Showing papers on "Transformation (genetics) published in 1972"
TL;DR: Covalently-closed, catenated, and open (nicked) circular forms of R-factor DNA are all effective in transformation, but denaturation and sonication abolish the transforming ability of R.factor DNA in this system.
Abstract: Transformation of E. coli cells treated with CaCl2 to multiple antibiotic resistance by purified R-factor DNA is reported. Drug resistance is expressed in a small fraction of the recipient bacterial population almost immediately after uptake of DNA, but full genetic expression of resistance requires subsequent incubation in drugfree medium before antibiotic challenge. Transformed bacteria acquire a closed circular, transferable DNA species having the resistance, fertility, and sedimentation characteristics of the parent R factor. Covalently-closed, catenated, and open (nicked) circular forms of R-factor DNA are all effective in transformation, but denaturation and sonication abolish the transforming ability of R-factor DNA in this system.
2,907 citations
TL;DR: An eightfold auxotrophic strain of Bacillus subtilis was constructed and its transformability was strongly reduced as compared with both the UV-resistant parental strain and the other, moderately UV-sensitive, strain.
Abstract: An eightfold auxotrophic strain of Bacillus subtilis was constructed. It was about equally well transformable for all markers. When this strain was used as recipient in transformation, single marker transformation frequencies of 0.5–2.0% were obtained. The markers were located relatively to each other using marker frequency analysis. Two UV-sensitive derivatives, equally well transformable as the parental multiple auxotroph, were isolated. One was highly sensitive to UV irradiation, was host cell reactivation-negative and did not show DNA breakdown or recovery of DNA synthesis after exposure to UV. Using UV-inactivated transforming DNA, this strain's transformability was strongly reduced as compared with both the UV-resistant parental strain and the other, moderately UV-sensitive, strain.
198 citations
Journal Article•
TL;DR: Recloned, carcinogen-sensitive, BALB/3T3 cell lines present a reliable in vitro quantitative bioassay model for the study of chemical carcinogenesis.
Abstract: Sublines from a BALB/3T3 line were sensitive to a variety of carcinogens. A quantitative system of chemical transformation resulted in cell lines that caused fibrosarcomas when injected into mice (106 cells/mouse); no tumors developed from control lines (108). Transformation, indicated by criss-crossing of fibroblast-like cells not seen in controls, was scored in discrete colonies at 10 to 11 days or in foci after 3 weeks. Transformation was observed with carcinogenic polycyclic hydrocarbons, aflatoxin B1, N -acetoxy-2-fluorenylacetamide, and N -methyl- N′ -nitro- N -nitrosoguanidine but not with diethylnitrosoamine or noncarcinogens. Transformation rate increased (based on transformed colonies/total colonies or original cell inoculum used), and cloning efficiency decreased as concentration of carcinogen was increased. The dose-response relationship was consistent with a one-hit phenomenon. The Poisson distribution of frequency of transformed colonies per dish indicates that transformation is due to induction. Transformed cell lines from carcinogen-transformed colonies or foci had decreased doubling time and increased saturation densities relative to control lines. Recloned, carcinogen-sensitive, BALB/3T3 cell lines present a reliable in vitro quantitative bioassay model for the study of chemical carcinogenesis.
120 citations
TL;DR: Inhibition of either protein or RNA synthesis, but not DNA synthesis, prevented the induction of increased hexose uptake and hyaluronic acid synthesis after a shift of RSV-BH-Ta-infected cells from 41 to 36 C, therefore, biochemical changes are secondary to a more basic change responsible for morphological transformation.
Abstract: Chick embryo cells infected with a mutant (Ta) of the Bryan high-titer strain of Rous sarcoma virus (RSV-BH) are morphologically transformed at 36 C but appear similar to uninfected cells at 41 C. When cells infected with RSV-BH-Ta are switched from 41 to 36 C, morphological changes characteristic of transformation are observable within 10 min. The transformation is reversible; cells shifted from 36 to 41 C have been observed to lose their transformed morphology within 1 hr. The transformation after a shift in temperature is unaffected by inhibition of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), or protein synthesis, demonstrating that the proteins involved in the morphological change are already present. Transformed cells infected with RSV-BH or RSV-BH-Ta take up hexose and synthesize hyaluronic acid at higher rates than uninfected cells or RSV-BH-Ta-infected cells grown at 41 C. However, inhibition of either protein or RNA synthesis, but not DNA synthesis, prevented the induction of increased hexose uptake and hyaluronic acid synthesis after a shift of RSV-BH-Ta-infected cells from 41 to 36 C. Therefore, these biochemical changes are secondary to a more basic change responsible for morphological transformation.
105 citations
TL;DR: Plasmid and probably also chromosomal characters have been genetically transformed in Staphylococcus aureus and recipient cells show competence throughout the exponential growth phase with a maximum at early times.
Abstract: Plasmid and probably also chromosomal characters have been genetically transformed in Staphylococcus aureus. Recipient cells show competence throughout the exponential growth phase with a maximum at early times.
