Inter-bacterial mutualism promoted by public goods in a system characterized by deterministic temperature variation

Area of Science:

• Microbiology
• Ecology
• Biogeochemistry

Background:

• Mutualism is widespread in nature but less documented in bacterial communities.
• Abiotic stress is hypothesized to promote microbial mutualism, yet research is limited.

Purpose of the Study:

• To investigate the role of temperature as an abiotic stressor in promoting bacterial mutualism within a composting system.
• To identify specific bacterial strains and mechanisms involved in temperature-induced mutualistic interactions.

Main Methods:

• Monitoring microbial communities in a quasi-natural composting system with temperature variations (20°C-70°C).
• Employing genomic analyses and culturing experiments to identify bacterial strains and interactions.
• Analyzing approximately 3000 bacterial pairings to quantify mutualism and competition frequencies.

Main Results:

• Temperature variation selected for stress-tolerant strains, including *Thermobifida fusca* and *Saccharomonospora viridis*.
• Mutualistic interactions emerged between these selected strains and others, facilitated by cobalamin sharing.
• Mutualism was observed in ~39.1% of pairings involving *T. fusca* and *S. viridis*, while competition was rare (~13.9%).

Conclusions:

• High temperatures can significantly favor mutualism over competition in bacterial communities.
• Nutrient sharing, specifically cobalamin, plays a key role in temperature-driven bacterial mutualism.
• The study provides evidence for temperature-mediated microbial community restructuring favoring cooperation.