Novel organisation and regulation of the pic promoter from enteroaggregative and uropathogenic Escherichia coli

ABSTRACT

The serine protease autotransporters of the Enterobacteriaceae (SPATEs) are a large family of virulence factors commonly found in enteric bacteria. These secreted virulence factors have diverse functions during bacterial infection, including adhesion, aggregation and cell toxicity. One such SPATE, the Pic mucinase (protein involved in colonisation) cleaves mucin, allowing enteric bacterial cells to utilise mucin as a carbon source and to penetrate the gut mucus lining, thereby increasing mucosal colonisation. The pic gene is widely distributed within the Enterobacteriaceae, being found in human pathogens, such as enteroaggregative Escherichia coli (EAEC), uropathogenic E. coli (UPEC) and Shigella flexneri 2a. As the pic promoter regions from EAEC strain 042 and UPEC strain CFT073 differ, we have investigated the regulation of each promoter. Here, using in vivo and in vitro techniques, we show that both promoters are activated by the global transcription factor, CRP (cyclic AMP receptor protein), but the architectures of the EAEC and the UPEC pic promoter differ. Expression from both pic promoters is repressed by the nucleoid-associated factor, Fis, and maximal promoter activity occurs when cells are grown in minimal medium. As CRP activates transcription in conditions of nutrient depletion, whilst Fis levels are maximal in nutrient-rich environments, the regulation of the EAEC and UPEC pic promoters is consistent with Pic’s nutritional role in scavenging mucin as a suitable carbon source during colonisation and infection.

KEYWORDS:

• Bacterial gene regulation
• CRP
• enteroaggregative Escherichia Coli (EAEC)
• Fis
• mucin
• Pic
• uropathogenic E. coli (UPEC)
• virulence

Acknowledgement

This work was supported by BBSRC research grants BB/R017689/1 and BB/W00285X/1 to D.F.B. and S.J.W.B. The authors extend their appreciation for the support of the Saudi Cultural Bureau in London (UK SACB) and Princess Nourah bint Abdulrahman University (PNU), KSA. for funding Munirah Alhammadi.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/21505594.2022.2111754

Data availability statement

All data relating to this article are present in the article and the accompanying Supplementary Material.

Additional information

Funding

This work was supported by the Biotechnology and Biological Sciences Research Council [BB/R017689/1 and BB/W00285X/1] and the Saudi Cultural Bureau in London (UK SACB) and Princess Nourah bint Abdulrahman University (PNU), KSA.