Some characteristics of streptococci competent for uptake of deoxyribonucleic acid

1970 ◽  
Vol 16 (5) ◽  
pp. 345-350 ◽  
Author(s):  
R. Pakula ◽  
P. Ray ◽  
L. R. Spencer
Keyword(s):  
Methylene Blue ◽  
Deoxyribonucleic Acid ◽  
Dna Uptake ◽  
Competent Cells ◽  
Characteristic Features

The degree of competence for uptake of deoxyribonucleic acid (DNA uptake) of the Challis streptococcus was found to be strictly related to the concentration of cell-bound competence-provoking factor (CPF). Antibodies against competent cells and antibodies against crude concentrates of CPF inhibited DNA uptake by competent cells. Both types of antibodies interacted also with soluble CPF and reduced its capacity to induce competence. Two characteristic features of competent streptococci were revealed: high precipitability at low pH's and a reduced capacity to absorb methylene blue.

Some features of competent streptococci

1972 ◽  
Vol 18 (4) ◽  
pp. 487-491 ◽  
Author(s):  
R. Pakula ◽  
L. R. Spencer
Keyword(s):  
Cell Proliferation ◽  
Dna Synthesis ◽  
Deoxyribonucleic Acid ◽  
Competence Development ◽  
Dna Uptake ◽  
Related Strain ◽  
Competent Cells ◽  
Insoluble Material ◽  
Competence Factor

The Wicky Streptococcus was rendered competent for deoxyribonucleic acid (DNA) uptake with the competence factor (CF) derived from a related strain. Initiation of competence resulted in an almost immediate decline of the rate of cell proliferation and of incorporation of 14C-uracil into acid-insoluble material. DNA synthesis was affected in the later stage of competence development. The competent cells were penicillin resistant.

scholarly journals Competence for Deoxyribonucleic Acid Uptake and Deoxyribonuclease Action External to Cells in the Genetic Transformation of Diplococcus pneumoniae

1973 ◽  
Vol 114 (1) ◽  
pp. 152-163 ◽  
Author(s):  
S. Lacks ◽  
B. Greenberg
Keyword(s):  
Protein Synthesis ◽  
Genetic Transformation ◽  
Deoxyribonucleic Acid ◽  
Acid Uptake ◽  
Dna Uptake ◽  
Temperature Dependent ◽  
Competent Cells ◽  
Wild Strains

A mutant of Diplococcus pneumoniae that apparently does not require activator can become competent for uptake of deoxyribonucleic acid (DNA) when grown in dilute cultures or in the presence of trypsin. Development of competence in both mutant and wild strains is temperature dependent, being 10-fold greater at 30 C than at 37 C. Induction of competence on a shift from 37 to 30 C requires protein synthesis and the presence of Mg 2+ and Ca 2+ ; uptake of DNA does not require protein synthesis. Competence decays exponentially at higher temperatures. As well as taking up DNA, competent cells release oligonucleotide fragments of donor DNA in the medium external to the cells. Normal strains release fragments comparable in amount to the DNA taken up; but, in a mutant selected for inability to degrade DNA in agar, the amount of fragments formed external to the cells is only 40% of DNA uptake. Requirements for external deoxyribonuclease action are identical to those for DNA uptake: prior development of competence and the presence during treatment with DNA of Mg 2+ ions and a source of energy.

THE EFFECT OF "COMPETASE" ON DNA UPTAKE IN PROVOKED TRANSFORMATION OF A STREPTOCOCCUS

1965 ◽  
Vol 11 (5) ◽  
pp. 823-827 ◽  
Author(s):  
R. Pakula ◽  
A. H. W. Hauschild
Keyword(s):  
Deoxyribonucleic Acid ◽  
Brain Heart Infusion ◽  
Streptomycin Resistance ◽  
Brain Heart Infusion Broth ◽  
Dna Uptake ◽  
Retarding Effect ◽  
Competence Factor ◽  
Effect On Growth

The competence-provoking factor produced by the highly transformable group H streptococcus, strain Challis, was used to provoke efficient transformability in the poorly transformable group H streptococcus, strain Wicky. Transformations to streptomycin resistance were carried out with C14-labelled DNA which was extracted from bacteria fed with thymidine-2-C14.When cultures of strain Wicky were grown in Difco brain–heart infusion broth, supplemented with serum, and treated with competence factor and deoxyribonucleic acid, 25 to 40% of viable units were transformed while no transformation occurred without the factor. At the same time, the incorporation of C14 into cells treated with competence factor was higher than incorporation of C14 into untreated cells.Crude preparations of the competence factor had a retarding effect on growth of the streptococcus, irrespective of whether DNA was added.

Semiconducting Polymer Dot-Based Ratiometric Fluorescence Nanoprobe for DNA Detection

2021 ◽  
Vol 21 (11) ◽  
pp. 5776-5783
Author(s):  
Zhen-Hu Gong ◽  
Zong-Nan Wei ◽  
Yi-Zhang Liu ◽  
Lu-Fei Xiao
Keyword(s):  
Methylene Blue ◽  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Deoxyribonucleic Acid ◽  
Experimental Conditions ◽  
Semiconducting Polymer ◽  
Electron Transfer Mechanism ◽  
Fluorescence Nanoprobe ◽  
Polymer Dots ◽  
Semiconducting Polymer Dots

A ratiometric fluorescent deoxyribonucleic acid probe was synthesized using the photoinduced electron transfer mechanism, involving the interactions between different fluorescent components and electron acceptors. Double-emission carboxyl functionalized semiconducting polymer dots were synthesized using the nanoprecipitation method and applied as the flurophore, while methylene blue was used as the electron acceptor. Photoinduced electron transfer between different polymer dots components and methylene blue can achieve ratiometric modulation of the overall fluorescence in the system. The addition of deoxyribonucleic acid restores the fluorescence intensity, because the stronger interactions between deoxyribonucleic acid and methylene blue results in methylene blue being separated from the polymer dots. Under the optimized experimental conditions, system fluorescence was restored to its maximum when the concentration of deoxyribonucleic acid reached 200 nM, the linear range was 0.006-200 nM (R2 = 0.995). This probe was reasonably free from interference, showing a good response to deoxyribonucleic acid, with strong application data from actual samples.

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