Methanopyrus kandleri

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A Microbial Biorealm page on the genus Methanopyrus kandleri

Classification

Higher order taxa

cellular organisms

Doomain: Archaea

Phylum: Euryarchaeota

Class: Methanopyri

Order: Methanopyrales

Family: Methanopyraceae

Genus: Methanopyrus


Species

NCBI: Taxonomy

Methanopyrus kandleri

Description and significance

Methanopyrus kandleri is a Gram positive, rod-shaped, anaerobic methanogen that is classified as an archaeon (2,7,8). M. kandleri, is also one of the most exceptional extremophiles known today. Not only is it a hyperthermophile, but it is also a thriving halophile. It can survive in temperatures up to 110 degrees Celsius which makes it the most temperature resistant species of all the other methanogens (4,6). M. kandleri's hyperthermophilic properties are matched by its halophillic tendencies. Intracellular salt content of trianionic cDPG (cyclic 2,3-diphosphoglycerate) and K+ have been measured at concentrations as high as 1.1M and 3M, respectively (3). Its ability to live in these harsh environments is thought to be credited towards its methanogenic metabolism (4).


Genome structure

The entire genome of M. kandleri has been sequenced by Fidelity Systems in Maryland using a customized sequencing method made specifically for this archaeon called direct genomic sequencing. This process has four phases: the skimming shotgun phase, the direct sequencing phase, the gap closure and assembly verification phase, and finally the computational genome analysis (2). This method actually took advantage of a very unique topoisomerase V found only in M. kandleri to help sequence this genome (5). For more on topoisomerase V, see Cell Structure and metabolism or Current Research. By this method, the genome was determined to be a single chromosome that was 1,694,969 base pairs (bp) long. This method proved to work very well since there was only about 1 error per 40 kb (2). The sequence showed very high levels of guanine and cytosine content, which is most likely an adaptation to the extreme environments it lives in (6). Nucleotides 1694501-747 were believed to contain the origin of replication for this chromosome. In this genome, 1,692 protein-coding genes and 39 structural RNA genes were found. These proteins have the highest ratio between negatively and positively charged amino acids and therefore M. kandleri has the lowest isoelectric point in all archaeon (2). M. kandleri is said to have a very high number of orphan genes (5). Although the 16S rRNA and EF-1alpha sequences phylogenically placed M. kandleri relatively far away from the other species of methanogens, the complete sequencing of the genome showed the similarities between the members of this monophyly group (2,6,7). For more on the classification of this organism, see Current Research.


Cell structure and metabolism

M. kandleri is a gram positive archaeon, which means that it has only one cell membrane that is surrounded by a thick cell wall (2). Because M. kandleri is a hyperthermophile as well as a halophile, many structural changes must take place in order to survive. One example of these changes can be seen in the cell membrane of this organism. The cell membranes show an unusual archaeic characteristic of having unsaturated lipids; specifically terpenoid lipids which are primative lipids thought to be the origin of phytantyl diethers, found in all other archaea (2,5). Although it was believed that only eukaryotes contained proteins called histones that condense DNA, it was recently discovered that methanogens also had a protein that does this. The histone found in M. kandleri, called HMK, differs from those found in both eukaryotes and other methanogens. HMK is twice as long as other methanogenic histones, but is believed to bind DNA similar to those of eukaryotes based on spatial similarities (10). Another structural rarity can be seen in the reliance of enzymes on intracellular salt content. This salt concentration greatly affects activity and thermostability of enzymes; specifically enzymes involved in methanogenic processes. The two enzymes proven to show sensetivity to salt concentrations are formylmethanofuran:tetrahydromethanopterin formyltransferase and N5,N10-methenyltetrahydromethanopterin cyclohydrolase. In order to protect itself from osmolysis due to high intracellular salt concentrations, M. kandleri is surrounded by a pseudomurien sacculus (2,3,8). The enzyme topoisomerase V is the most rare topoisomerase known and is only found in M. kandleri. When first discovered it was believed to be related to topoisomerase I, but when it was closely examined it was determined that they were in a class of their own (2,5,11). Another extremely rare enzyme found in M. kandleri is a two-subunit reverse gyrase (2,12).

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required

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.

Edited by student of Rachel Larsen