title: Periplasmic flagellar export apparatus protein, FliH, is involved in post-transcriptional regulation of FlaB, motility and virulence of the relapsing fever spirochete Borrelia hermsii.
abstract: Spirochetes are bacteria characterized in part by rotating periplasmic flagella that impart their helical or flat-wave morphology and motility. While most other bacteria rely on a transcriptional cascade to regulate the expression of motility genes, spirochetes employ post-transcriptional mechanism(s) that are only partially known. In the present study, we characterize a spontaneous non-motile mutant of the relapsing fever spirochete Borrelia hermsii that was straight, non-motile and deficient in periplasmic flagella. We used next generation DNA sequencing of the mutant's genome, which when compared to the wild-type genome identified a 142 bp deletion in the chromosomal gene encoding the flagellar export apparatus protein FliH. Immunoblot and transcription analyses showed that the mutant phenotype was linked to the posttranscriptional deficiency in the synthesis of the major periplasmic flagellar filament core protein FlaB. Despite the lack of FlaB, the amount of FlaA produced by the fliH mutant was similar to the wild-type level. The turnover of the residual pool of FlaB produced by the fliH mutant was comparable to the wild-type spirochete. The non-motile mutant was not infectious in mice and its inoculation did not induce an antibody response. Trans-complementation of the mutant with an intact fliH gene restored the synthesis of FlaB, a normal morphology, motility and infectivity in mice. Therefore, we propose that the flagellar export apparatus protein regulates motility of B. hermsii at the post-transcriptional level by influencing the synthesis of FlaB.
authors.affiliation: Public Health Ontario, Toronto, Ontario, Canada ; University of Toronto, Toronto, Ontario, Canada. cyril.guyard@gmail.com
authors.forename: Cyril
authors.initials: C
authors.lastname: Guyard
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Raffel
authors.forename: Merry E
authors.initials: ME
authors.lastname: Schrumpf
authors.forename: Eric
authors.initials: E
authors.lastname: Dahlstrom
authors.forename: Daniel
authors.initials: D
authors.lastname: Sturdevant
authors.forename: Stacy M
authors.initials: SM
authors.lastname: Ricklefs
authors.forename: Craig
authors.initials: C
authors.lastname: Martens
authors.forename: Stanley F
authors.initials: SF
authors.lastname: Hayes
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Fischer
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Hansen
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Porcella
authors.forename: Tom G
authors.initials: TG
authors.lastname: Schwan
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D001898:Borrelia / Q000472:pathogenicity* / Q000502:physiology* / Q000648:ultrastructure; D004195:Disease Models, Animal; D005407:Flagella / Q000378:metabolism / Q000648:ultrastructure; D005408:Flagellin / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D005816:Genetic Complementation Test; D016680:Genome, Bacterial; D006801:Humans; D051379:Mice; D009154:Mutation; D016366:Open Reading Frames; D055550:Protein Stability; D012323:RNA Processing, Post-Transcriptional; D012061:Relapsing Fever / Q000382:microbiology*; D014158:Transcription, Genetic; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D005408:Flagellin; C069250:fliH protein, Bacteria; C416532:flaB flagellin