Hydrogenogenic community
A MiSeq sequencer (Illumina) was used to create the sequencing library. The primers targeted the V4-V5 variable regions of the 16S ribosomal RNA sequence of prokaryotes (Bacteria and Archaea). A computer pipeline developed by INRA operating with Mothur (version 1.36.1) was used for the processing of the sequences. Barcodes, primers, sequences with homopolymers greater than 8 bp as well as chimeras have been removed from the sequence files. The sequences showing 100% homology to each other were grouped together into unique sequences, then into OTU1 (operational taxonomic unit), which will subsequently be identified.