Abstract
We have uncovered a new role for the bacterial flagellum in sensing external wetness. An investigation into why mutants in the chemotaxis signaling pathway of Salmonella typhimurium exhibit fewer and shorter flagella than wild-type when propagated on a surface, first showed that the mutants downregulate only a small set of genes on swarm media--class 3 or 'late' motility genes, and genes associated with the pathogenicity island SPI-1 TTSS (type three secretion system). Based on observations that swarm colonies of the mutants appear less hydrated, we tested a model in which the flagellum itself is a sensor: suboptimal external hydration interferes with secretion of flagellin subunits, inhibiting filament growth and blocking normal export of the class 3 transcription inhibitor FlgM. We provide strong experimental support for the model. In addition, the data show that the flagellar and SPI-1 TTSS are coupled via regulatory proteins. These studies implicate the flagellum, a bacterial organ for motility, in sensing the external environment to modulate not only its own biogenesis but other physiological functions as well.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Bacterial Proteins / genetics
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Bacterial Proteins / physiology
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Chemotaxis / genetics
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Chemotaxis / physiology*
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Culture Media
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Flagella / physiology*
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Flagellin / genetics
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Flagellin / metabolism
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Gene Expression Profiling
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Gene Expression Regulation, Bacterial
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Genomic Islands / genetics
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Genomic Islands / physiology
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Models, Biological
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Molecular Sequence Data
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Oligonucleotide Array Sequence Analysis
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Salmonella typhimurium / genetics
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Salmonella typhimurium / pathogenicity
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Salmonella typhimurium / physiology*
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Salmonella typhimurium / ultrastructure
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Virulence / genetics
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Water
Substances
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Bacterial Proteins
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Culture Media
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Water
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Flagellin
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FlgM protein, Bacteria
Associated data
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GENBANK/GSM23126
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GENBANK/GSM23127
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GENBANK/GSM23128
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GENBANK/GSM23150
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GENBANK/GSM23151
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GENBANK/GSM23152
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GENBANK/GSM23876
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GENBANK/GSM23877
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GENBANK/GSM23878
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GENBANK/GSM23896
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