Verification of recombinants after positive or negative
selection
After spread onto corresponding selective agar plates, colony PCR was
used for identification of positive recombinants. A general principle
for designing diagnostic PCR primer is: one primer is surrounding the
target region and the other is inside the donor DNA. Two paired primers
surrounding each side of the target region respectively were also
designed in some case to display the different size of target DNA
between the original strains and positive recombinants.