Protist-facilitated particle transport using emulated soil micromodels

Area of Science:

• Environmental microbiology
• Soil science
• Pore-scale transport phenomena

Background:

• Subsurface microbial processes are crucial for ecosystem function.
• Understanding particle transport at the pore scale is key to predicting subsurface behavior.
• Micromodels offer a direct visualization method for pore-scale phenomena.

Purpose of the Study:

• To quantify the effect of the soil ciliate Colpoda sp. on particle transport in emulated soil micromodels.
• To elucidate the mechanisms driving protist-facilitated transport.
• To explore potential applications of this transport mechanism.

Main Methods:

• Utilized emulated soil micromodels with defined pore geometries.
• Introduced fluorescent beads with and without Colpoda sp. into the micromodels.
• Quantified bead abundance over time using confocal microscopy and direct cell counts.

Main Results:

• Protist presence dramatically increased bead abundance in micromodel channels compared to controls.
• Bead accumulation was significantly higher with protists (e.g., 790 mm(-2) at 10 days) versus without (45 mm(-2) at 10 days).
• Transport patterns indicated complex protist behaviors, not simple diffusion.

Conclusions:

• Colpoda sp. actively facilitates particle transport in porous media.
• Protist-facilitated transport involves particle uptake, egestion, and motility within microhabitats.
• This mechanism holds potential for enhancing soil mixing and targeted delivery in agriculture and remediation.