Though digging through a latrine from the 14th century is not the most glamorous of tasks, scientists have found viruses that contain genes for antibiotic resistance in fossilized human feces from ancient Belgium.
The feces are from a time long before antibiotics were used, and the investigators say it provides evidence that the human gut has remained unchanged after centuries.
They publish the results of their study in the journal Applied and Environmental Microbiology.
But how does one find fecal samples from 700 years ago? The scientists say their research began when an urban renewal project in Belgium uncovered latrines from the 1300s beneath a square.
In 1996, the specimen was excavated and collected from inside a closed barrel, which was frequently used as a toilet in that era. The team notes that the barrel was still intact when it was found, which suggests the sample was protected from contamination for centuries.
Additionally, the team took "extensive precautions" to avoid contamination of the sample both at the site and in the lab.
After analyzing the ancient feces, the team found phages, which are viruses that infect bacteria, rather than eukaryotic organisms - such as plants, animals and fungi.
They compared the fossilized sample's DNA virome with the viromes of 21 modern human stool specimens and found that many of the viral sequences were related to viruses known today to infect bacteria in stools.
The researchers say this includes both bacteria that live harmlessly - and sometimes helpfully - in the human gut and human pathogens.
'Ancient reservoir of resistance genes'
Viruses found in the 700-year-old fecal samples are related to viruses known today, suggesting the human gut has remain unchanged after centuries.
One of the study authors, Christelle Desnues of Aix Marseille Université in France, says that although the phage communities from the ancient sample were taxonomically different from those in modern human samples, the functions they carry out appear to be the same.
She says this demonstrates how the human gastrointestinal tract has remained unchanged after so many centuries, even in the wake of changing diets and conditions. It also supports the theory that the viral community plays a vital role in the human gut and human health in general - for example, as part of the human metabolic system.
Desneus' own research indicates that the bacteriophage infecting gut bacteria may help maintain this "good" bacteria.
Of the genes found in the phage, she and her team found antibiotic resistance genes and genes resistant to toxic compounds, which is a normal part of life, Desneus notes, citing that toxins and antibiotics are common in nature.
She suggests that the resistance genes may be protecting the gut bacteria from toxic compounds and adds:
"Our evidence demonstrates that bacteriophages represent an ancient reservoir of resistance genes and that this dates at least as far back as the Middle Ages."
She says the reason they were interested in viruses is "because these are 100 times more abundant than human cells in our bodies, but their diversity is still largely unexplored."
The team is currently working on further studies of the ancient fecal samples, which involves the fungi and parasites found in them. Desnues says this will have implications for microbiologists, historians, anthropologists and evolutionists.
In 2013, Medical News Today reported on a study that suggested a quarter of the population have 40% less intestinal bacteria than what is needed to maintain good health.