These viruses invade gut bacteria, but what they do is still a mystery.

Scientists have identified more than 70,000 previously unknown viruses that live in the human gut and infect the bacteria that live there  — but how they impact our bodies is a mystery.

The gut microbiome, or the community of microbes that we carry around in our digestive system, plays an important role in food digestion and regulating the immune system, Live Science previously reported. But many studies have also linked imbalances in gut microbes to conditions including liver disease, obesity and allergies.

Yet shockingly little is known about the microbiome. Although the microbiome includes a variety of microorganisms — including bacteria and viruses — previous studies have focused mainly on gut bacteria because they are easier to detect.