Interaction with Lambda, T4 and P1 phages.

A. Plating of Lula and various Lambdas on each other's lysogens. Strains are: non-lysogen, AB1157; Lambda i21 lysogen, MO (λi²¹); Lula lysogen, EL103. B. The lysogeny test. First, fresh colonies of a non-lysogen (AB1157), a Lula single lysogen (EL103) and a Lula/lambda double lysogen (MO (λi²¹)(phi80)(λ vir^R)) are streaked horizontally from left to right across two vertical phage lines — the left one made with a high-titer stock of Lula, the right one made with a high-titer stock of Lambda. The next day, since the non-lysogen grew equally well both before and after crossing the Lula streak, we took cells from indicated locations, streaked them to single colonies and passed these clones through “Lula contamination” test (Fig. 1D). The test confirmed that, although no lysis is apparent, cells become Lula lysogens after crossing the Lula line. C. Lula lysogens do not plate T4. Serial dilutions of T4 stock were spotted by 10 µl on lawns of either a non-lysogen (AB1157), Lula lysogen (EL103) or Lambda lysogen (EL104). D. Interaction of Lula and Lambda lysogens with P1. The P1 columns: P1 lysate was prepared in parallel on the two cultures of the same density, and the resulting P1 phage titer was determined either at 42°C (to inhibit Lula) or on a Lambda lysogen (to inhibit Lambda). “Lula” or “Lambda” columns: either mock-infected or P1-infected corresponding lysogen was taken through the “preparation of P1 lysate” procedure, and the titer of the phage was determined in the resulting lysate by plating in the presence of 20 mM Sodium Citrate (to inhibit P1). The values are averages of two measurements. Strains are: non-lysogen, AB1157; Lula lysogen, EL103; Lambda lysogen, EL104.