BIOCHEMICAL AND GENETIC-ANALYSIS OF LAMBDA(W), THE NEWLY ISOLATED LAMBDOID PHAGE

Otherwise isogenic Escherichia coli CP78 (relA(+)) and CP79 (relA(-)) strains are commonly used in studies on the stringent control, the bac terial response to amino acid starvation. We found that these strains are lysogenic for a phage which is spontaneously induced with a low fr equency, producing virions able to infect other E. coli strains. Genet ic studies, restriction analysis of the phage DNA genome, and electron microscopy revealed that this phage is very similar to, but not ident ical with, bacteriophage lambda(.) We called the newly isolated phage lambda(W) and found that most of CP78/CP79 ancestor strains are lysoge nic for this phage.