Blumenthal R M, Cotterman M M
Department of Microbiology, Medical College of Ohio, Toledo 43699.
Gene. 1988 Dec 25;74(1):271-3.
A procedure has been developed that permits the positive selection of mutants in a DNA methyltransferase (MTase) gene. The stringency of this selection can be varied so as to yield null mutants only, or a mixture of null and partially defective mutants. The procedure was developed with the PvuII MTase gene (pvuIIM), which was subcloned into a bacteriophage lambda vector. Growth of this lambda pvuIIM construct on an mcrB+ host selected for non-methylating mutants, and the stringency of selection was proportional to the number of consecutive lytic cycles. Many cytosine MTases have been found to generate substrates for mcrB-mediated restriction, and this procedure should be applicable to a number of cytosine MTase genes.
