Labeling the deoxyribonucleic acid of Anacystis nidulans

Cloning and characterization of a plasmid DNA from anacystis nidulans 6301

A plasmid DNA of Anacystis nidulans 6301 was isolated by CsCl-EtBr centrifugation. The Mr of the plasmid, named pBA1, was estimated to be 5.04 +/- 0.26 X 10(6) by electron microscopic analysis and 5.2 X 10(6) by agarose gel electrophoresis. The pBA1 DNA was opened at a unique site with BamHI and cloned in pBR322 vector propagated in Escherichia coli HB101 cells. The recombinant plasmid, named pBAS18, was digested with various restriction endonucleases and its cleavage map was constructed. Based on this result, the cleavage map of the pBA1 plasmid is presented.

Incorporation of deoxyribonucleosides into DNA of coryneform bacteria and the relevance of deoxyribonucleoside kinases

In order to obtain basic knowledge of the salvage pathways for DNA synthesis, the ability of Brevibacterium ammoniagenes ATCC 6872 and Micrococcus luteus ATCC 15932 for incorporation of nucleobases and nucleosides was investigated. Only adenine and uracil are incorporated by B. ammoniagenes, whereas M. luteus additionally can utilize deoxyadenosine and, less efficiently, thymidine. In M. luteus, the demonstration of deoxyadenosine kinase and thymidine kinase explains the incorporation data. Uptake of thymidine is of short duration because of rapid breakdown of exogenously supplied thymidine to thymine. At a 540-fold excess pyrimidine deoxyribonucleosides inhibit 14C incorporation from thymidine nearly totally and purine deoxyribonucleosides cut by half the uptake rate, probably by interfering with transport of thymidine. However, as no cessation of thymidine incorporation occurs at these concentrations of purine deoxyribonucleosides, incorporation is finally enhanced. During the initial period of this reduced uptake considerable protection of thymidine from breakdown to thymine is provided by deoxyguanosine, but not by deoxyadenosine. At a 108-fold excess there is actually no inhibition of thymidine uptake by deoxyguanosine and only an insignificant impairment by deoxyadenosine resulting in an ultimate enhancement of 14C incorporation up to 20% of the exogenously supplied thymidine. As there is no salvage pathway for thymidine in B. ammoniagenes due to the absence of thymidine kinase, labelling with adenine and hydrolyzing of the 'contaminated' RNA fraction with 1 M KOH is recommended for measurements of overall DNA synthesis in this strain.

Isolation of membrane-associated folded chromosomes from Anacystis nidulans

Particles containing folded DNA were isolated from the blue-green alga Anacystis nidulans. The structure of these particles is vesicle-like and similar to that of membrane-associated nuclear bodies which had been isolated from Escherichia coli under comparable conditions. The sedimentation constant is between 8000 and 9000 Svedbergs. The DNA is inside the particles and is attached to the thylakoid membranes.

Non-specific incorporation of nucleic acid precursors in Blastomyces dermatitidis and Histoplasma capsulatum

Incorporation of thymidine, thymidine monophosphate (TMP), thymidine triphosphate (TTP), uridine and orotic acid into DNA, RNA and protein in Blastomyces dermatitidis and Histoplasma capsulatum was studied utilizing a specific acid hydrolysis technique developed for these fungi. Thymidine was incorporated to the greatest extent (approximately 0.5% of added label) followed by uridine, orotic acid, TMP and TTP. In Blastomyces, uridine and orotic acid labeled primarily RNA. TMP and TTP labeled RNA, DNA and protein at nearly the same level. In Histoplasma RNA was labeled poorly by any of these precursors. TMP and TTP labeled DNA predominately and protein to a slightly lower level. Deoxyadenosine or uridine media supplements of 250 micrograms/ml did not enhance incorporation. All precursors tested were found to be nonspecific in that RNA, DNA and protein were labeled. All data indicate that neither RNA nor DNA synthesis can be specifically measured in whole cells or acid precipitates by any of these precursors. Specific radiometric monitoring with these isotopes therefore requires the separation of these macromolecules.

Cyanobacterial plasmids: their widespread occurrence, and the existence of regions of homology between plasmids in the same and different species

The results of screening of 29 diverse cyanobacterial (blue-green algal) strains for plasmid (CCC DNA) content are reported. Approximately one-half of the strains were shown to contain one or more CCC DNAs. CCC DNAs from four unicellular marine cyanobacteria were characterized in more detail. These strains contained multiple plasmids. Two kinds of Southern hybridization experiments allowed us to show that different plasmids within the same strain, and different plasmids within different strains, can ( but do not always) contain restricted regions of sequence homology. We suggest that these regions of homology may be analogous to the transposable genetic elements of bacterial plasmids. This, together with indirect but compelling evidence for interspecific (or intergeneric) plasmid transfer, indicates that CCC DNAs (although as yet genetically cryptic) may play a role in the ecology and evolution of obligately autotrophic prokaryotes, as they do in the ecology and evolution of the better-known heterotrophic bacteria.

