The function of cedA of Escherichia coli and its relevance to urinary tract infections

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Urinary Tract Infections (UTIs) are one of the most common bacterial infections worldwide. Eighty per cent of UTIs are caused by uropathogenic Escherichia coli (UPEC) which undergoes a multistage infection cycle. The regulatory mechanisms that control the stages of bacterial cell filamentation during dispersal from overwhelmed bladder cells, and filament reversal (re-division) to form rod cells and allow for reinfection are unresolved. Previous work showed that overexpression of an E. coli gene, cedA, prevents filamentation in a mutant strain of E. coli, called dnaA(cos). cedA was also shown to be under positive selection in UPEC strains and upregulated 8-fold during the dispersal (including filamentation) stage of the UPEC infection cycle in cultured human bladder cells. We found that dnaA(cos)-mediated filamentation employs multiple pathways to lead to filamentation, suggesting that expression of cedA can prevent and/or reverse filamentation generally. We individually surveyed several other known pathways to filamentation and found that cedA can partially prevent filamentation caused by expression of ftsZ-yfp, recAtif (SOS response), and mild filamentation of zwf. cedA overexpression prevented the dispersal of filaments from infected bladder epithelial cells, via inhibition of bacterial growth and/or filamentation at this infection stage, and promoted division in wild-type (WT) cells grown under standard laboratory conditions. Finally, we developed an infection growth competition assay aimed to test preliminary results from a previous genetic screen that suggested cedA might be required for the dispersal stage of UPECs infection cycle. Results revealed that cedA is dispensable for survival during the dispersal/filamentation and recovery (post-infection) stages of the infection cycle. However, division regulator, slmA, known to help prevent division from occurring over the DNA, appeared to play a role in the recovery stage. Understanding how it achieves this requires further work. Overall, the work presented suggests E. coli’s cedA has a general stimulatory effect on cell division. Possibly through metabolic regulators of division, and might control cell size under certain environmental conditions when its expression is induced, including the dispersal and recovery phases of UPECs infection cycle. Based on our results, we hypothesise that cedA prevents filamentation in the subset of intracellular bacterial communities that do not generate filaments during dispersal, possibly allowing for other types of differentiated bacteria that may benefit the species during the sudden change in conditions associated with dispersal. Therefore, this thesis initiates research into understanding the importance of cedA during infection and this may lead to possible future therapeutics for UTIs.
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