A Positive Selection for Nucleoside Kinases in E. coli
BW14012 cells expressing one of the two proteins were mixed at a 1:10,000 ratio (tatHSV-TK:tatHSV-TKD) ratio. Twenty colonies formed when 500,000 CFUs (determined under non-selective conditions) were plated on 40 μg/ml AZT. PCR-amplified hsvtk genes from these 20 colonies indicated that all twenty contained tatHSV-TK. Expected band sizes of tatHSV-TK and tatHSV-TKD in this PCR assay are 1226 bp and 1160 bp, respectively.