Zur Frage des Zeitpunktes der Entscheidung zwischen abortivem oder rekombinativem Verhalten eines transduzierten Chromosomenfragmentes in der Empfängerzelle

1965 ◽  
Vol 20 (4) ◽  
pp. 284-289
Author(s):  
F. Kaudewitz ◽  
H. Schmieger
Keyword(s):  
Donor Cell ◽  
Cell Populations ◽  
Linkage Data ◽  
Wild Type ◽  
Isolated Cells ◽  
Auxotrophic Strain ◽  
Chromosomal Fragment ◽  
E Coli ◽  
Selection For ◽  
Arabinose Fermentation

In wild-type transduction of auxotrophic strain E. coli B/r/thr-1/leu-1/ara-12 colonies auxotrophic for leucine or threonine do not all arise at the same time after plating. In such crosses 48 hrs. after plating from about 20% of minute colonies grown from single abortively transduced cells there can be isolated cells capable to form genetically stable colonies prototrophic for leucine or threonine. Turbidity-measurements on cell populations derived from isolated minute colonies prove that such leu+-cells arise on the plate up to at least 96 hrs. after transduction. Linkage-data of the sites leu+-1 or thr+-1 with ara-12 for these cells disprove the occurence of the thr+ or leu+-state by backmutation. Transduction with E. coli B/r/ara-5 as donor with selection for arabinose-fermentation demonstrates the failure of delayed arising leu+ or thr+-cells in crosses yielding no minute colonies caused by abortive transduction. The experiments are discussed as evidence for the occurence of recombination between the acceptor-chromosome and the abortively transduced chromosomal fragment of a donor cell within a minute colony many cell generations after injection of this fragment.

scholarly journals REGULATION OF NEWLY EVOLVED ENZYMES. III EVOLUTION OF THE ebg REPRESSOR DURING SELECTION FOR ENHANCED LACTASE ACTIVITY

Genetics ◽  
1977 ◽  
Vol 85 (2) ◽  
pp. 193-201
Author(s):  
Barry G Hall ◽  
Norma D Clarke
Keyword(s):  
Regulatory Gene ◽  
Enzyme Synthesis ◽  
Lactase Activity ◽  
Wild Type ◽  
Regulatory Mutation ◽  
E Coli ◽  
Lactose Induction ◽  
A Cell ◽  
Lactose Utilization ◽  
Selection For

ABSTRACT The evolution of lactose utilization by lacZ deletion strains of E. coli occurs via mutations in the ebg genes. We show that one kind of mutation in the regulatory gene ebgR results in a repressor which retains the ability to repress synthesis of ebg enzymes, but which permits 4.5-fold more ebg enzyme synthesis during lactose induction than does the wild-type repressor. A comparison between the growth rate of various ebg  + strains on lactose and the amount of ebg enzyme synthesized by these strains shows that the rate of enzyme synthesis permitted by the wild-type repressor is insufficient for growth on lactose as a sole carbon source by a cell with the most active ebg lactase yet isolated. We conclude, therefore, that the evolution of lactose utilization requires both a structural and a regulatory mutation.

ucFabV Requires Functional Reductase Activity to Confer Reduced Triclosan Susceptibility in Escherichia coli

2015 ◽  
Vol 25 (6) ◽  
pp. 394-402 ◽  
Author(s):  
Taylor L. Fischer ◽  
Robert J. White ◽  
Katherine F.K. Mares ◽  
Devin E. Molnau ◽  
Justin J. Donato
Keyword(s):  
Escherichia Coli ◽  
Reductase Activity ◽  
Acid Synthesis ◽  
Temperature Sensitive ◽  
Wild Type ◽  
E Coli ◽  
Enoyl Acp Reductase ◽  
Selection For

