Analyzing the fecal sample for its viral components, researchers found a range of phages -- viruses that infect bacteria. Scientists say the phages are closely related to the modern viruses, ones that attach themselves to the different kinds of bacteria living in the gastrointestinal systems of humans.
"This is the first paper to analyze an ancient DNA viral metagenome," Rebecca Vega Thurber of Oregon State University, Corvallis, who was not involved in the research, said in a news release.
Lead researcher Christelle Desnues and her colleagues at Aix Marseille Université, in France, found that some of the phages contained antibiotic resistance genes. Antibiotics were not invented by physicians until several centuries later, but antimicrobial substances occur in nature, and it's likely the resistance genes are meant to protect the gut bacteria that play host to the viruses.
Desnues says it's evidence that though diets have much evolved, the bacteria and viruses that play an important -- but still little understood -- role in aiding digestion have not seemed to change much.
"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," said Desnues. "We were interested in viruses because these are 100 times more abundant than human cells in our bodies, but their diversity is still largely unexplored."
The details of the Belgian fossil fecal study was published in the journal Applied and Environmental Microbiology.