title: Vancomycin Reduces Cell Wall Stiffness and Slows Swim Speed of the Lyme Disease Bacterium.
abstract: Borrelia burgdorferi, the spirochete that causes Lyme disease, is a tick-transmitted pathogen that requires motility to invade and colonize mammalian and tick hosts. These bacteria use a unique undulating flat-wave shape to penetrate and propel themselves through host tissues. Previous mathematical modeling has suggested that the morphology and motility of these spirochetes depends crucially on the flagellar/cell wall stiffness ratio. Here, we test this prediction using the antibiotic vancomycin to weaken the cell wall. We found that low to moderate doses of vancomycin (≤2.0 μg/mL for 24 h) produced small alterations in cell shape and that as the dose was increased, cell speed decreased. Vancomycin concentrations >1.0 μg/mL also inhibited cell growth and led to bleb formation on a fraction of the cells. To quantitatively assess how vancomycin affects cell stiffness, we used optical traps to bend unflagellated mutants of B. burgdorferi. We found that in the presence of vancomycin, cell wall stiffness gradually decreased over time, with a 40% reduction in the bending stiffness after 36 h. Under the same conditions, the swimming speed of wild-type B. burgdorferi slowed by ∼15%, with only marginal changes to cell morphology. Interestingly, our biophysical model for the swimming dynamics of B. burgdorferi suggested that cell speed should increase with decreasing cell stiffness. We show that this discrepancy can be resolved if the periplasmic volume decreases as the cell wall becomes softer. These results provide a testable hypothesis for how alterations of cell wall stiffness affect periplasmic volume regulation. Furthermore, since motility is crucial to the virulence of B. burgdorferi, the results suggest that sublethal doses of antibiotics could negatively impact spirochete survival by impeding their swim speed, thereby enabling their capture and elimination by phagocytes.
authors.affiliation: Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Harman
authors.affiliation: Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona.
authors.forename: Alex E
authors.initials: AE
authors.lastname: Hamby
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut.
authors.forename: Ross
authors.initials: R
authors.lastname: Boltyanskiy
authors.affiliation: Department of Internal Medicine, Yale University, New Haven, Connecticut.
authors.forename: Alexia A
authors.initials: AA
authors.lastname: Belperron
authors.affiliation: Department of Internal Medicine, Yale University, New Haven, Connecticut.
authors.forename: Linda K
authors.initials: LK
authors.lastname: Bockenstedt
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut; Department of Physics, University of Bayreuth, Bayreuth, Bavaria, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Kress
authors.affiliation: Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Dufresne
authors.affiliation: Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona; Department of Physics, University of Arizona, Tucson, Arizona. Electronic address: wolg@email.arizona.edu.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Wolgemuth
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001696:Biomechanical Phenomena / Q000187:drug effects; D025065:Borrelia burgdorferi / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D002473:Cell Wall / Q000187:drug effects*; D008193:Lyme Disease / Q000382:microbiology*; D055595:Mechanical Phenomena / Q000187:drug effects*; D009068:Movement / Q000187:drug effects*; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin