Averaged EOP on host cells +/− plasmids with cloned O genea.

aThe average EOP per indicated phage was relative to that phage plating on strain 594 cells. The standard errors were all bThe precise O sequence (ATG = 38686–39582 plus TAA stop codon that replaces normal TGA stop at end of O) was cloned to make plasmids pcIpR-O-timm and p434′pR-O-timm. In each plasmid, gene O occupies the position corresponding to λ gene cro (in phage) and the consensus Shine Dalgarno sequence for cro was maintained ahead of O in pcIpR-O-timm [75], [76]. In p434′pR-O-timm, the SD differed by one bp compared to the SD in pcIpR-O-timm because of the slightly different sequence ahead of cro in imm434 DNA [77]. The O gene within pcIpR-O-timm is transcribed from pR and regulated by cI[Ts]857 repressor: at 30° O is repressed, at 39° and 42° O is expressed, or fully expressed. Gene O is constitutively expressed from pR in p434′pR-O-timm.cThe column for plating at 30°, 39° and 42° yielded equivalent phage titers on 594 and the EOP was set to 1. Plaques ranged between 0.5–2 mm in diameter.dPlaques formed were tiny.ePlaques ranged from 0.3–1 mm diameter.fnd is not done, since equivalent results were expected as seen for λcI72.