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  • 1
    Electronic Resource
    Electronic Resource
    Fusidic acid-resistant EF-G perturbs the accumulation of ppGpp (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Reductions in growth rate caused by fusidic acid-resistant EF-G mutants in Salmonella typhimurium correlate strongly with increased mean cell size. This is unusual because growth rate and cell size normally correlate positively. The global transcription regulator molecule ppGpp has a role in co-ordinating growth rate and division, and its basal level normally correlates inversely with cell size at division. We show that fusidic acid-resistant EF-G mutants have perturbed ppGpp basal levels during steady-state growth and perturbed induced levels during starvation. One mutation, fusA1, associated with the slowest growth rate and largest cell size, causes a reduction in the basal level of ppGpp to one-third of that found in the wild-type strain. Other fusA mutants with intermediate or wild-type growth rates and cell sizes have either normal or increased basal levels of ppGpp. There is an inverse relationship between the basal level of ppGpp in vivo and the degree to which translation dependent on mutant EF-G is inhibited by ppGpp in vitro. This enhanced interaction between mutant EF-G and ppGpp correlates with an increased KM for GTP. Our results suggest that mutant EF-G modulates the production of ppGpp by the RelA (PSI) pathway. In conclusion, fusidic acid-resistant EF-G mutations alter the level of ppGpp and break the normal relationship between growth rate and cell size at division. It would not be surprising if other phenotypes associated with these mutants, such as loss of virulence, were also related to perturbations in ppGpp levels effected through altered transcription patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01967.x
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  • 2
    Electronic Resource
    Electronic Resource
    Biological cost and compensatory evolution in fusidic acid-resistant Staphylococcus aureus (2001)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 40 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Fusidic acid resistance resulting from mutations in elongation factor G (EF-G) of Staphylococcus aureus is associated with fitness costs during growth in vivo and in vitro. In both environments, these costs can be partly or fully compensated by the acquisition of secondary intragenic mutations. Among clinical isolates of S. aureus, fusidic acid-resistant strains have been identified that carry multiple mutations in EF-G at positions similar to those shown experimentally to cause resistance and fitness compensation. This observation suggests that fitness-compensatory mutations may be an important aspect of the evolution of antibiotic resistance in the clinical environment, and may contribute to a stabilization of the resistant bacteria present in a bacterial population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02389.x
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  • 3
    Electronic Resource
    Electronic Resource
    Novel ribosomal mutations affecting translational accuracy, antibiotic resistance and virulence of Salmonella typhimurium (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Many mutations in rpsL cause resistance to, or dependence on, streptomycin and are restrictive (hyperaccurate) in translation. Dependence on streptomycin and hyperaccuracy can each be reversed phenotypically by mutations in either rpsD or rpsE. Such compensatory mutations have been shown to have a ram phenotype (ribosomal ambiguity), increasing the level of translational errors. We have shown recently that restrictive rpsL alleles are also associated with a loss of virulence in Salmonella typhimurium. To test whether ram mutants could reverse this loss of virulence, we have isolated a set of rpsD alleles in Salmonella typhimurium. We found that the rpsD alleles restore the virulence of strains carrying restrictive rpsL alleles to a level close to that of the wild type. Unexpectedly, three out of seven mutant rpsD alleles tested have phenotypes typical of restrictive alleles of rpsL, being resistant to streptomycin and restrictive (hyperaccurate) in translation. These phenotypes have not been previously associated with the ribosomal protein S4. Furthermore, all seven rpsD alleles (four ram and three restrictive) can phenotypically reverse the hyperaccuracy associated with restrictive alleles of rpsL. This is the first demonstration that such compensations do not require that the compensating rpsD allele has a ribosomal ambiguity (ram) phenotype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01142.x
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  • 4
    Electronic Resource
    Electronic Resource
    Suppression of rpsL phenotypes by tuf mutations reveals a unique relationship between translation elongation and growth rate (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 7 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have found a simple relationship between bacterial growth rate and the translation elongation rate. Thus, for a set of defined ribosomal protein S12 mutations which reduce the efficiency of the ternary complex ribosome interaction (and restrict the frequency of translational errors) there is a linear relationship between growth rate and translation elongation rate. When these mutants are combined with defined EF-Tu mutants (which increase the probability of translational errors) both the elongation rate and growth rate reductions are reversed. The reductions and reversals are described by a unique linear relationship. We interpret this to mean that these two types of mutation exert opposing effects on the same molecular interaction. We suggest that this interaction is in the initial selection of the aminoacyl-tRNA on the ribosome. The slope of the relationship between translation elongation rate and growth rate, defined in per cent of the wild-type rates, is close to 1. Interestingly, the reversal of the elongation and growth phenotypes is Incomplete, suggesting that the ribosomal mutants have an additional defect which is not compensated for by the ternary complex interaction. Our results show that the efficiency of the ternary complex ribosome interaction limits the translation elongation rate, which in turn correlates with changes in exponential growth rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01118.x
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  • 5
    Electronic Resource
