TN5041 - A CHIMERIC MERCURY RESISTANCE TRANSPOSON CLOSELY-RELATED TO THE TOLUENE DEGRADATIVE TRANSPOSON TN4651

This paper reports the discovery and characterization of Tn5041, a nov el-type transposon vehicle for dissemination of mercury resistance in natural bacterial populations. Tn5041 (14876 bp), identified in a Pseu domonas strain from a mercury mine, is a Tn3 family mercury resistance transposon far outside the Tn21 subgroup. As in other Tn3 family tran sposons, Tn5041 duplicates 5 bp of the target sequence following inser tion. Tn5041 apparently acquired its mer operon as a single ended reli c of a transposon belonging to the classical mercury resistance transp osons of the Tn21 subgroup. The putative transposase and the 47 bp ter minal inverted repeats of Tn5041 are closely related to those of the t oluene degradative transposon Tn4651 and fall into a distinct subgroup on the fringe of the Tn3 family. The amino acid sequence of the putat ive resolvase of Tn5041 resembles site-specific recombinases of the in tegrase family. Besides the mer operon and putative transposition gene s, Tn5041 contains a 4 kb region that accommodates a number of apparen tly defective genes and mobile elements.