Flow loading induces oscillatory trajectories in a bloodstream parasite

Area of Science:

• Microbiology and Parasitology
• Fluid Dynamics
• Biophysics

Background:

• Understanding microswimmer dynamics in fluid flow is essential for fields ranging from environmental science to medicine.
• The African trypanosome, a unicellular parasite, serves as a model organism to study complex biological motility.
• Microbial pathogenesis often involves navigating and interacting within host fluid environments.

Purpose of the Study:

• To investigate the swimming dynamics of isolated African trypanosomes in bounded flow.
• To determine the influence of flow velocity and cell orientation on trypanosome trajectories.
• To elucidate the role of self-propulsion in microswimmer behavior under flow conditions.

Main Methods:

• Utilized a microfluidics platform to subject African trypanosomes to controlled flow.
• Observed and analyzed cell trajectories using microscopy and motion tracking.
• Compared the behavior of motile trypanosomes with immotile controls.

Main Results:

• African trypanosomes exhibited oscillatory paths, well-described by sine waves, in response to flow.
• Trajectory frequency and amplitude were dependent on flow velocity and initial cell orientation.
• Self-propulsion was critical for trypanosome movement, maintaining directed motion against flow up to 40 times their swimming speed.

Conclusions:

• Microswimmer self-propulsion plays a vital role in navigating complex fluid environments, even at high flow rates.
• The observed oscillatory dynamics provide insights into general microswimmer transport mechanisms.
• Findings may have implications for understanding microbial pathogenesis and parasite transport within hosts.