Recovery of Methanotrophic Activity Is Not Reflected in the Methane-Driven Interaction Network after Peat Mining

Aerobic methanotrophs are crucial in ombrotrophic peatlands, driving the methane and nitrogen cycles. Peat mining adversely affects methanotrophs, but activity and community composition/abundances may recover after restoration. Considering that the methanotrophic activity and growth are significantly stimulated in the presence of other microorganisms, the methane-driven interaction network which encompasses methanotrophs and nonmethanotrophs (i.e., the methanotrophic interactome), may also be relevant in conferring community resilience. Yet, little is known of the methanotrophic interactome's response to and recovery from disturbances. Here, we determined the recovery of the methanotrophic interactome as inferred by a co-occurrence network analysis comparing pristine and restored peatlands. We coupled a DNA-based stable isotope probing (SIP) approach using [C-13]CH4 to a co-occurrence network analysis derived from the C-13-enriched 16S rRNA gene sequences to relate the response in methanotrophic activity to the structuring of the interaction network. Methanotrophic activity and abundances recovered after peat restoration since 2000. Methylomonaceae taxa were the predominantly active methanotrophs in both peatlands, but the peatlands differed in the relative abundances of Methylacidiphilaceoe and Methylocystis. However, bacterial community compositions were distinct in both peatlands. Likewise, the methanotrophic interactome was profoundly altered in the restored peatland. Structuring of the interaction network after peat mining resulted in the loss of complexity and modularity, indicating a less connected and efficient network, which may have consequences in the event of recurring/future disturbances. Therefore, determining the response of the methane-driven interaction network, in addition to relating methanotrophic activity to community composition/abundances, provided a more comprehensive understanding of the resilience of the methanotrophs. IMPORTANCE Microbial resilience against and recovery from disturbances are often determined with regard to microorganisms' activity and community composition/abundances. Rarely has the response of the network of interacting microorganisms been considered, despite accumulating evidence showing that microbial interaction modulates community functioning. Comparing the methane-driven interaction networks of a pristine peatland and a restored peatland, our findings revealed that the metabolically active microorganisms were less connected and formed less-modular hubs in the restored peatland, which is indicative of a less complex network that may have consequences with recurring disturbances and environmental changes. This also suggests that the resilience and full recovery in the methanotrophic activity and abundances do not reflect on the interaction network. Therefore, it is relevant to consider the interaction-induced response, in addition to documenting changes in activity and community composition/abundances, to provide a comprehensive understanding of the resilience of microorganisms to disturbances.

Automated summary

The study found that the methane-driven interaction network in a restored peatland was less complex and modular, potentially leading to consequences with recurring disturbances and environmental changes, indicating that the rebuilt interaction network may not fully recover and reflect on the resilience of the methanotrophs.