Microbial competition reduces metabolic interaction distances to the low µm-range

Area of Science:

• Microbial Ecology
• Systems Biology
• Biophysics

Background:

• Metabolic interactions shape microbial communities and ecosystem functions.
• Concentration gradients of exchanged metabolites limit interaction distances, especially under competition.
• Previous studies often used 2D systems or ignored competition, not reflecting natural conditions.

Purpose of the Study:

• To analyze how cell-to-cell distance impacts unidirectional cross-feeding in a 3D aqueous system with competition.
• To quantify effective interaction distances considering competition and metabolite removal.
• To investigate the role of spatial structures and cell properties on metabolic interactions.

Main Methods:

• Utilized a reaction-diffusion model to compute effective interaction distances.
• Experimentally verified findings using a synthetic consortium of producer, receiver, and competitor cells (1 µm size).
• Employed an aggregation protocol and varied receiver cell product affinity.

Main Results:

• Metabolic interaction distances were reduced to the low micrometer range in 3D systems with competition.
• Receivers could not interact with producers 15 µm away due to flattened product concentration gradients.
• Within producer-receiver aggregates, even low-affinity receivers could interact with producers.

Conclusions:

• Competition and metabolite removal in 3D systems significantly constrain metabolic interaction distances.
• Concentration gradients act as a crucial physical constraint on cellular interactions in microbial communities.
• Spatial organization, like aggregation, can overcome limitations imposed by diffusion and competition.