title: Viscosity-dependent variations in the cell shape and swimming manner of Leptospira.
abstract: Spirochaetes are spiral or flat-wave-shaped Gram-negative bacteria that have periplasmic flagella between the peptidoglycan layer and outer membrane. Rotation of the periplasmic flagella transforms the cell body shape periodically, allowing the cell to swim in aqueous environments. Because the virulence of motility-deficient mutants of pathogenic species is drastically attenuated, motility is thought to be an essential virulence factor in spirochaetes. However, it remains unknown how motility practically contributes to the infection process. We show here that the cell body configuration and motility of the zoonotic spirochaete Leptospira changes depending on the viscosity of the medium. Leptospira swim and reverse the swimming direction by transforming the cell body. Motility analysis showed that the frequency of cell shape transformation was increased by increasing the viscosity of the medium. The increased cell body transformation induced highly frequent reversal of the swimming direction. A simple kinetic model based on the experimental results shows that the viscosity-induced increase in reversal limits cell migration, resulting in the accumulation of cells in high-viscosity regions. This behaviour could facilitate the colonization of the spirochaete on host tissues covered with mucosa.
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
authors.forename: Kyosuke
authors.initials: K
authors.lastname: Takabe
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Tahara
authors.affiliation: Present address: Department of Microbiology and Hygiene, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.|Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
authors.forename: Md Shafiqul
authors.initials: MS
authors.lastname: Islam
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
authors.forename: Samia
authors.initials: S
authors.lastname: Affroze
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
authors.forename: Seishi
authors.initials: S
authors.lastname: Kudo
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Nakamura
mesh_terms: D005407:Flagella; D007919:Leptospira / Q000166:cytology / Q000472:pathogenicity / Q000502:physiology; D009092:Mucous Membrane / Q000382:microbiology / Q000502:physiology*; D037521:Virulence Factors / Q000502:physiology; D014783:Viscosity
chemical_list: D037521:Virulence Factors