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Nitrogen metabolism in haloarchaea.

Bonete MJ, Martínez-Espinosa RM, Pire C, Zafrilla B, Richardson DJ - Saline Syst. (2008)

Bottom Line: It was described as a denitrifier and it is also able to grow using NO3(-), NO2(-) or NH4(+) as inorganic nitrogen sources.This review summarizes the advances that have been made in understanding the N-cycle in halophilic archaea using Hfx mediterranei as a haloarchaeal model.The results obtained show that this microorganism could be very attractive for bioremediation applications in those areas where high salt, nitrate and nitrite concentrations are found in ground waters and soils.

View Article: PubMed Central - HTML - PubMed

Affiliation: División de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain. mjbonete@ua.es

ABSTRACT
The nitrogen cycle (N-cycle), principally supported by prokaryotes, involves different redox reactions mainly focused on assimilatory purposes or respiratory processes for energy conservation. As the N-cycle has important environmental implications, this biogeochemical cycle has become a major research topic during the last few years. However, although N-cycle metabolic pathways have been studied extensively in Bacteria or Eukarya, relatively little is known in the Archaea. Halophilic Archaea are the predominant microorganisms in hot and hypersaline environments such as salted lakes, hot springs or salted ponds. Consequently, the denitrifying haloarchaea that sustain the nitrogen cycle under these conditions have emerged as an important target for research aimed at understanding microbial life in these extreme environments.The haloarchaeon Haloferax mediterranei was isolated 20 years ago from Santa Pola salted ponds (Alicante, Spain). It was described as a denitrifier and it is also able to grow using NO3(-), NO2(-) or NH4(+) as inorganic nitrogen sources. This review summarizes the advances that have been made in understanding the N-cycle in halophilic archaea using Hfx mediterranei as a haloarchaeal model. The results obtained show that this microorganism could be very attractive for bioremediation applications in those areas where high salt, nitrate and nitrite concentrations are found in ground waters and soils.

No MeSH data available.


Related in: MedlinePlus

Orientation of the NarGH complex in Hfx mediterranei membranes. Informatic analysis of the nar operon as well as NarGH activity assays carried out with whole cells have revealed that archaeal Nars are a new type of enzyme with the active site facing the positive side of the membrane (pNarG).
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Figure 3: Orientation of the NarGH complex in Hfx mediterranei membranes. Informatic analysis of the nar operon as well as NarGH activity assays carried out with whole cells have revealed that archaeal Nars are a new type of enzyme with the active site facing the positive side of the membrane (pNarG).

Mentions: Therefore, based on subunit composition, subcellular location of the active site and nar gene organization, it can be concluded that archaeal Nars are a new type of enzyme with the active site facing the outside and anchored to the membrane by a cytochrome b (as it has been proposed for Hfx mediterranei system) or stabilized by the lipid environment in the membrane as described for the P. aerophilum Nar [57]. This system could be an ancient respiratory nitrate reductase, although the nitrite formed could also be assimilated. The outside location of the catalytic site of NarG in the halophilic archaeal Nar has important bioenergetic implications because to be energy-conserving require the coupling of this process to a proton-motive complex [23], instead of the typical redox-loop mechanisms, the NarI subunit described in bacteria. On the other hand, it seems that an active nitrate-uptake system would not be required for respiratory nitrate reduction in archaea, thus increasing the energetic yield of the nitrate reduction process (Fig 3).


Nitrogen metabolism in haloarchaea.

Bonete MJ, Martínez-Espinosa RM, Pire C, Zafrilla B, Richardson DJ - Saline Syst. (2008)

Orientation of the NarGH complex in Hfx mediterranei membranes. Informatic analysis of the nar operon as well as NarGH activity assays carried out with whole cells have revealed that archaeal Nars are a new type of enzyme with the active site facing the positive side of the membrane (pNarG).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2483277&req=5

Figure 3: Orientation of the NarGH complex in Hfx mediterranei membranes. Informatic analysis of the nar operon as well as NarGH activity assays carried out with whole cells have revealed that archaeal Nars are a new type of enzyme with the active site facing the positive side of the membrane (pNarG).
Mentions: Therefore, based on subunit composition, subcellular location of the active site and nar gene organization, it can be concluded that archaeal Nars are a new type of enzyme with the active site facing the outside and anchored to the membrane by a cytochrome b (as it has been proposed for Hfx mediterranei system) or stabilized by the lipid environment in the membrane as described for the P. aerophilum Nar [57]. This system could be an ancient respiratory nitrate reductase, although the nitrite formed could also be assimilated. The outside location of the catalytic site of NarG in the halophilic archaeal Nar has important bioenergetic implications because to be energy-conserving require the coupling of this process to a proton-motive complex [23], instead of the typical redox-loop mechanisms, the NarI subunit described in bacteria. On the other hand, it seems that an active nitrate-uptake system would not be required for respiratory nitrate reduction in archaea, thus increasing the energetic yield of the nitrate reduction process (Fig 3).

Bottom Line: It was described as a denitrifier and it is also able to grow using NO3(-), NO2(-) or NH4(+) as inorganic nitrogen sources.This review summarizes the advances that have been made in understanding the N-cycle in halophilic archaea using Hfx mediterranei as a haloarchaeal model.The results obtained show that this microorganism could be very attractive for bioremediation applications in those areas where high salt, nitrate and nitrite concentrations are found in ground waters and soils.

View Article: PubMed Central - HTML - PubMed

Affiliation: División de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Alicante, Alicante, Spain. mjbonete@ua.es

ABSTRACT
The nitrogen cycle (N-cycle), principally supported by prokaryotes, involves different redox reactions mainly focused on assimilatory purposes or respiratory processes for energy conservation. As the N-cycle has important environmental implications, this biogeochemical cycle has become a major research topic during the last few years. However, although N-cycle metabolic pathways have been studied extensively in Bacteria or Eukarya, relatively little is known in the Archaea. Halophilic Archaea are the predominant microorganisms in hot and hypersaline environments such as salted lakes, hot springs or salted ponds. Consequently, the denitrifying haloarchaea that sustain the nitrogen cycle under these conditions have emerged as an important target for research aimed at understanding microbial life in these extreme environments.The haloarchaeon Haloferax mediterranei was isolated 20 years ago from Santa Pola salted ponds (Alicante, Spain). It was described as a denitrifier and it is also able to grow using NO3(-), NO2(-) or NH4(+) as inorganic nitrogen sources. This review summarizes the advances that have been made in understanding the N-cycle in halophilic archaea using Hfx mediterranei as a haloarchaeal model. The results obtained show that this microorganism could be very attractive for bioremediation applications in those areas where high salt, nitrate and nitrite concentrations are found in ground waters and soils.

No MeSH data available.


Related in: MedlinePlus