87 citations
TL;DR: It was concluded that the absence of ATP-dependent DNase and perhaps to a lesser extent, the presence of exonuclease I both contribute to the capacity for transformation in E. coli K12.
84 citations
TL;DR: A multiple auxotrophic derivative of Bacillus subtilis 168 (strain BR151 carrying lys-3, trpC2, metB10) was transformed with deoxyribonucleic acid (DNA) isolated from B. subtil is 168 to prepare donor DNA, and adverse side effects can occur after incorporation of a segment of foreign DNA.
Abstract: A multiple auxotrophic derivative of Bacillus subtilis 168 (strain BR151 carrying lys-3, trpC2, metB10) was transformed with deoxyribonucleic acid (DNA) isolated from B. subtilis 168, Bacillus amyloliquefaciens H, B. subtilis HSR, Bacillus pumilus, and Bacillus licheniformis. Transformation with heterologous DNA occurred at a very low frequency for the three auxotrophic markers. Heterologous transformation to rifampin resistance was 100 to 1,000 times more efficient than transformation to prototrophy. Transformants from the various heterologous exchanges were used to prepare donor DNA. The fragment of integrated DNA from the heterologous (foreign) species, termed the "intergenote," was capable of transforming BR151 with an efficiency almost equal to that of homologous DNA. When BR151 DNA contained the Rfm(R) (rifampin resistance) intergenote from B. amyloliquefaciens H, the frequency of transformation was frequently greater than that of the homologous DNA. Accompanying this increased efficiency was a marked change in the physiology of the cells. The growth rate of the transformants carrying this intergenote was approximately one-half that of either parental strain. Thus, in a prokaryotic transformation system, adverse side effects can occur after incorporation of a segment of foreign DNA.
65 citations
TL;DR: The probability that a marker in the intact fraction will be integrated, as a function of the length of the donor strand after entry, is calculated, which has a linear dependence on strand length for activities below 40% of maximum, and extrapolates to zero activity at 77,000 daltons per strand.
Abstract: The fate of label introduced as donor deoxyribonucleic acid (DNA) into competent cells of Diplococcus pneumoniae was determined immediately after entry at 25 C, as a function of the size of the donor DNA. Part of the label is found to be acid soluble, part has been incorporated into chromosomal DNA, apparently through reincorporation of degraded donor DNA, and part is found in single strands of length smaller than that of the input donor DNA strands. The last fraction apparently constitutes the precursor for integration of intact donor genetic markers and is referred to as the intact fraction. For large donor DNA the intact fraction contains over 80% of the total intracellular label, but the median strand length has been reduced to 2.2 × 106 daltons. For small donor molecules (1 × 105 to 6 × 105 daltons per strand) the fraction intact increases with donor size from 10 to 50% of the total intracellular label, and the median strand length of this fraction is half that of the donor strands. By combining these results with earlier data on the size dependence of the yield of transformants per unit of total intracellular donor label, we have calculated the probability that a marker in the intact fraction will be integrated, as a function of the length of the donor strand after entry. This probability has a linear dependence on strand length for activities below 40% of maximum, and extrapolates to zero activity at 77,000 daltons per strand.
65 citations
TL;DR: It is shown that transformation by DNA is responsible for this recombination in mixed cultures of auxotrophic and streptomycin-resistant mutant derivatives of Thermo-actinomyces vulgaris strain t9 growing on agar medium.
Abstract: Summary: Genetic recombination occurs with a rather high frequency (up to 10-3) in mixed cultures of auxotrophic and streptomycin-resistant mutant derivatives of Thermo-actinomyces vulgaris strain t9 growing on agar medium. It is shown that transformation by DNA is responsible for this recombination. Certain other newly isolated strains resemble t9 in being competent for transformation and are interfertile with each other and with t9. Some other strains are incompetent but can act as donors to the first set of strains. A fully synthetic minimal medium and conditions for efficient mutagenesis have been defined.
49 citations
29 citations
TL;DR: In vitro assay systems useful for chemical carcinogenesis studies exploit the observation that preinfection of cells with “nontransforming” RNA tumour viruses lead not only to accelerated transformation but also to transformation not inducible by the carcinogens alone.
Abstract: A NUMBER of in vitro assay systems1–4, useful for chemical carcinogenesis studies, exploit the observation that preinfection of cells with “nontransforming” RNA tumour viruses lead not only to accelerated transformation but also to transformation not inducible by the carcinogens alone1.
TL;DR: The results suggest that specific alterations in the metabolism of certain LMN RNAs may occur during the PHA-induced transformation of human lymphocytes.
TL;DR: The transformation of lymphocytes by phytohemagglutinin and the uptake of thymidine by DNA are completely inhibited by 17 mlU/ml L-glu taminase GA.
