Biochemistry and Molecular Biology, Dalhousie University, 5850 College Street, Halifax, Nova Scotia, Canada B3H 1X5. ford@dal.ca
Whether or not bacteria have species is a perennially vexatious question. Given what we now know about variation among bacterial genomes, we argue that there is no intrinsic reason why the processes driving diversification and adaptation must produce groups of individuals sufficiently coherent in their genetic and phenotypic properties to merit the designation 'species'--although sometimes they might.