Ferroplasma

Genus of archaea

Ferroplasma is a genus of Archaea that belong to the family Ferroplasmaceae. Members of the Ferroplasma are typically acidophillic, pleomorphic, irregularly shaped cocci. The archaean family Ferroplasmaceae was first described in the early 2000s. To date very few species of Ferroplasma have been isolated and characterized. Isolated species include Ferroplasma acidiphilum, Ferroplasma acidarmanus, and Ferroplasma thermophilum. A fourth isolate Ferroplasma cupricumulans was later determined to belong to a separate genus. Variations in the tetraether lipids of the family Ferroplasmaceae are used for chemotaxonomic identification at the genus and species level because many members possess identical 16S rRNA sequences. During this reaction ferrous iron, which can be utilized by Ferroplasma, is also regenerated leading to a "propagation cycle" where pH is lowered. The reaction can be described by the following equation:

FeS2 + 14Fe^3+ + 8H2O > 15Fe^2+ + 2SO4^2 + 16H+

Ferroplasma species are often present at AMD sites where they participate in this cycle through the biotic oxidation of ferrous iron. It also produces fewer toxic byproducts. Studies have shown that the inclusion of Ferroplasma thermophilum along with the bacteria Acidithiobacillus caldus and Leptospirillum ferriphilum can bioaugment the leaching process of chalcopyrite and increase the rate at which copper is recovered.

Ferroplasma acidiphilum has been shown to grow as a chemomixotroph and to grow synergistically with the acidophilic bacteria Leptospirillum ferriphilum. The strain Ferroplasma acidiphilum YT is a facultative anaerobe with all the required genes for arginine fermentation. Although it is unclear whether Ferroplasma acidiphilum YT uses its arginine fermentation pathway, the pathway itself is an ancient metabolism that traces back to the last universal common ancestor (LUCA) of the three domains of life.

Ferroplasma acidarmanus Fer1 was isolated from mine samples collected at Iron Mountain, California. Iron Mountain (CA) is a former mine that is known for its acid mine drainage (AMD) and heavy metal contamination. In addition to being acidophilic, F. acidarmanus Fer1 is highly resistant to both copper and arsenic.

In 2006 Ferroplasma cupricumulans was isolated from leachate solution collected from the Myanmar Ivanhoe Copper company (MICCL) mining site in Myanmar.

In 2008, Zhou, et al. described the isolation of the organism Ferroplasma thermophilum L1T from a chalcopyrite column reactor that was inoculated with acid mine drainage (AMD) from the Daye copper mine in China’s Hubei province. In aerobic conditions with low concentrations of yeast extract F. thermophilum grows by oxidizing ferrous iron. However, in anaerobic conditions F. thermophilum reduces ferric iron and sulfate. This makes F. thermophilum ecologically important for iron and sulfur cycling at pyrite rich mine sites.