Natronomonas
Encyclopedia
In taxonomy
, Natronomonas is a genus of the Halobacteriaceae
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of Natronomonas pharaonis consists of three circular replicons, the chromosome
which is 2,595,221 bp in length, a typical haloarchaeal 131-kb plasmid, and a unique multicopy 23-kb plasmid. Its choromosome has a high G + C content (63.4%). Also, a high proportion of acidic amino acids (average 19.3%) is found in the proteins of N. pharaonis which results in low isoelectric points (average pI 4.6). This is considered to be one of the adaptive features of haloarchaea, which are known to apply the salt-in strategy (high internal salt concentrations) in order to survive in their hypersaline environment (Falb et al). Further, it is noteworthy that because the archaeon lacks the genetic encoding for key enzymes for glycolytic pathways, it is not capable of sugar utilization.
The archaeon grows under highly alkaline conditions of pH around 11, which causes reduced levels of ammonia in addition to low availability of metal ions. The genome analysis shows that, in its nitrogen metabolism process, the archaeon has three mechanisms that supply ammonia, which is then assimilated into glutamate: direct uptake of ammonia, uptake of nitrate and subsequent reduction to ammonia, and uptake of urea which is split by urease to release ammonia. The green arrows in the figure represent the transporters for exogenous nitrogen source ammonia (AmtB
), nitrate (NarK), and urea (UrtA-E), and the blue arrows represent the enzymes for reduction of nitrate (NarB + Nir A) and hydrolysis of urea (UreA-G). Other abbreviations: GlnA + GltB = glutamate; 2-OG = oxoglutarate; fdx = ferredoxin.
It is probable that Natronomonas uses ferredoxin and not NADH as the electron donor for all three reductive conversions. This is evident from the occurrence of conserved ferredoxin-binding residues within the N. pharaonis NirA protein and ferredoxin dependence of nitrate and nitrite reductases in the halophile Haloferax mediterranei.
s in Egypt and Kenya, which show pH values around 11.
Alpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
, Natronomonas is a genus of the Halobacteriaceae
Halobacteriaceae
In taxonomy, the Halobacteriaceae are a family of the Halobacteriales in the domain Archaea.- Overview :Halobacteriaceae are found in water saturated or nearly saturated with salt. They are also called halophiles, though this name is also used for other organisms which live in somewhat less...
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Description and Significance
Natronomonas pharaonis is an aerobic, extremely haloalkaliphilic archaeon that grows optimally in 3.5M NaCl and at pH 8.5, but is sensitive to high magnesium concentrations.Genome Structure
The genomeGenome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
of Natronomonas pharaonis consists of three circular replicons, the chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
which is 2,595,221 bp in length, a typical haloarchaeal 131-kb plasmid, and a unique multicopy 23-kb plasmid. Its choromosome has a high G + C content (63.4%). Also, a high proportion of acidic amino acids (average 19.3%) is found in the proteins of N. pharaonis which results in low isoelectric points (average pI 4.6). This is considered to be one of the adaptive features of haloarchaea, which are known to apply the salt-in strategy (high internal salt concentrations) in order to survive in their hypersaline environment (Falb et al). Further, it is noteworthy that because the archaeon lacks the genetic encoding for key enzymes for glycolytic pathways, it is not capable of sugar utilization.
Cell Structure and Metabolism
Natronomonas, like the other members of Halobacteriaceae, has a distinct physiological characteristics because it not only requires high NaCl concentrations but also high pH and low Mg2+ concentrations for growth. It usually utilizes amino acids as the carbon source, but the series of studies discovered that the archaeon has a high degree of nutritional self-sufficiency. Also, in contrast to other alkaliphiles, which use sodium Na+ instead of protons H+ as coupling ion between respiratory chain and ATP synthase, Natronomonas uses protons as coupling ion.The archaeon grows under highly alkaline conditions of pH around 11, which causes reduced levels of ammonia in addition to low availability of metal ions. The genome analysis shows that, in its nitrogen metabolism process, the archaeon has three mechanisms that supply ammonia, which is then assimilated into glutamate: direct uptake of ammonia, uptake of nitrate and subsequent reduction to ammonia, and uptake of urea which is split by urease to release ammonia. The green arrows in the figure represent the transporters for exogenous nitrogen source ammonia (AmtB
Ammonia transporter
Ammonia transporters are structurally related membrane transport proteins called Amt proteins , methylammonium/ammonium permeases or RhAG, RhBG, and RhCG Rh family members in mammals. The RhAG, RhBG and RhCG proteins constitute solute carrier family 42...
), nitrate (NarK), and urea (UrtA-E), and the blue arrows represent the enzymes for reduction of nitrate (NarB + Nir A) and hydrolysis of urea (UreA-G). Other abbreviations: GlnA + GltB = glutamate; 2-OG = oxoglutarate; fdx = ferredoxin.
It is probable that Natronomonas uses ferredoxin and not NADH as the electron donor for all three reductive conversions. This is evident from the occurrence of conserved ferredoxin-binding residues within the N. pharaonis NirA protein and ferredoxin dependence of nitrate and nitrite reductases in the halophile Haloferax mediterranei.
Ecology
Strains of N. pharaonis were first isolated from highly saline soda lakeSoda Lake
Soda Lake is a dry lake at the terminus of the Mojave River in the Mojave Desert of San Bernardino County, California. The lake has standing water during wet periods, and water can be found beneath the surface....
s in Egypt and Kenya, which show pH values around 11.