Genes encoding virulence determinants are transferred between species in many different environments. In this review we describe gene transfer events to and from different species of bacteria, from bacteria to plants, and from plants to bacteria. Examples of the setting for these transfer events include: the GI tract, the rumen, the oral cavity, and in food matrixes. As a case study, the flux of virulence factors from E.coli O157:H7 is described as an example of gene flow in the environment.