The Influence of the Growth Environment on the Stability of a Drug Resistance Plasmid in Escherichia coli K12

Abstract

201Populations of Escherichia coli K12 containing the plasmid TP120 which coded for resistance to ampicillin, streptomycin, sulphonamide and tetracycline were grown in a chemostat under carbon-limited and phosphorus-limited conditions. With time, resistance to one or more of the drugs was lost, resulting in the production of mutant populations which were more competitive than the parent population. The resistance to tetracycline was always lost under both carbon and phosphorus limitations, but resistance to the other three drugs was lost only during phosphate-limited growth. Strains of E. coli which had lost resistance to one or more of the drugs were capable of higher maximum specific growth rates than the parent strain.

Organization of the Bacterial Chromosome

“…In the absence of selection, plasmid R46, which confers resistance to ampicillin, streptomycin, sulfonamide, and tetracycline, was maintained for extended periods; however, examination of the antibiotic sensitivities revealed that some drug resistance determinants were lost (109). In continuous cultures inoculated with a mixture of organisms, strains containing the modified plasmids displaced the parental strains containing the intact plasmid.…”

“…Maintenance of a 52-kb plasmid (R46) in E. coli in carbonlimited or phosphate-limited continuous culture showed that some components of plasmids were preserved while others were lost (109). In the absence of selection, plasmid R46, which confers resistance to ampicillin, streptomycin, sulfonamide, and tetracycline, was maintained for extended periods; however, examination of the antibiotic sensitivities revealed that some drug resistance determinants were lost (109).…”

“…At the same time, maintenance of the plasmid and the expression of the genes (some of which may interfere with organismic processes) are costs associated with the presence of plasmids (109,137). A balance of these effects has been measured in E. coli with small, nonconjugative plasmids (viz., pACYC184 and other ColEl derivatives) in both serial (34) and continuous (137) cultures.…”

Enhancement of bacterial competitive fitness by apramycin resistance plasmids from non-pathogenicEscherichia coli

“…The carriage of conjugative resistance plasmids is generally thought to engender a competitive fitness disadvantage on host bacteria in the absence of selective pressure for resistance phenotypes (Goodwin & Slater 1979). Therefore, a reduction in antibiotic use could result in a decrease in the prevalence of corresponding resistance determinants.…”

Investigation of the Instability of Plasmids Directing the Expression of Met-Prochymosin in Escherichia coli

“…Various plasmids have been found to be unstable in E. coli grown in continuous culture with glucose, phosphate or magnesium limitations (Godwin & Slater, 1979;Jones, I. et al, 1980;Noack et al, 1981 ;Jones & Melling, 1984). However, nitrogen limitation has been observed to have little influence on the stability of pBR325 (Roth et al, 1980;Wouters et al, 1980;Noack et al, 1981).…”