Determination of the base composition of deoxyribonucleic acid from its buoyant density in CsCl

Properties of two marine bacteriophages

Chen, Peter K. (Georgetown University, Washington, D.C.), Ronald V. Citarella, Omar Salazar, and Rita R. Colwell. Properties of two marine bacteriophages. J. Bacteriol. 91:1136-1139. 1966.-Various properties have been determined for two bacteriophages, NCMB 384 and 385, and their host, NCMB 397, a Cytophaga sp., isolated from the marine environment. The purified bacteriophages have been subjected to serological analysis, results of which indicate a high degree of relatedness. Purified, highly polymerized deoxyribonucleic acid (DNA) prepared from the host strain showed an overall base composition of 37 moles% guanine + cytosine (buoyant density of 1.696 g/cc). The bacteriophage DNA, in the native configuration, from NCMB 384 and 385 banded at 1.691 g/cc in a CsCl gradient and the denatured bacteriophage DNA demonstrated a bimodal peak. Stability tests of the bacteriophages in various buffers and diluents suggest a requirement for inorganic cations, most likely Na(+) and Mg(++), for retention of viability.

The action of gamma-rays on deoxyribonucleohistone in solution

Measurements have been made by light scattering of the decrease, resulting from γ -irradiation, in the molecular weight and radius of gyration of deoxyribonucleohistone ( DNH ) in 0·7 mM phosphate buffer (pH 6·8). The number of fractures produced depended on a power of the dosage intermediate between one and two. The relative constancy of the radius of gyration at doses up to about 1 eV/P atom, while the mean molecular weight decreased, suggested that dissociation of the histone from the DNA core might be occurring. Similar measure­ments on DNH dissolved in 2M potassium chloride solutions showed that the DNA core was degraded during irradiation and this was confirmed by the increase observed in the width of the band which was obtained when the DNH was centrifuged to equilibrium in a density-gradient of caesium chloride. Irradiation also caused denaturation, since the buoyant density of the DNA component of the DNH increased and there was a decrease in ultra-violet hypochromicity, as determined after heating the irradiated solutions. From integral sedimentation-distribution curves at zero concentration it was inferred that all the DNH molecules, apart from some aggregated material, had undergone the same fractional decrease in sedimentation coefficient, and hence in molecular weight, irrespective of their original size. The irradiated DNH also showed an increased anionic electrophoretic mobility, which is consistent with the loss of a cationic fragment from the molecule. Calculations have shown that the observed molecular-weight changes could be explained by a mechanism which combines dissociation of histone by a ‘one-hit’ process and degradation of the DNA by a ‘two-hit’ process. It is suggested that an attack on the DNA , resulting in the breakage of one of the two chains, and the consequent disorganization of the helix in the vicinity of the break, would be the most likely cause of dissociation of the histone.

Mitochondrial DNA in yeast and some mammalian species

Yeast DNA, in a cesium chloride density gradient, shows a minor or satellite band with a density lower than that of the main nuclear component. The DNA isolated from purified mitochondria of yeasts corresponds in density to this satellite band. In solution, this DNA more easily undergoes renaturation as compared to DNA from cell nuclei. The ease of this renaturation is presumably due to a homogeneity greater than that of nuclear DNA. Mitochondrial DNA isolated from several mammalian species has the same or higher density than nuclear DNA, but differs in its ready renaturability.

