Figure 1.

(a) Topology of the λ S holin. It is not known how the holin oligomerizes to form the permeabilizing lethal membrane lesion. (b) Scheme for inducible expression of the cloned lysis genes. The λ antiterminator gene Q is cloned in the plasmid pQ under control of a lac/ara hybrid promoter, which is inducible with IPTG and arabinose. The λ lysis genes lie in an overlapping cluster in the λ lysis cassette located downstream of the late gene promoter, pR′, on the compatible plasmid pS105. Expression of the lysis genes follows transactivation of pR′ by Q.