    Electronic Resource
    Growth and translation elongation rate are sensitive to the concentration of EF-Tu (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 8 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have used quantitative immunoblotting to estimate the amount of EF-Tu in a variety of S. typhimurium strains with wild-type, mutant, insertionally inactivated or plasmid-borne tuf genes. In the same strains we have measured translation elongation rate, exponential growth rate and the level of nonsense codon readthrough. In the wild-type strain, at moderate to fast growth rates, our data show that EF-Tu makes up 8–9% of total cell protein. Strains with either of the tuf genes insertionally inactivated have 65% of the wild-type EF-Tu level, irrespective of which tuf gene remains active, or whether that gene is wild-type or a kirromycin-resistant mutant. Strains with only one active tuf gene have reduced growth and translation elongation rates. From the magnitude of the reduction in elongation rate relative to the level of EF-Tu we calculate that in glucose minimal medium the in vivo saturation level of wild-type ribosomes by ternary complexes is only 63%. Strains with a ribosome mutation causing a poor interaction with ternary complex are non-viable on minimal medium when the level of EF-Tu is reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01619.x
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  • 6
    Electronic Resource
    Electronic Resource
    Hyper-susceptibility of a fusidic acid-resistant mutant of Salmonella to different classes of antibiotics (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 247 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Fusidic acid resistance (FusR) in Salmonella enterica serovar Typhimurium is caused by mutations in fusA, encoding elongation factor G (EF-G). Pleiotropic phenotypes are observed in FusR mutants. Thus, the fusA 1 allele (EF-G P413L) is associated with slow growth rate, reduced ppGpp and RpoS levels, reduced heme levels, and increased sensitivity to oxidative stress. The fusA 1–15 allele, (EF-G P413L and T423I) derived from fusA 1 in a selection for growth rate compensation, is partially compensated in each of these phenotypic defects but maintains its resistance to fusidic acid. We show here that the fusA 1 allele is associated with sensitivity to ultraviolet light and increased susceptibility to the inhibitory action of several unrelated antibiotic classes (β-lactam, fluoroquinolone, aminoglycoside, rifampicin, and chloramphenicol). The fusA 1–15 allele, in contrast, is less susceptible to UV and to other antibiotics than fusA 1. The hyper-susceptibility to multiple antibiotics associated with fusA 1 and fusA 1–15 is revealed in a novel growth competition assay at sub-MIC concentrations, but not in a standard MIC assay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.05.007
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  • 7
    Electronic Resource
    Electronic Resource
    The isolation and mapping of EF-Tu mutations in Salmonella typhimurium (1986)
    Springer
    Molecular genetics and genomics 202 (1986), S. 108-111 
    Details
    ISSN: 1617-4623
    Keywords: EF-Tu ; Translation ; Kirromycin ; Mocimycin ; Salmonella typhimurium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The first isolation of EF-Tu mutations in Salmonella typhimurium is reported. The mutations were isolated by selecting for resistance to the antibiotic mocimycin (= kirromycin). The mocimycin resistant phenotype is the result of mutations in each of two genes, tufA and tufB. Strains mutant in only one of the two tuf genes are sensitive to mocimycin. The spontaneous mutation rate of each of the two tuf genes to a mocimycin resistant phenotype differs by an order of magnitude. tufA maps at minute 71–72, closely linked to rpsL. tufB maps at minute 88–89, closely linked to rpoB. These map positions correspond to the locations of tufA and tufB in E. coli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330525
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  • 8
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    Antibiotic resistance by high-level intrinsic suppression of a frameshift mutation in an essential gene (2020)
    National Academy of Sciences
    Details
    Publication Date: 2020-01-28
    Description: A fundamental feature of life is that ribosomes read the genetic code in messenger RNA (mRNA) as triplets of nucleotides in a single reading frame. Mutations that shift the reading frame generally cause gene inactivation and in essential genes cause loss of viability. Here we report and characterize a +1-nt frameshift mutation, centrally located in rpoB, an essential gene encoding the beta-subunit of RNA polymerase. Mutant Escherichia coli carrying this mutation are viable and highly resistant to rifampicin. Genetic and proteomic experiments reveal a very high rate (5%) of spontaneous frameshift suppression occurring on a heptanucleotide sequence downstream of the mutation. Production of active protein is stimulated to 61–71% of wild-type level by a feedback mechanism increasing translation initiation. The phenomenon described here could have broad significance for predictions of phenotype from genotype. Several frameshift mutations have been reported in rpoB in rifampicin-resistant clinical isolates of Mycobacterium tuberculosis (Mtb). These mutations have never been experimentally validated, and no mechanisms of action have been proposed. This work shows that frameshift mutations in rpoB can be a mutational mechanism generating antibiotic resistance. Our analysis further suggests that genetic elements supporting productive frameshifting could rapidly evolve de novo, even in essential genes.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Evolutionary consequences of drug resistance: shared principles across diverse targets and organisms (2015)
    Springer Nature
    Details
    Publication Date: 2015-07-07
    Print ISSN: 1471-0056
    Electronic ISSN: 1471-0064
    Topics: Biology , Medicine
    Published by Springer Nature
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  • 10
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    Structure-activity relationship studies on the inhibition of the bacterial translation of novel Odilorhabdins analogues (2020)
    Elsevier
    Details
    Publication Date: 2020-06-01
    Print ISSN: 0968-0896
    Electronic ISSN: 1464-3391
    Topics: Chemistry and Pharmacology , Medicine
    Published by Elsevier
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