Fimbriae are important virulence factors for Salmonella pathogenesis. They mediate adhesion to host cells (including plants), food, stainless steel and much more. The fimbrial systems are organised in gene clusters of four to fifteen genes that code for structural, assembly and regulatory proteins. There are three kinds of fimbriae depending on their mode of assembly. The chaperone/usher (CU) fimbriae use a dedicated chaperone and usher protein to coordinate the subunit biogenesis on the cell surface. The curli fimbriae are assembled by nucleation/precipitation pathway. The type IV fimbria assembly requires a transmembrane apparatus and ATP to energise the reaction. Several fimbriae are conserved among Salmonella serovars, while some are present in a limited set or only specific serovars. Expression and regulation of fimbrial genes are not well understood, and most Salmonella fimbriae are poorly expressed during in vitro culture, which further complicates research concerning their regulation and role during infection. However, Salmonella fim gene cluster, coding for type-1 fimbriae, was widely studied and presents its own set of regulators. Investigating fimbrial distribution, expression and regulation will further elucidate their roles in bacterial pathogenesis and host specificity. Furthermore, fimbriae are important for developing efficient diagnostic tests and antimicrobial strategies against Salmonella.
Part of the book: Current Topics in Salmonella and Salmonellosis