Effects of toluene permeabilization and cell deenergization on tetracycline resistance in Escherichia coli

Abstract

Resistance to tetracycline (Tcr) mediated by TnlO and related Tcr determinants involves an inner membrane protein, TET (similar but not identical for different determinants), and a proton motive force-dependent efflux of tetracycline which keeps the drug away from its intracellular target, the ribosome (L. M. McMurry, R. E. Petrucci, Jr., and S. B. Levy, Proc. Natl. Acad. Sci. USA 77:3974-3977, 1980). However, the amount of tetracycline accumulated by bacteria does not always correlate with their resistance levels, suggesting that an additional resistance mechanism may be present. When we permeabilized susceptible and resistant TnlObearing cells with toluene, we found that protein synthesis in the two strains became equally sensitive to tetracycline. Therefore, the protein synthesis machinery was not a source of resistance, and an intact membrane was required for resistance. To determine whether resistance was entirely dependent on energy, we measured susceptibility to tetracycline after inhibition of proton motive force by starvation and specific inhibitors. An 80 to 90% loss of Tcr (measured by protein synthesis) resulted from partial deenergization of resistant cells. A remaining resistance (10-to 20-fold greater than that of susceptible cells) could not be eliminated by further deenergization. These findings indicated that, to a major extent, expression of TnlO resistance required energy, presumably for tetracycline efflux. They also suggested the existence of a small component of Tcr having little or no energy dependence. Whether this component depends on tetracycline efflux or some other mechanism is not known, but presumably both high-and low-energy components of resistance reflect activity of TET protein.

tRNA modification activity is necessary for Tet(M)-mediated tetracycline resistance

“…Although the analyses described above indicate that the defect Protein synthesis in non-plasmid-containing strains, either wild type or mutant, is very sensitive to inhibition by added tetracycline (Fig. 2); confirming previous observations to this effect (28) p.g/ml) compared with the low resistance levels of sensitive plasmid-free strains (0.8 pLg/ml) and the high levels of fully resistant strains (25 K.g/ml for MV3/pVB202; Table 2). Protein synthesis in S30 extracts paralleled the results obtained here with permeabilized cells (not shown).…”

Extremely High Frequency Electromagnetic Radiation Enforces Bacterial Effects of Inhibitors and Antibiotics

“…1 and 2 [10,14] and these antibiotics [32][33][34][35][36] on bacteria occurs through membranous mechanisms: changes in the properties of membrane proteins and namely in the F 0 F 1 -ATPase can mediate such action. Differences in membrane proteome [41], membrane permeabilization, discharging protonmotive force [32,36], which is generated by the F 0 F 1 -ATPase under fermentation conditions (for review, see [31]), disturbances in H + , K + and Na + transport [35], alterations in appropriate transport systems, and lowering ATP level [32,34] increase sensitivity to antibiotics. In addition, alteration in DNA gyrase and other changes in gene expression or protein synthesis are also important in sensitivity to antibiotics (for review, see [42]).…”

“…This might be due to the role a membrane plays in bactericidal effects of tetracycline and chloramphenicol [32][33][34][35][36]. These antibiotics were effective in decreasing E. coli K12(k) specific growth rate: the effects were obtained in a concentration-dependent manner (for 2-10 lM, not shown) as determined before by different groups [33,37].…”

Ribonucleases control distinct traits of Pseudomonas putida lifestyle

“…Besides, it is also noteworthy the fact that our pnp mutant strain does not show sensitivity to tetracycline antibiotics, a characteristic present in the E . coli pnp mutant (McMurry et al ., 1986).…”