Whiting, Gail Corinne;
(1990)
Effects of ColV on survival of E. coli.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The object of this thesis was to examine how the presence of the F-like plasmid ColV,I-K94 in strains of Escherichia coli affects survival in the environment. E. coli is a frequently-isolated water pollutant and is used as a water quality indicator. It is known that ColV plasmids cause increased virulence in pathogenic E. coli strains. The presence of the ColV,I-K94 plasmid in E. coli strains causes enhanced adhesion to surfaces; probably mediated by the plasmid-encoded sex pili as it is dependent on the presence of derepressed levels of transfer components. Attachment of ColV+ organisms to glass beads led to increased resistance to treatment with a weak acid at pH 3.5, to antibiotics, to detergents and to other inhibitory agents. Attachment to naturally-occurring particles in the aquatic environment also resulted in increased resistance of organisms to inhibitory agents. Organisms present in the natural aquatic environment may be subject to adverse environmental conditions and this may affect their sensitivity to potential chemical inhibitors. Cold-shocked ColV+ and Col- strains became less sensitive to treatment with either Cu2+ ions or acrylic acid. Conjugation is an important mechanism for dissemination of plasmids throughout the natural environment and may be of Public Health significance for virulence and resistance plasmids. The transfer frequency of the ColV plasmid was studied under a variety of adverse conditions such as in poor medium, in acid and alkaline pH, at sub-optimal temperatures and in the presence of a range of inhibitory agents. Starvation-survival is an important concept in ecology because it concerns the long-term survival of individuals in unfavourable conditions. Stress induced by starvation was examined to discover if this increased the sensitivity of organisms to inhibitory agents. Acid and alkaline pHs are increasingly common in rivers, streams and estuaries as a result of agricultural and industrial effluents. The habituation of ColV+ strains to acid and alkaline pH was studied in order to assess its relevance for survival of E. coli strains in natural waters.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Effects of ColV on survival of E. coli |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| Keywords: | Biological sciences; F-like plasmid |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10120397 |
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