A new discipline emerging at the interface between cell biology and microbiology. One major focus of this new field is on the interference of pathogenic bacteria with many eukaryotic cell functions, such as maturation of intracellular compartments, internal cellular communication, or even cell division and differentiation. The study of cellular mcirobiology in this respect, is providing a sophisticaled tool kit for mammalian cell biologists. (Ref: Science 271:315, 1996).