MECHANICAL HOST-PATHOGEN INTERACTIONS OF HEALTHCARE-ASSOCIATED INFECTIONS

Abstract

Mechanical cues are a ubiquitous feature of host-pathogen interactions. While the effect of physical forces on eukaryotic host cell biology is well-established, their role in regulating the behaviors of pathogenic bacteria is only emerging. Here I describe how Pseudomonas aeruginosa, a leading cause of healthcare-associated infections, senses and responds to forces generated by fluid flow. I develop a microfluidic model of P. aeruginosa infections, where surface-attached bacteria are exposed to tunable flow-generated forces. I use RNA-seq to discover an active transcriptional response to fluid flow and identify froABCD, a colonization determinant, as the first flow-regulated operon described in this pathogen. A froABCD transcriptional reporter serves as a surrogate for the global P. aeruginosa flow response and is regulated specifically by shear stress. Further, I discover that froABCD transcription is regulated by a previously uncharacterized sigma factor/anti-sigma factor pair, FroR/FroI. Validating the use of the froABCD as a flow reporter, we provide evidence that the entire P. aeruginosa flow response is regulated by FroI. Together, these data are the first evidence that a flow-generated force regulates gene expression in surface-attached P. aeruginosa. This work makes a fundamental contribution to the growing body of evidence that the hallmarks of bacterial pathogenesis are regulated by the integration of a diverse set of environmental cues, including physical forces.