Lithosyntrophy: Obligate syntrophy in a phosphite-oxidizing, methanogenic culture

Area of Science:

• Microbiology
• Biogeochemistry
• Environmental Science

Background:

• Anaerobic digestion relies on syntrophic bacteria and archaea for methane production.
• Interspecies electron transfer is crucial for these reactions, often involving hydrogen (H2).
• Syntrophic bacteria typically oxidize organic compounds, maintaining low H2 levels.

Purpose of the Study:

• To describe a novel mode of microbial interaction termed "lithosyntrophy."
• To investigate the oxidation of phosphite by bacteria coupled to hydrogen production.
• To understand the dependency of phosphite-oxidizing bacteria on methanogens.

Main Methods:

• Physiology experiments
• Thermodynamic calculations
• Genomic annotation
• Metaproteomics analysis

Main Results:

• Identified *Candidatus* Phosphitivorax anaerolimi Phox-21 as a lithosynthetic bacterium.
• Demonstrated phosphite oxidation coupled to hydrogenogenesis and methanogenesis.
• Revealed Phox-21 is a mixotroph, assimilating acetate for biomass.
• Uncovered a mechanism involving electron-confurcating hydrogenase for H2 production.

Conclusions:

• Lithosyntrophy enables energy generation from inorganic compounds, linking phosphorus and carbon redox cycles.
• This interaction is vital for transferring reducing equivalents and phosphorus in anoxic ecosystems.
• Discovered a new metabolic pathway with significant biogeochemical implications.