Archaea; Euryarchaeota; Archaeoglobi; Archaeoglobales; Archaeoglobaceae[Others may be used. Use NCBI link to find]
Description and Significance
F.placidus was found in a submarine hypothermal vent off the coast of Vulcano, Italy. It is a neutophilic hyperthermophile that can grow best at 85C , but can not grow below 65C or above 95C . It is a coccus Archaea and has shown to grow chemolithoautotrophically. It grows through the oxidation of Fe(II) coupled to the reduction of nitrate or by oxidizing H2 coupled to the reduction of S2O32-. There is now reason to also believe that it can grow heterotrophically when it Fe(III) oxide is provided as an electron acceptor. F.placidus possesses flagella for motility and has an S-layer for its cell wall. It is an anaerobic Fe(II) oxidizing archaea and is coccoid in shape. It is the first hyperthermophile and Archaea known to oxidize aromatic compunds to carbon dioxide anaerobically. This suggests that organisms like F.placidus were around during early Earth, and may have led to the formation of iron banded formation that are often found in ancient rocks. It has a doubling time of 2.8 hours and can fix carbon dioxide at a specific rate of .33 micromol min-1. Ferroglobus placidus is the only species in the genus Ferroglobus. Ferroglobus placidus is the first and only hyperthermophile discovered to grow anaerobically by oxidizing aromatic compounds, such as benzoate, phenol, and benzaldehyde, coupled to the reduction of ferric iron Fe(III) to ferrous iron Fe(II). This is also the first example of an Archaea oxidizing aromatic compounds. It now gives rise to an idea that many more organisms might be able to oxidize aromatic compounds in hot environments.
The genome is currently being sequenced and will be released July of 2009.
Cell Structure, Metabolism and Life Cycle
Metabolically Ferroglobus placidus is anaerobic and is an Fe(II)oxidizer. Ferrous iron, H2, and sulfide serve as electron donors and NO3- is used as an electron acceptor. However, in the presence of H2, S2O32-, is used an electron acceptor. F. placidus is interesting in the fact that it can produce Fe(III) from Fe(II) under anoxic conditions. This is interesting in that Fe(III) was formed in ancient rocks and it was assumed that Fe(II) was oxidized by oxygen that was produced by cyanobacteria. This is now being questioned, due to the discovery of anoxic routes to produce Fe(III) in other ways. F. placidus can also use aromatic compounds for reducing ferric iron to ferrous iron. It fixes CO2 by the enzyme carbon monoxide dehydrogenase, as in Archaeoglobus species. Some experiments have also shown that it can catalyze the reduction of two molecules of nitrite to one N2O with the intermediate being NO. This shows that there is some possible capacity for denitrification. F.placidus did not support growth when nitrate was added, although it can grow with H2 and Fe(II).
Ecology and Pathogenesis
F. placidus has optimal growth at 85C and has a temperature range of 65C to 95C. The pH of the environment it like to grow in is 7,neutral. It is a strictly anerobic archeaon, that was discovered in a hyperthermal vent off the coast of Vulcano, Italy. This organism has given rise to the idea that there may be more organisms that might live in hot environments that have aromatic compounds or Fe(III). It has been undocumented for causing any diseases.
Hafenbradl,D., Keller,M., Dirmeier,R., Rachel,R., RoBmagel,P., Burggraf, S., Huber,H., Stetter,K. "Ferroglobus placidus gen.nov.,sp.nov., a novel hyperthermophilic archaeum that oxidizes Fe2+ at neutral pH under anoxic conditions." Archives of Microbiology. 1996. Volume 166. p.308-314.
Tor,J.M., Lovley,D.R., "Anerobic degradation of aromatic compounds coupled to Fe(III) reduction by Ferroglobus placidus." Environmental Microbiology. 2001. p. 281-287.
Tor,J.M., Kashefi,K.,Lovley,D.R. "Acetate Oxidation Coupled to Fe(III) Reduction in Hyperthermophilic Microorganisms." Applied and Environmental Microbiology. 2001. Volume 67. p.1363-1365.
Vorholt,J.A., Hafenbradl,D., Stetter, K.O., Thauer, R.K. "Pathways of autotrophic CO2 fixation and dissimilatory nitrate reduction to N2O in Ferroglobus placidus." Arch Microbiol. 1997. Volume 167. p. 19-23.
Page authored by Jerome S. Nypaver and Xiaorui Nui, students of Prof. Jay Lennon at Michigan State University.