Tet 42, a novel tetracycline resistance determinant isolated from deep terrestrial subsurface bacteria

Abstract

Tet 42, a novel tetracycline resistance determinant from deep subsurface bacteria, was characterized and found to have a 30% sequence similarity to TetA(Z). The protein is a putative efflux pump that shares characteristics with previously characterized pumps, including a divergently transcribed TetR repressor, a conserved GxxSDRxGRR motif, and transmembrane domains.

FIG. 1.

Amino acid sequence comparison for TetA(42) and the two most closely related sequences, TetA(Z) and TetA(30). White letters on a black background indicate amino acids that are identical in two of the three sequences. GenBank accession numbers for TetA(Z) and TetA(30) are AAD25063 and AAD09860, respectively.

FIG. 2.

DNA sequence of the 71-bp tetA(42)-tetR(42) intergenic region. Putative TetR(42) binding operators are in boldface and overlined. Each asterisk indicates the center of the inverted repeat for an operator. The −35 and −10 potential promoter sequences are indicated.

FIG. 3.

Phylogenetic tree based on distance matrix analysis of amino acid sequences for Tet 42 and representative tetracycline resistance determinants that have been reported previously. GenBank accession numbers are given to the right of each resistance determinant. Scale bar, 10 substitutions per 100 amino acids.