Document Detail

Detection of nonintegrated plasmid deoxyribonucleic acid in the folded chromosome of Escherichia coli: physiochemical approach to studying the unit of segregation.
MedLine Citation:
PMID:  1090568     Owner:  NLM     Status:  MEDLINE    
Physiocochemical evidence presented indicates plasmid deoxyribonucleic acid (DNA) can associate with host chromosome without linear insertion of the former into the latter. This conclusion is based on the observation that covalently closed circular (CCC) plasmid DNA can cosediment with undegraded host chromosome in a neutral sucrose gradient. When F plus bacteria are lysed under conditions that preserve chromosome, approximately 90% of CCC F sex factor plasmid (about 1% of the total DNA) is found in folded chromosomes sedimenting at rates between 1,500 and 4,000s. The remaining 10% of the CCC F DNA sediments at the rate (80S) indicative of the free CCC plasmid form. Reconstruction experiments in which 80S, CCC F DNA is added to F plus or F minus bacteria before cell lysis show that exogenous F DNA does not associate with folded chromosomes. In F plus bacteria, F plasmid is harbored at a level of one or two copies per chromosomal equivalent. In bacteria producing colicin E1, the genetic determinant of this colicin, the Col E1 plasmid, is harbored at levels of 10 to 13 copies per chromosomal equivalent; yet, greater than 90% of these plasmids do not cosediment with the 1,800S species of folded chromosome. However, preliminary evidence suggests one or two Col E1 plasmids may associate with the 1,800S folded chromosome. Based on evidence presented in this and other papers, we postulate F plasmid can link to folded chromosome because the physicochemical structure of the plasmid resembles a supercoiled region of the chromosome and, therefore, is able to interact with the ribonucleic acid that stabilizes the folded chromosome structure. Implications of this model for F plasmid replication and segregation are discussed.
B C Kline; J R Miller
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of bacteriology     Volume:  121     ISSN:  0021-9193     ISO Abbreviation:  J. Bacteriol.     Publication Date:  1975 Jan 
Date Detail:
Created Date:  1975-05-27     Completed Date:  1975-05-27     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2985120R     Medline TA:  J Bacteriol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  165-72     Citation Subset:  IM    
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MeSH Terms
Carbon Radioisotopes
Centrifugation, Density Gradient
Chromosomes, Bacterial / metabolism*
Colicins / biosynthesis
DNA, Bacterial / metabolism*
DNA, Circular / metabolism
Escherichia coli / metabolism*
Extrachromosomal Inheritance*
Reg. No./Substance:
0/Carbon Radioisotopes; 0/Colicins; 0/DNA, Bacterial; 0/DNA, Circular; 10028-17-8/Tritium; 50-89-5/Thymidine; 65-71-4/Thymine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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