Pyelonephritis Associated Pili Case Study

Bacteria have to developed a variety of mechanisms that allow them to enter the cells of their host, whether to replicate or to transmit the pathogen.

One method of this is through pili. Pili are thin rods anchored to the outer membrane of bacteria with an adhesin at the tip. This adhesin is what gives the bacteria their binding specificity. Pili can serve a variety of roles such as, adhesion or the transfer of material during bacterial conjugation. Fimbria are a type of pili that are solely for attachment to host cells. Pili were thought to only be present in gram negative bacteria but research shows they occur in gram positive bacteria as well. It has also been shown that some pili, such as type IV pili, have more complex functions which in this case is force driven contraction.
This is commonly found in Escherichia Coli (E.coli) and especially in uropathogenic E.coli (UPEC) where it is present in the urinary tract and kidney. This pilus is encoded by the pap gene cluster. This cluster has both a regulatory and a biosynthesis role for the fimbrial sub units, and other structures associated with the pili. The P pili in UPEC is a typical example of the chaperone/usher pathway. The chaperone protein in UPEC is papD, it transports pili sub units to the assembly platform on the outer membrane. The usher for papD is papC. PapC allows the movement of the pili sub units to the surface of the bacteria so they can be constructed. P pili bind through the papG adhesin to certain glycolipids on the upper urinary tract of the host. Variants of papG recognise a group of related receptors, the differential expression of papG adhesins is the driving force behind the tissue and host binding specificity of