<b><i>Background/Aims:</i></b> We previously identified the Triclo1 fosmid in a functional metagenomic selection for clones that increased triclosan tolerance in <i>Escherichia coli</i>. The active enzyme encoded by Triclo1 is ucFabV. Although ucFabV is homologous to FabV from other organisms, ucFabV contains substitutions at key positions that would predict differences in substrate binding. Therefore, a detailed characterization of ucFabV was conducted to link its biochemical activity to its ability to confer reduced triclosan sensitivity. <b><i>Methods:</i></b> ucFabV and a catalytic mutant were purified and used to reduce crotonoyl-CoA in vitro. The mutant and wild-type enzymes were introduced into <i>E. coli</i>, and their ability to confer triclosan tolerance as well as suppress a temperature-sensitive mutant of FabI were measured. <b><i>Results:</i></b> Purified ucFabV, but not the mutant, reduced crotonoyl-CoA in vitro. The wild-type enzyme confers increased triclosan tolerance when introduced into <i>E. coli</i>, whereas the mutant remained susceptible to triclosan<i>. </i>Additionally, wild-type ucFabV, but not the mutant, functionally replaced FabI within living cells. <b><i>Conclusion:</i></b> ucFabV confers increased tolerance through its function as an enoyl-ACP reductase. Furthermore, ucFabV is capable of restoring viability in the presence of compromised FabI, suggesting ucFabV is likely facilitating an alternate step within fatty acid synthesis, bypassing FabI inhibition.

scholarly journals Identification of valine/leucine/isoleucine and threonine/alanine/glycine proton-spin systems of Escherichia coli adenylate kinase by selective deuteration and selective protonation

1991 ◽  
Vol 273 (2) ◽  
pp. 311-316 ◽  
Author(s):  
I Bock-Möbius ◽  
M Brune ◽  
A Wittinghofer ◽  
H Zimmermann ◽  
R Leberman ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Adenylate Kinase ◽  
Spin Systems ◽  
Proton Spin ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Auxotrophic Strain ◽  
E Coli ◽  
Selective Deuteration ◽  
The One

Adenylate kinase from two types of Escherichia coli strains, a wild-type and a leucine-auxotrophic strain, was purified. On the one hand, growing the leucine-auxotrophic bacteria on a medium containing deuterated leucine yielded E. coli adenylate kinase with all leucine residues deuterated. On the other hand, by growing the wild-type bacteria on deuterated medium with phenylalanine, threonine and isoleucine present as protonated specimens, 80% randomly deuterated enzyme with protonated phenylalanine, threonine and isoleucine residues could be prepared. Use of these proteins enabled identification of the spin systems of these amino acid residues in the n.m.r. spectra of the protein.

scholarly journals Balance between promiscuity and specificity in phage λ host range

2020 ◽  
Author(s):  
Bryan Andrews ◽  
Stanley Fields
Keyword(s):  
Host Range ◽  
Host Resistance ◽  
Fitness Landscape ◽  
Tail Fiber ◽  
Wild Type ◽  
E Coli ◽  
General Ability ◽  
Novel Host ◽  
Selection For ◽  
Resistance To Viruses

AbstractAs hosts acquire resistance to viruses, viruses must overcome that resistance to re-establish infectivity, or go extinct. Despite the significant hurdles associated with adapting to a resistant host, viruses are evolutionarily successful and maintain stable coevolutionary relationships with their hosts. To investigate the factors underlying how pathogens adapt to their hosts, we performed a deep mutational scan of the region of the λ tail fiber tip protein that mediates contact with the λ host, E. coli. Phages harboring amino acid substitutions were subjected to selection for infectivity on wild type E. coli, revealing a highly restrictive fitness landscape, in which most substitutions completely abrogate function. By comparing this lack of mutational tolerance to evolutionary diversity, we highlight a set of mutationally intolerant and diverse positions associated with host range expansion. Imposing selection for infectivity on three λ-resistant hosts, each harboring a different missense mutation in the λ receptor, reveals hundreds of adaptive variants in λ. We distinguish λ variants that confer promiscuity, a general ability to overcome host resistance, from those that drive host-specific infectivity. Both processes may be important in driving adaptation to a novel host.

scholarly journals SELECTION FOR A LARGE GENETIC DUPLICATION IN SALMONELLA TYPHIMURIUM

Genetics ◽  
1975 ◽  
Vol 80 (2) ◽  
pp. 227-237
Author(s):  
Daniel S Straus ◽  
George R Hoffmann
Keyword(s):  
Salmonella Typhimurium ◽  
Simple Procedure ◽  
Selective Medium ◽  
Reca Gene ◽  
Wild Type ◽  
E Coli ◽  
Selection For ◽  
Spontaneous Frequency ◽  
Very High ◽  
Tandem Duplications

ABSTRACT Salmonella typhimurium strains containing a duplication of nearly a third of the genome have been isolated by a simple procedure involving selection for improved utilization of L-malate as sole carbon source. The duplication occurs at a very high spontaneous frequency. Strains containing the duplication can be isolated selectively on malate medium, or by a non-selective procedure involving Hfr conjugation. When strains containing the duplication are maintained on non-selective medium, the duplication is readily lost. Genetic evidence suggests that the duplication is chromosomal and tandem. The fact that the recA gene is included in the duplication has been used to obtain evidence that the recA1 marker is recessive to its wild-type allele. Unlike tandem duplications previously described in E. coli, the duplication described in this report appears to have unique endpoints