Further studies of infectious DNA extracted from mycobacteriophages

Results of the previous investigation in which it was found that DNA extracted from D29 mycobacteriophage was infectious for Mycobacterium smegmatis 607, have been extended. DNA extracted from mycobacteriophage D4 and D32 produced plaques when plated on their respective hosts; D28 DNA, extracted in the same manner and tested under similar conditions, failed to show infectivity. Species barriers were not crossed by mycobacteriophage DNA; bacteria resistant to intact phage were not infected with the phage DNA. The efficiency of plating of the DNA is very much lower than that of intact phage; infection of a given host was not accomplished by DNA when titration for plaque formation by the intact phage was less than 10(9) PFU. The base composition of DNA extracted from the four mycobacteriophages and the three propagating hosts was very similar. The bases were paired, adenine with thymine and guanine with cytosine. A relatively higher per cent of guanine-cytosine than of adenine-thymine, was found. The buoyant density of each DNA in CsCl was linearly related to its guanine-cytosine content whereas with the exception of D28 DNA, thermal denaturation temperatures failed to show this relationship. However, the thermal transition profiles were characteristic of double stranded DNA. Additional evidence that D29 DNA forms complexes with basic proteins was obtained. Binding between calf thymus histone and between RNAase and D29 DNA readily occurs with a resultant loss in DNA infectivity. Trypsin and D29 DNA are only weakly reactive.

Physicochemical properties of fowlpox virus deoxyribonucleic acid and its anomalous infectious behavior

Randall, Charles C. (University of Mississippi, Jackson), Lanelle G. Gafford, Richard L. Soehner, and James M. Hyde. Physicochemical properties of fowlpox virus deoxyribonucleic acid and its anomalous infectious behavior. J. Bacteriol. 91:95-100. 1966.-Deoxyribonucleic acid (DNA) was extracted from fowlpox virus-infected tissue, purified inclusions, and purified virus by five variations of detergent and phenol methods. Phenol methods gave a poor yield, whereas detergent techniques extracted up to 78% of the DNA. The buoyant density was 1.695 g/ml, and the melting temperature in 7.2 m NaClO(4) was 39 C, both approximately equivalent to a guanine plus cytosine content of 35 moles per cent. Further proof of the double-stranded nature of the DNA was shown by the characteristic behavior toward deoxyribonuclease, formaldehyde, and heat. Infectious DNA was obtained by the various methods described, but this manifestation of biological activity was capricious and for unknown reasons was often not evident. The infectivity could not be related quantitatively to the amount of DNA employed. Furthermore, the infectious nature of fowlpox virus DNA was demonstrable only when the route of infection was the chorioallantoic membrane. In contrast, whole virus infected both membrane and chick skin with equal efficiency.

Nucleotide composition of nucleic acids of fungi. II. Deoxyribonucleic acids

Storck, Roger (The University of Texas, Austin). Nucleotide composition of nucleic acids from fungi. II. Deoxyribonucleic acids. J. Bacteriol. 91:227-230. 1966.-The nucleotide composition of the deoxyribonucleic acids (DNA) present in extracts of 30 species of fungi was determined. The results were analyzed, together with those in the literature. It was found that the content, in moles per cent of guanine plus cytosine (GC content), varied from 38 to 63% in a distribution composed of 9 species of zygomycetes, 14 of ascomycetes, and 9 each of deuteromycetes and basidiomycetes. The GC content ranges were: 38 to 48% for the zygomycetes, 38 to 54% for the ascomycetes, 47 to 62% for the deuteromycetes, and 44 to 63% for the basidiomycetes. The GC content ranged from 38 to 40% for four Mucor species. The base composition of fungal DNA appears, therefore, to have a taxonomic and phylogenetic significance.

Fractionation of deoxyribonucleic acid from phage-infected bacteria

1. DNA has been isolated in 90% yield from T5-infected cultures of Escherichia coli ;pulse'-labelled with [(3)H]thymidine. It had a buoyant density in caesium chloride solution identical with the DNA of mature T5 phage, and no components of unusual buoyant density were detected. 2. The DNA preparation was resolved into two major components of differing specific activity on a column of kieselguhr coated with methylated serum albumin. The DNA of high specific activity could be eluted from the column only with 2n-ammonia, and the firm binding did not appear to be due to an artifact of preparation. 3. A similar fractionation into two DNA components of differing specific activity was observed when the ;pulse'-labelled culture was lysed with sodium dodecyl sulphate and the lysate rocked with phenol. The DNA of high specific activity was found in the interface precipitate between the phenol and aqueous layers. 4. The amounts of DNA in the two fractions were measured at different times after infection and the radioactivity content of each was determined at various times after a short ;pulse' of [(3)H]thymidine. The interface fraction contained the replicating phage DNA, and the DNA from mature phage particles appeared in the aqueous fraction. 5. Analogous results were obtained with T2-infected E. coli. In the presence of chloramphenicol the DNA in the interface fraction was not converted into DNA extractable into the aqueous layer. Since chloramphenicol prevents the condensation of DNA into phage heads, it is suggested that any DNA in extended configuration is trapped inside the rigid-layer framework of the cell wall. 6. Treatment with lysozyme released much of the DNA from the interface precipitate. This DNA was firmly bound by the chromatographic column and had the same buoyant density in caesium chloride solution as normal T5-phage DNA. Sucrose-gradient sedimentation studies showed that it was heterogeneous and that as much as 60% sedimented faster than T5-phage DNA.

