Characterization of a Class II Defective Transposon Carrying Two Haloacetate Dehalogenase Genes from Delftia acidovorans Plasmid pUO1

The two haloacetate dehalogenase genes, dehH1 and dehH2 , on the 65-kb plasmid pUO1 from Delftia acidovorans strain B were found to be located on transposable elements. The dehH2 gene was carried on an 8.9-kb class I composite transposon (Tn Had1 ) that was flanked by two directly repeated copies of IS 1071 , IS 1071 L and IS 1071 R. The dehH1 gene was also flanked by IS 1071 L and a truncated version of IS 1071 (IS 1071 N). Tn Had1 , dehH1 , and IS 1071 N were located on a 15.6-kb class II transposon (Tn Had2 ) whose terminal inverted repeats and res site showed high homology with those of the Tn 21 -related transposons. Tn Had2 was defective in transposition because of its lacking the transposase and resolvase genes. Tn Had2 could transpose when the Tn 21 -encoded transposase and resolvase were supplied in trans . These results demonstrated that Tn Had2 is a defective Tn 21 -related transposon carrying another class I catabolic transposon.