Bacteria containing an outer membrane and LPS or LOS. In this course we will discuss the following gram-negative bacteria: Vibrio cholerae, the Bordetellae, Neisseriae, Yersiniae, Salmonellae, Chlamydiae, and Pseudomonas. These bacteria lose the crystal violet color after decolorizing by alcohol; they stain pink after treatment with safranin (Lecture: The Bacterial Cell: Structure, Function, Growth, and Gene Regulation I, 1/24/02)