|Diagram of a human digestive system (Photo credit: Wikipedia)
The viruses in the fecal sample are phages, which are viruses that infect bacteria, rather than infecting eukaryotic organisms such as animals, plants, and fungi. Most of the viral sequences the researchers found in the ancient coprolite (fossil fecal sample) were related to viruses currently known to infect bacteria commonly found in stools (and hence, in the human gastrointestinal tract), including both bacteria that live harmlessly, and even helpfully in the human gut, and human pathogens, says corresponding author Christelle Desnues of Aix Marseille Université.
The communities of phage within the coprolite were different, taxonomically, from communities seen within modern human fecal samples, but the functions they carry out appear to be conserved, says Desnues. That reinforces the hypothesis that the viral community plays a fundamental role within the human gastrointestinal tract, and one which remains unchanged after centuries, even while the human diet and other human conditions have been changing.
Over the last five years, considerable evidence has emerged that bacteria inhabiting the gut play an important role in maintaining human health, for example, as part of the human metabolic system, says Desnues. Her own research suggests that the bacteriophage infecting the gut bacteria may help maintain these bacteria. Among the genes found in the phage are antibiotic resistance genes and genes for resistance to toxic compounds. Both toxins and antibiotics are common in nature, and Desnues suggests that the resistance genes may simply be protecting the gut bacteria from them.
Source: Heritage Daily