GENETICS OF 5-FLUORODEOXYURIDINE-RESISTANT MUTANTS OF NEUROSPORA CRASSA

1973 ◽  
Vol 15 (4) ◽  
pp. 831-844 ◽  
Author(s):  
G. R. Hoffmann ◽  
H. V. Malling ◽  
T. J. Mitchell
Keyword(s):  
Neurospora Crassa ◽  
Ultraviolet Light ◽  
Resistance Genes ◽  
Linkage Studies ◽  
Linkage Groups ◽  
Mechanisms Of Resistance ◽  
Growth Tube ◽  
Light Resistance ◽  
Resistant Mutants

Mutants resistant to inhibitory concentrations of 5-fluorodeoxyuridine (FdUrd) were induced by ultraviolet light. Resistance was demonstrated by growth-tube experiments and by plating efficiencies in the presence and in the absence of FdUrd. Linkage studies involving five mutants revealed the existence of at least two loci conferring resistance to the inhibitor. These loci, designated fdu-1 and fdu-2, were assigned to Linkage Groups VII and IV, respectively. Both resistance genes are recessive to their sensitive alleles in heterokaryons. Resistance to FdUrd is stable both in the presence and in the absence of the inhibitor. Possible mechanisms of resistance to FdUrd are discussed.

THE PRODUCTION OF A DDT-RESISTANT STRAIN OF AEDES AEGYPTI MARKED ON ALL THREE LINKAGE GROUPS

1974 ◽  
Vol 16 (4) ◽  
pp. 883-888 ◽  
Author(s):  
J. P. Margham ◽  
R. J. Wood
Keyword(s):  
Aedes Aegypti ◽  
Resistance Genes ◽  
Resistant Strain ◽  
Genetic Background ◽  
Adult Stage ◽  
Susceptible Strain ◽  
Linkage Studies ◽  
Linkage Groups ◽  
Resistant Strains ◽  
Major Resistance Genes

DDT-resistant strains marked on all three linkage groups have been produced by selection at the adult stage after outcrossing a resistant strain (BANGKOK-HR) to a marked susceptible strain (64). The most resistant and viable line (BANGKOK-MR) was kept for linkage studies. The production of a marked resistant strain was not entirely straightforward. In the absence of a suitable genetic background, major resistance genes conferred little or no DDT tolerance and could not be selected. Selection at the adult stage produced resistance in larvae as well as in adults. Resistance was achieved more rapidly in larvae than in adults

Die Aufnahme der Zucker Sorbose, Fructose und Glucose durch Sorbose-resistente Mutanten von Neurospora crassa

1967 ◽  
Vol 22 (3) ◽  
pp. 327-335 ◽  
Author(s):  
Walter Klingmüller
Keyword(s):  
Neurospora Crassa ◽  
Nitrous Acid ◽  
Acid Treatment ◽  
Chromosome Complement ◽  
Sugar Metabolism ◽  
Type I ◽  
Linkage Groups ◽  
Saturation Kinetics ◽  
Resistant Mutants ◽  
Energy Dependent

Sorbose-resistant mutants of Neurospora crassa, arising spontaneously or after nitrous acid treatment, can be mapped in at least 6 separate geneloci, scattered over the chromosome complement. Neither combined enzymatic optic tests, nor radio-paperchromatography give evidence for altered enzymes of sugar metabolism or gain of the ability to phosphorylate and utilize sorbose in these mutants.The increase of radioactivity of germinated conidia as a function of time of incubation with 14C-labelled sorbose revealed that the mutants have a decreased rate of active (energy-dependent) sorbose uptake as compared to the wildtype. No difference in rate of either fructose or glucose uptake between mutants and wildtype could be found.Uptake of sorbose exhibited saturation kinetics for mutants and wildtype. Km values of the mutants were nearly equal to that of the wildtype; there are indications that Vmax is lowered in some of them. If supernatants of conidia of 2 mutants (sorr Α-1 and sorrB-57), mapping in separate linkage groups and thus representing two separate genes, were added to pregerminated wildtype conidia, their rate of sorbose-uptake was not depressed. These 2 mutants are therefore not of the excretor-type, i. e. they must be transport-defective mutants. Data available so far exclude that the mutants have a defect in a common carbohydrate carrier, or in a carrier specific for sorbose transport. It is concluded that mutants sorr Α-1 and sorr B-57 are permease-mutants, with genes A and B coding for 2 separate permeases or permease-subunits.

scholarly journals Mechanisms of Resistance in Multiple-Antibiotic-Resistant Escherichia coli Strains of Human, Animal, and Food Origins

2004 ◽  
Vol 48 (10) ◽  
pp. 3996-4001 ◽  
Author(s):  
Yolanda Sáenz ◽  
Laura Briñas ◽  
Elena Domínguez ◽  
Joaquim Ruiz ◽  
Myriam Zarazaga ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Amino Acid ◽  
Resistance Genes ◽  
Antibiotic Resistance Genes ◽  
Mechanisms Of Resistance ◽  
Antibiotic Resistant ◽  
E Coli ◽  
Class 1 ◽  
Human Animal

ABSTRACT Seventeen multiple-antibiotic-resistant nonpathogenic Escherichia coli strains of human, animal, and food origins showed a wide variety of antibiotic resistance genes, many of them carried by class 1 and class 2 integrons. Amino acid changes in MarR and mutations in marO were identified for 15 and 14 E. coli strains, respectively.

