We're pleased to reprint here in slightly shorted form a recent post from Lucas’ Thoughtomics, a Scientific American blog whose aim is “Exploring evolution through genes, computers and history." By kind permission.
Microbiologists have long noted something odd about the Halobacteria (and not only their misleading name. They got it before the Archaea became known). In all their evolutionary analyses, they found that Halobacteria are part of a branch of archaea, the ‘methanogens’. What bothers microbiologists is that methanogens and Halobacteria couldn’t be more different. In every scheme ever devised to differentiate among microorganisms, methanogens and Halobacteria end up on opposing sides of the divide. If microbes were spices, methanogens would be the pepper to the halobacterial salt.
Methanogens are the self-reliant survivalists, able to liberate energy from the most basic of molecules. A pinch of hydrogen (H2), a dash of carbon dioxide (CO2) and a spoonful of minerals is all a methanogen needs to carve out a living. This sober lifestyle has earned them the moniker of ‘rock eaters’ (lithotrophs).
Click "source" to read more.