The Effect of Mianserin on Lifespan of Caenorhabditis elegans is Abolished by Glucose

2021 ◽  
Vol 13 ◽  
Author(s):  
Abdullah Almotayri ◽  
Jency Thomas ◽  
Mihiri Munasinghe ◽  
Markandeya Jois
Keyword(s):  
Caenorhabditis Elegans ◽  
Scaffolding Protein ◽  
Lifespan Extension ◽  
Wild Type ◽  
E Coli ◽  
C Elegans ◽  
Risk Of Death ◽  
Increased Risk ◽  
Antidepressant Use ◽  
Extension Effect

Background: The antidepressant mianserin has been shown to extend the lifespan of Caenorhabditis elegans (C. elegans), a well-established model organism used in aging research. The extension of lifespan in C. elegans was shown to be dependent on increased expression of the scaffolding protein (ANK3/unc-44). In contrast, antidepressant use in humans is associated with an increased risk of death. The C. elegans in the laboratory are fed Escherichia coli (E. coli), a diet high in protein and low in carbohydrate, whereas a typical human diet is high in carbohydrates. We hypothesized that dietary carbohydrates might mitigate the lifespan-extension effect of mianserin. Objective: To investigate the effect of glucose added to the diet of C. elegans on the lifespan-extension effect of mianserin. Methods: Wild-type Bristol N2 and ANK3/unc-44 inactivating mutants were cultured on agar plates containing nematode growth medium and fed E. coli. Treatment groups included (C) control, (M50) 50 μM mianserin, (G) 73 mM glucose, and (M50G) 50 μM mianserin and 73 mM glucose. Lifespan was determined by monitoring the worms until they died. Statistical analysis was performed using the Kaplan-Meier version of the log-rank test. Results: Mianserin treatment resulted in a 12% increase in lifespan (P<0.05) of wild-type Bristol N2 worms but reduced lifespan by 6% in ANK3/unc-44 mutants, consistent with previous research. The addition of glucose to the diet reduced the lifespan of both strains of worms and abolished the lifespan-extension by mianserin. Conclusion: The addition of glucose to the diet of C. elegans abolishes the lifespan-extension effects of mianserin.

129 Genomic Relationship Between PRRSV Wild-type Infection and PRRSV Vaccination for Antibody Response and Reproductive Performance

2021 ◽  
Vol 99 (Supplement_1) ◽  
pp. 18-18
Author(s):  
Leticia P Sanglard ◽  
Felipe Hickmann ◽  
Yijian Huang ◽  
Kent A Gray ◽  
Daniel Linhares ◽  
...  
Keyword(s):  
Antibody Response ◽  
Reproductive Performance ◽  
Genetic Correlations ◽  
Clinical Signs ◽  
Respiratory Syndrome Virus ◽  
Wild Type ◽  
Large White ◽  
Selection For ◽  
Indicator Trait ◽  
Type Infection

Abstract Immunoglobulin G antibody response, measured as sample-to-positive (S/P) ratio, to Porcine Reproductive and Respiratory Syndrome virus (PRRSV) has been proposed as an indicator trait for improved reproductive performance in PRRSV-infected purebred sows and PRRSV-vaccinated crossbred gilts. In this study, we investigated the genetic correlations (rg) of S/P ratio following a PRRSV outbreak and PRRSV-vaccination with performance in non-exposed and PRRSV-exposed sows. PRRSV outbreak phase was defined based on previously described methodologies after the detection of typical clinical signs of PRRSV infection. 541 Landrace sows had S/P ratio measured at ~54 days after the beginning of the PRRSV outbreak (S/Poutbreak), and 906 Landrace x Large White naïve F1 gilts had S/P ratio measured at ~50 days after vaccination with a commercial modified live PRRSV vaccine (S/PVx). 711 and 428 Landrace sows had reproductive performance recorded before and during the PRRSV outbreak, respectively. 811 vaccinated F1 animals had farrowing performance for up to 3 parities. All animals were genotyped for ~28K SNPs. The estimate of rg of S/Poutbreakwith S/PVx was high (rg±SE = 0.72±0.18). Estimates of rg of S/Poutbreak with reproductive performance in F1 sows were low to moderate, ranging from 0.05±0.23 (number stillborn) to 0.30±0.20 (total number born). Estimates of rg of S/PVxwith reproductive performance in non-infected purebred sows were moderate and favorable with number born alive (0.50±0.23), but low (0 to -0.11±0.23) with litter mortality traits. Estimates of rg of S/PVx were moderate and negative (-0.47±0.18) with the number of mummies in PRRSV-infected purebred sows and low with other traits (-0.29±0.18 for total number born to 0.05±0.18 for number stillborn). These results indicate that selection for antibody response following a PRRSV outbreak collected in purebred sows and to PRRSV vaccination collected in commercial crossbred gilts may increase litter size of non-infected and PRRSV-exposed purebred and commercial crossbred sows.

