(62m) Mechanical Properties of Escherichia Coli F-Pili

The dissemination of antibiotic resistance in bacterial populations is an increasing public health threat to both domestic animals and humans. Bacteria that have acquired resistance to one or more antibiotics create a challenge for the treatment of disease because antibiotics that were once effective become less so. There are several means by which bacteria acquire genes for antibiotic resistance, but the interest of our studies pertains to bacterial conjugation. Bacterial conjugation involves the transfer of genetic material directly from one bacterial cell to another. In the common gram negative bacterium Escherichia coli, a specialized extracellular filament known as the F-pilus mediates the initial contact between two bacteria during conjugation. Currently, the structure, function, and mechanical properties of the F-pilus are unknown. Our study hypothesized that F-pilus flexibility is an important functional property, allowing the filaments to sample a large interstitial volume for potential DNA recipients. Using images of F-pili derived from electron micrographs, we determined the persistence length of F-pili, which is one measure of flexural rigidity. Our results show that F-pili are among the most flexible protein filaments normally produced by cells. These and related ongoing studies are pertinent for understanding the dissemination of antibiotic resistance in bacterial populations.