The force awakens: The dark side of mechanosensing in bacterial pathogens

For many bacteria, the ability to sense physical stimuli such as contact with a surface or a potential host cell is vital for survival and proliferation. This ability, and subsequent attachment, confers a wide range of benefits to bacteria and many species have evolved to take advantage of this. Despite the impressive diversity of bacterial pathogens and their virulence factors, mechanosensory mechanisms are often conserved. These include sensing impedance of flagellar rotation and resistance to type IV pili retraction. There are additional mechanisms that rely on the use of specific membrane-bound adhesins to sense either surface proximity or shear forces. This review aims to examine these mechanosensors, and how they are used by pathogenic bacteria to sense physical features in their environment. We will explore how these sensors generate and transmit signals which can trigger modulation of virulence-associated gene expression in some of the most common bacterial pathogens: Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli and Vibrio species.