Pyrococcus abyssi

A Microbial Biorealm page on the genus Pyrococcus abyssi

Classification

Higher order taxa

Archaea; Euryarchaeota; Thermococci; Thermococcales; Thermococcaceae; Pyrococcus

Species

NCBI: Taxonomy

Pyrococcus abyssi; 272844

Description and significance

Because of their unique ability to survive in these extreme conditions, the genome of P. abyssi has been completely sequenced. Since not much has been studied on hyperthermophiles, especially pyroccocus species,P. abyssi has been used as a model organism in the laboratories. Hopefully through the analysis of this organism, better understanding and greater genetic tools can be achieved through it's study.

Genome structure

The genome of P. abyssi is circular and contains 1.76Mb. It has a GC content of 44%. The genome content has not been explored as of yet. Most of the functionality that is known of the P. abyssi genome has come from the comparison to similiar genomes with known functions through BLAST. The comparison of the genome's of P. abyssi and P. horikoshii revealed that archaea's terminus of replication is a major region for replication, similar to that of bacteria. Comparison to another species of pyrococcus, P. furiosus, reveals an "identification of DNA reorganization linked to IS-like elements and DNA integration within tRNA genes" (1). Besides similiarities to these 2 other pyrococcus species, P. abyssi also contains genes which are crenarchaeal and bacterial like. However, these genes are mainly for the use of transport.

P. abyssi has a plasmid, pGT5, which replicates via a rolling circle mechanism. The plasmids of hyperthermophiles have not been studied extensively as some of the other archaea's due to the limited number of organisms that can survive in these extreme conditions. The importance of the study of these organism's genomes and plasmids is to understand their mechanisms of DNA replication, repair, and recombination, especially since it is so different from our own(3).

Cell structure and metabolism

This organism has a gram-positive cell membrane (1). P. abyssi breaks down peptides and sugars in order to use ATP as an energy source. When grown in vitro, it was found that this organism grows in the presence of starch, maltose and pyruvate. Instead of using NADH as an electron carrier, P. abyssi utilizes ferrodoxin. Nonetheless, ferrodoxin functions in a similar manner when it is reoxidized, leading to the creation of a electrochemical gradient which is needed for ATP synthesis. An ATPase is needed for pumping ions across the membrane, thus creating ATP. It is not known whether hydrogen or sodium ions are pumped across the membrane to create the membrane potential.(1) A sodium/hydrogen antiport is used to maintain a pH of 7 in the cytoplasm.

Ecology

Pyrococcus abyssi is found near deep sea hyperthermal vents off of the Southwest region of the Pacific Ocean. This organism is classified as a hyperthermophile since it's environment can reach temperatures as high as 102C and pressures can be up to 200 atmospheres. This organism was collected in the smoker material and sea water surrounding these hyperthermal vents.

Pathology

This organism is not known to be pathogenic to humans, plants or animals although studies have shown that it possesses a virus-like particle, PAV1. This particle is virus-like since it can reside in a host cell and cause the host cell to continuously release it into the environment. PAV1 resides stably inside of it's host cell without any prophage activity. The infectivity of this particle has not yet been studied due to a lack of a better plaque assay(2).

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

1.Georges N. Cohen, Valérie Barbe, Didier Flament, Michael Galperin, Roland Heilig, Odile Lecompte, Olivier Poch, Daniel Prieur, Joël Quérellou, Raymond Ripp, Jean-Claude Thierry, John Van der Oost, Jean Weissenbach, Yvan Zivanovic, Patrick Forterre (2003) An integrated analysis of the genome of the hyperthermophilic archaeon Pyrococcus abyssi Molecular Microbiology 47 (6), 1495–1512.

2.C. Geslin,* M. Le Romancer, G. Erauso, M. Gaillard, G. Perrot, and D. Prieur. 2003. PAV1, the First Virus-Like Particle Isolated from a Hyperthermophilic Euryarchaeote, “Pyrococcus abyssi”.J Bacteriol. 2003 July; 185(13): 3888–3894.

3.G Erauso, S Marsin, N Benbouzid-Rollet, M F Baucher, T Barbeyron, Y Zivanovic, D Prieur, and P Forterre. "Sequence of plasmid pGT5 from the archaeon Pyrococcus abyssi: evidence for rolling-circle replication in a hyperthermophile". J Bacteriol. 1996 June; 178(11): 3232–3237.

Edited by Stephine Chow