Mining Metagenomic Data to Understand the Lifestyle of Atmospheric Methane Oxidizing Bacteria in Antarctic Surface Soil

Abstract

Atmospheric CH4 oxidation by atmospheric methane oxidizing bacteria (atmMOB) is of importance to understanding the global CH4 flux in relation to climate change. However, little is known about the potential for an active biological atmospheric CH4 sink in the Antarctic. Previously, CH4 uptake at atmospheric concentrations was observed in cryosol samples from the Taylor Dry Valley, Antarctica. This study sought to gain greater insight into the identity and activity of the atmMOB within these cryosols. The taxonomic identity and physiology of atmMOB remain one of the great mysteries of environmental microbiology, fueling a desire for greater understanding of the genetic blueprint underlying the process of atmospheric CH4 oxidation. Using PCR amplification of a well-established atmMOB marker gene, pmoA, a DNA clone library was generated and metagenomic sequencing of four CH4-oxidizing soils resulted in the successful construction of putative genome bins for these atmMOB. Novel genetic information supported the hypothesis that these bacteria are related to Gammaproteobacteria and USC γ methanotrophs, as well as to the non-methanotrophic genus, Nitrosococcus. The presence of functional genes involved in other metabolic pathways support existing hypotheses that atmMOB may contain the potential for alternative carbon sources. Ultimately, this research marks a significant leap in understanding the terrestrial environmental impact of atmMOB and provides the first direct genetic evidence for an active, biological Antarctic CH4 sink.