scholarly journals Larger increases in sensitivity to paracatalytic inactivation than in catalytic competence during experimental evolution of the second β-galactosidase of Escherichia coli

1997 ◽  
Vol 325 (1) ◽  
pp. 117-121 ◽  
Author(s):  
Sergei V. CALUGARU ◽  
Srinivasan KRISHNAN ◽  
Calvin J. CHANY ◽  
Barry G. HALL ◽  
Michael L. SINNOTT
Keyword(s):  
Escherichia Coli ◽  
Rate Constants ◽  
Experimental Evolution ◽  
First Generation ◽  
Bacterial Resistance ◽  
Enzyme Inactivation ◽  
Third Generation ◽  
Wild Type ◽  
Lower Effect ◽  
Partial Inactivation

Second-order rate constants (M-1·s-1) at 25 °C and pH 7.5 for inactivation of first-generation (ebga and ebgb), second-generation(ebgab and ebgabcd) and third-generation (ebgabcde) experimental evolvants of the title enzyme by 2′,4′-dinitrophenyl 2-deoxy-2-fluoro-β-d-galactopyranoside are 0.042, 0.30, 10, 24 and 57 respectively. Only partial inactivation is observed, except forebgabcde. At a single high inactivator concentration, inactivation of the wild-type ebgo is also seen. The changes in sensitivity to the paracatalytic inactivator (over a range of 103.3) are larger than changes in kcat/Km for lactose (over a range of 102.7) or nitrophenyl galactosides (over a range of only 101.3), or changes in degalactosylation rate (over a range of 101.7). These data raise the possibility that evolution in the reverse sense, towards insensitivity to a paracatalytic inactivator with a proportionally lower effect on transformation of substrate, may become a mechanism for the development of bacterial resistance to antibiotics that act by paracatalytic enzyme inactivation.

scholarly journals Local adaptation mediated niche expansion in correlation with genetic richness

2021 ◽  
Author(s):  
Masaomi Kurokawa ◽  
Issei Nishimura ◽  
Bei-Wen YING
Keyword(s):  
Escherichia Coli ◽  
Local Adaptation ◽  
High Throughput ◽  
Experimental Evolution ◽  
Environmental Gradient ◽  
Growth Curves ◽  
Quantitative Relationship ◽  
Central Issue ◽  
Wild Type ◽  
Niche Expansion

As a central issue in evolution and ecology, the quantitative relationship among the genome, adaptation and the niche was investigated. Local adaptation of five Escherichia coli strains carrying either the wild-type genome or reduced genomes was achieved by experimental evolution. A high-throughput fitness assay of the ancestor and evolved populations across an environmental gradient of eight niches resulted in a total of 80 fitness curves generated from 2,220 growth curves. Further analyses showed that the increases in both local adaptiveness and niche broadness were negatively correlated with genetic richness. Local adaptation caused common niche expansion, whereas niche expansion for generality or speciality was decided by genetic richness. The order of the mutations accumulated stepwise was correlated with the magnitude of the fitness increase attributed to mutation accumulation. Pre-adaptation probably participated in coordination among genetic richness, local adaptation and niche expansion.

Intrathecal Administration of Amikacin for Treatment of Meningitis Secondary to Cephalosporin-Resistant Escherichia Coli

1993 ◽  
Vol 27 (7-8) ◽  
pp. 870-873 ◽  
Author(s):  
Sandra L. Preston ◽  
Laurie L. Briceland
Keyword(s):  
Escherichia Coli ◽  
Bacterial Resistance ◽  
Generation Cephalosporin ◽  
Intrathecal Administration ◽  
Neurosurgical Procedures ◽  
Third Generation ◽  
E Coli ◽  
Efficacious Treatment ◽  
Clonic Seizures ◽  
Third Generation Cephalosporins

