Magnetotactic navigation in complex environments

• Applicant: Professor Dr. Stefan Klumpp
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Biophysics ; Microbial Ecology and Applied Microbiology
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446142122

• Final Report Year: 2025

Final Report Abstract

Magnetotactic bacteria align naturally in magnetic fields and use magnetic directionality to find their preferred habitat. They provide a model system to study magnetic steering as a mechanism for the remote control of microswimmers. A challenge for magnetic navigation is the presence of obstacles as magnetic directionality results in straight paths, while avoiding obstacles requires deviations from the straight path. Such conditions are typical for magnetotactic bacteria which often live in sediment (mud). Here we used microfluidics and active particle simulations to study their swimming through near-realistic obstacle arrays produced as mimics of sand samples. We observed optimal flow of bacteria at magnetic field near the geomagnetic field strength and characterized the competition between overall directionality and local trapping in ‘corners’ of the obstacles. Optimality under physiological conditions suggests that the magnetic moment off the bacteria is adapted to the conditions in their habitat. In addition, we discovered that in the magnetotactic strain SS-5, the swimming speed is increased in the presence of a magnetic field. We exclude that this is an apparent effect due to straighter trajectories, and thus propose that this strain can actually sense the magnetic field beyond passive alignment. Finally, we developed Bayesian methods for the analysis of trajectories of individual bacteria, based on either time discretization or on Brownian bridges. These were used to study the collisions with obstacles and to provide an underpinning for the phenomenological description of alignment with obstacle surfaces by a wall torque.

Publications

• Clinical Translation of Inorganic Nanoparticles and Engineered Living Materials for Cancer Therapy. ChemPlusChem, 89(10).
  Gandarias, Lucía & Faivre, Damien
  
• Colloquium : Magnetotactic bacteria: From flagellar motor to collective effects. Reviews of Modern Physics, 96(2).
  Marmol, M.; Gachon, E. & Faivre, D.
  
• Escape problem of magnetotactic bacteria - physiological magnetic field strength help magnetotactic bacteria navigate in simulated sediments.
  Codutti, Agnese , Charsooghi, Mohammad A , Marx, Konrad , Cerdá-Doñate, Elisa , Munoz, Omar , Zaslansky, Paul , Telezki, Vitali , Robinson, Tom , Faivre, Damien & Klumpp, Stefan
  
• Bayesian inference of wall torques for active Brownian particles. Europhysics Letters, 149(5), 57001.
  Lambert, S.; Duchêne, M. & Klumpp, S.
  
• Inference of wall torques from active particle simulations. GRO.data, V1
  S. Lambert, M. Duchene & S. Klumpp
  
• Patterns of active dipolar particles in external magnetic fields. Physical Review E, 112(6).
  Telezki, Vitali & Klumpp, Stefan
  
• Physiological magnetic field strengths help magnetotactic bacteria navigate in simulated sediments. eLife, 13.
  Codutti, Agnese; Charsooghi, Mohammad A.; Marx, Konrad; Cerdá-Doñate, Elisa; Muñoz, Omar; Zaslansky, Paul; Telezki, Vitali; Robinson, Tom; Faivre, Damien & Klumpp, Stefan