Kasugamycin inhibition of nonsense suppression by thymine-requiring strains of Escherichia coli K12

1993 ◽  
Vol 39 (4) ◽  
pp. 448-450 ◽  
Author(s):  
E. Tiganos ◽  
M. B. Herrington
Keyword(s):  
Escherichia Coli ◽  
Thymidylate Synthase ◽  
Aminoglycoside Antibiotic ◽  
Nonsense Suppression ◽  
Resistance Mutations ◽  
Escherichia Coli K12 ◽  
Translational Accuracy ◽  
Frame Shift

Thymine-requiring strains of Escherichia coli suppress nonsense and frame-shift mutations. This appears to occur during translation, suggesting that the lack of activity of an enzyme thymidylate synthase, required for the synthesis of a DNA precursor, alters the fidelity of translation. The aminoglycoside antibiotic kasugamycin, which enhances translational accuracy in vitro, prevents thymine-requiring cells from suppressing. The inhibition of suppression by kasugamycin is not prevented by the introduction of two different kasugamycin-resistance mutations, although the dose required for inhibition increases. These observations support the conclusion that suppression occurs during translation.Key words: suppression, kasugamycin, translation, thymine-requiring.

scholarly journals Biological Cost of Single and Multiple Norfloxacin Resistance Mutations in Escherichia coli Implicated in Urinary Tract Infections

2005 ◽  
Vol 49 (6) ◽  
pp. 2343-2351 ◽  
Author(s):  
Patricia Komp Lindgren ◽  
Linda L. Marcusson ◽  
Dorthe Sandvang ◽  
Niels Frimodt-Møller ◽  
Diarmaid Hughes
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract ◽  
Infection Model ◽  
Resistance Mutations ◽  
Topoisomerase Iv ◽  
E Coli ◽  
Tract Infections ◽  
Subsequent Selection

ABSTRACT Resistance to fluoroquinolones in urinary tract infection (UTIs) caused by Escherichia coli is associated with multiple mutations, typically those that alter DNA gyrase and DNA topoisomerase IV and those that regulate AcrAB-TolC-mediated efflux. We asked whether a fitness cost is associated with the accumulation of these multiple mutations. Mutants of the susceptible E. coli UTI isolate Nu14 were selected through three to five successive steps with norfloxacin. Each selection was performed with the MIC of the selected strain. After each selection the MIC was measured; and the regions of gyrA, gyrB, parC, and parE, previously associated with resistance mutations, and all of marOR and acrR were sequenced. The first selection step yielded mutations in gyrA, gyrB, and marOR. Subsequent selection steps yielded mutations in gyrA, parE, and marOR but not in gyrB, parC, or acrR. Resistance-associated mutations were identified in almost all isolates after selection steps 1 and 2 but in less than 50% of isolates after subsequent selection steps. Selected strains were competed in vitro, in urine, and in a mouse UTI infection model against the starting strain, Nu14. First-step mutations were not associated with significant fitness costs. However, the accumulation of three or more resistance-associated mutations was usually associated with a large reduction in biological fitness, both in vitro and in vivo. Interestingly, in some lineages a partial restoration of fitness was associated with the accumulation of additional mutations in late selection steps. We suggest that the relative biological costs of multiple mutations may influence the evolution of E. coli strains that develop resistance to fluoroquinolones.

Transcription of the argF and argI genes of the arginine biosynthetic regulon of Escherichia coli K12, performed in vitro

1977 ◽  
Vol 155 (1) ◽  
pp. 7-18 ◽  
Author(s):  
Don Sens ◽  
William Natter ◽  
Robert T. Garvin ◽  
Eric James
Keyword(s):  
Escherichia Coli ◽  
Escherichia Coli K12

Evidence for the existence of three promoters for the deo operon of Escherichia coli K12 in vitro

1979 ◽  
Vol 133 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Poul Valentin-Hansen ◽  
Karin Hammer-Jespersen ◽  
R.S. Buxton
Keyword(s):  
Escherichia Coli ◽  
Escherichia Coli K12 ◽  
Deo Operon

scholarly journals Purification and some properties of nitrate reductase (EC 1.7.99.4) from Escherichia coli K12

1976 ◽  
Vol 153 (3) ◽  
pp. 533-541 ◽  
Author(s):  
R A Clegg
Keyword(s):  
Escherichia Coli ◽  
Aqueous Solution ◽  
Nitrate Reductase ◽  
Cell Envelope ◽  
Purification Procedure ◽  
Benzyl Viologen ◽  
Escherichia Coli K12 ◽  
Enzyme Subunits ◽  
Triton X

1. Nitrate reductase was purified 134-fold from Escherichia coli K12. The purification procedure involves the release by Triton X-100 of the enzyme from the cell envelope. i. The purified enzyme exists in aqueous solution either as a monomer (mol. wt. about 220 000) or as an associated form (probably a tetramer; mol.wt. about 880 000). 3. The purified enzyme has three subunits with apparent mol.wts. of 150 000, 67000 and 65000. An additional subunit of apparent mol.wt. 20000 is present in a haem-containing fraction that is also produced by the preparative procedure described. 4. None of the enzyme subunits is present in the cell envelope of cells grown in the absence of nitrate. 5. Reversible changes in the activity of nitrate reductase in vitro with FMNH2 as reductant can be induced under circumstances which are without effect on the reduced Benzyl Viologen-NO3-activity.

scholarly journals Restrictive Streptomycin Resistance Mutations Decrease the Formation of Attaching and Effacing Lesions in Escherichia coli O157:H7 Strains

2013 ◽  
Vol 57 (9) ◽  
pp. 4260-4266 ◽  
Author(s):  
Chun Chen ◽  
Carla A. Blumentritt ◽  
Meredith M. Curtis ◽  
Vanessa Sperandio ◽  
Alfredo G. Torres ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Ribosomal Subunit ◽  
Streptomycin Resistance ◽  
Resistance Mutations ◽  
Content Type ◽  
E Coli ◽  
Enterocyte Effacement ◽  
Translocated Proteins

ABSTRACTStreptomycin binds to the bacterial ribosome and disrupts protein synthesis by promoting misreading of mRNA. Restrictive mutations on the ribosomal subunit protein S12 confer a streptomycin resistance (Strr) phenotype and concomitantly increase the accuracy of the decoding process and decrease the rate of translation. Spontaneous Strrmutants ofEscherichia coliO157:H7 have been generated forin vivostudies to promote colonization and to provide a selective marker for this pathogen. The locus of enterocyte effacement (LEE) ofE. coliO157:H7 encodes a type III secretion system (T3SS), which is required for attaching and effacing to the intestinal epithelium. In this study, we observed decreases in both the expression and secretion levels of the T3SS translocated proteins EspA and EspB inE. coliO157:H7 Strrrestrictive mutants, which have K42T or K42I mutations in S12. However, mildly restrictive (K87R) and nonrestrictive (K42R) mutants showed slight or indistinguishable changes in EspA and EspB secretion. Adherence and actin staining assays indicated that restrictive mutations compromised the formation of attaching and effacing lesions inE. coliO157:H7. Therefore, we suggest thatE. coliO157:H7 strains selected for Strrshould be thoroughly characterized beforein vivoandin vitroexperiments that assay for LEE-directed phenotypes and that strains carrying nonrestrictive mutations such as K42R make better surrogates of wild-type strains than those carrying restrictive mutations.

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