FimY of Salmonella enterica serovar Typhimurium functions as a DNA-binding protein and binds the fimZ promoter

Type 1 fimbria and P pili: regulatory mechanisms of the prototypical members of the chaperone-usher fimbrial family

Adherence to both cellular and abiotic surfaces is a crucial step in the interaction of bacterial pathogens and commensals with their hosts. Bacterial surface structures known as fimbriae or pili play a fundamental role in the early colonization stages by providing specificity or tropism. Among the various fimbrial families, the chaperone-usher family has been extensively studied due to its ubiquity, diversity, and abundance. This family is named after the components that facilitate their biogenesis. Type 1 fimbria and P pilus, two chaperone-usher fimbriae associated with urinary tract infections, have been thoroughly investigated and serve as prototypes that have laid the foundations for understanding the biogenesis of this fimbrial family. Additionally, the study of the mechanisms regulating their expression has also been a subject of great interest, revealing that the regulation of the expression of the genes encoding these structures is a complex and diverse process, involving both common global regulators and those specific to each operon.

Zingerone inhibits biofilm formation and enhances antibiotic efficacy against Salmonella biofilm

Salmonella enterica serovar Typhi is a significant cause of typhoid fever and a major public health problem. The ability of S. Typhi to form biofilms on living and non-living surfaces results in antibiotic resistance and poses a major challenge in health care. In this study, we assessed the ability of zingerone alone and in combination with antibiotics against the motility phenotypes and biofilm-forming ability of S. Typhi. Results showed that zingerone effectively reduced the swimming, swarming, and twitching phenotypes and exhibited biofilm inhibition potential. Moreover, zingerone enhanced the antibiofilm activity of ciprofloxacin and kanamycin. Microscopic analysis revealed a thinner biofilm in the presence of zingerone, which may have enhanced the antibiofilm efficacy of the antibiotics. The microscopic analysis showed that the presence of zingerone resulted in a reduction in the thickness of the biofilm, potentially increasing the antibiofilm efficacy of the antibiotics. In silico molecular docking and simulation studies further indicated that zingerone may bind to the fimbriae subunits (FimA, FimC, FimH, and FimY) of S. Typhi and form stable interactions. These findings provide important insights into the potential of zingerone to target biofilm-associated Salmonella infections. Further research is considered a promising option for designing innovative approaches to prevent infections associated with biofilms. Schematic representation of the role of zingerone in biofilm, motility inhibition and molecular interactions with biofilm associated proteins.

Arginine within a specific motif near the N-terminal of FimY is critical for the maximal production of type 1 fimbriae in Salmonella enterica serovar Typhimurium

An important Salmonella serovar for both human and animals Salmonella Typhimurium possesses 13 gene clusters that have the potential to produce fimbrial structure, among which the type 1 fimbriae with the binding specificity to mannose residue is the most commonly found type. Six structural genes and five regulatory genes comprise the fim gene cluster that is responsible for the production of type 1 fimbriae in S. Typhimurium. The fimY gene encodes a positive regulator for type 1 fimbrial expression since a deletion in fimY abolished the production of fimbriae. The N-terminal portion of FimY contains amino acid residues that exhibit some similarity as those found in the proteins possessing the PilZ domain, which is engaged in cyclic di-GMP binding. A fimY allele that had a change from arginine to alanine at position 7 (R7A) or 7 and 11 (R7/11A) generated by site-directed mutagenesis in a 6 RRERH11 R motif near N-terminal, when cloned in pACYC184 and transformed into a fimY-deleted strain, decreased the expression of fimA and fimZ. The number of type 1 fimbriae in these two transformants was also less than those of the other transformants that contained different fimY alleles in pACYC184 when observed in electron microscopy. However, changing from arginine to alanine at position 11 (R11A) remained the same as the wild-type fimY allele. It is likely that the arginine at the 7th position of FimY is critical for its maximal activating activity upon fimZ. Another motif 83 DI85 SLWIEK91 G motif did not affect the function of FimY. Although FimY has the two aforementioned motifs, which contain some amino acids that are present within those of the PilZ domain proteins, secondary structure prediction analysis did not reveal that FimY has a conformation commonly observed in PilZ-like proteins. Therefore, FimY and PilZ domain proteins are not homologs. Further investigation for a detailed analysis of FimY is thus warranted.

Everything You Always Wanted to Know About Salmonella Type 1 Fimbriae, but Were Afraid to Ask

Initial attachment to host intestinal mucosa after oral infection is one of the most important stages during bacterial pathogenesis. Adhesive structures, widely present on the bacterial surface, are mainly responsible for the first contact with host cells and of host-pathogen interactions. Among dozens of different bacterial adhesins, type 1 fimbriae (T1F) are one of the most common adhesive organelles in the members of the Enterobacteriaceae family, including Salmonella spp., and are important virulence factors. Those long, thin structures, composed mainly of FimA proteins, are responsible for recognizing and binding high-mannose oligosaccharides, which are carried by various glycoproteins and expressed at the host cell surface, via FimH adhesin, which is presented at the top of T1F. In this review, we discuss investigations into the functions of T1F, from the earliest work published in 1958 to operon organization, organelle structure, T1F biogenesis, and the various functions of T1F in Salmonella-host interactions. We give special attention to regulation of T1F expression and their role in binding of Salmonella to cells, cell lines, organ explants, and other surfaces with emphasis on biofilm formation and discuss T1F role as virulence factors based on work using animal models. We also discuss the importance of allelic variation in fimH to Salmonella pathogenesis, as well as role of FimH in Salmonella host specificity.