Conjugation kinetics of pLS20cat without and with replacing the recipient growth medium.

Conjugation kinetics of pLS20cat was determined as described in Materials and Methods using strains PKS11 and PKS7 as donor and recipient strain, respectively. At each time point donor cells were mixed with recipient cells either directly (broken line) or after the recipient growth medium had been replaced with fresh LB medium (continuous line), and plated on selective agar plates after a 15 min mating period. t = 0 corresponds to the end of the exponential growth phase. Control experiments showed that the centrifugation step did not affect conjugation efficiency (not shown).