5), A hundred ng of W3110 DNA, reaction buffer (10 mM Tris-HCl pH 8.3, 50 mM KCl, 1.5 mM MgCl2, 0.01% gelatin) and 5 units of a heat-stable Vent DNA polymerase (from Biolabs) and under the following situations: 96° C., 1.5 min; 62° C., 1 min; 72° C., 3 min. The PCR experiments were carried out in 30 cycles in a thermocycler (Gene ATAQ Controller, from Pharmacia) within the presence of 200 μM deoxynucleotide triphosphates (dATP, dCTP, dGTP, dTTP), in every case 1 μM of the corresponding oligonuc...