Question

What would the discovery of a bacterial species that is a methanogen imply about the evolution of the methane-producing pathway?

Short answer

The original methane-producing organisms are the Archaea. With the help of metagenomics, it was identified that the organisms that produce methanogens belong to the euryarchaeotes.

So, if a bacterial species is a methanogen, it can be said that the methanogen-producing pathway evolved from the euryarchaeotes.

Step-by-step solution

Methanogens

Methanogens are organisms that create methane as a consequence of low oxygen levels in theenvironment. Themethanogens are usually prokaryotic organisms that belong to the domain Archaea.

Evolution of methanogens

According to conclusions of molecular clock investigations measured by the horizontal gene transfer, methanogens differentiated from Euryarchaeota not less than 3.5 billion years ago, with methanogenesis itself possibly developing earlier.

As the molecular clock investigation employs several genes, these investigations do not fully support the ancestors of methanogens.

Methane producing pathway

Methane is the end product developed during the degradation of any organic molecule under anaerobic conditions. Methanogens have a particular enzyme known as methyl-coenzyme M reductase (Mcr) that allows them to create methane. Methanogens are the only organisms that produce methane.

The evolution of the methane-producing pathway has become a part of methanogens as they have a close evolutionary history with the euryarchaeota. The bacterial species that is a methanogen has, thus, obtained the methane-producing pathway from the euryarcheota, which includes organisms like archaea.