An Improved Tn7-based System for the Single-copy Insertion of Cloned Genes into Chromosomes of Gram-negative Bacteria

A system is described for the single-copy, stable insertion of cloned DNA sequences into the chromosomes of Gram- bacteria. Two narrow-host-range plasmids form the basis of this system: the 'carrier' plasmid contains the mini Tn7-Km transposon, into which foreign DNA can be cloned; the 'helper' plasmid provides the Tn7 transposition functions in trans. Both plasmids are readily transferred into Gram- bacteria by conjugation. The functionality of this system has been demonstrated in Rhodospirillum rubrum.