Many infection processes start with primary adhesion of pathogenic bacteria to host cells. The Gram-negative uropathogenic Escherichia coli (UPEC) bacteria, invades the urinary tract region and cause in some cases severe infections, pyelonephritis, if they can withstand the rinsing action of urine and ascend to the kidney, via the bladder and ureters. To mediate adhesion, UPEC express quaternary surface organelles that are assembled from ∼103 identical subunits into a helix-like coil, with a single adhesin located at the tip. It is believed that the single adhesin mediate attachment to host cells while the helix-like structures act as shock absorbers to dampen the irregularly shear forces induced by urine flow. To unravel the biomechanical properties of such quaternary structures, in particular in terms of their force-elongation and kinetic behavior, Force-Measuring Optical Tweezers (FMOT) have been used. A plethora of different types of pili have been identified in the literature and we show, using FMOT, that those dissimilarities might reflect the host environment. For example, we have found differences among pili expressed at diverse environment inside the urinary tract, which imply that pili presumably have evolved to resist specific forces under in vivo conditions. It is thus worth striving for understanding bacterial adhesion in order to figure out alternative to the over-abundance of antibiotics worldwide.