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Abstract

For the isolation of plasmids from cyanobacteria phenol extraction of cleared lysates proved the most satisfactory method. Plasmids ranging in size from 2.6 to at least 30 MDa were isolated. Using restriction endonuclease enzymes maps of cryptic plasmids from the filamentous cyanobacteria Anabaena variabilis PCC 7118 pGL1: 3.6 MDa, Nostoc PCC 6705 pGL2: 2.6 generated. Selectable markers were introduced onto pGL2 and pGL3 by fusing them to the vector pBR328, using their single restriction sites for Cla I. The recombinant plasmids generated were characterized orientation of the insert and the single sites for restriction endonucleases. A method for isolating larger cyanobacterial plasmids (> 20 MDa) was devised. Chromosomal DNA from nine species of filamentous cyanobacteria is suggested to be extensively modified methylated by its resistance to cleavage by a number of restriction endonucleases. A remarkably similar pattern of DNA modification in these species contrasts with the known heterogeneity of their type II restriction endonuclease content, (especially in: Nostoc PCC 73102). The use of isoschizomers demonstrates the presence of the methylase in the filamentous strains analogous to the dam enzyme of Escherichia coli.

Additional information

Authors: LAMBERT G L UNIVERSITY OF LIVERPOOL (UK) CARR N G UNIVERSITY OF WARWICK (UK) , UNIVERSITY OF LIVERPOOL (UK);UNIVERSITY OF WARWICK (UK)
Bibliographic Reference: EUR 9684 EN (1985) MF, 33 P., BFR 150, BLOW-UP COPY BFR 165, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
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