This 2009 colorized 8000X electron micrograph image provided by the Centers for Disease Control and Prevention shows a large grouping of Gram-negative Legionella pneumophila bacteria.Fountains and hospitals don't mix, a new study suggests. The water features may be a source of calming negative ions, but they can also be a source of legionella, the bacteria that causes Legionnaire's disease.THE CANADIAN PRESS/AP-Janice Haney Carr