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Kaur, Sumeet (2013) Some aspects of biofilm formation by enteropathogenic Escherichia coli. Doctoral thesis, London Metropolitan University.
Microorganisms growing as collective communities called 'biofilms' are widely recognised today. Biofilms impact almost all aspects of human life: personal, medical and industrial. Escherichia coli are model organisms for the study of biofilms. In this work, eight enteropathogenic E. coli (EPEC) and three Shigella sonnei strains (a bacterium that is very similar to E. coli and is often implicated in diseases that are similar to those caused by EPEC) were investigated for their biofilm forming abilities in relation to a number of factors. These included nutrient availability, pH, temperature, time, sodium chloride concentration and iron availability. E. coli were able to form biofilms under all conditions tested; however, S. sonnei was not able to form any biofilms under any of the tested settings and therefore studies on this microorganism were discontinued. The results of the investigations into biofilm-forming abilities directed the subsequent research. These included estimation of antibiotic resistance, examination of structural development of biofilms and the inspection of biofilm behaviour at genetic and proteomic levels. A modification of Calgary Biofilm Device was employed to estimate resistance to nine antibiotics in biofilm form. A Stovall Flow Cell was employed to study the structure of biofilms formed by one (selected) strain E. coli NCIMB 555 which was transformed to express gfp in order to visualize the biofilm morphology. E. coli NCIMB 555 (un-transformed) biofilms were also grown to study proteins expression and gene regulation of six targeted genes. Of these four genes were up-regulated, one was down-regulated and one was expressed at a similar level to planktonic forms. This study contributes to the existing knowledge of the biofilm formation by E. coli under a number of conditions, their antibiotic resistance and gene- and protein-expression associated. The findings of the work have highlighted the need for more work especially in the field of antibiotic resistance.
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