New insights in gut-liver axis in wild-type murine imiquimod-induced lupus

Lupus ◽  
2021 ◽  
Vol 30 (6) ◽  
pp. 926-936
Author(s):  
Georges Maalouly ◽  
Joelle Hajal ◽  
Charbel Noujeim ◽  
Michel Choueiry ◽  
Hussein Nassereddine ◽  
...  
Keyword(s):  
Tight Junction ◽  
Fecal Calprotectin ◽  
Liver Inflammation ◽  
Tight Junction Proteins ◽  
Wild Type ◽  
Imiquimod Cream ◽  
E Coli ◽  
Intestinal Pathology ◽  
Nfκb Pathway ◽  
Junction Proteins

Background Intestinal and hepatic manifestations of lupus seem to be underestimated in comparison to other major organ lesions. Although recent data point to gut-liver axis involvement in lupus, gut permeability dysfunction and liver inflammation need to be more investigated. Objective This study aims to assess fecal calprotectin, intestinal tight junction proteins and liver inflammation pathway in wild-type murine imiquimod- induced lupus. Methods C57BL/6 mice were topically treated on their right ears with 1.25 mg of 5% imiquimod cream, three times per week for six weeks. Fecal calprotectin was collected at day 0, 22 and 45. Renal, liver and intestinal pathology, as well as inflammatory markers, intestinal tight junction proteins, and E. coli protein in liver were assessed at sacrifice. Results At six weeks, lupus nephritis was confirmed on histopathology and NGAL and KIM-1 expression. Calprotectin rise started at day 22 and persists at day 45. Protein expression of Claudine, ZO-1 and occludin was significantly decreased. E. coli protein was significantly increased in liver with necro-inflammation and increased TLR4, TLR7, and pNFκB/NFκB liver expression. Conclusion This study is the first to demonstrate early fecal calprotectin increase and liver activation of TLR4- NFκB pathway in wild-type murine imiquimod-induced lupus.

Developing a Genetic System in Deinococcus radiodurans for Analyzing Mutations

Genetics ◽  
2004 ◽  
Vol 166 (2) ◽  
pp. 661-668
Author(s):  
Mandy Kim ◽  
Erika Wolff ◽  
Tiffany Huang ◽  
Lilit Garibyan ◽  
Ashlee M Earl ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Deinococcus Radiodurans ◽  
Genetic System ◽  
Base Change ◽  
Base Substitution ◽  
Wild Type ◽  
Base Pairs ◽  
E Coli ◽  
Radiation Induced ◽  
Induced Mutagenesis

Abstract We have applied a genetic system for analyzing mutations in Escherichia coli to Deinococcus radiodurans, an extremeophile with an astonishingly high resistance to UV- and ionizing-radiation-induced mutagenesis. Taking advantage of the conservation of the β-subunit of RNA polymerase among most prokaryotes, we derived again in D. radiodurans the rpoB/Rif r system that we developed in E. coli to monitor base substitutions, defining 33 base change substitutions at 22 different base pairs. We sequenced &gt;250 mutations leading to Rif r in D. radiodurans derived spontaneously in wild-type and uvrD (mismatch-repair-deficient) backgrounds and after treatment with N-methyl-N′-nitro-N-nitrosoguanidine (NTG) and 5-azacytidine (5AZ). The specificities of NTG and 5AZ in D. radiodurans are the same as those found for E. coli and other organisms. There are prominent base substitution hotspots in rpoB in both D. radiodurans and E. coli. In several cases these are at different points in each organism, even though the DNA sequences surrounding the hotspots and their corresponding sites are very similar in both D. radiodurans and E. coli. In one case the hotspots occur at the same site in both organisms.

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