Mutagenesis at the ad-3A and ad-3B loci in haploid UV-sensitive strains of Neurospora crassaI. Development of isogenic strains and spontaneous mutability

1980 ◽  
Vol 71 (1) ◽  
pp. 53-65 ◽  
Author(s):  
F DESERRES ◽  
H INOUE ◽  
M SCHUPBACH
Keyword(s):  
Spontaneous Mutability ◽  
Isogenic Strains

scholarly journals INHERITANCE OF SPONTANEOUS MUTABILITY IN YEAST

Genetics ◽  
1971 ◽  
Vol 69 (1) ◽  
pp. 17-27
Author(s):  
R C von Borstel ◽  
Katherine T Cain ◽  
C M Steinberg
Keyword(s):  
Spontaneous Mutability

Genetic Transformation of Streptococcus sanguis (Challis) with Cryptic Plasmids from Streptococcus ferus

1980 ◽  
Vol 28 (3) ◽  
pp. 692-699 ◽  
Author(s):  
Francis L. Macrina ◽  
Patricia H. Wood ◽  
Kevin R. Jones
Keyword(s):  
Genetic Transformation ◽  
Streptococcus Mutans ◽  
Restriction Enzyme ◽  
Deoxyribonucleic Acid ◽  
Cryptic Plasmid ◽  
Common Ancestry ◽  
Erythromycin Resistance ◽  
Streptococcus Sanguis ◽  
Cryptic Plasmids ◽  
Isogenic Strains

By using the basic methodology initially published by Kretschmer et al. (J. Bacteriol. 124 :225-231, 1975), we have been able to introduce phenotypically cryptic plasmids from Streptococcus ferus (formerly Streptococcus mutans subsp. ferus ) into Streptococcus sanguis by genetic transformation. In this system, the entry of the cryptic plasmids is selected indirectly. This is effected with transforming deoxyribonucleic acid mixtures in which the cryptic plasmid deoxyribonucleic acid is present in an approximate 10-fold molar excess with respect to a plasmid (pVA1) known to confer erythromycin resistance. Under such conditions, 5 to 10% of the pVA1-containing erythromycin-resistant transformants were cotransformed with cryptic plasmid deoxyribonucleic acid. pVA1 may be selectively eliminated by growth of its S. sanguis host strain at 42°C, enabling the construction of isogenic strains with and without S. ferus cryptic plasmids. Comparative physiological studies of such strains have failed to reveal any plasmid-conferred phenotypes in S. sanguis. With this procedure, we have been able to physically separate two small cryptic plasmids (2.4 × 10 6 and 2.8 × 10 6 daltons) of S. ferus. Although these plasmids were found naturally to exist in a single S. ferus host, they were able to replicate independently of one another in S. sanguis. Restriction enzyme fingerprinting indicated that these plasmids did not share a common ancestry.

scholarly journals Impact of Different Carbapenems and Regimens of Administration on Resistance Emergence for Three Isogenic Pseudomonas aeruginosa Strains with Differing Mechanisms of Resistance

2010 ◽  
Vol 54 (6) ◽  
pp. 2638-2645 ◽  
Author(s):  
Arnold Louie ◽  
Adam Bied ◽  
Christine Fregeau ◽  
Brian Van Scoy ◽  
David Brown ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Free Time ◽  
Wild Type ◽  
Resistance Mutations ◽  
Drug Concentrations ◽  
Cell Kill ◽  
Liquid Chromatography Tandem Mass ◽  
Full Period ◽  
Serial Samples ◽  
Isogenic Strains

