Forget needles in haystacks. Try finding the tip of a needle in a virus. Scientists have long known that a group of viruses called bacteriophages have a knack for infiltrating bacteria and that some begin their attack with a protein spike. But the tip of this spike is so small that no one knew what it was made of or exactly how it worked. Now a team of researchers has found a single iron atom at the head of the spike, a discovery that suggests phages enter bacteria in a different way than surmised.

Wherever there are bacteria you will find bacteriophages; digestive tracts, contaminated water, and feces are usually a good start. These viruses begin their dirty work by drilling into the outer membrane of bacteria. Once completely through all of a bug’s defenses, the phages inject their DNA, which essentially turns the bacterium into phage-producing factories. Eventually, the microbes become filled with so many viruses that they burst, releasing a new horde of phages into the environment.