Before the advent of antibiotics, pneumonia claimed so many lives -- and was so feared -- that it was called the "captain of the ship of death." Now, at a time when the new antibiotics have proved futile against resistant strains of bacteria, researchers are using a different tactic to keep this ship at bay. Instead of using synthetic weapons, they are using nature's: an enzyme that has proved so effective at killing Streptococcus pneumoniae that it has been put on the front lines in the battle against infectious disease.