Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen causing hemorrhagic colitis and hemolytic uremic syndrome. EHEC colonizes the intestinal tract through a range of virulence factors encoded by the locus of enterocyte effacement (LEE), as well as Shiga toxin. Although the factors involved in colonization and disease are well characterized, how EHEC regulates its expression in response to a host encounter is not well understood. Here, we report that EHEC perceives attachment to host cells as a mechanical cue that leads to expression of LEE-encoded virulence genes. This signal is transduced via the LEE-encoded global regulator of LEEencoded regulator (Ler) and global regulator of Ler and is further enhanced by levels of shear force similar to peristaltic forces in the intestinal tract. Our data suggest that, in addition to a range of chemical environmental signals, EHEC is capable of sensing and responding to mechanical cues to adapt to its host's physiology.enterohemorrhagic Escherichia coli | locus of enterocyte effacement | attaching/effacing pathogens | gastrointestinal infection | mechanosensing

Outer membrane vesicles (OMVs) are nanosized proteoliposomes derived from the outer membrane of Gram-negative bacteria. They are ubiquitously produced both in culture and during infection, and are now recognized to play crucial roles during host-microbe interactions. OMVs can transport a broad range of chemically diverse cargoes, including lipids and lipopolysaccharides, membrane embedded and associated proteins and small molecules, peptidoglycan and nucleic acids. Particularly virulence factors such as adhesins and toxins are often enriched in OMVs. Here, we discuss a variety of ways in which OMVs facilitate hostmicrobe interactions, including their contributions to biofilm formation, nutrient scavenging, and modulation of host cell function. We particularly examine recent findings regarding outer membrane vesicle-host cell interactions in the oral cavity and the gastrointestinal tract.

Here we present new enzyme-responsive polyion complex (PIC) nanoparticles prepared from antimicrobial poly(ethylene imine) and an anionic enzyme-responsive peptide targeting Pseudomonas aeruginosa's elastase.