FIG. 7.

Complementation between phage-encoded and plasmid-encoded T4 and RB69 DNA polymerase accessory proteins. The abilities of polymerase accessory proteins to be functionally exchanged between T4 and RB69 were examined by burst size measurements (Materials and Methods) and qualitative spot tests. (A) Results of plasmid-phage complementation tests involving gene 45 and genes 44 and 62 together; (B and C) results of similar tests involving genes 44 and 62 separately. In the “Spot test” blocks, each pair of spots represents growth responses (cell lysis) from 5 μl of two phage concentrations, ∼10⁴ and ∼10⁷/ml, respectively. Numbers shown in parentheses in the “Relative burst size” blocks are the actual bursts corresponding to the 1.0 reference values for the pairs of infections compared. Note that although the T4 and RB69 counterparts of gp45 and the gp44/62 complex can exchange effectively, with some preferences by the gene functions to support replication of the phage from which they originated (values in panel A), the gp44(RB69)/gp62(T4) combination is largely inactive for phage replication (C). Also note that plasmid-expressed wild-type (wt) RB69 gene 44 is inhibitory to replication of wild-type T4 (T4 wt phage on pRB69g44-bearing host [B]).