ABSTRACT We compared drugs (imipenem and doripenem), doses (500 mg and 1 g), and infusion times (0.5 and 1.0 [imipenem], 1.0 and 4.0 h [doripenem]) in our hollow-fiber model, examining cell kill and resistance suppression for three isogenic strains of Pseudomonas aeruginosa PAO1. The experiments ran for 10 days. Serial samples were taken for total organism and resistant subpopulation counts. Drug concentrations were determined by high-pressure liquid chromatography-tandem mass spectrometry (LC/MS/MS). Free time above the MIC (time > MIC) was calculated using ADAPT II. Time to resistance emergence was examined with Cox modeling. Cell kill and resistance emergence differences were explained, in the main, by differences in potency (MIC) between doripenem and imipenem. Prolonged infusion increased free drug time > MIC and improved cell kill. For resistance suppression, the 1-g, 4-h infusion was able to completely suppress resistance for the full period of observation for the wild-type isolate. For the mutants, control was ultimately lost, but in all cases, this was the best regimen. Doripenem gave longer free time > MIC than imipenem and, therefore, better cell kill and resistance suppression. For the wild-type organism, the 1-g, 4-h infusion regimen is preferred. For organisms with resistance mutations, larger doses or addition of a second drug should be studied.

scholarly journals γ-Glutamyltransferase Is a Helicobacter pylori Virulence Factor but Is Not Essential for Colonization

2001 ◽  
Vol 69 (6) ◽  
pp. 4168-4173 ◽  
Author(s):  
K. J. McGovern ◽  
T. G. Blanchard ◽  
J. A. Gutierrez ◽  
S. J. Czinn ◽  
S. Krakowka ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Virulence Factor ◽  
Bacterial Load ◽  
H Pylori ◽  
Glutamyl Transpeptidase ◽  
Isogenic Strains

ABSTRACT The contribution of glutamyl transpeptidase (GGT) (γ-glutamyltransferase [EC 2. 3. 2. 2]) to Helicobacter pylori virulence was investigated in piglets and mice using GGT-deficient isogenic strains. All animals became colonized. However, the bacterial load was significantly lower for mutant bacteria than for parent strains. These results suggest that GGT activity provides an advantage to H. pylori in colonization.

scholarly journals Identification of the Haemophilus influenzae tolC Gene by Susceptibility Profiles of Insertionally Inactivated Efflux Pump Mutants

2004 ◽  
Vol 48 (4) ◽  
pp. 1416-1418 ◽  
Author(s):  
Catherine M. Trepod ◽  
John E. Mott
Keyword(s):  
Escherichia Coli ◽  
Haemophilus Influenzae ◽  
Efflux Pump ◽  
Antimicrobial Compounds ◽  
The Third ◽  
Susceptibility Profiles ◽  
Isogenic Strains

ABSTRACT Isogenic strains containing insertional disruptions of 10 Haemophilus influenzae Rd genes were investigated for their effects on the susceptibility of the organism to various classes of antimicrobial compounds. MIC results show that HI1462, which encodes an Escherichia coli TolC homolog, is the third component of the H. influenzae AcrAB pump.

Changes in host cell membrane activities in response to adhesion of Neisseria gonorrhoeae

1986 ◽  
Vol 32 (2) ◽  
pp. 83-88 ◽  
Author(s):  
G. M. Wiseman ◽  
C. F. Martin
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Host Cell ◽  
Pyruvate Kinase ◽  
Bacterial Adhesion ◽  
Hypochlorous Acid ◽  
Cell Model ◽  
Anion Transport ◽  
Polymorphonuclear Neutrophils ◽  
Host Cell Membrane ◽  
Isogenic Strains

Physiological changes in host cell model membranes (intact human erythrocytes and ghosts) as a consequence of bacterial adhesion were studied with special reference to Neisseria gonorrhoeae. Membrane activities examined were transport of K+, Cl− ions, pyruvate kinase, Na–K-dependent ATPase, and cAMP. We found that K+ and Cl− transport were affected, more so in membranes with attached pilated (P+) organisms than in those with apilated (P−) isogenic strains. In N. gonorrhoeae and in several other species of gram-negative bacteria studied, hemagglutination titres were directly correlated with effects on anion transport, suggesting that perturbations in anion transport are an immediate result of adhesion. Of three P+ gonococcus strains tested, two depressed Na–K–ATPase activity in the membrane, indicating a possible effect on the Na–K pump. Pyruvate kinase activity associated with the membrane appeared to be stimulated by attached gonococci, again by P+ strains to higher levels than P− organisms. Clearly, some enzyme properties of host membranes are intrinsically affected by bacterial adhesion. Human polymorphonuclear neutrophils were also investigated, and with some exceptions, changes observed in leukocyte enzyme activities tended to parallel those in erythrocytes. Since hypochlorous acid production is considered to be an important microbicidal mechanism in neutrophils, interference with Cl− transport could jeopardize their role in host defense.

