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Title: Population structure and siderophore production in commensal Escherichia coli
Author: Searle, Laura
ISNI:       0000 0004 5993 9258
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2015
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The factors involved in the diversity, transition and persistence of commensal Escherichia coli, both between and within hosts, are not fully understood. The aim of this project was to develop and use comparative approaches to investigate traits associated with colonisation of the gut by taking advantage of two collections of natural isolates of E. coli, the ECOR (host-associated) and GMB (plant-associated) collections. A new method for uniquely tagging and monitoring individual E. coli strains was developed to facilitate the assessment of large numbers of strains in complex environments, such as the gut. Competition studies between ‘barcoded’ strains show that this technique has a high sensitivity enabling the identification of E. coli present in the population at low levels, which may be undetected using currently available methods. Together with genome-wide association studies, barcoding is a powerful tool for identifying adaptive traits associated with the environment. One trait linked to E. coli gut colonisation is production of the siderophore enterobactin. Comparisons of siderophore production and the distribution of siderophore loci between the GMB and ECOR collections highlighted that faecal strains produce higher levels of siderophores and possess a larger number of siderophore systems at the population level. However, while our epidemiological data indicated a role for siderophore biosynthesis in the GI-tract, we did not observe significant differences in the competitiveness of siderophore biosynthesis mutants in a mouse model. Whether this is linked to the ability of mutants to cheat and use siderophores generated by the wild-type strain or to obtain iron through other ways remains to be determined. Overall, this study provides further details on the factors determining how the environment shapes the associated E. coli populations. This knowledge is essential to assess the relationship between the environment, the associated E. coli populations and the risk they represent to human health.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available