Enlarge Image Nasty Surprise. A computer model of the peptidomimetic shown against a background of the Pseudomonas aeruginosa microbe. Credit: Science/AAAS When a bacterium evolves resistance to a particular antibiotic, it's problematic. When it evolves defenses against antibiotics in general, as Pseudomonas aeruginosa has done, it's terrifying. But now researchers have devised an antibiotic that attacks the germ in a completely new way that appears to overwhelm those defenses. P. aeruginosa is a highly adaptable bacterium that lives almost everywhere. Although a healthy immune system can stop it from causing serious problems, it mercilessly exploits almost any weakness in...