Groundwater microbial communities across the terrestrial subsurface

Area of Science:

• Microbiology
• Geochemistry
• Ecology

Background:

• Terrestrial subsurface groundwater harbors a vast biome crucial for microbial life.
• Microbes in groundwater face energy scarcity due to lack of photosynthesis, isolation, and slow geochemical turnover.
• The ecological principles governing microbial survival in these oligotrophic conditions are not well understood.

Purpose of the Study:

• To propose a framework of 'microbial frugality' explaining microbial persistence in energy-limited groundwater.
• To identify key evolutionary and physiological traits enabling survival near the energetic minimum.
• To understand the role of these traits in sustaining microbial life and biogeochemical cycling.

Main Methods:

• Conceptual framework development based on existing literature and data.
• Analysis of microbial traits such as replication rates, genome size, and metabolic strategies.
• Investigation of the 'necromass pump' concept for internal carbon cycling.

Main Results:

• Microbial frugality involves low replication rates, genome streamlining, metabolic versatility, and standby metabolism.
• The necromass pump, or continuous recycling of microbial biomass, creates an internal carbon reservoir.
• These traits enable microbial persistence in groundwater and mirror strategies in the marine deep biosphere.

Conclusions:

• Microbial frugality is a key strategy for life in extreme oligotrophic groundwater ecosystems.
• The interdependence and necromass recycling highlight the significant role of groundwater microbes in biogeochemical cycles.
• Convergent evolutionary solutions exist for life in energy-limited environments across different Earth biomes.