Regulatory interplay between pap operons in uropathogenic Escherichia coli

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Pathogenic bacteria utilize surface organelles for adherence, motility, and protein export.
• Coordinating expression of multiple surface organelles is crucial to prevent interference and immune evasion.
• Phase variation limits surface factor expression but struggles with homologous structures controlled by shared regulators.

Purpose of the Study:

• Investigate regulatory cross-talk between pyelonephritis-associated pili (pap) operons in Escherichia coli.
• Determine mechanisms for coordinating surface organelle expression beyond phase variation.
• Understand how bacteria sort their cell surface to prevent interference.

Main Methods:

• Analysis of regulatory regions and regulators in Escherichia coli isolates.
• Examination of allelic variation in pap operons.
• Assessing the synergistic effects of regulatory variations on fimbrial operon coexpression.

Main Results:

• Allelic variation in regulatory regions and regulators limits coexpression of homologous fimbrial operons.
• The regulator papI is under positive selection, with variants affecting related pap operon activation.
• Variations in the PapB binding site alter pap operon activation sensitivity.

Conclusions:

• Regulatory cross-talk between pap operons ensures sequential expression of surface organelles.
• This coordinated regulation prevents interference and excessive immune stimulation.
• The findings illustrate a novel mechanism for bacterial surface sorting and expression control.