FlgN is required for flagellum-based motility by Bacillus subtilis.
The assembly of the bacterial flagellum is exquisitely controlled. Flagellar biosynthesis is underpinned by a specialized type III secretion system that allows export of proteins from the cytoplasm to the nascent structure. Bacillus subtilis regulates flagellar assembly using both conserved and species-specific mechanisms. Here, we show that YvyG is essential for flagellar filament assembly. We define YvyG as an orthologue of the Salmonella enterica serovar Typhimurium type III secretion system chaperone, FlgN, which is required for the export of the hook-filament junction proteins, FlgK and FlgL. Deletion of flgN (yvyG) results in a nonmotile phenotype that is attributable to a decrease in hag translation and a complete lack of filament polymerization. Analyses indicate that a flgK-flgL double mutant strain phenocopies deletion of flgN and that overexpression of flgK-flgL cannot complement the motility defect of a ΔflgN strain. Furthermore, in contrast to previous work suggesting that phosphorylation of FlgN alters its subcellular localization, we show that mutation of the identified tyrosine and arginine FlgN phosphorylation sites has no effect on motility. These data emphasize that flagellar biosynthesis is differentially regulated in B. subtilis from classically studied Gram-negative flagellar systems and questions the biological relevance of some posttranslational modifications identified by global proteomic approaches.
Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
Lynne S
LS
Cairns
Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
Victoria L
VL
Marlow
Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
Taryn B
TB
Kiley
Centre for Bacterial Cell Biology, Newcastle University, Newcastle upon Tyne, United Kingdom.
Christopher
C
Birchall
Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, United Kingdom.
Adam
A
Ostrowski
Centre for Bacterial Cell Biology, Newcastle University, Newcastle upon Tyne, United Kingdom.
Phillip D
PD
Aldridge
Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, United Kingdom n.r.stanleywall@dundee.ac.uk.
Nicola R
http://orcid.org/0000-0002-5936-9721
NR
Stanley-Wall
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005407:Flagella / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D008969:Molecular Sequence Data; D009068:Movement; D009154:Mutation
D001426:Bacterial Proteins; C087498:FlgN protein, Bacteria