Studies with deoxyribonucleic acid from blue-green algae

Craig, Ian; Leach, C. K.; Carr, N. G.

doi:10.1007/bf00407105

Cited by 35 publications

(17 citation statements)

References 23 publications

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“…The data on DNA base composition in Tables 1 to 5 include all values now available for cyanobacteria, derived both from the present study and from preceding publications (Edelman et al, 1967;Craig et al, 1969;Kaye et al, 1967;Stanier et al, 1971;Rippka et al, 1974). A careful comparison of cyanobacterial strain histories (Rippka et al, 1979) has shown that a few of the strains, previously assumed to be of independent origin, are probably identical isolates; in such cases, a value for only one strain is included in the tabulations.…”

Section: Resultsmentioning

confidence: 94%

Deoxyribonucleic Acid Base Composition of Cyanobacteria

Herdman

Janvier

Waterbury

et al. 1979

Journal of General Microbiology

172

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The DNA base compositions of 176 strains of cyanobacteria were determined by thermal denaturation or by CsCl density gradient centrifugation. A summary of all data now available for this prokaryotic group is presented and the taxonomic and evolutionary implications are discussed. et al. (1967) reported mean DNA base compositions for a limited number of strains of cyanobacteria, representative of many different sub-groups. More extensive data were published by Stanier et al. (1971) for one sub-group, the unicellular cyanobacteria. In this paper we present data for a large number of additional strains, broadly representative of this major prokaryotic taxon. I N T R O D U C T I O N Edelman METHODS Strains.The strains examined are all maintained in the Pasteur Culture Collection (PCC) and havenow been deposited in the American Type Culture Collection (ATCC). They are identified here by both PCC and ATCC strain numbers. Full strain histories, media employed for cultivation and the explanation of generic terminology are given by Rippka et al. (1979). An additional strain (Oscillatoria agardhii) was isolated by Dr F. I. Kappers from the Veluwemeer, The Netherlands, and is now in pure culture as strain PCC 7805.Extraction of DNA. DNA for use in thermal denaturation experiments was purified by a method modified from that of Britten et al. (1968). Harvested cells (approximately 5 g wet wt) were suspended in 20 ml lysis mixture containing 8 M-urea, 1 M-NaClO,, 0.01 M-EDTA (disodium salt) and 1 % (w/v) sodium dodecyl sulphate (SDS) in 0.24 M-phosphate buffer (pH 7-0), disrupted by passage through a French press at 76 MPa, and partially deproteinized by shaking with an equal volume of chloroform/3-methylbutan-l-ol (24: 1, v/v) at room temperature for 30 min. Following centrifugation at 3000 g for 15 min the upper (aqueous) phase, containing DNA, was retained. DNA-grade hydroxyapatite (HAP; 2 g; Bio-Rad) was suspended in 20 ml 0.24 M-phosphate buffer (pH 7.0), boiled for 30 min, centrifuged at low speed, and washed twice with 15 ml MUP (Britten et al., 1968) containing 8 M-urea in 0.24 M-phosphate buffer (pH 7.0), being sedimented after each wash by brief low-speed centrifugation. The deproteinized nucleic acid solution was mixed with the washed HAP and stirred (5 min) to permit binding of DNA. The bound DNA was purified by washing the mixture (by centrifugation) seven times with 15 ml MUP, to remove RNA and residual protein, and then four times with 15 ml 0.014 M-phosphate buffer (pH 7.0), to remove urea. The purified DNA was eluted Present address :

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Section: Resultsmentioning

confidence: 94%

Deoxyribonucleic Acid Base Composition of Cyanobacteria

Herdman

Janvier

Waterbury

et al. 1979

Journal of General Microbiology

172

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“…Second, because cells of Anabaena sp. have multiple genomic equivalents as calculated from the genetic complexity (3,22) and the amount of DNA per cell (7) and are linked, isolation of recessive mutants requires both segregation of mutant and wild-type forms of the genome and physical disjunction of adjacent cells of a filament bearing the two genomic forms (8). Golden and Wiest (18) first introduced an insertional mutation into the chromosome ofAnabaena sp.…”

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confidence: 99%

Use of a conditionally lethal gene in Anabaena sp. strain PCC 7120 to select for double recombinants and to entrap insertion sequences

1990

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Use of the sacB gene (J. L. Ried and A. Collmer, Gene 57:239-246, 1987) provides a simple, effective, positive selection for double recombinants in Anabaena sp. strain PCC 7120, a filamentous cyanobacterium. This gene, which encodes the secretory levansucrase of Bacillus subtilis, was inserted into the vector portion of a suicide plasmid bearing a mutant version of a chromosomal gene. Cells of colonies in which such a plasmid had integrated into the Anabaena chromosome through single recombination were plated on solid medium containing 5% sucrose. Under this condition, the presence of the sacB gene is lethal. A small fraction of the cells from initially sucrose-sensitive colonies became sucrose resistant; the majority of these sucrose-resistant derivatives had undergone a second recombinational event in which the sacB-containing vector had been lost and the wild-type form of the chromosomal gene had been replaced by the mutant form. By the use of this technique, we mutated two selected genes in the chromosome of Anabaena sp. strain PCC 7120. The conditionally lethal nature of the sacB gene was also used to detect insertion sequences from this Anabaena strain. Sucrose-resistant colonies derived from cells bearing a sacB-containing autonomously replicating plasmid were analyzed. Five different, presumed insertion sequences were found to have inserted into the sacB gene of the plasmids in these colonies. One of them, denoted IS892, was characterized by physical mapping. It is 1.7 kilobases in size and is present in at least five copies in the genome of Anabaena sp. strain PCC 7120.

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“…For Cyanophyceae see, for instance, Edelman et al (1967), Craig, Leach & Carr (1969), Stanier et al (1971, Stare (1980), and Lachance (1981). Within a genus the GC content does not usually show large differences.…”

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confidence: 99%