraveled the mysterious mechanism behind the armpit’s ability to produce the pungent odor of body odor.
Researchers at York University traced the source of the armpit odor to a particular enzyme in a certain microbe that lives in the human armpit.
To demonstrate that the enzyme was the chemical culprit, the scientists transferred it to an innocent member of the armpit microbe community and noted, to their delight, that it also began to emit foul smells.
The work paves the way for more effective deodorants and antiperspirants, scientists believe, and suggests that humans may have inherited the mephitic microbes from our ancestral primate ancestors.
“We have discovered how odor is produced,” said Professor Gavin Thomas, a senior microbiologist on the team. “What we really want to understand now is why.”
Humans do not produce the sharpest constituents of BO directly. Unpleasant odors, known as thioalcohols, are released as a by-product when microbes delight in other compounds they find on the skin.
York’s team previously discovered that most microbes on the skin cannot produce thioalcohols. But other tests revealed that an underarm-dwelling species, Staphylococcus hominis, was a major contributor. Bacteria produce the foul fumes when they consume an odorless compound called Cys-Gly-3M3SH, which is released by the sweat glands in the armpit.
Humans come with two types of sweat glands. The eccrine glands cover the body and open directly onto the skin. They are an essential component of the body’s cooling system. The apocrine glands, on the other hand, open up in the hair follicles and crowd into particular places: the armpits, nipples, and genitals. Its role is not so clear.
Writing in the journal Scientific Reports, York scientists describe how they delved into Staphylococcus hominis to learn how it produced thioalcohols. They discovered an enzyme that converts the Cys-Gly-3M3SH released by the apocrine glands into thioalcohol acid, 3M3SH.
Thomas said: “Bacteria absorb the molecule and eat a little, but the rest spit it out, and that’s one of the key molecules that we recognize as body odor.”
After discovering the “BO enzyme,” the researchers confirmed its role by transferring it to Staphylococcus aureus, a common relative that normally has no role in body odor. “By simply moving the gene, we got Staphylococcus aureus that made body odor,” said Thomas.
“Our noses are extremely good at detecting these thio alcohols at extremely low thresholds, so they are really important for body odor. They have a very characteristic cheese and onion smell that you would recognize. They are incredibly spicy. “
The research, a collaboration with Unilever, raises new possibilities for deodorants that target only the most active BO-producing microbes, without touching the rest of the underarm microbial community. “If you can have a more specific approach that selectively removes Staphylococcus hominis, it could be more durable,” said Thomas.
Michelle Rudden and others in the study then looked at the genetic relationships between dozens of Staphylococcus species. The analysis tentatively suggests that only a few inherited the BO enzyme from an ancient microbial ancestor about 60 million years ago.
Since apocrine glands only secrete compounds that produce BO from puberty onward, odors may have played a role in the formation of humanity. “All we can say is that this is not a new process. BO was definitely present as humans evolved, “said Thomas. “It is not impossible to imagine that these were important in the evolution of humans. Before I started using deodorants and antiperspirants, in the last 50 to 100 years, everyone definitely smelled. “
