The Tetracycline Resistance Gene tet(M) Exhibits Mosaic Structure

Plasmid. 1996 May;35(3):156-63. doi: 10.1006/plas.1996.0018.


Tetracycline resistance genes of the M class, tet(M), are typically found on mobile genetic elements as the conjugative transposons of gram-positive bacteria. By comparing the sequences of eight different tet(M) genes (from Enterococcus faecalis, Streptococcus pneumoniae, Staphylococcus aureus, Ureaplasma urealyticum, and Neisseria), a mosaic structure was detected which could be traced to two distinct alleles. The two alleles displayed a divergence of 8% and a different G/C content. The block structure of these genes provides evidence for the contribution of homologous recombination to the evolution and the heterogeneity of the tet(M) locus. Unlike described cases of chromosomally located mosaic loci, tet(M) is a relatively recently acquired determinant in the species examined and it would appear that mosaic structure within tet(M) has evolved after acquisition of the gene by the mobile genetic elements upon which it is located.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Base Sequence
  • DNA, Bacterial*
  • Enterococcus faecalis / genetics
  • Molecular Sequence Data
  • Mosaicism / genetics*
  • Neisseria gonorrhoeae / genetics
  • Neisseria meningitidis / genetics
  • Sequence Homology, Nucleic Acid
  • Staphylococcus aureus / genetics
  • Streptococcus pneumoniae / genetics
  • Tetracycline Resistance / genetics*
  • Ureaplasma urealyticum / genetics


  • Bacterial Proteins
  • DNA, Bacterial
  • Tet M resistance protein, Bacteria