Body odour enzyme existed 'before evolution of modern humans' © Getty Images

Body odour enzyme existed ‘before evolution of modern humans’

Researchers have identified the cause of the smell produced by armpits as a particular enzyme.

Scientists have discovered what lies behind the armpit’s ability to produce the pungent characteristic smell known as body odour or BO.

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Researchers from the University of York have previously shown that only a few bacteria in your armpit are the real culprits behind BO. But now, working with Unilever scientists, they have identified a unique BO enzyme found only in the bacteria that live under the arm that is responsible for the armpit odour.

The study, published in Scientific Reports, highlights how particular bacteria have evolved a specialised enzyme to produce some of the key molecules recognised as BO.

The armpits are home to a diverse community of bacteria that is part of your natural skin microbiome. When the bacteria in the armpit encounter sweat, they produce pungent products called thioalcohols which are responsible for the odour.

Read more about the skin microbiome:

The researchers identified Staphylococcus hominis as one of the main microbes behind body odour. They discovered the enzyme by transferring it to non-odour producing bacteria and found that it also began to produce a smell.

Co-first author Dr Michelle Rudden from the group of Professor Gavin Thomas in the University of York’s department of biology, said: “Solving the structure of this BO enzyme has allowed us to pinpoint the molecular step inside certain bacteria that makes the odour molecules.

“This is a key advancement in understanding how body odour works, and will enable the development of targeted inhibitors that stop BO production at source without disrupting the armpit microbiome.”

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The researchers say that this BO enzyme was present in S. hominis long before the emergence of Homo sapiens as a species, suggesting that body odour existed prior to the evolution of modern humans.

Am I more bacteria than human?

There are more bacterial cells in your body than human cells, but the ratio isn’t as extreme as once thought. A 2016 study at the Weizmann Institute of Science in Israel found that our total cell count is 56 per cent bacteria (compared with earlier estimates of 90 per cent). And because bacteria are much smaller, their total mass is only about  200g. So by weight, we are more than 99.7 per cent human.

Even so, we shouldn’t underestimate the contribution bacteria make to our body, nor feel threatened by it. Most of our ‘human’ cells contain structures called mitochondria, which we rely on to convert glucose into compounds we can use for energy.  

These mitochondria probably began as free-living bacteria before they embarked on a symbiotic relationship with us. The only reason that we don’t include them in our tally of bacteria is that they never leave the confines of human cell membranes, though they are, in many respects, independent organisms with their own DNA. 

Like all multicellular animals, we can’t easily point to individual components and say “This is part of me, and this is not”. Your body is like a city – it has a collective identity that goes beyond its individual inhabitants. The pigeons and squirrels that call London home are just as much a part of it as the humans who live there.

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