title: FlgM is secreted by the flagellar export apparatus in Bacillus subtilis.
abstract: The bacterial flagellum is assembled from over 20 structural components, and flagellar gene regulation is morphogenetically coupled to the assembly state by control of the anti-sigma factor FlgM. In the Gram-negative bacterium Salmonella enterica, FlgM inhibits late-class flagellar gene expression until the hook-basal body structural intermediate is completed and FlgM is inhibited by secretion from the cytoplasm. Here we demonstrate that FlgM is also secreted in the Gram-positive bacterium Bacillus subtilis and is degraded extracellularly by the proteases Epr and WprA. We further demonstrate that, like in S. enterica, the structural genes required for the flagellar hook-basal body are required for robust activation of σ(D)-dependent gene expression and efficient secretion of FlgM. Finally, we determine that FlgM secretion is strongly enhanced by, but does not strictly require, hook-basal body completion and instead demands a minimal subset of flagellar proteins that includes the FliF/FliG basal body proteins, the flagellar type III export apparatus components FliO, FliP, FliQ, FliR, FlhA, and FlhB, and the substrate specificity switch regulator FliK.
authors.affiliation: Indiana University, Department of Biology, Bloomington, Indiana, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Calvo
authors.affiliation: Indiana University, Department of Biology, Bloomington, Indiana, USA dbkearns@indiana.edu.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Kearns
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D005407:Flagella / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; C071266:FlgM protein, Bacteria