Complementation Assays

Complementation tests were used to assay the ability of mutant proteins expressed from plasmids to replace the missing functions of phages in which specific genes are inactivated by amber (am) mutations. Operationally, serial dilutions of phage were spotted on lawns of bacteria expressing wild-type or mutant HK97 genes and the results used to compute a crude relative efficiency of plating (EOP) of the mutant relative to the wild type control. A value of 10 or 3 was given for each fully or partly cleared spot, multiplied together to give an estimate of the phage titer and divided by the titer obtained using the wild-type-expressing strain.