Establishing the Role of FNR in the Regulation of Uropathogenic Escherichia coli Group 2 Capsules

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Urinary tract infections (UTIs) are a healthcare burden worldwide. Uropathogenic Escherichia coli (UPEC) is the causative agent of nearly 80% of all UTIs. Several virulence and fitness factors contribute to the virulence of UPEC, including the expression of adhesins, toxins and capsules. Group 2 capsules are the primary capsule type associated with UPEC taking part in the pathogenesis of UTI. The expression of a capsule on the cell surface is dependent on the kps gene cluster. Two promoters drive the transcription of kps, PR1 and PR3. Recent findings have shed light on the PR1 region, which consists of three tandem promoters; PR1-1, PR1-2 and PR1-3. In addition, several regulatory proteins are proven to act on PR1 promoters. This study aims to confirm the interplay of PR1 promoters and to examine the possible effect of the regulatory protein FNR on the regulation of Group 2 capsule in UTI89 strain, specifically the FNR role on the activity of the PR1 promoters. FNR is considered a significant protein, driving the switch between aerobic and anaerobic metabolism. An fnr mutation was introduced into strains with different mutations in PR1-1, PR1-2 and PR1-3, that also have a transcriptional fusion with lacZ. This allowed transcriptional activity to be measured during aerobic and anaerobic growth by assaying β-galactosidase activity. Results confirmed that PR1-1 is an independent promoter required for Group 2 transcription, PR1-2 on the other hand, is dependent on PR1-1 activity. On the contrary, PR1-3 have shown not to affect the transcription. Furthermore, mutations in fnr showed no significant effect on transcription with the approach used. This study extended prior work examining group 2 capsule expression, but further research is needed to understand the role of PR1-3 as a promoter and FNR role in regulating capsule expression in anaerobic conditions.