Newly discovered gut virus lives in half the world's population

Odds are, there's a virus living inside your gut that has gone undetected by scientists for decades. A new study led by researchers at San Diego State University has found that more than half the world's population is host to a newly described virus, named crAssphage, which infects one of the most common types of gut bacteria, Bacteroidetes.

This phylum of bacteria is thought to be connected with obesity, diabetes and other gut-related diseases.

Robert A. Edwards, a bioinformatics professor at SDSU, and his colleagues stumbled upon the discovery quite by accident. Working with visiting researcher and corresponding author on the study Bas E. Dutilh, now at Radboud University Medical Center in The Netherlands, the researchers were using results from previous studies on gut-inhabiting viruses to screen for new viruses.

In the DNA fecal samples from 12 different individuals, they noticed a particular cluster of viral DNA, about 97,000 base pairs long, that the samples all had in common. When Edwards and his colleagues checked this discovery against a comprehensive listing of known viruses, they came up empty.

The researchers then screened for the virus across the database of the National Institute of Health's Human Microbiome Project (HMP), and Argonne National Laboratory's MG-RAST database, and again found it in abundance in samples derived from human feces.

To prove that the viral DNA they discovered in their computer data actually exists in nature, fellow SDSU virologist John Mokili used a technique known as DNA amplification to locate the virus in the original samples used to build NIH's database. "So we have a biological proof that the virus they found with the computer actually exists in the samples," Mokili said.