Anaerobiosis, DNA, Archaeal - genetics, Amino Acid Sequence, Gene Library, Hydrogenase - genetics, Iron-Sulfur Proteins - genetics, Molecular Sequence Data, Hydrogenase - chemistry, Iron-Sulfur Proteins - chemistry, Phylogeny, Biodiversity, Archaea - classification, Bacteria - genetics, Sequence Analysis, DNA, Sequence Homology, Nucleic Acid, Genetic Variati...