Natronomonas Pharaonis
A Microbial Biorealm page on the genus Natronomonas Pharaonis
Classification
Higher order taxa
Archaea; Euryarchaeota; Halobacteria; Halobacteriales; Halobacteriaceae; Natronomonas
Species
Natronomonas pharaonis
Description and significance
Natronomonas pharaonis is an aerobic, haloalkaliphilic archaeon that is sensitive to high concentrations of magnesium, but grows the best in conditions of 3.5 M NaCl and at a pH of 8.5. The first isolated strains of Natronomonas pharaonis were found in the soda lakes of Egypt and Kenya. These soda lakes are highly saturated with salt and have a pH of 11. Genome analysis shows adaptation strategies of alkaliphiles in regards to its respiratory chain, nitrogen metabolism, and its cell envelope.
Genome structure
The genome of N. pharaonis consists of three circular replicons, one 2.6-Mb chromosome and two plasmids (PL131 - 131kb, PL23 - 23kb). Its chromosome is GC-rich (63.4% GC) with an integrated copy of PL23. N. pharaonis also contains a high amount of acidic amino acids (average 19.3%) in its cytoplasmic proteins. This results in low isoelectric points (average pI 4.6), which is an adaptive feature of haloarchaea in order to survive in its hypersaline environment.
Cell structure and metabolism
Natronomonas pharaonis has a high degree of nutritional self-sufficiency. It contains the correct enzymes for the biosynthesis of amino acids and coenzymes. However, because it lacks key enzymes of glycolytic pathways, N. pharaonis will most likely not be able to use sugar. The genome analysis shows that N. pharaonis supplies ammonia through three main mechanisms, allowing them to survive in extreme pH conditions, which reduce levels of ammonium ions.
Current Research
"Genome-wide proteomics of Natronomonas pharaonis" January 2007. A shotgun sequencing approach and SDS-PAGE was used to reach further conclusions about N. pharaonis's cellular physiology. A set of identified proteins consist of about 60% of the cytosolic proteins involved in metabolism and genetic information processing. Among the halophilic archaea, many of these proteins show a high genetic variablility.
"Large-Scale Identification of N-Terminal Peptides in the Halophilic Archaea Halobacterium salinarum and Natronomonas pharaonis" April 2007. A combined fractional diagonal chromatography (COFRADIC) and a strong cation exchange chromatography (SCX)were two methods used to characterize the proteins of N-terminal peptides. This data allowed for the correct assignment of start codons as well as showing that 60% of proteins undergo methionine cleavage, instead of 13-18%.
References
Falb, M., Pfeiffer, F., Palm, P., Rodewald, K., Hickmann, V., Tittor, J., and Oesterhelt, D. "Living with two extremes: Conclusions from the genome sequence of Natronomonas pharaonis." Genome Research. 2005. 15. p. 1336-1343. (http://www.genome.org/cgi/reprint/15/10/1336)
Oesterhelt, D. "Natronomonas pharaonis - overview." Max Planck Institute of Biochemistry. 2007. (http://www.biochem.mpg.de/en/research/rd/oesterhelt/web_page_list/Org_Napha/index.html)
Edited by student of Rachel Larsen and Kit Pogliano
KMG