OBJECTIVE: To report a case of gram-negative bacillary meningitis (GNBM) secondary to cephalosporin-resistant Escherichia coli that was treated with intrathecal and intravenous amikacin and intravenous imipenem/cilastatin (I/C). CASE SUMMARY: A patient who had undergone two recent neurosurgical procedures developed GNBM and bacteremia. He was treated empirically with ceftazidime. Both bloodstream and cerebrospinal fluid isolates were identified as E. coli, resistant to third-generation cephalosporins, penicillins, tobramycin, and gentamicin. The patient was subsequently treated with intravenous and intrathecal amikacin plus intravenous I/C He experienced subjective and objective improvement on days 2–4 of antimicrobial therapy; two generalized tonic-clonic seizures occurred on days 7 and 12. Intrathecal amikacin was discontinued after 6 days, and intravenous amikacin and I/C were discontinued after 23 and 27 days, respectively. The patient's mental status did not completely return to premeningitis baseline. DISCUSSION: Third-generation cephalosporins are the treatment of choice for GNBM. In the case reported herein, bacterial resistance to these agents prompted the use of a therapy that has not been well studied and is also considered to be less safe and perhaps less efficacious. Treatment of GNBM with an intrathecally administered aminoglycoside or with intravenous I/C plus an aminoglycoside is reviewed. CONCLUSIONS: Patients with GNBM secondary to third-generation cephalosporin-resistant organisms may require therapies that may be less effective and more toxic. Further study of alternative agents is warranted.

scholarly journals The lactose/H+ carrier of Escherichia coli: lac YUN mutation decreases the rate of active transport and mimics an energy-uncoupled phenotype

1985 ◽  
Vol 227 (1) ◽  
pp. 287-297 ◽  
Author(s):  
J K Wright ◽  
R Seckler
Keyword(s):  
Escherichia Coli ◽  
Active Transport ◽  
Rate Constants ◽  
Ph Dependence ◽  
Maximal Velocity ◽  
Chemiosmotic Theory ◽  
Wild Type ◽  
Terminal Sequence ◽  
Simple Interpretation

The Escherichia coli K12 strain X71-54 carries the lac YUN allele, coding for a lactose/H+ carrier defective in the accumulation of a number of galactosides [Wilson, Kusch & Kashket (1970) Biochem. Biophys. Res. Commun. 40, 1409-1414]. Previous studies proposed that the lower accumulation in the mutant be due to a faulty coupling of H+ and galactoside fluxes via the carrier. Immunochemical characterization of the carriers in membranes from mutant and parent strains with an antibody directed against the C-terminal decapeptide of the wild-type carrier leads to the conclusion that the mutant carrier is similar to the wild-type in terms of apparent Mr, C-terminal sequence, and level of incorporation into the membrane. The pH-dependence of galactoside transport was compared in the mutant and the parent. At pH 8.0-9.0, mutant and parent behave similarly with respect to the accumulation of beta-D-galactosyl 1-thio-beta-D-galactoside and to the ability to grow on the carrier substrate melibiose. At pH 6.0, both the maximal velocity for active transport and the level of accumulation of beta-D-galactosyl-1-thio-beta-D-galactoside are lower in the mutant. The mutant also is unable to grow on melibiose at pH 5.5. However, at pH 6.0 and low galactoside concentrations, the symport stoichiometry is 0.90 H+ per galactoside in the mutant as compared with 1.07 in the parent. These observations suggest that symport is normal in the mutant and that the lower rate of transport in the mutant is responsible for the phenotype. At higher galactoside concentrations, accumulation is determined not only thermodynamically but also kinetically, contrary to a simple interpretation of the chemiosmotic theory. Therefore lower rates of active transport can mimic the effect of uncoupling H+ and galactoside symport. Examination of countertransport in poisoned cells at pH 6.0 reveals that the rate constants for the reorientation of the loaded and unloaded carrier are altered in the mutant. The reorientation of the unloaded carrier is slower in the mutant. However, the reorientation of the galactoside-H+-carrier complex is slower for substrates like melibiose, but faster for substrates like lactose. These findings suggest that lactose-like and melibiose-like substrates interact with the carrier in slightly different ways.

scholarly journals Second-generation 4,5,6,7-tetrahydrobenzo[d]thiazoles as novel DNA gyrase inhibitors

