Bacillus anthracis (anthrax) cells being killed by a molecule studied by Penn State University researcher Kenneth Keiler. The molecule is naturally fluorescent and it looks blue when it is excited by ultraviolet light in the microscope. Keiler and his team found that certain molecules inhibit the growth of very distantly related bacteria by stopping trans-translation, which is a "quality control" mechanism that is found in all species of bacteria. Credit: Keiler lab, Penn State University