Physiological magnetic field strengths help magnetotactic bacteria navigate in simulated sediments

Area of Science:

• Microbiology
• Biophysics
• Environmental Science

Background:

• Bacterial motility research traditionally uses bulk solutions, not complex natural habitats.
• Magnetotactic bacteria possess internal nanomagnets and respond to Earth's magnetic field.
• Understanding bacterial navigation in confined spaces is crucial for ecological roles.

Purpose of the Study:

• To investigate magnetotactic bacterial swimming in a near-realistic, sediment-mimicking microfluidic environment.
• To determine the effect of varying magnetic field strengths on bacterial motility and throughput.
• To elucidate the mechanisms of bacterial navigation and potential evolutionary adaptations in complex settings.

Main Methods:

• Microfluidic channels were engineered with obstacles based on micro-computer tomography of sediment samples.
• Swimming behavior of magnetotactic bacteria was characterized within these channels under controlled magnetic fields.
• Computer simulations using an active Brownian particle model were employed to validate experimental findings.

Main Results:

• Swimming throughput was maximal at physiological magnetic field strengths.
• Computer simulations confirmed that strong magnetic fields impede bacterial movement due to trapping in confined spaces.
• Weak magnetic fields resulted in inefficient, near-random swimming directions, while reduced field strength facilitated bacterial escape.

Conclusions:

• Magnetotactic bacteria exhibit optimal motility in complex environments at physiological magnetic field strengths.
• Evolutionary adaptations in magnetotactic bacteria likely balance magnetic properties for efficient navigation and orientation.
• The study provides insights into microbial strategies for movement in challenging, heterogeneous habitats.