An improved bacterial colony lysis procedure enables direct DNA hybridisation using short (10, 11 bases) oligonucleotides to cosmids

We describe here a procedure for in situ bacterial colony lysis that gives much more intense hybridisation signals which do not change significantly upon reusal of filters. This is achieved by proteolysing the debris with proteinase K (without shaking) followed by blotting the DNA down onto the nylon membrane. The procedure is a much simplified version of the original experiment with the addition of the steaming step in alkali which contribute to the signal increase.