Figure 3.

Luciferase (luc)-encoding phage is resistant to DNase I treatment. Mice (eight per group) were injected ID at the tail base with 1 × 10¹¹ PFU of gpD (luc) phage that were either treated with 10 U of DNase I for 30 min at 37°C prior to injection, or not exposed to DNase I. As a control, mice (four per group) were injected with 1 × 10¹¹ PFU of matching phage that lacked the luc expression cassette (no luc), which were physically mixed with 5 μg of lambda luc DNA and then either treated with 10 U of DNase I for 30 min at 37°C prior to injection, or not exposed to DNase I. Twenty-four hours later, luc expression was measured at the tail base site of injection. DNase I treatment had no detectable effect on luc expression levels in mice that were injected with gpD (luc) phage (P > 0·05, Student's two-tailed t-test). However, the amount of DNase I added was sufficient to degrade 5 μg of exogenous DNA (compare luc expression levels in the two no luc groups).