vector dephosphorylation and ligation - how does it work? (Aug/17/2007 )

Hi everybody,
I have a very basic question regarding ligation:
if ligation is creating a phosphodiester bond between the 3' hydroxyl of one nucleotide and the 5' phosphate of another, then how can we obtain ligated products after dephosphorylation of a vector ?
My only explanation is, that one phosphodiester in one strand is enough for the ligation. But this would mean, that after ligation into a dephosphorylated vector we would have two nicks at the two "insertion sites" of the insert. Maybe the bacteria repairs these nicks later?
What, if I ligate just two linkers ? Would one phosphorylated site be enoug`h?
Does anybody know more about this?
Thank yu very much in advance...

You are right - basically one strand is ligated and the other is repaired by the bacteria