Aerobic methanotrophs and the associated microbial network: resilience and stress response.

Abstract

Microorganisms are a source, as well as a sink for methane, a potent primary greenhouse gas (GHG). Methane emissions would have been higher if not for the aerobic methane-oxidizers (methanotrophs) consuming the produced methane before being released into the atmosphere. These “low-affinity” methanotrophs thrive in niches where methane and oxygen availability overlap, and are of particular relevance in high methane-emitting environments (e.g., rice paddies, landfill covers, river sediments), whereas the “high-affinity” methanotrophs are responsible for consuming atmospheric methane at trace levels in well aerated soils. Although shown to be resilient to sporadic disturbances, less is known on how methanotrophs respond to recurring/compounded disturbances, and the role of the accompanying non-methanotrophs in modulating methanotrophic activity remains to be determined. Hence, the central hypothesis was: Methanotrophs are resilient to environmental disturbances, but recurring or compounded disturbances may have a cumulative effect, compromising methanotrophic activity, which is also modulated by interactions with the biotic environment. The hypothesis was addressed by microcosm- and mesocosm-based studies, capitalizing on stable isotopes, trace gas analytics, and state-of-the art molecular analyses of specific genes and gene transcripts.