Transposon Tn5403, a mobilization-helper element: Complete nucleotide sequence and distribution in aquatic strains

Abstract Tn 5403 , a new transposable element, was found in a Klebsiella pneumoniae strain (KIIIA) isolated from an aquatic environment following a pollution accident. It was identified by its ability to mobilize ori T-deleted recombinant plasmids and thus can be proposed as a ‘helper’ element participating in the transfer mechanisms of non-conjugative plasmids. Nucleotides sequence analysis shows that the element consists of 3663 bp. Two open reading frames (ORFs) are found: one ( tnp A) encoding a putative transposase and the other ( tnp R) a putative resolvase. The two ORFs are transcribed in opposite directions and are separated by a putative recombination site (res). Results obtained with a specific probe suggest that Tn 5403 or a similar element is present in different Enterobacteriaceae strains isolated from the same river three years after the isolation of the Tn 5403 -harbouring KIIIA strain.