Pyrococcus horikoshii

Pyrococcus horikoshii

Classification:

Higher Order Taxa Domain: Archaea; Phylum: Euryarchaeota; Class: Thermococci ; Order: Thermococcales  ; Family: Thermococcaceae ; Genus: Pyrococcus.

Species Pyrococcus horikoshii

NCBI: Taxonomy http://www.ncbi.nlm.nih.gov/sites/entrez?db=genome&cmd=Retrieve&dopt=Overview&list_uids=134

Description and Significance

Pyrococcus horikoshii thrives at an optimal temperature of 98 oC and dwells at a depth of 1395m, categorizing it has a hyperthermophilic extermophiles, one of four species with the same characteristics from the Pyrococcous genus. (4) In the Pyrcoccous genus, species all dwell at an optimal growth temperature of nearly 100 oC, greater than others from the Archaea genera, as well as dwell at a great sea depth than the other arcahaeons (7). Pyrococcus horikoshii is also obligately heterotrophic, as well as an obligate anaerobe (5).

Pyrococcus horikoshii OT3 was first isolated from a hydrothermal fluid sample obtained from the Okinawa Trough vents in the Pacific Ocean (4). The sample strain was then analyze and sequenced by assembling the sequence of the physical map-based contigs of fosmid clones, and then gap-filled was preformed with long polymeraze chain reaction (PCR) products. Of the 2061 total open reading frames (ORFs) assigned, 1202 ORFs (58.3%) did not show any significant similarities to any sequences from the databases (6).

The proteins and enzymes produced by Pyrococcus horikoshii exhibit great heat resistant qualities, and are being utilized for these qualities in the different industrial fields of chemistry, food, and medical supplies.

Genomic Structure The entire genome of Pyrococcus horikoshii was 1,738,505 bp in length, which is the smallest of the 3 already sequenced Pyrococcus species, P. furiosus and P. abyssi. The G-C (guanine-cytosine) content is 41.9%. A total of 2061 ORFs (open reading frames) were assigned as protein-coding regions, 406 (19.7%) of which showed similarity to searches against databases, 453 (22.0%) sequenced without known functions, and 1202 (58.3%) with no significant similarity to any sequences from databases. Only 3% of the sequenced ORF assigned were organism specific, most of which were conserved in P. abyssi, P. furiosus, and Thermococcus kodakaraensis. Of the RNA genes identified one was 16S-23S rRNA operon, two were 5S rRNA genes and 46 were tRNA genes (6). Phylogenetic analysis of the 16S rRNA encoding sequences classified the isolate sample into the genus Pyrococcus (5).