Electrotransformation of Xanthomonas campestris by RF DNA of filamentous phage φLf

Conditions were optimized for electrotransformation of Xanthomonas campestris pv. campestris by the replicative form (RF) DNA of filamentous phase phi Lf. Early logarithmic cells were washed exhaustively with deionized water and subjected to a pulse at a field strength of 12.5 kV/cm with a 25 microF capacitor and a 400 omega resistor. An efficiency of 5.1 x 10(7) pfu per microgram RF DNA was obtained. Under the same conditions, the broad host range plasmid pLAFR1 (21.6 kb) transformed X. campestris strains at efficiencies around 10(5) pfu per microgram DNA prepared from XcP20H. The advantages of the protocol used in the present study are that the cells can be washed with water instead of complex buffer, and the DNA used can be prepared by the alkaline method of Birnboim & Doly without purification by ultracentrifugation.