Antibiotic susceptibility profiles and frequency of resistance genes in clinical Shiga toxin-producing Escherichia coli isolates from Michigan over a 14-year period

2021 ◽  
Author(s):  
Sanjana Mukherjee ◽  
Heather M. Blankenship ◽  
Jose A. Rodrigues ◽  
Rebekah E. Mosci ◽  
James T. Rudrik ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Resistance Genes ◽  
Shiga Toxin ◽  
Antibiotic Susceptibility ◽  
Genetic Relatedness ◽  
Antibiotic Resistance Genes ◽  
Genomic Analysis ◽  
Mechanisms Of Resistance ◽  
Susceptibility Profiles

Background: Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen that contributes to over 250,000 infections in the US each year. Because antibiotics are not recommended for STEC infections, resistance in STEC has not been widely researched despite an increased likelihood for the transfer of resistance gene from STEC to opportunistic pathogens residing within the same microbial community. Methods: Between 2001 and 2014, 969 STEC isolates were collected from Michigan patients. Serotyping and antibiotic susceptibility profiles to clinically relevant antibiotics were determined using disc diffusion, while epidemiological data was used to identify factors associated with resistance. Whole genome sequencing was used to examine genetic relatedness and identify genetic determinants and mechanisms of resistance in the non-O157 isolates. Results: Increasing frequencies of resistance to at least one antibiotic was observed over the 14 years (p=0.01). While the non-O157 serogroups were more commonly resistant than O157 (Odds Ratio: 2.4; 95% Confidence Interval:1.43-4.05), the frequency of ampicillin resistance among O157 isolates was significantly higher in Michigan compared to the national average (p=0.03). Genomic analysis of 321 non-O157 isolates uncovered 32 distinct antibiotic resistance genes (ARGs). Although mutations in genes encoding resistance to ciprofloxacin and ampicillin were detected in four isolates, most of the horizontally acquired ARGs conferred resistance to aminoglycosides, β-lactams, sulfonamides and/or tetracycline. Conclusions: This study provides insight into the mechanisms of resistance in a large collection of clinical non-O157 STEC isolates and demonstrates that antibiotic resistance among all STEC serogroups has increased over time, prompting the need for enhanced surveillance.

scholarly journals Isolation and characterization of a new class of amino-acid-analogue-resistant mutants inAspergillus nidulansusing reduced carbon flow

1979 ◽  
Vol 34 (2) ◽  
pp. 121-130 ◽  
Author(s):  
Mahavir Singh ◽  
Umakant Sinha
Keyword(s):  
Amino Acid ◽  
Aromatic Amino Acids ◽  
Sole Source ◽  
Amino Acid Analogue ◽  
Linkage Groups ◽  
Isolation And Characterization ◽  
Acid Analogue ◽  
Amino Acid Analogues ◽  
Resistant Mutants ◽  
Growth Requirement

SUMMARYFour recessive amino-acid-analogue-resistant mutants were isolated on a medium containing acetate as the sole carbon source and the amino acid analogues p-fluorophenylalanine and ethionine. None of the mutants showed any growth requirement. Analysis of growth on media containing an amino acid as the sole nitrogen source indicated that two mutants out of the four possess normal systems for utilization of acidic, neutral, basic and aromatic amino acids. The mutantsfpa70 andfpa71 showed reduced growth on tryptophan as the sole source of nitrogen. Three new loci, identified after preliminary genetic analysis, were located on three linkage groups: one each on linkage groups I, VI and VIII.

scholarly journals An electrophoretic karyotype of Neurospora crassa.

1988 ◽  
Vol 8 (4) ◽  
pp. 1469-1473 ◽  
Author(s):  
M J Orbach ◽  
D Vollrath ◽  
R W Davis ◽  
C Yanofsky
Keyword(s):  
Neurospora Crassa ◽  
Electric Fields ◽  
Gel Electrophoresis ◽  
Electrophoretic Karyotype ◽  
Dna Molecules ◽  
Linkage Groups ◽  
Homogeneous Electric Field ◽  
Chromosomal Dna ◽  
Molecular Karyotype ◽  
Electrophoresis System

A molecular karyotype of Neurospora crassa was obtained by using an alternating-field gel electrophoresis system which employs contour-clamped homogeneous electric fields. The migration of all seven N. crassa chromosomal DNAs was defined, and five of the seven molecules were separated from one another. The estimated sizes of these molecules, based on their migration relative to Schizosaccharomyces pombe chromosomal DNA molecules, are 4 to 12.6 megabases. The seven linkage groups were correlated with specific chromosomal DNA bands by hybridizing transfers of contour-clamped homogeneous electric field gels with radioactive probes specific to each linkage group. The mobilities of minichromosomal DNAs generated from translocation strains were also examined. The methods used for preparation of chromosomal DNA molecules and the conditions for their separation should be applicable to other filamentous fungi.

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