FimA, FimF, and FimH Are Necessary for Assembly of Type 1 Fimbriae on Salmonella enterica Serovar Typhimurium

Abstract

ABSTRACTSalmonella entericaserovar Typhimurium is a Gram-negative member of the familyEnterobacteriaceaeand is a common cause of bacterial food poisoning in humans. The fimbrial appendages are found on the surface of many enteric bacteria and enable the bacteria to bind to eukaryotic cells.S. Typhimurium type 1 fimbriae are characterized by mannose-sensitive hemagglutination and are assembled via the chaperone/usher pathway.S. Typhimurium type 1 fimbrial proteins are encoded by thefimgene cluster (fimAICDHFZYW), withfimAICDHFexpressed as a single transcriptional unit. The structural components of the fimbriae are FimA (major subunit), FimI, FimH (adhesin), and FimF (adaptor). In order to determine which components are required for fimbrial formation inS. Typhimurium, mutations infimA,fimI,fimH, andfimFwere constructed and examined for their ability to produce surface-assembled fimbriae.S. Typhimurium SL1344ΔfimA, -ΔfimH, and -ΔfimFmutants were unable to assemble fimbriae, indicating that these genes are necessary for fimbrial production inS. Typhimurium. However, SL1344ΔfimIwas able to assemble fimbriae. InEscherichia colitype 1 and Pap fimbriae, at least two adaptors are expressed in addition to the adhesins. However,E. colitype 1 and Pap fimbriae have been reported to be able to assemble fimbriae in the absence of these proteins. These results suggest differences between theS. Typhimurium type 1 fimbrial system and theE. colitype 1 and Pap fimbrial systems.