New insights into shear-sensitivity in dinoflagellate microalgae

Area of Science:

• Biophysics
• Cell Biology
• Marine Biology

Background:

• Shear-sensitive microalgae often exhibit growth inhibition under turbulence.
• Cell fragility and breakage are hypothesized causes for this phenomenon.
• Understanding microalgal responses to hydrodynamic forces is crucial for cultivation and ecological studies.

Purpose of the Study:

• To investigate if microalgal growth inhibition is caused by cell breakage due to shear stress.
• To quantify the energy dissipation rates (EDR) at which microalgae and animal cells experience damage.
• To explore potential mechanosensory responses in microalgae exposed to hydrodynamic forces.

Main Methods:

• A modified flow contraction device was employed to apply controlled hydrodynamic forces.
• Shear-sensitive microalgae and animal cells were subjected to varying energy dissipation rates (EDR).
• Cell breakage and membrane fluidity were assessed as indicators of physical damage and cellular response.

Main Results:

• Microalgae exhibited no cell breakage even at extremely high EDR (around 10^12 Wm^-3).
• Animal cells, in contrast, showed significant damage at much lower EDR (10^7 Wm^-3).
• Low EDR (approx. 4x10^5 Wm^-3) increased microalgal membrane fluidity, suggesting mechanosensory activation, while animal cells showed no such change.

Conclusions:

• Microalgal growth inhibition is unlikely due to shear-induced cell fragility.
• Microalgae possess remarkable resilience to hydrodynamic forces compared to animal cells.
• Hydrodynamic forces may trigger mechanosensory pathways in microalgae, influencing cellular behavior and membrane properties.