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Host mutations (miaA and rpsL) reduce tetracycline resistance mediated by Tet(O) and Tet(M)
D E Taylor1, C A Trieber, G Trescher
1Department of Medical Microbiology & Immunology, University of Alberta, Edmonton, Canada. diane.taylor@ualberta.ca
Abstract:
The effects of mutations in host genes on tetracycline resistance mediated by the Tet(O) and Tet(M) ribosomal protection proteins, which originated in Campylobacter spp. and Streptococcus spp., respectively, were investigated by using mutants of Salmonella typhimurium and Escherichia coli. The miaA, miaB, and miaAB double mutants of S. typhimurium specify enzymes for tRNA modification at the adenosine at position 37, adjacent to the anticodon in tRNA. In S. typhimurium, this involves biosynthesis of N6-(4-hydroxyisopentenyl)-2-methylthio-adenosine (ms2io6A). The miaA mutation reduced the level of tetracycline resistance mediated by both Tet(O) and Tet(M), but the latter showed a greater effect, which was ascribed to the isopentenyl (i6) group or to a combination of the methylthioadenosine (ms2) and i6 groups but not to the ms2 group alone (specified by miaB). In addition, mutations in E. coli rpsL genes, generating both streptomycin-resistant and streptomycin-dependent strains, were also shown to reduce the level of tetracycline resistance mediated by Tet(O) and Tet(M). The single-site amino acid substitutions present in the rpsL mutations were pleiotropic in their effects on tetracycline MICs. These mutants affect translational accuracy and kinetics and suggest that Tet(O) and Tet(M) binding to the ribosome may be reduced or slowed in the E. coli rpsL mutants in which the S12 protein is altered. Data from both the miaA and rpsL mutant studies indicate a possible link between stability of the aminoacyl-tRNA in the ribosomal acceptor site and tetracycline resistance mediated by the ribosomal protection proteins.
Insights
Host gene mutations impact tetracycline resistance. Mutations affecting tRNA modification (miaA) and ribosomal protein S12 (rpsL) in bacteria like Salmonella and E. coli reduce resistance mediated by Tet(O) and Tet(M) proteins.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- Tetracycline resistance is often mediated by ribosomal protection proteins, Tet(O) and Tet(M).
- The influence of host genetic factors on the efficacy of these resistance mechanisms is not fully understood.
- Tetracycline resistance is a significant concern in bacterial infections.
Purpose of the Study:
- To investigate how mutations in host genes affect tetracycline resistance conferred by Tet(O) and Tet(M) proteins.
- To elucidate the role of tRNA modification and ribosomal protein alterations in modulating tetracycline resistance levels.
Main Methods:
- Utilized mutant strains of Salmonella typhimurium and Escherichia coli with specific genetic modifications.
- Introduced mutations in host genes miaA, miaB (affecting tRNA modification), and rpsL (encoding ribosomal protein S12).
- Assessed the impact of these mutations on tetracycline minimum inhibitory concentrations (MICs) mediated by Tet(O) and Tet(M).
Main Results:
- Mutations in miaA significantly reduced tetracycline resistance for both Tet(O) and Tet(M), with a more pronounced effect on Tet(M).
- The miaB mutation, affecting only a specific tRNA modification group, had a lesser impact than miaA.
- Mutations in E. coli rpsL genes, altering ribosomal protein S12, also decreased tetracycline resistance mediated by Tet(O) and Tet(M).
Conclusions:
- Host gene mutations, particularly those affecting tRNA modification and ribosomal protein S12, can significantly diminish tetracycline resistance.
- The findings suggest a link between the stability of aminoacyl-tRNA in the ribosomal acceptor site and the effectiveness of ribosomal protection proteins.
- Understanding these host-pathogen interactions is crucial for developing strategies to combat tetracycline resistance.