The dialogue between protozoa and bacteria in a microfluidic device.

Area of Science:

• Microbiology
• Protozoology
• Bioengineering

Background:

• Protozoa are crucial in regulating bacterial populations in natural ecosystems.
• Understanding protozoan behavior, particularly chemotaxis, is key to microbial ecology.
• Chemotaxis, the directed movement in response to chemical stimuli, influences predator-prey dynamics.

Purpose of the Study:

• To investigate the chemotactic response of Euglena to Listeria bacterial cells using a novel microfluidic device.
• To identify the chemical cues and volatile organic compounds (VOCs) responsible for Euglena's attraction to Listeria.

Main Methods:

• A three-channel microfluidic device with a nitrocellulose membrane was fabricated.
• Euglena suspension was placed in the central channel, while Listeria suspension or controls were in side channels.
• Filtrates and headspace volatile organic compounds (VOCs) from Listeria were tested for their chemotactic effects on Euglena.

Main Results:

• Euglena cells showed significant migration towards Listeria, indicating a positive chemotactic response.
• Euglena were attracted to Listeria filtrates across various molecular weight cutoffs, suggesting small molecule attractants.
• Euglena responded rapidly to specific Listeria VOCs, including decanal, 3,5-dimethylbenzaldehyde, and ethyl acetate.

Conclusions:

• This study demonstrates the utility of microfluidic devices for studying protozoa-bacteria interactions.
• Small molecules and volatile organic compounds released by Listeria act as chemical cues for Euglena chemotaxis.
• Bacterial VOCs play a significant role in enabling protozoa to locate bacterial populations.