The phaZ minus mutant of P. putida KT2440 was created
by a double homologous recombination as shown in
Fig. 1b and as described by Simon et al. [32] and Schweizer
and Hoang [31]. Three ml of both early-log-phase cultures
of donor pK18C1C2-bearing E. coli S17-1 and recipient
P. putida KT2440 grown in LB medium were mixed and
centrifuged to harvest cells; the pellet was resuspended
in 100 μl of LB medium, which was then dropped on a