Reshuffling of Rhs components to create a new element

RhsF has been identified as the fourth member of the RhsABCF subfamily of genetic elements. This new element is found in Escherichia coli ECOR-50 and several other strains but not in strain K-12. A novel feature of RhsF is that it represents a new arrangement of components previously uniquely associated with RhsA and RhsC of strain K-12.