title: The blue-green alga agmenellum quadruplicatum contains covalently closed DNA circles.
abstract: 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.
mesh_terms: D002499:Centrifugation, Density Gradient; D000458:Cyanobacteria / Q000032:analysis* / Q000254:growth & development; D004270:DNA, Circular; D004587:Electrophoresis, Agar Gel; D008970:Molecular Weight; D009690:Nucleic Acid Conformation
chemical_list: D004270:DNA, Circular