Generally, incubation after electroporation could facilitate the
survival of transformants. The pulsed cells were incubated in LB
medium for different lengths of time ranging from 1 h to 5 h prior to
plating on selective plates. The results showed that transformation
efficiency increased during the initial 3 h (Fig. 6), and the maximal
transformation efficiency reached 1.53 × 108 transformants/μg of
pBBR1MCS DNA at the recovery period of 3 h. Incubation for more
than 3 h led the number of transformants to decrease gradually and
the number of viable cells to increase significantly. It suggested that
the optimal recovery time for S. maltophilia S21 was 3 h.