Regulation and binding specificities of novel fimbriae of Salmonella enterica serovar Typhimurium.
Final Report Abstract
Salmonella enterica serotype Typhimurium only expresses type 1-fimbriae under standard laboratory conditions, but after deletion of the respective biosynthesis genes (fimAICDHF) a second structure, termed Pef-fimbriae, is expressed. Here we show that expression of Pef-fimbriae in a fimAICDHF mutant was abrogated when a plasmid expressing the fimA 5’-untranslated region (fimA-UTR) was introduced. The regulation of expression of Pef-fimbriae by the fimA-UTR transcript required the RNA binding protein CsrA, because a csrA mutant was unable to elaborate Pef-fimbriae. Conversely, an increased availability of CsrA in a strain carrying mutations in csrB and csrC, encoding two small non-coding RNAs that bind and sequester CsrA, resulted in enhanced expression of Peffimbriae. Similarly, inactivation of sirA, encoding a positive regulator of csrB and csrC, increased pef-expression. CsrA was shown to bind the fimA-UTR and pefA-UTR transcript in an RNA gel-shift assay. Collectively, these data support the hypothesis that the small RNAs csrB and csrC along with the highly transcribed fimA-mRNA titrate CsrA levels in the cell, thereby preventing binding and stabilization of the pef-transcript by CsrA. This novel post-transcriptional regulatory mechanism ensures hierarchical expression of type 1-fimbriae and Pef-fimbriae in S. Typhimurium.
Publications
- (2011). Intestinal inflammation allows Salmonella to use ethanolamine to compete with the microbiota, Proc. Natl. Acad. Sci. U.S.A. 108: 17480-17485
Thiennmitr P, Winter SE, Winter MG, Xavier MN, Tolstikov V, Huseby DL, Sterzenbach T, Tsolis RM, Roth JR, Bäumler AJ
- (2011). Salmonella Virulence Mechanisms and their Genetic Basis, Salmonella in domestic animals. CAB International
Sterzenbach T, Crawford RW, Winter SE, Bäumler AJ
