Fluidic bacterial diodes rectify magnetotactic cell motility in porous environments

Area of Science:

• Microbiology
• Biophysics
• Fluid Dynamics

Background:

• Directed motility allows microbes to navigate environments for resources.
• Motility competes with fluid flow in porous habitats, impacting biofilms and disease.
• Microscopic understanding of microswimmer transport in pores is lacking.

Purpose of the Study:

• To investigate the transport regimes of microswimmers in constricted pores under directed motility.
• To develop a model predicting microswimmer behavior in pore flows.

Main Methods:

• Microfluidic experiments with individual magnetotactic bacteria.
• Development of a comprehensive Langevin model.

Main Results:

• Identified three distinct transport regimes: swimming upstream, pore trapping, and downstream advection.
• Observed diode-like transport behavior, accurately predicted by the Langevin model.
• Demonstrated that disorder in higher-dimension geometries extends the trapping regime.

Conclusions:

• Microswimmer transport in pores exhibits diode-like characteristics.
• The findings have implications for microbial survival in sediments and potential biotechnological applications.
• The study provides a microscopic understanding of microswimmer transport in complex flow environments.