Submitted to: Infection and Immunity
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/2/2006
Publication Date: 6/1/2006
Citation: Ledeboer, N.A., Frye, J.G., Mcclelland, M., Jones, B.D. 2006. Salmonella enterica serovar typhimurium requires the lpf, pef, and tafi fimbriae for biofilm formation on hep-2 tissue culture cells and chicken intestinal epithelium. Infection and Immunity. 74(6):3156-3169. Interpretive Summary: Many bacteria are able to attach to surfaces and grow in a slime like layer called a biofilm. Biofilm formation plays an important role in Salmonella colonization of hosts and persistence within the environment. The mechanisms used by Salmonella to form biofilms are mostly unknown. To determine what genes are involved in biofilm formation, we used DNA microarrays to detect the genes expressed by Salmonella during biofilm formation on human and chicken intestinal cells. We identified five fimbriae gene clusters that were induced during biofilm formation. Fimbriae are hair like appendages that enable bacteria to attach to surfaces and each other. We also found that Salmonella lacking these fimbriae genes were defective in biofilm formation and that these genes were necessary for colonization of chickens. This data is useful for scientists investigating ways to inhibit biofilm formation by Salmonella to prevent infections and persistent contamination of rearing and processing environments.
Technical Abstract: To investigate how biofilm growth affects gene expression in Salmonella, we compared global gene expression during planktonic growth and biofilm growth. Microarray results indicated that the transcription of ~100 genes were significantly altered by growth in a biofilm. These genes encode proteins with a wide range functions include antibiotic resistance, central metabolism, conjugation, intracellular survival, membrane transport, regulation, and fimbrial biosynthesis. Mutations in the bovine colonization factor fimbriae, long polar fimbriae, plasmid encoded fimbriae, thin aggregative fimbriae, and Sth fimbriae were constructed in S. Typhimurium strain BJ2710 and the mutants were found to have various biofilm phenotypes on plastic, HEp-2 cells and chicken intestinal tissue. The pef and csg mutants were defective for biofilm formation on each of the surfaces tested, while the lpf mutant exhibited a complete loss in ability to form biofilm on chicken intestinal tissue but only an intermediate loss of biofilm on tissue culture cells and plastic surfaces. The bcf mutant formed increased biofilm on both HEp-2 cells and chicken intestinal epithelium while the sth mutant had no detectable biofilm defects. In all instances, the mutants could be restored to a wild type phenotype by a plasmid carrying the functional genes. This is the first work to identify the genomic responses of Salmonella to biofilm formation on host cells and highlights the importance of fimbriae in adhering to and adapting to a eukaryotic cell surface. Understanding these interactions is likely to provide new insights for intervention strategies in Salmonella colonization and infection.