These novel groups of archaea named ARMAN-1, ARMAN-2 (Candidatus Micrarchaeum acidiphilum ARMAN-2), and ARMAN-3 were missed by previous PCR-based surveys of the mine community because the ARMANs have several mismatches with commonly used PCR primers for 16S rRNA genes.

Prior to their discovery, all of the Archaea shown to be associated with Iron Mountain belonged to the order Thermoplasmatales (e.g., Ferroplasma acidarmanus).

Recently, closely related organisms have been detected in an acidic boreal mire or bog in Finland,[4] another acid mine drainage site in extreme environments of Rio Tinto, southwestern Spain,[5] at a weak-alkaline deep subsurface hot spring in Yunohama, Japan[6] and in a pyrite mine in the Harz Mountains in Germany[7] Using cryo-electron tomography, a 3D characterization of uncultivated ARMAN cells within mine biofilms[8] revealed that they are right at the cell size predicted[citation needed] to be the lower limit for life, 0.009 μm3 and 0.04 μm3.

3D reconstructions of ARMAN cells in the environment has revealed that a small number of them attach to other Archaea of the order Thermoplasmatales (Baker et al. 2010 [9]).

The genomes of ARMAN-4 and ARMAN-5 (roughly 1 Mb as well) have unusually small average gene lengths, similar to those seen in endosymbiotic and parasitic bacteria.

It is difficult to elucidate many of the commonly known metabolic pathways in ARMAN due to the unusually high number of unique genes that have been identified in their genomes.