Donor and recipients cells were mixed 1:1 (vol/vol, 0.1 to 1 ml), pelleted (2,000g for 10 min), resuspended in 10–100 µl LB + 300 µM DAP, pipetted onto a LB + 300 µM DAP plate and incubated at 37 °C for 2 h

Mu Free Donor (MFDpir) or B2155, which contain integrated rp4-based transfer machinery