Mechanism of toxicity of putrescine in Anacystis nidulans

Putrescine is lethal to the cyanobacterium Anacystis nidulans at extracellular pH values at which significant concentrations of the nonprotonated diamine rapidly diffuse into the cell and accumulate as the charged form. Although over 98% of the accumulated putrescine is not metabolized, a small fraction is rendered trichloroacetic acid-insoluble, and about 90% of this is bound as putrescinie to proteins and cell structures. Various synthetic functions were studied in the presence of a bacteriostatic (40 microM) and a bacteriocidal (150 microM) concentration of putrescine at pH 9.5. Under lethal conditions, protein synthesis was completely inhibited after 45 min and CO2 fixation after 100 min, whereas nucleic acid synthesis was less affected. Spermidine was lost from the cell and its synthesis was arrested. These functions were much less inhibited at 40 microM putrescine. Ribosomes from putrescine-killed cells were found to be irreversibly dissociated into 30S and 50S subunits. Some putrescine (1-4 molecules) cosedimented with each subunit.

Ultraviolet light-induction and photoreactivation of thymine dimers in a cyanobacterium, Anacystis nidulans

Partially photoreactivable mutant of Anacystis nidulans demonstrates partial photorepair of thymine dimers. The wild type which is completely photoreactivable at the conditions studied shows higher level of thymine dimer photolysis.

Genetics of Rhodospirillaceae

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[Incorporation of thymidine into the DNA of actinomycetes. I. Incorporation of exogenous thymidine into the DNA of Thermoactinomyces vulgaris]

The incorporation of exogenous thymidine and thymine into acid-insoluble material of Thermoactinomyces vulgaris has been studied during germination and subsequent growth. Thymine is not incorporated. The incorporation of thymidine stops after a short time due to the rapid breakdown of thymidine to thymine and deoxyribose-1-phosphate by the inducible thymidine phosphorylase. Deoxyadenosine enhances the incorporation of thymidine as well as of thymine and prolongs the tine of uptake. Uridine stimulates only the incorporation of thymidine but not of thymine. These effects can be explained by the function of these substances within the salvage pathway. Deoxyadenosine acts as donor of deoxyribosyl groups being necessary for the conversion of thymine to thymidine by thymidine phosphorylase and uridine inhibits thymidine phosphorylase, and thereby it prevents the degradation of thymidine to thymine. Thymidine is incorporated into alkali-, RNase-and protease-stable, hot TCA-soluble and DNase-sensitive material. That means that the cellular DNA of T. vulgaris can be specifically labelled by radioactive thymidine in the presence of deoxyadenosine and uridine, respectively.

Synthesis of DNA during the cell cycle of synchronous Anacystis nidulans

Cells of Anacystis nidulans strain 1402-1 incorporate [methyl-(3)H]thymidine or [8-(3)H]adenine into DNA; in synchronous cultures (21/2 h full light, 1/2 h weak light, 5 h dark), this incorporation occurs in the dark to different extents according to the labeled precursor offered or to its specific activity. The specific activity of in vivo, uniformly labeled DNA decreases to half the initial value when the cells are grown in the absence of radioactive DNA precursors during the light phase; it does not decrease during the following dark phase. If unlabeled thymidine is given during the dark phase, the specific activity of the DNA starts to decrease at the onset of the next light phase. The time course of the decrease supports the hypothesis that all cells start their DNA replication immediately after illumination and that the first cells have completed if after 1.25 h. The slowest cells then need 3.75 h for completion of DNA replication. It is discussed whether the incorporation during the dark might be due to pool size effects.

The blue-green alga agmenellum quadruplicatum contains covalently closed DNA circles

This paper reports the first direct visualization of covalently closed, circular DNA from a blue-green alga. Agmenellum quadruplicatum lysates, fractionated on CsCl-ethidium bromide density gradients, yield a minor band of covalently closed DNA circles which we have analyzed by electron microscopy and agarose gel electrophoresis. The DNA consists of a number of a discrete classes of DNA circles ranging in molecular weight from 3 X 10(6) daltons to 65-80 X 10(6) daltons. The function of these circles is at present entirely unknown.