Termite mounds contain soil-derived methanotroph communities kinetically adapted to elevated methane concentrations

Area of Science:

• Microbiology
• Environmental Science
• Biogeochemistry

Background:

• Termite mounds mitigate significant methane (CH4) emissions, but the specific microbes responsible for methane consumption remain unidentified.
• Understanding these microbial communities is crucial for assessing their role in regulating greenhouse gas fluxes from terrestrial ecosystems.

Purpose of the Study:

• To characterize the abundance, composition, and methane oxidation kinetics of methanotroph communities within termite mounds.
• To identify the key microbial groups involved in methane mitigation in these unique environments.

Main Methods:

• Employing three independent methods to analyze methanotroph communities in termite mounds from Northern Australia.
• Utilizing methane monooxygenase gene sequencing and reconstructing a metagenome-assembled genome.
• Estimating in situ methane oxidation kinetics using reaction rates and analyzing mound porosity.

Main Results:

• Methanotrophs are rare but distinct microbial members in termite mounds compared to surrounding soils.
• Upland soil cluster α (USCα) affiliated methanotrophs were the most abundant, with Methylocystis and TUSC also detected.
• Methane oxidation in mounds exhibited high methane affinities (low micromolar range), significantly higher than upland soils but lower than landfill soils.

Conclusions:

• Termite mound environments select for distinct methanotroph communities kinetically adapted to elevated methane concentrations.
• Methanotroph abundance and partial methane mitigation are limited by factors other than methane availability.
• Upland soil cluster α plays a predominant role, suggesting greater functional diversity than previously recognized.