Anaerobic Eury- and Crenarchaeota inhabit ectomycorrhizas of boreal forest Scots pine

Members of the euryarchaeotal genera Methanolobus and Halobacterium as well as group 1.1c Crenarchaeota were enriched from ectomycorrhizal samples and cultured under anaerobic conditions. 16S rRNA gene sequences of Methanolobus were obtained in a H2 + CO2 atmosphere and autofluorescent putatively methanogenic microbial cells were detected by epifluorescence microscopy of the anaerobic methane-producing enrichment cultures. Halobacterium and group 1.1c Crenarchaeota grew anaerobically when either H2 or CH4 was added to the atmosphere. Group 1.1c Crenarchaeota were also enriched under aerobic conditions on mineral media, but only when methane or methanol was added as carbon sources. The 16S rRNA gene sequences of 1.1c Crenarchaeota grown under both anaerobic and aerobic conditions were highly similar. Our study demonstrates the growth of group 1.1c Crenarchaeota and Halobacteria derived from non-extreme soil environment in non-saline enrichments under anaerobic conditions. The results suggest that 1.1c Crenarchaeota may play a role in the cycling of C-1 substrates in the boreal forest soil ecosystem.

Research highlights
► Anaerobic and aerobic enrichments of boreal forest soil Group 1.1c crenarchaeota on C-1 carbon.
► Methanogens detected in boreal forest tree mycorrhiza for the first time.
► Halobacteria-like 16S rRNA sequences in anaerobic and aerobic enrichments with methane.
► Boreal forest soil archaea may be involved in C-1 carbon cycling in the soil ecosystem.