Observing grazing behavior transitions in Cafeteria roenbergensis with video-rate two-photon microscopy

Area of Science:

• Microbiology
• Aquatic Ecology
• Microbial Ecology

Background:

• Heterotrophic nanoflagellates (HNFs) are crucial for aquatic microbial community structure and nutrient cycling.
• Direct observation of HNF grazing on bacteria is challenging due to rapid movement and transient interactions.

Purpose of the Study:

• To develop and apply a novel microscopy technique for real-time, high-resolution imaging of microbial predator-prey interactions.
• To investigate the dynamics of grazing in the HNF *Cafeteria roenbergensis*.

Main Methods:

• Utilized video-rate two-photon fluorescence microscopy for real-time imaging.
• Observed interactions between fluorescently stained bacteria and autofluorescent HNFs.
• Quantitatively analyzed grazing sequences (contact, capture, ingestion, digestion) at single-cell resolution.

Main Results:

• Captured the complete grazing sequence in real-time, revealing phase-specific durations and saturation kinetics.
• Documented a previously unobserved transition in grazing dynamics related to flagellate feeding states (starved vs. fed).
• Demonstrated the technique's ability to track motile microorganisms effectively.

Conclusions:

• Video-rate two-photon microscopy is a powerful tool for studying rapid in situ microbial interactions.
• The findings provide new insights into the feeding behavior and dynamics of HNFs.
• This technique has broad applicability for diverse microbe-microbe systems and studying feeding/communication processes.