Question about Conjugation. Kind of urgent.

[az_0k]

Hi all.
I just have a little question regarding conjugation. I did my first conjugation experiment last tuesaday between the donor E. coli pKM101 with ampicilin resistance plasmid and the plasmid-fre recipient E. coli WL400 strain. I noticed that the two cultures were washed in saline solution (0.85% NaCl) prior to conjugation. Could someone please tell me the significance of this washing step? Thank you very much

[canalon]

To wash everything that could inhibit the conjugation...