2020 ◽  
Vol 12 (4) ◽  
pp. 277-297 ◽  
Author(s):  
Andraž Lamut ◽  
Žiga Skok ◽  
Michaela Barančoková ◽  
Lucas J Gutierrez ◽  
Cristina D Cruz ◽  
...  
Keyword(s):  
First Generation ◽  
Bacterial Resistance ◽  
Dna Gyrase ◽  
Wild Type ◽  
Topoisomerase Iv ◽  
Starting Point ◽  
Good Starting Point ◽  
Resistant Strains ◽  
Gyrase Inhibitors ◽  
Nanomolar Range

Aim: DNA gyrase and topoisomerase IV are essential bacterial enzymes, and in the fight against bacterial resistance, they are important targets for the development of novel antibacterial drugs. Results: Building from our first generation of 4,5,6,7-tetrahydrobenzo[ d]thiazole-based DNA gyrase inhibitors, we designed and prepared an optimized series of analogs that show improved inhibition of DNA gyrase and topoisomerase IV from Staphylococcus aureus and Escherichia coli, with IC50 values in the nanomolar range. Importantly, these inhibitors also show improved antibacterial activity against Gram-positive strains. Conclusion: The most promising inhibitor, 29, is active against Enterococcus faecalis, Enterococcus faecium and S. aureus wild-type and resistant strains, with minimum inhibitory concentrations between 4 and 8 μg/ml, which represents good starting point for development of novel antibacterials.

scholarly journals The effect of spatial structure on adaptation in Escherichia coli

2007 ◽  
Vol 4 (1) ◽  
pp. 57-59 ◽  
Author(s):  
Lilia Perfeito ◽  
M. Inês Pereira ◽  
Paulo R.A Campos ◽  
Isabel Gordo
Keyword(s):  
Escherichia Coli ◽  
Spatial Structure ◽  
Experimental Evolution ◽  
Petri Dish ◽  
Mutation Rates ◽  
Wild Type ◽  
Clonal Interference ◽  
Genetic Studies ◽  
Significant Difference ◽  
The Cost

Populations of organisms are generally organized in a given spatial structure. However, the vast majority of population genetic studies are based on populations in which every individual competes globally. Here we use experimental evolution in Escherichia coli to directly test a recently made prediction that spatial structure slows down adaptation and that this cost increases with the mutation rate. This was studied by comparing populations of different mutation rates adapting to a liquid (unstructured) medium with populations that evolved in a Petri dish on solid (structured) medium. We find that mutators adapt faster to both environments and that adaptation is slower if there is spatial structure. We observed no significant difference in the cost of structure between mutator and wild-type populations, which suggests that clonal interference is intense in both genetic backgrounds.

scholarly journals PmrD Is Required for Modifications to Escherichia coli Endotoxin That Promote Antimicrobial Resistance

2015 ◽  
Vol 59 (4) ◽  
pp. 2051-2061 ◽  
Author(s):  
Erica J. Rubin ◽  
Carmen M. Herrera ◽  
Alexander A. Crofts ◽  
M. Stephen Trent
Keyword(s):  
Escherichia Coli ◽  
Protein Interactions ◽  
Lipid A ◽  
Bacterial Resistance ◽  
Functional Divergence ◽  
Polymyxin B ◽  
Growth Conditions ◽  
Wild Type ◽  
Content Type ◽  
E Coli

ABSTRACTInSalmonella enterica, PmrD is a connector protein that links the two-component systems PhoP-PhoQ and PmrA-PmrB. WhileEscherichia coliencodes a PmrD homolog, it is thought to be incapable of connecting PhoPQ and PmrAB in this organism due to functional divergence from theS. entericaprotein. However, our laboratory previously observed that low concentrations of Mg2+, a PhoPQ-activating signal, leads to the induction of PmrAB-dependent lipid A modifications in wild-typeE. coli(C. M. Herrera, J. V. Hankins, and M. S. Trent, Mol Microbiol 76:1444–1460, 2010,http://dx.doi.org/10.1111/j.1365-2958.2010.07150.x). These modifications include phosphoethanolamine (pEtN) and 4-amino-4-deoxy-l-arabinose (l-Ara4N), which promote bacterial resistance to cationic antimicrobial peptides (CAMPs) when affixed to lipid A. Here, we demonstrate thatpmrDis required for modification of the lipid A domain ofE. colilipopolysaccharide (LPS) under low-Mg2+growth conditions. Further, RNA sequencing shows thatE. colipmrDinfluences the expression ofpmrAand its downstream targets, including genes coding for the modification enzymes that transfer pEtN andl-Ara4N to the lipid A molecule. In line with these findings, apmrDmutant is dramatically impaired in survival compared with the wild-type strain when exposed to the CAMP polymyxin B. Notably, we also reveal the presence of an unknown factor or system capable of activatingpmrDto promote lipid A modification in the absence of the PhoPQ system. These results illuminate a more complex network of protein interactions surrounding activation of PhoPQ and PmrAB inE. colithan previously understood.

