Abstract
Type IV pili (Tfp) are ubiquitous outside appendages found in both pathogenic and commensal bacteria. These long (up to several tens of micrometers) and thin (4 to 10 m in diameter) multifunctional polymers undergo cycles of elongations and retractions critical for most of the functions that they mediate (DNA uptake, motility, infection, biofilm formation…). The Neisseria genus, which encompasses both human pathogens (Neisseria gonorrhoeae and Neisseria meningitidis) and many human commensals (e.g. Neisseria elongata), has emerged as a model system for the study of Tfp. Here we will compare the use, biophysical parameters and impact of Tfp retraction forces by a human pathogen and a human commensal of the Neisseria genus. By doing so we will evaluate the importance of physical forces in the balance between pathogenicity and commensalism and hope to convey the interest of mechanomicrobiology the study of the role physical forces in microbial physiology and evolution.