An Investigation into the utilisation of ethanolamine by uropathogenic E. coli
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Date
2019
Authors
Dadswell, Katherine
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Publisher
University College Cork
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Abstract
Urinary tract infections (UTIs) are one of the most common bacterial infections worldwide with E. coli as the causal organism responsible for 75% of all cases. Uropathogenic E. coli (UPEC) naturally reside in the gastrointestinal tract (GI tract) and infect the urinary tract via migratory ascension of the urethra. Ethanolamine, an amino alcohol found naturally in phospholipids as phosphatidylethanolamine, can be metabolised by bacteria to be used as an alternate source of nitrogen and carbon. Within the GI tract ethanolamine provides pathogenic bacteria with a competitive advantage over the commensal bacteria. The ability of bacteria to utilise ethanolamine is dependent on the presence of the ethanolamine utilisation (eut) operon encoding enzymes and bacterial microcompartment packaging. Recent studies suggest the regulator of the eut operon, eutR, can modulate the expression of virulence factors in Enterohaemorrhagic E. coli (EHEC). Transcriptome analysis of UPEC in active UTIs has found that the eut operon is expressed within the urinary tract and confers a competitive advantage in the murine urinary tract, but the exact mechanism conferring this advantage is not known. The aim of this thesis was to investigate the utilisation of ethanolamine by UPEC. This thesis provides evidence that ethanolamine is present in the urine at concentrations of approximately 0.57mM and correlated with the expression of the eut operon in UPEC infected urine. Additionally, the ability to metabolise ethanolamine by the eut operon is conserved across UPEC in this cohort (Cork University Hospital, Cork). Ethanolamine provides UPEC with a growth advantage as a sole nitrogen source in modified M9 minimal medium and an artificial urine medium (AUM). Metabolite analysis shows that the growth advantage observed in both media correlates with ethanolamine metabolism. Expression of eut operon genes and electron microscopy evidence of bacterial microcompartment formation was found in UPEC strain U1 metabolising ethanolamine in AUM. Mutational analysis confirmed a requirement for a functional eut operon to metabolise ethanolamine and suggests that ethanolamine is utilised by UPEC as an additional carbon source. Ethanolamine provide U1 with a competitive growth advantage at 10mM concentrations in vitro. RT-PCR provides evidence that suggests ii ethanolamine regulated the expression of type 1 fimbriae in U1. In conclusion, this thesis supports the hypothesis that ethanolamine provides UPEC with a growth advantage in urine with a potential role in the pathogenicity of UTIs.
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Keywords
UPEC , Ethanolamine , UTI , Metabolism , Bacterial microcompartments , Escherichia coli
Citation
Dadswell, K. 2019. An Investigation into the utilisation of ethanolamine by uropathogenic E. coli. PhD Thesis, University College Cork.