The morbidostat, as a whack-a-mole game, maintaining constant evolutionary pressure despite the evolution of protective mechanisms. An Escherichia coli culture is monitored for growth over time. As soon as the culture has grown to exceed a threshold optical density, an antibiotic pulse is added (shown as a hammer whack). If a mutation results in protection from the antibiotic (shown as a protective hat), the antibiotic level is again increased by the computer-controlled morbidostat. As the bacteria develop more protective mechanisms (stronger helmet), the antibiotic level is further increased (heavier/nastier hammer).