Mutualistic cross-feeding in microbial systems generates bistability via an Allee effect

Area of Science:

• Microbial Ecology
• Theoretical Biology
• Mathematical Modeling

Background:

• Mutualistic interactions, like metabolic cross-feeding, are common in microbial ecosystems.
• These interactions can lead to bistability, a state where outcomes depend on initial conditions.
• Existing models often lack nutrient explicit details or intuitive explanations for bistability.

Purpose of the Study:

• To reduce a nutrient-explicit model of mutualistic cross-feeders.
• To establish an explicit link between nutrient dynamics and population growth models.
• To understand how chemostat parameters influence bistability in microbial mutualisms.

Main Methods:

• Theoretical reduction of a nutrient-explicit model for two mutualistic cross-feeders.
• Analysis of a chemostat system with varying dilution rates.
• Relating the reduced model to a growth model incorporating an Allee effect.

Main Results:

• Bistability in microbial mutualism is driven by the dilution rate in a chemostat.
• The dilution rate transforms a weak Allee effect into a strong one.
• Sufficient production of cross-fed nutrients over consumption is key for this effect.

Conclusions:

• The study provides a clear link between experimental parameters and bistability.
• Predicts conditions under which mutualistic microbial species can survive or go extinct.
• Offers insights into managing microbial ecosystems through nutrient and dilution rate control.