Fig. 1.

Construction diagram of integration plasmids pGBHC-upp-LFEC. a Schematic diagram of LFEC. b Schematic diagram of the insertion of LFEC between homologous arms. The wild-type thyA was replaced by LFEC through homologous recombination, which occurs after the temperature reaches 43 °C due to the application of the temperature-sensitive plasmid. c Schematic diagram of the insertion of LFEC into pGBHCupp plasmids