This laboratory image shows Staphylococcus aureus bacteria streaked in the shape of a sex steroid, like testosterone. The left shape is of wild-type S. aureus, with the lighter halo around the shape indicating hemolysis, or the breakdown of red blood cells, releasing their hemoglobin into the surrounding fluid. The right shape is a quorum-sensing mutant strain of S. aureus, which cannot damage blood cells. Photo courtesy UT Southwestern Testosterone, long implicated in sex-ba