title: Analysis of a Spontaneous Non-Motile and Avirulent Mutant Shows That FliM Is Required for Full Endoflagella Assembly in Leptospira interrogans.
abstract: Pathogenic Leptospira strains are responsible for leptospirosis, a worldwide emerging zoonotic disease. These spirochetes are unique amongst bacteria because of their corkscrew-like cell morphology and their periplasmic flagella. Motility is reported as an important virulence determinant, probably favoring entry and dissemination of pathogenic Leptospira in the host. However, proteins constituting the periplasmic flagella and their role in cell shape, motility and virulence remain poorly described. In this study, we characterized a spontaneous L. interrogans mutant strain lacking motility, correlated with the loss of the characteristic hook-shaped ends, and virulence in the animal model. Whole genome sequencing allowed the identification of one nucleotide deletion in the fliM gene resulting in a premature stop codon, thereby preventing the production of flagellar motor switch protein FliM. Genetic complementation restored cell morphology, motility and virulence comparable to those of wild type cells. Analyses of purified periplasmic flagella revealed a defect in flagella assembly, resulting in shortened flagella compared to the wild type strain. This also correlated with a lower amount of major filament proteins FlaA and FlaB. Altogether, these findings demonstrate that FliM is required for full and correct assembly of the flagella which is essential for motility and virulence.
authors.affiliation: Institut Pasteur, Unité Biologie des Spirochètes, Paris, France.|Laboratoire Lyon Gerland, Merial, Lyon, France.
authors.forename: Célia
authors.initials: C
authors.lastname: Fontana
authors.affiliation: Institut Pasteur, Unité Biologie des Spirochètes, Paris, France.
authors.forename: Ambroise
authors.initials: A
authors.lastname: Lambert
authors.affiliation: Institut Pasteur, Unité Biologie des Spirochètes, Paris, France.
authors.forename: Nadia
authors.initials: N
authors.lastname: Benaroudj
authors.affiliation: Centre de Recherche Clinique de Saint Vulbas, Merial, Saint Vulbas, France.
authors.forename: David
authors.initials: D
authors.lastname: Gasparini
authors.affiliation: Institut Pasteur, Ultrapole, Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Gorgette
authors.affiliation: Laboratoire Lyon Gerland, Merial, Lyon, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Cachet
authors.affiliation: Laboratoire Lyon Gerland, Merial, Lyon, France.
authors.forename: Natalia
authors.initials: N
authors.lastname: Bomchil
authors.affiliation: Institut Pasteur, Unité Biologie des Spirochètes, Paris, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Picardeau
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D005407:Flagella / Q000502:physiology* / Q000648:ultrastructure; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D007921:Leptospira interrogans / Q000502:physiology* / Q000648:ultrastructure; D009154:Mutation; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C066821:FliM protein, Bacteria