IS derivatives of Tn3 family transposons.
Another source of ambiguity for classification
purposes occurs in the Tn3 family (Nicolas, et al., 2015) (Figs 1.15.1 and 1.15.2). Tn3 family members are quite variable. They include a number of diverse passenger
genes which can represent entire operons, notably mercury resistance, or
individual genes involved in antibiotic resistance, breakdown of halogenated
aromatics or virulence [e.g. (Liebert, et al., 1999)]. They often
carry integron recombination platforms enabling them to incorporate additional
resistance genes by recruiting integron cassettes (Mazel, 2006). Members are quite characteristic: they have long
relatively well conserved IR and a particularly long Tpase (950 to 1025 aa).
They also encode a site-specific recombination ("resolution") system necessary
for completion of their transposition (Nicolas, et al., 2015). There are a
number of different resolution systems associated with different members of
this family (Fig 1.15.2) IS1071, (Fig 1.15.1) composed of Tn3-like IR and
Tpase gene but lacking both the site-specific recombination system and
passenger genes was identified many years ago (Nakatsu, et al., 1991). This clearly
accords with the definition of an IS. Several other examples have now been
identified (e.g. ISVsa19, ISShfr9, ISBusp1).
CA, Hall RM & Summers AO (1999) Transposon Tn21, Flagship of the Floating
Genome. Microbiology and Molecular
Biology Reviews 63: 507-522.
- Mazel D
(2006) Integrons: agents of bacterial evolution. Nat Rev Microbiol 4:
C, Ng J, Singh R, Straus N & Wyndham C (1991) Chlorobenzoate catabolic
transposon Tn5271 is a composite class I element with flanking class II
insertion sequences. Proc.Natl.Acad.Sci.U.S.A. 88: 8312-8316.
- Nicolas E, Lambin M, Dandoy D, Galloy
C, Nguyen N, Oger CA & Hallet B (2015) The Tn3-family of Replicative
Transposons. Microbiol Spectr 3.