Nanoarchaeum equitans
A Microbial Biorealm page on the genus Nanoarchaeum equitans
Classification
Higher order taxa
Archaea; Nanoarchaeota; Nanoarchaeum
Species
Nanoarchaeum equitans
Description and significance
Nanoarchaeum equitans, which means "riding the fire sphere", is a hyperthermophile that also acts as an obligate symbiont to the archaea Ignicoccus hospitalis. It is spherical and is only 400 nm in diameter, making it one of the smallest known living organisms. It is also the only known archaeal parasite.
It was first discovered in 2002 in an undersea hydrothermal vent off the coast of Iceland by Karl Stetter. It was first seen as tiny dots on the surface of Ignicoccus hospitalis. Its genome is extremely small, making it one of the smallest non-viral genomes ever sequenced. The significance of its genome was that ss rRNA-based sequencing comparisons placed its branching point early in the archaeal lineage, representing the new archaeal kingdom Nanoarchaeota. As such, it is the only known member of this lineage.
Genome structure
Nanoarchaeum equitans has one of the smallest genomes of any sequenced microbe with only 490,885 base pairs. It was first sequenced in 2003. This sequenced genome was of strain Kin4-M which was found in hot-water geysers on the ocean floor near Iceland.
The genome has one circular chromosome, about 550 protein genes, 46 RNA genes, and has a GC content of %31.6. The genome encodes the machinery for information processing and repair, but lacks genes for lipid, cofactor, amino acid, or nuleotide biosynthesis. It is also one of the most compact genomes, with 95% of the DNA used to encode proteins or stable RNAs. Unlike the similarly small genomes of bacterial parasites that are undergoing reductive evolution, Nanoarchaeum equitans has few pseudogenes or extensive regions of noncoding DNA. Another interesting feature is that there are many split genes that code for different functional domains of the encoded protein and are found in different places along the chromosome. To get full function, the two domains must be synthesized independently and brought together.
Cell structure and metabolism
Interesting features and/or cell structures. How it gains energy. Important molecules it produces.
Nanoarchaeum equitans is spherical and extremely small, with a size of only 400 nm in diameter. This marks it as one of the smallest known living cells. It has no flagella and can only grow attached to the specific archaeal host Ignicoccus hospitalis.
Due to the lack of genes encoding several vital metabolic pathways, Nanoarchaeum equitans relies on its host to acquire many biomolecules such as lipids, amino acids, and nucleotides.
Ecology
Nanoarchaeum equitans is a hyperthermophile, with its ideal environment having a temperature of 90 degrees Celsius. It also prefers to be in places rich in sulfur, hydrogen, and carbon dioxide since it lacks the means to metabolize these compounds on its own. Nanoarchaeum equitans has no significant contribution or effect on its environment.
Nanoarchaeum equitans acts as an obligate symbiont that lives on the surface of the crenarchaeon Ignicoccus hospitalis. Since Nanoarchaeum equitans cannot live apart from this host, it represents the only known example of an archaeal parasite.
Pathology
Nanoarchaeum equitans is not a pathogen. However, it does act as a parasite to Ignicoccus hospitalis and cannot survive without it.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Although it may not produce any useful compounds or enzymes, Nanoarchaeum equitans may be useful in biotechnology. This is because its small genome and small number of genes could make it easier to genetically engineer which will help for future research into industrial chemicals that work well in extreme environments, such as enzymes that break down harmful substances in oil wells.
Current Research
Summaries of recent research here. At least 3 required.
References
Edited by Robert Rishwain, student of Rachel Larsen and Kit Pogliano
