We constructed a Tn5 derivative for potential use in transposon mutage
nesis of Neisseria gonorrhoeae. It was incorporated into the chromosom
e apparently at random following transformation; but the insertion eve
nts were dependent on a functional RecA and independent of a functiona
l transposase. Furthermore, in most cases there was an incomplete tran
sposon inserted with little or no IS50 insertion sequence. These obser
vations suggest that Tn5 transposition may not be possible in N. gonor
rhoeae and that this organism may have an unexplored illegitimate reco
mbination system.