The Tn916/Tn1545 family of conjugative transposons

The conjugative transposon Tn916 was first discovered in the late 1970s and is, together with the related conjugative transposon Tni545, the paradigm of a large family of related conjugative transposons known as the Tn916/Tn/545 family, which are found in an extremely diverse range of bacteria. With the huge increase in bacterial genomic sequence data available, due to the widespread use of next generation sequencing, more putative conjugative transposons belonging to the Tn916/Tn1545 family are being reported. Many of these are capable of excision, integration and conjugation. Nearly all of the Tn916/Tn1545-like elements discovered to date encode tetracycline resistance however, increasingly resistance to other antimicrobials is being found. Some of the members of the Tn916/Tn/545 family of elements are composite structures which contain smaller mobile genetic elements which are also capable of transposition. Tn916/Tn/545 Tn1545-like elements themselves are also found within larger and more complex elements. This review will give an overview of the current knowledge of the Tn916/Tn/545 family of conjugative transposons highlighting recently characterized composite elements carrying additional and novel resistance genes.