Nitrogen - A New Route to Boosting Gut Bugs!

Whether you are a cow, a sheep, a goat or a human, it pays to have a good relationship with the bacteria in your gut. So could we use nitrogen more smartly to broker intestinal harmony? Dr Gavin Stewart is investigating. 

Animals produce nitrogen compounds as byproducts of living. “Fish will produce ammonia, birds produce uric acid and mammals (including humans) produce urea, which makes up one of the major constituents of urine,” explains Dr Stewart, who is a lecturer in comparative physiology at UCD School of Biology and Environmental Science.

But in ruminant mammals such as cows, sheep and goats, nitrogen can be ‘recycled’ and used by bacteria in the intestine, which can make use of the supposed waste. 

“Ruminants recycle urea into the rumen and the bacteria have a urease enzyme which mammals don’t possess, so the bacteria break down urea into ammonia and carbon dioxide and they can use the ammonia as nitrogen source for themselves,” says Dr Stewart. “This means the bacteria are able to grow quite well, and the bacteria break down cellulose and produce short-chain fatty acids, which the animal can use as energy source.”

This two-way relationship keeps both mammal and bacterium happy, and is one of the reasons that ruminants can survive on relatively low quality diet, according to Dr Stewart, who is exploring the dynamics of urea ‘salvage’ in the gut. “Our studies have shown that urea transporters are important in the gut of ruminants for moving urea across the gut wall to the bacteria,” he says. 

And now, with Professor Alan Baird from UCD School of Veterinary Medicine, he is looking at urea transport in the human intestine, where again a relationship with the resident bacteria can play an important role in general health.

“We are looking at where the urea transporters occur naturally in the gut, which will help us to better understand how humans may be using nitrogen to support the bacteria in our own guts,” says Dr Stewart.

The work could have applications in new approaches to influence the gut microbes, he explains.   

“If you want to change the bacterial population in your gut, one way could be to overload it with an intake of new bacteria - maybe through oral supplements, which aren’t always effective as the bacteria might not make it to the colon, or through enemas, which aren’t convenient. Managing the nitrogen supply to bacteria in the gut could offer another route to controlling the microbes that live there.”

Dr Gavin Stewart, Lecturer from UCD School of Biology and Environmental Science, was interviewed by freelance journalist Dr Claire O'Connell. Posted on the 7th August 2015.