Metabolite release by nitrifiers facilitates metabolic interactions in the ocean

Area of Science:

• Marine microbiology
• Biogeochemical cycles
• Microbial ecology

Background:

• Chemoautotroph-heterotroph interactions are vital for deep-ocean carbon cycling.
• Nitrifiers, abundant ocean chemoautotrophs, have poorly understood metabolite release and transfer mechanisms.
• Understanding these transfers is key to marine microbial ecology.

Purpose of the Study:

• To characterize the exo- and endometabolomes of key nitrifying microbes.
• To investigate metabolite release and availability to heterotrophic communities.
• To elucidate the role of nitrifier-released compounds in marine microbial interactions.

Main Methods:

• Metabolomic analysis of ammonia-oxidizing Nitrosopumilus adriaticus and nitrite-oxidizing Nitrospina gracilis.
• Comparative analysis of axenic and co-culture systems with a heterotrophic bacterium.
• Exometabolome and transcriptome profiling to identify dynamic metabolite production and consumption.

Main Results:

• Nitrifiers release labile organic compounds, with N. adriaticus favoring amino acids like glycine.
• Endometabolome composition did not predict exometabolite release, suggesting active secretion mechanisms.
• Co-cultures revealed dynamic B vitamin (B2, B5, B7 precursors) production and consumption between nitrifiers and heterotrophs.

Conclusions:

• B vitamins and their precursors are significant in governing metabolic interactions between marine nitrifiers and heterotrophs.
• Nitrifiers actively release metabolites, influencing the availability of essential organic compounds in the deep ocean.
• These findings highlight the critical role of microbial metabolism in deep-sea biogeochemical processes.