Salmonella Pathogenicity Island 4-Mediated Adhesion Is Coregulated with Invasion Genes in Salmonella enterica

• Published in: Infection and Immunity Vol. 75; no. 10; pp. 4697 - 4709
• Main Authors: Gerlach, Roman G, Jäckel, Daniela, Geymeier, Nina, Hensel, Michael
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.10.2007
• Subjects: Adhesins, Bacterial - genetics; Animals; Artificial Gene Fusion; Bacterial Adhesion - genetics; Bacterial Adhesion - physiology; Bacterial Proteins - genetics; Bacterial Proteins - physiology; Bacteriology; Biological and medical sciences; Cell Line; Dogs; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gene Expression Regulation, Bacterial; Genes, Reporter; Genomic Islands - genetics; Luciferases - analysis; Luciferases - genetics; Microbiology; Miscellaneous; Molecular Pathogenesis; Salmonella enterica; Salmonella typhimurium - genetics; Salmonella typhimurium - physiology; Trans-Activators - genetics; Trans-Activators - physiology; Salmonella; Bacteria; Pathogenicity island; Gene; Adhesion; Enterobacteriaceae
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.00228-07

Salmonella pathogenicity island 4 (SPI4) encodes a type I secretion system and the cognate substrate protein, SiiE. We have recently demonstrated that SiiE is a giant nonfimbrial adhesin involved in the adhesion of Salmonella enterica serovar Typhimurium to polarized epithelial cells. We also observed that under in vitro culture conditions, the synthesis and secretion of SiiE coincided with the activation of Salmonella invasion genes. These observations prompted us to investigate the regulation of SPI4 genes in detail. A novel approach for the generation of reporter gene fusions was employed to generate single-copy chromosomal fusions to various genes within SPI4, and the expression of these fusions was investigated. We analyzed the regulation of SPI4 genes and the roles of various regulatory systems for SPI4 expression. Our data show that the expression of SPI4 genes is coregulated with SPI1 invasion genes by the global regulator SirA. Expression of a SPI4 gene was also reduced in the absence of HilA, the central local regulator of SPI1 gene expression. Both SirA and HilA functions were required for the secretion of SiiE and the SPI4-mediated adhesion. Our data demonstrate that SPI4-mediated adhesion, as well as SPI1-mediated invasion, are tightly coregulated by the same regulatory circuits and induced under similar environmental conditions.