Salmonella enterica causes significant disease in humans and animals. Like many gram-negative pathogens utilizes its flagellar organelles for motility. Flagellar motility is essential for Salmonella virulence and the establishment of biofilms. Assembly of the flagellum requires a specialized secretion apparatus, which is a member of family of secretion systems, termed type III secretion (T3S) systems that are used by plant and animal pathogens to secrete virulence determinants into host cells. The flagellar T3S system exports proteins from the cytoplasm into a central channel of the flagellar structure during the assembly process. Proteins polymerize into place at the tip of the elongating structure. This proposal will support research designed to characterize the flagellar assembly process and determine the mechanisms used by the flagellar T3S system that selects specific substrates and what determines how substrates are ordered for secretion with respect to each other. This proposal specifically addresses the mechanisms of secretion substrate selection, the type III secretion-specificity switch mediated by FliK, the flagellar rod assembly, and the formation of the PL-ring outer membrane pore that couples rod completion to hook growth initiation. In addition, the coupling of flagellar gene expression to the global regulatory pathways at the flagellar master control operon, flhDC, will be analyzed. In addition the mechanisms by which the numerous regulators we recently discovered control flhDC both at the level of operon transcription and post-transcriptional control. Regulators of flagellar gene expression include H- NS, CrsA, PhoPQ, DnaK, cAMP-CAP, LhrA, RtsB, SlyA FimZ, PefI-SrgD, RcsB, OmpR, EcnR, FliT and YdiV. Research will focus on the coupling of flhDC expression with SpiI virulence gene expression through the recently discovered FliZ-HilD-EcnR pathway, and the putative cyclic di-GMP phosphodiesterase protein YdiV.

Public Health Relevance

Salmonella enterica causes significant disease in humans and animals. Like many gram-negative pathogens utilizes its flagellar organelles for motility and pathogenesis. Both motility- and virulence-associated type III secretion systems play important roles in the infection process and their characterization provides numerous potential drug targets for development of therapeutic agents.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Prokaryotic Cell and Molecular Biology Study Section (PCMB)
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Flicker, Paula F
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University of Utah
Schools of Arts and Sciences
Salt Lake City
United States
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Hendrix, Roger W; Ko, Ching-Chung; Jacobs-Sera, Deborah et al. (2015) Genome Sequence of Salmonella Phage χ. Genome Announc 3:
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Singer, Hanna M; Kühne, Caroline; Deditius, Julia A et al. (2014) The Salmonella Spi1 virulence regulatory protein HilD directly activates transcription of the flagellar master operon flhDC. J Bacteriol 196:1448-57
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Guo, Shukui; Alshamy, Israa; Hughes, Kelly T et al. (2014) Analysis of factors that affect FlgM-dependent type III secretion for protein purification with Salmonella enterica serovar Typhimurium. J Bacteriol 196:2333-47
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Chevance, Fabienne F V; Le Guyon, Soazig; Hughes, Kelly T (2014) The effects of codon context on in vivo translation speed. PLoS Genet 10:e1004392
Singer, Hanna M; Erhardt, Marc; Hughes, Kelly T (2014) Comparative analysis of the secretion capability of early and late flagellar type III secretion substrates. Mol Microbiol 93:505-20

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