title: Developmental-stage-specific plasmid supercoiling in Chlamydia trachomatis.
abstract: Chlamydia trachomatis elementary body (EB) and reticulate body (RB) developmental stages have polymorphic plasmid DNA. Several plasmid forms separated by gel electrophoresis were identified as topoisomers by treatment with topoisomerase I. Among these topoisomers was one form unique to EBs and one form unique to RBs. The unique EB plasmid topoisomer was characterized as highly supercoiled, on the basis of band migrations by gel electrophoresis and its appearance by electron microscopy. The unusual physical state of this topoisomer was probably mediated, in part, by DNA-specific structural proteins. The unique RB plasmid topoisomer was a supercoiled form of lower superhelical density than the other identified topoisomers. Developmental-stage-specific differences in super-helical density of plasmid DNA suggest cause-and-effect relationships between DNA topology and metabolic activity in RBs and metabolic quiescence in EBs.
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco 94143-0412.
authors.forename: M V
authors.initials: MV
authors.lastname: Solbrig
authors.forename: M L
authors.initials: ML
authors.lastname: Wong
authors.forename: R S
authors.initials: RS
authors.lastname: Stephens
mesh_terms: D015139:Blotting, Southern; D002692:Chlamydia trachomatis / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry; D004278:DNA, Superhelical / Q000737:chemistry*; D003720:Densitometry; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D010957:Plasmids; D012150:Polymorphism, Restriction Fragment Length; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D004278:DNA, Superhelical; D015719:Single-Strand Specific DNA and RNA Endonucleases; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II