Fig. 6

Schematic diagram of scarless chromosome engineering using λRed recombinase. First, an auxotrophic mutant with an essential gene knocked out is constructed using λRed recombinase and an antibiotic-resistance marker. The auxotrophic phenotype of the mutant is then recovered using λRed recombinase and a DNA fragment in which the essential gene and a target module are assembled by overlap extension polymerase chain reaction