Transposition and the evolution of antibiotic resistance.

Abstract

Structure at the ends of bacteriophage Mu DNA B. Allet Department of Molecular Biology, University of Geneva, 30, quai Ernest-Ansermet, CH-1211 Geneva 4 Bacteriophage Mu exhibits genetic properties that are analogous in many details to those of established insertion mutants in procaryotic and eucaryotic chromosomes (for a review, see DNA insertion Elements, Plasmids and Episomes [1977], Cold Spring Harbor Monograph Series, edited by A.I. Bukhari. J .A Shapiro and S.L. Adya). These properties, which include the ability to be transposed, and to delete DNA adjacent to the insertion site, seem to involve invariant DNA sequences in the insertion elements. In Mu these particular sequences must lie at the ends of the viral genome, and these ends are covalently bound to heterogenous bacterial DNA in vegetative, but presumably not in lysogenic Mu DNA. We have analyzed the nucleotide sequences at the 2 ends of the Mu DNA using the Maxam and Gilbert method. In some cases, these ends were present in a genetic material derived from lysogenic Mu. They were included in plaqueforming 2-1ac-Mu hybrid particles constructed by recombination between Mu lysogen and lac 2plac5. In one case the Mu SE (or variable) end was present in a plasmid constructed with a vegetative Mu DNA fragment and pMB 9. Our analyses lead to 3 main conclusions. 1. They show that a short stretch of 5 identical bases is located at each Mu end. oriented as an inverted repeat. 2. They strongly suggest that identical Mu end sequences are present in lysogenic and vegetative DNA. 3. They demonstrate that the heterogenous bacterial DNA bound to vegetative Mu DNA is completely removed during lysogenization, thus implying that the transposition and deletion events are. at least in part, site specific.