In the PNAS Early Edition this week, researchers at the University of Victoria and the National Institute of Allergy and Infectious Diseases report that they've inserted nine "essential genes" from Arctic bacteria into mammalian pathogenic bacteria "to construct stable, temperature-sensitive bacterial vaccines." One ligA gene, the team writes, "was shown to render Francisella tularensis, Salmonella enterica, and Mycobacterium smegmatis temperature-sensitive." Three tempe