The molecular mechanisms of tetracycline resistance in the pneumococcus

Tetracycline resistance in the pneumococcus is a result of the acquisition of one of two resistance determinants, tet(M) or tet(O), These genes encode ribosomal protection proteins that have homology to the elongation factors G and Tu, Tet(M) and Tet(O) both have GTPase activity that appears to be i mportant in the displacement of tetracycline from the ribosome, Modificatio n of tRNA may also be important for tetracycline resistance. Transcription of tet(M) is thought to be regulated by transcriptional attenuation. Transc ription of tet(O) is constitutive, however, upstream of the gene are sequen ces that also appear to be involved in transcriptional attenuation. tet(M) is transferred on the conjugative transposons, Tn1545 and Tn5151. It is not yet known whether tet(O) is transported on transposons or plasmids, or whe ther it is chromosomally integrated, in pneumococci.