title: Sensing wetness: a new role for the bacterial flagellum.
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.
authors.affiliation: Section of Molecular Genetics and Microbiology & Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Wang
authors.forename: Asaka
authors.initials: A
authors.lastname: Suzuki
authors.forename: Susana
authors.initials: S
authors.lastname: Mariconda
authors.forename: Steffen
authors.initials: S
authors.lastname: Porwollik
authors.forename: Rasika M
authors.initials: RM
authors.lastname: Harshey
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D002633:Chemotaxis / Q000235:genetics / Q000502:physiology*; D003470:Culture Media; D005407:Flagella / Q000502:physiology*; D005408:Flagellin / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D044404:Genomic Islands / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D012486:Salmonella typhimurium / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology* / Q000648:ultrastructure; D014774:Virulence / Q000235:genetics; D014867:Water
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D014867:Water; D005408:Flagellin; C071266:FlgM protein, Bacteria