Abstract: The transformation of lymphocytes by phytohemagglutinin and the uptake of thymidine by DNA are completely inhibited by 17 mlU/ml L-glu taminase GA:1.2. The transformation is also inhibited by 1,700 ml
01 Jan 1972
TL;DR: The frequency of induced r mutants among the am + transformants increased linearly with increasing hydroxylamine dose, while the transforming DNA was inactivated at a progressively decreasing rate, explained in terms of a diminishing target size.
Journal Article•
01 Jan 1972
TL;DR: Inina prokaryotic transformation system, adverse sideeffects can occur after incorporation of a segment offoreign DNA.
Abstract: H,B.subtilis HSR,Bacillus pumilus, andBacillus licheniformis. Transformation withheterologous DNA occurred ata verylowfrequency forthethreeauxotrophic markers. Heterologous transformation torifampin resistance was 100to1,000 times moreefficient thantransformation toprototrophy. Transformants from thevarious heterologous exchanges wereusedtopreparedonorDNA.Thefragmentofintegrated DNA fromtheheterologous (foreign) species, termedthe "intergenote," was capable oftransforming BR151withan efficiency almost equal tothatofhomologous DNA.WhenBR151DNA contained theRfmR(rifampin resistance) intergenote fromB.amyloliquefaciens H,thefrequency of transformation was frequently greater thanthatofthehomologous DNA.Accompanying thisincreased efficiency was a markedchange inthephysiology of thecells. Thegrowth rateofthetransformants carrying thisintergenote was approximately one-half thatofeither parental strain. Thus,ina prokaryotic transformation system, adverse sideeffects can occurafter incorporation ofa segment offoreign DNA.
TL;DR: A study of the intrinsic fluorescence of actin and the changes which occur upon polymerization as a prelude to an intensive study of conformational and microenvironmental changes in actin.
TL;DR: Osmotic shocking of competent Bacillus subtilis reduced transformability by 80–90% through depressing the uptake of radioactive DNA, but the supernatant solution from competent cultures restored both transformability and efficiency.
Abstract: Osmotic shocking of competent Bacillus subtilis reduced transformability by 80–90% through depressing the uptake of radioactive DNA The supernatant solution from competent cultures restored both t
TL;DR: d-CS had an enhancing effect on transformation when deoxyribonucleic acid uptake or phenotypic expression was allowed to occur in its presence, and it inhibited transformation in group H streptococcus, strain Challis, by preventing the development of the competent state.
Abstract: d-Cycloserine (d-CS), a selective inhibitor of bacterial cell wall biosynthesis, inhibited transformation in group H streptococcus, strain Challis, by preventing the development of the competent state. The incubation of strain Challis cells with d-CS resulted in the production of a substance which inhibited the action of competence factor on these cells. d-CS had an enhancing effect on transformation when deoxyribonucleic acid uptake or phenotypic expression was allowed to occur in its presence.
Journal Article•
TL;DR: The enol acetate (VI), derived from α-santonin, was irradiated and hydrolysed to give the cyclodecadienone (VIII), which yielded dihydronovanin (XI) upon reduction followed by acetylation as mentioned in this paper.
Abstract: The enol acetate (VI), derived from α-santonin, was irradiated and hydrolysed to give the cyclodecadienone (VIII), which yielded dihydronovanin (XI) upon reduction followed by acetylation.
01 Jan 1972
TL;DR: Skin extract of newborn rats increases the insolubilization of collagen in skin slices in vitro, and this effect is destroyed by heating and inhibited by lathyrogens.
Abstract: Skin extract of newborn rats increases the insolubilization of collagen in skin slices in vitro. The effect is destroyed by heating and inhibited by lathyrogens. Purified collagen in the precipitated form is. on the contrary, transformed to the more soluble forms by skin extract.
TL;DR: It is shown that even the K2HP04 buffer salts from different firms also influence the cell multiplication and the competence, and the multiplication was quicker in the medium containing BDH, than in the Fisher, Riedel and Merck buffer respectively.
Abstract: The transformation and transfection are influenced by both endogenous (Young: and Spizizen, 1961, 1963; Spizizen, 1964; Charpak and Dedonder, 1965) and exogenous factors which affect one another during growth. The exogenous factors, such as, the composition of the media, the temperature, the aeration and the inoculum size strongly influence the physiological condition of the cells. The effect of these environmental factors are reflected in the generation times (Horv~th, 1967, 1968). The development of competence was investigated in MGY liquid medium. T-medium was used for transformation and MG-agar for selection of transformants. The composition of media has been described previously (Horvs 1967). The procedure of transfeetion was previously described in detail (Horvs 1969). The composition of the media is one of the most important things in transformation. In the following we would like to show that even the K2HP04 buffer salts from different firms also influence the cell multiplication and the competence.When different kinds of K 2 H P 0 4 (pro anal.) were used in the transformation experiments some differences were found, which are collected in Table I. I t is seen tha t the values of the beginning and the peak of competence were not the same and there are big differences in the times which are necessary for the rise periods of competence. The frequencies of the transformation also were not the same. The multiplication of the ceils was quicker in the medium containing BDH, than in the Fisher, Riedel and Merck buffer respectively. The bigger the rate of the cell