Microbial material cycling, energetic constraints and ecosystem expansion in subsurface ecosystems

Area of Science:

• Environmental Microbiology
• Biogeochemical Cycles
• Mathematical Modeling

Background:

• Microbes harvest energy from chemical reactions, driving environmental material cycles through catabolic interactions.
• These interactions involve microbes utilizing by-products from other microbes as resources, forming complex ecological networks.

Purpose of the Study:

• To investigate a mathematical model of mutualistic catabolic interactions between two microbe types cycling an element.
• To understand how these interactions affect microbial abundance, material flux, and niche expansion, particularly under energetic limitations.

Main Methods:

• Development and analysis of a simple mathematical model simulating element cycling (A to A_e and A_e to A) by two distinct microbe types.
• Evaluation of microbial abundance, material flux rates, and niche expansion based on model parameters and chemical energy availability (Gibbs energy).

Main Results:

• Each microbe type showed increased steady-state abundance in the presence of the other, indicating mutual benefit.
• Microbial presence accelerated material flux, and coupled catabolic reactions facilitated niche expansion via the abundant resource premium.
• The plausibility of these mutualistic interactions was directly linked to the system's available chemical energy.

Conclusions:

• Mutualistic catabolic interactions are crucial for microbial survival and function, especially in energy-limited environments like subsurface ecosystems.
• These interactions enhance ecosystem productivity and expand microbial realized niches, contributing to overall ecosystem function and resilience.