Fig. 1

Relative frequency of metagenomic reads for different marker genes at Sites E26, E29, and E44. a Community composition based on reconstruction of full-length 16S rRNA genes from the metagenomes. Eukaryotes and unassigned reads are not shown. b Relative occurrences of hydrogenases with different metal cofactors. c Relative abundance of different subtypes of NiFe hydrogenases. d Relative abundance of mcrA genes indicative of different types of methanogenesis