# Metabolic interplay in a synthetic consortium: insights into the mediating role of a minority species

## TL;DR

This study explores how a minority bacterial species mediates interactions in a synthetic microbial community, influencing hydrogen production and reshaping relationships between other species.

## Contribution

The study reveals the previously underestimated role of a minority species as a mediator in microbial consortia.

## Key findings

- N. vulgaris acts as a mediator between C. acetobutylicum and E. coli, enabling their interaction.
- Hydrogen production increases in the C. acetobutylicum/N. vulgaris consortium under nutritional starvation.
- N. vulgaris protects and reshapes the relationship between other species in the community.

## Abstract

Microbial interactions are pivotal components of Earth's ecosystems, driving essential processes that sustain life, regulate environmental conditions, and ensure ecosystem resilience. A comprehensive understanding of these relationships is imperative for leveraging their potential in environmental solutions and biotechnological innovations. In this study, we explore the intricate bacterial interplay between three key players involved in biomass degradation: Clostridium acetobutylicum (Gram-positive), Escherichia coli, and Nitratidesulfovibrio vulgaris Hildenborough (Gram-negative) using synthetic reconstituted consortium. N. vulgaris independently cooperates with both C. acetobutylicum and E. coli through thigh physical interactions and transfer of biological material to ensure its survival. These interactions are dependent of nutritional starvation and provokes with a rise of hydrogen production in the consortium C. acetobutylicum/N. vulgaris. However, prior studies showed that E. coli does not exchange cytoplasmic material with C. acetobutylicum. To probe the stability of these microbial interactions and the hydrogen production, we monitored growth and metabolic kinetics in pure and co-cultures. Our findings reveal a surprising shift: N. vulgaris emerges as an unexpected mediator and protector, reshaping the relationship between E. coli and C. acetobutylicum. This study highlights the underestimated influence of minority species like N. vulgaris in microbial communities, shedding a new light on their ecological and functional roles.