Correlation of DNA adenine methylase activity with spontaneous mutability in Escherichia coli K-12

Gene ◽  
1984 ◽  
Vol 28 (1) ◽  
pp. 123-125 ◽  
Author(s):  
M.G. Marinus ◽  
Anthony Poteete ◽  
Judy A. Arraj
Keyword(s):  
Escherichia Coli ◽  
Dna Adenine Methylase ◽  
Spontaneous Mutability ◽  
K 12 ◽  
Methylase Activity

scholarly journals Metabolism of a 5-nitroimidazole in susceptible and resistant isogenic strains of Bacteroides fragilis.

1997 ◽  
Vol 41 (7) ◽  
pp. 1495-1499 ◽  
Author(s):  
J P Carlier ◽  
N Sellier ◽  
M N Rager ◽  
G Reysset
Keyword(s):  
Metabolic Pathways ◽  
Enzymatic Reaction ◽  
Bacteroides Fragilis ◽  
Susceptible Strain ◽  
Ring Cleavage ◽  
Anaerobic Conditions ◽  
Resting Cell ◽  
Electron Reduction ◽  
Classical Reduction ◽  
Isogenic Strains

We investigated the metabolism of dimetridazole (1,2-dimethyl-5-nitroimidazole) (DMZ) by the resting cell method in a susceptible strain of Bacteroides fragilis and in the same strain containing the nimA gene, which conferred resistance to 5-nitroimidazole drugs. In both cases, under strict anaerobic conditions DMZ was metabolized without major ring cleavage or nitrate formation. However, one of two distinct metabolic pathways is involved, depending on the susceptibility of the strain. In the susceptible strain, the classical reduction pathway of nitroaromatic compounds is followed at least as far as the nitroso-radical anion, with further formation of the azo-dimer: 5,5'-azobis-(1,2-dimethylimidazole). In the resistant strain, DMZ is reduced to the amine derivative, namely, 5-amino-1,2-dimethylimidazole, preventing the formation of the toxic form of the drug. The specificity of the six-electron reduction of the nitro group, which is restricted to 4- and 5-nitroimidazole, suggests an enzymatic reaction. We thus conclude that nimA and related genes may encode a 5-nitroimidazole reductase.

scholarly journals Impact of Bacterial Biofilm Formation on In Vitro and In Vivo Activities of Antibiotics

1998 ◽  
Vol 42 (4) ◽  
pp. 895-898 ◽  
Author(s):  
Silvia Schwank ◽  
Zarko Rajacic ◽  
Werner Zimmerli ◽  
Jürg Blaser
Keyword(s):  
Animal Model ◽  
Staphylococcus Epidermidis ◽  
Biofilm Formation ◽  
Bacterial Biofilm ◽  
Phenotypic Resistance ◽  
Vitro Model ◽  
The Impact ◽  
Isogenic Strains

ABSTRACT The impact of bacterial adherence on antibiotic activity was analyzed with two isogenic strains of Staphylococcus epidermidis that differ in the features of their in vitro biofilm formation. The eradication of bacteria adhering to glass beads by amikacin, levofloxacin, rifampin, or teicoplanin was studied in an animal model and in a pharmacokinetically matched in vitro model. The features of S. epidermidis RP62A that allowed it to grow on surfaces in multiple layers promoted phenotypic resistance to antibiotic treatment, whereas strain M7 failed to accumulate, despite initial adherence on surfaces and growth in suspension similar to those for RP62A. Biofilms of S. epidermidis M7 were better eradicated than those of strain RP62A in vitro (46 versus 31%;P < 0.05) as well as in the animal model (39 versus 9%; P < 0.01).

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