Phenethyl Alcohol I. Effect on Macromolecular Synthesis of Escherichia coli

Rosenkranz, Herbert S. (Columbia University, New York, N.Y.), Howard S. Carr, and Harry M. Rose . Phenethyl alcohol. I. Effect on macromolecular synthesis of Escherichia coli . J. Bacteriol. 89: 1354–1369. 1965.—An investigation of the mode of action of phenethyl alcohol produced the following results. Phenethyl alcohol had no effect on the physicochemical properties of isolated deoxyribonucleic acid (DNA). The DNA isolated from phenethyl alcohol-treated bacteria had physicochemical properties identical with those of DNA isolated from normal cells. The metabolic functions most sensitive to the inhibitory action of phenethyl alcohol appeared to be the process of enzyme induction and, possibly, the synthesis of messenger ribonucleic acid. Phenethyl alcohol did not affect the polyuridylic acid-mediated synthesis of polyphenylalanine in a cell-free amino acid-incorporating system.

Isolation of deoxyribonucleic acid from mitochondria of chick embryo heart and liver

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INCORPORATION OF BACTERIOPHAGE GENOME BY SPORES OF BACILLUS SUBTILIS

Takahashi , I. (Microbiology Research Institute, Ottawa, Ontario, Canada). Incorporation of bacteriophage genome by spores of Bacillus subtilis . J. Bacteriol. 87: 1499–1502. 1964—The buoyant density in a CsCl gradient of deoxyribonucleic acid (DNA) extracted from spores of Bacillus subtilis was found to be identical to that of DNA from vegetative cells. Density-gradient centrifugation of DNA of spores derived from cultures infected with phage PBS 1 revealed the presence of a minor band whose density corresponded to that of the phage DNA in addition to the spore DNA. No intermediate bands were present. The relative amount of the phage DNA present in the spores was estimated to be 11%, suggesting that spores of this organism may incorporate several copies of the phage genome. Although the possibility that true lysogeny may occur cannot be entirely eliminated, the results seem to indicate that the phage genomes incorporated into spores are not attached to the host chromosome in this system.

Base composition of deoxyribonucleic acid of sulfate-reducing bacteria deduced from buoyant density measurements in cesium chloride

Saunders, Grady F. (University of Illinois, Urbana), L. Leon Campbell, and John R. Postgate. Base composition of deoxyribonucleic acid of sulfate-reducing bacteria deduced from buoyant density measurements in cesium chloride. J. Bacteriol. 87:1073-1078. 1964.-The base composition of the deoxyribonucleic acid (DNA) of sulfate-reducing bacteria was calculated from buoyant density measurements in CsCl. The sporulating sulfate-reducing bacteria fell into two groups: Desulfovibrio orientis with a DNA base composition of 42% guanine plus cytosine (G + C), and Clostridium nigrificans with a DNA base composition of 45% G + C. The mesophilic relative of C. nigrificans had a DNA base composition of 46% G + C. Thirty strains of nonsporulating sulfate-reducing bacteria called D. desulfuricans were studied. They fell into three groups as judged by DNA base composition: group I (11 strains), 60 to 62% G + C; group II (13 strains), 54 to 56% G + C; and group III (6 strains), 46 to 47% G + C. These data underline the need for a taxonomic revision of this group of microorganisms.