scholarly journals Local adaptation mediated niche expansion in correlation with genetic richness

2021 ◽  
Author(s):  
Masaomi Kurokawa ◽  
Issei Nishimura ◽  
Bei-Wen Ying
Keyword(s):  
Escherichia Coli ◽  
Local Adaptation ◽  
High Throughput ◽  
Experimental Evolution ◽  
Environmental Gradient ◽  
Growth Curves ◽  
Quantitative Relationship ◽  
Central Issue ◽  
Wild Type ◽  
Niche Expansion

Abstract As a central issue in evolution and ecology, the quantitative relationship among the genome, adaptation and the niche was investigated. Local adaptation of five Escherichia coli strains carrying either the wild-type genome or reduced genomes was achieved by experimental evolution. A high-throughput fitness assay of the ancestor and evolved populations across an environmental gradient of eight niches resulted in a total of 80 fitness curves generated from 2,220 growth curves. Further analyses showed that the increases in both local adaptiveness and niche broadness were negatively correlated with genetic richness. Local adaptation caused common niche expansion, whereas niche expansion for generality or speciality was decided by genetic richness. The order of the mutations accumulated stepwise was correlated with the magnitude of the fitness increase attributed to mutation accumulation. Pre-adaptation probably participated in coordination among genetic richness, local adaptation and niche expansion.

scholarly journals Balance between Endogenous Superoxide Stress and Antioxidant Defenses

1998 ◽  
Vol 180 (6) ◽  
pp. 1402-1410 ◽  
Author(s):  
Amy Strohmeier Gort ◽  
James A. Imlay
Keyword(s):  
Escherichia Coli ◽  
Dna Damage ◽  
Superoxide Dismutase ◽  
Excellent Agreement ◽  
Redox Cycling ◽  
Enzyme Inactivation ◽  
Antioxidant Defenses ◽  
Wild Type ◽  
E Coli ◽  
Soxrs Regulon

ABSTRACT Cells devoid of cytosolic superoxide dismutase (SOD) suffer enzyme inactivation, growth deficiencies, and DNA damage. It has been proposed that the scant superoxide (O2 −) generated by aerobic metabolism harms even cells that contain abundant SOD. However, this idea has been difficult to test. To determine the amount of O2 − that is needed to cause these defects, we modulated the O2 − concentration insideEscherichia coli by controlling the expression of SOD. An increase in O2 − of more than twofold above wild-type levels substantially diminished the activity of labile dehydratases, an increase in O2 − of any more than fourfold measurably impaired growth, and a fivefold increase in O2 − sensitized cells to DNA damage. These results indicate that E. coli constitutively synthesizes just enough SOD to defend biomolecules against endogenous O2 − so that modest increases in O2 − concentration diminish cell fitness. This conclusion is in excellent agreement with quantitative predictions based upon previously determined rates of intracellular O2 − production, O2 −dismutation, dehydratase inactivation, and enzyme repair. The vulnerability of bacteria to increased intracellular O2 − explains the widespread use of superoxide-producing drugs as bactericidal weapons in nature. E. coli responds to such drugs by inducing the SoxRS regulon, which positively regulates synthesis of SOD and other defensive proteins. However, even toxic amounts of endogenous O2 −did not activate SoxR, and SoxR activation by paraquat was not at all inhibited by excess SOD. Therefore, in responding to redox-cycling drugs, SoxR senses some signal other than O2 −.

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