Pathogenic bacteria possess a vast array of resources that enable the colonization of host epithelial tissues. The continuous appearance of bacterial strains resistant to most antibiotic treatments—the so-called “superbugs”—is a pressing public health problem that requires urgent efforts to tackle the life-threatening infections caused by these pathogens.
One of the main events that initiate tissue colonization and the onset of an infection is the recognition of surfaces—host tissues—by the pathogenic bacteria. Bacteria cells swim free in liquid media and the proximity or direct contact with the host tissues (respiratory tract, urinary tract, etc.) provide mechanical cues that trigger cell responses that lead to tissue colonization and the onset of an infection process (Summary Image, 1 and 2). This mechanically induced detection of host tissues depends on proteins—mechanosensors—located on the surface of the bacteria cells. Understanding how these proteins respond to mechanical forces and how the bacterium processes this information to decide to start an infection offers an ideal target for developing therapeutic strategies that combat the first stages of bacterial colonization. For instance, drugs that alter the mechanical properties of these proteins responsible for surface detection would render the bacteria “blind” to the host tissue, abolishing colonization, and the subsequent infection.
With these premises, this project aimed to delve into the process of bacterial surface detection and adhesion by focusing on the nanomechanics of the protein PilY1, whose mechanical activation has been suggested as a key event in the process that leads to host tissue colonization (Summary Image, 3). We focused on the PilY1 protein of Pseudomonas aeruginosa, an opportunistic pathogen that causes recurrent infections in cystic fibrosis patients. PilY1 is a complex protein that possesses a mechanosensitive role (detection of surfaces), and an adhesive role (binding to host tissue proteins). To interrogate the role of mechanical forces on the functions of PilY1, we employed single-molecule force spectroscopy techniques. These techniques allow the manipulation with the force of single PilY1 proteins and determine their mechanical properties in the nanoscale—nanomechanics—which provides key information about proteins that carry out their functions under mechanical loads. Certain molecules bind to PilY1 and modulate the processes of surface recognition and adhesion, and conducting measurements in the absence and presence of these molecules can give insights into how they regulate PilY1 behavior under force and, more importantly, they provide knowledge for the development of strategies that interfere with colonization and pathogenesis (Summary Image, 4). Therefore, the objectives of this project aimed to identify and dissect the effect of mechanical forces on the functions of PilY1 and identify potential molecular strategies to interfere with them.
