Deadly bacteria
Gene transfer in bacteria
Things seem to be clearer about the recent bacterial infection that has affected mostly Northern Germany this May- June. 
This article in the New York Times clearly indicates the suspected evolution of the deadly strain. Certainly, the transfer of the toxin gene by bacteriophages (bacterial viruses) is only one way by which bacteria pick up new genes. Students need to learn about plasmid transfer in the topic of Genetic Engineering.