A virus hiding inside bacteria may help explain colorectal cancer

The gut bacterium Bacteroides fragilis has long presented researchers with a paradox. It has been associated with colorectal cancer, yet it also lives quite happily in most healthy people. A study by a Danish research team offers a possible clue. When they looked beyond the bacterium itself and into its genome, they found a previously unknown virus embedded within it—one that was significantly more common in cancer patients.