Clear plaque mutation sites linked to theimmIregion of the Salmonella phage P22

Abstract

SUMMARYA complete genetic map has been established for the P22 clear plaque forming mutationscir4-l,cir5-l andcir6-l. These are located within or closely linked to theimmIregion of P22 and represent a new class of clear plaque forming mutants located outside and rather distant from the immC region. They were mapped with respect to the markersmnt, vyand ant of theimmIregion and to genes16and9which span it. The threecirmutations complement each other and – with one possible exception – thecl,c2andc3mutations of theimmCregion. P22cir6-l – like P22cir5-l (Harveyet al.1981) – is suppressed by theant−am19 allele, whereas P22cir4-l is not. The results are discussed in terms of the regulation of earlyantexpression.