A BACTEROIDES TETRACYCLINE RESISTANCE GENE REPRESENTS A NEW CLASS OF RIBOSOME PROTECTION TETRACYCLINE RESISTANCE

The ribosome protection type of tetracycline resistance (Tc(r)) has been found in a variety of bacterial species, but the only two classes described previously, Tet(M) and Tet(O), shared a high degree of amino acid sequence identity (> 75%). Thus, it appeared that this type of resistance emerged recently in evolution and spread among different species of bacteria by horizontal transmission. We obtained the DNA sequence of a Tc(r) gene from Bacteroides, a genus of gram-negative, obligately anaerobic bacteria that is phylogenetically distant from the diverse species in which tet(M) and tet(O) have been found. The Bacteroides Tc(r) gene defines a new class of ribosome protection resistance genes, Tet(Q), and has a deduced amino acid sequence that was only 40% identical to Tet(M) or Tet(O). Like tet(M) and tet(O), tet(Q) appears to have spread by horizontal transmission, but only within the Bacteroides group.