Abstract :
The possibility that Methanothrix (formerly Methanosaeta) and Geobacter species cooperate via direct interspecies electron transfer (DIET) in terrestrial methanogenic environments is investigated in rice paddy soils. Genes with high sequence similarity to the gene for the PilA pilin monomer of the electrically conductive pili (e-pili) of Geobacter sulfurreducens accounted for over half of the PilA gene sequences in metagenomic libraries and 42% of the mRNA transcripts in RNA sequencing (RNA-seq) libraries. These results are consistent with a model in which Geobacter species are providing electrons to Methanothrix species for methane production through electrical connections of e-pili.