Reverse Chimney: Assessing the Role of Root-Associated Methanotrophs As A Key Component of Methane Sinks Patches In (Semi)Arid Ecosystems.

Abstract:

Our work takes the first steps towards linking symbiotic associations of microbes to desert plants with global methane cycling. Arid areas occupy 41% of the Earth’s terrestrial surface and are increasingly being converted into agricultural fields. Sustainable and productive use of arid land requires a better understanding of the functional traits of microbes inhabiting native arid environments. To improve our knowledge of native arid ecosystem functioning, we performed preliminary studies with soil samples collected from Anza-Borrego Desert State Park. The following discoveries were made: 1. Metagenomic data identified methane-consuming microbes (methanotrophs) as one of the main functional microbial groups in the rhizosphere of desert plants; 2. The abundance of methanotrophs and the consumption rate of atmospheric methane positively correlated with the presence of vegetation; 3. Genome annotations of methanotrophs from the rhizosphere of desert plants highlight a number of functions which can contribute to interactions with plants; 4. Methanotrophs improve plant survival during drought stress. Based on these data we propose that in arid environments plants facilitate methane transport (known as chimney effect) and cooperate with methane-consuming microbes to efficiently capture methane evolved in deeper soil layers and atmospheric methane (i.e. reverse chimney), which is then metabolized to provide supplemental resources for survival in water-limiting conditions. Our data suggest that the plant-methanotroph associations represent an overlooked sink of atmospheric methane in (semi)arid ecosystems. We show that supplementation with native Methylocaldum isolates from the Anza region can improve drought tolerance in crops (e.g. Sorghum). Furthermore, our work provides essential evidence that targeted engineering of association between crops and methanotrophs in (semi)arid soils can enhance atmospheric methane sink, ultimately influencing the global climate.