Despite the fact that all known methanogens depend on methanogenesis for growth, there is considerable variability both in terms of energy substrates utilized and catabolic pathways employed.

Selenium (named after the greek goddess of the moon), which is an essential trace element in many organisms, is found in the catalytic site of numerous redox-active enzymes in the form of selenocysteine within all three domains of life.

Despite the past progress, genetic analysis of methanogens is generally still not a routine approach. Many powerful techniques, which are commonly applied for other organisms have not yet been adapted for genetic analysis of methanogens.