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Factors influencing the copy number of F‐like plasmids in Escherichia coli and Salmonella typhimurium
Author(s) -
Pritchard J. J.,
Lemoine V. Rodriguez,
Rowbury R. J.
Publication year - 1979
Publication title -
zeitschrift für allgemeine mikrobiologie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0044-2208
DOI - 10.1002/jobm.19790190807
Subject(s) - plasmid , escherichia coli , biology , salmonella , strain (injury) , enterobacteriaceae , microbiology and biotechnology , low copy number , genetics , bacteria , gene , anatomy
The copy numbers of Flac , four F‐like plasmids and pLT2 were estimated in two strains of Salmonella typhimurium and (for all except pLT2) one strain of Escherichia coli. For organisms grown in casamino acids minimal medium, the plasmids spanned a 7–8 fold range of copy number with ColB‐K98 having the highest copy number in each strain and R124 the lowest. The copy number of ColB‐K98 was substantially greater than 1 in each of the strains tested. There was no clear relation between the plasmid size and copy number, although the plasmids studied spanned only a narrow size range. The copy number of individual plasmids was slightly reduced or not affected at all by the presence of a second plasmid in the same strain. Derivatives harbouring each of the plasmids were grown in three different media to ascertain how plasmid copy number responds to changes in growth rate. For each plasmid, the copy number increased with decreasing growth rate. Extracts from each of the three strains harbouring ColB‐K98 contained two distinct plasmid species. One appeared to be about twice as large as the other and both were absent from Col − segregants.