Use this URL to cite or link to this record in EThOS:
Title: The influence of the growth environment on the stability of a drug resistant plasmid in Escherichia coli K12 grown in chemostat culture
Author: Godwin, Dianne
ISNI:       0000 0001 3501 4929
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1980
Availability of Full Text:
Access from EThOS:
Access from Institution:
Populations of Escherichia coli K12 containing the plasmid TP120 which coded for resistance to ampicillin, streotomycin, sulphonamide and tetracycline were grown in continuous culture under carbon-limited and phosphor us-limited conditions. The maintenance of the plasmid TP120 was studied and it was discovered that 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 tetracycline resistance marker was always lost under carbon and phosphor us-limitations, but resistance to the other three drugs was lost only under phosphate- limited growth. A plasmid-minus strain was isolated on only one occasion. Strains of E. coli which had lost resistance to one or more drugs were shown to be smaller in size than the parent strain and were capable of higher maximum specific growth rates than the parent strain. Mixed culture competition experiments also demonstrated that evolved strains had lower Kq values than the original, parent strain. However the rate of carbon and phosphor U3 uptake measured in radiochemical experiments was unchanged for parent and evolved strains. The significance of plasmid stability within populations of bacteria in relation to the natural situation was also discussed.
Supervisor: Not available Sponsor: Medical Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR Microbiology