Higher order taxa:
Archaea; Euryarchaeota; Methanococci; Methanococcales; Methanocaldococcaceae; Methanococcus; Methanococcus maripaludis
Description and significance
Methanococcus maripaludis was originally isolated from a salt-marsh sediment in South Carolina. It is a member of the kingdom Archaea. More specifically, it is a member of the methanogenic archaea. “Methanogens are obligate anaerobes that carry out the reduction of carbon dioxide to methane using molecular hydrogen as the reductant” (1). This means that this species undergoes anaerobic metabolic processes with the final product being methane, utilizing H2 as an electron donor for CO2 reduction to methane.
Methanococcous maripaludis is a significant microbe because of its excellent laboratory growth behavior. This anaerobic archaea is helpful in “development of methods for growth on solid medium, enriching auxotrophic mutants, efficient transformation, and random insertional inactivation of genes” (2). It is because of these improvements to laboratory techniques that Methanococcus maripaludis is a popular archaebacteria for genetic manipulation.
The genome of Methanococcus maripaludis is similar to the genome of the more common Methanococcus jannaschii, with the difference being that Methanococcus maripaludis lacks inteins, DNA elements that are inserted in-frame and translated together with their host proteins. It contains a circular genome of 1.66Mb in length, with no extra-chromosomal elements. . This chromosome also contains 1,722 protein-coding genes and has a 33% Guanine-Cytosine content (GC content) (3).
Cell structure and metabolism
Methanococcus maripaludis is similar to Methanococcus voltae in its cell structure. “Methanococcus voltae is an archaebacterium and possess only a thin S-layer above the plasma membrane as its sole wall layer” (4). Also, similar to Methanococcus voltae, its source of mobility is via utilization of flagella.
Unlike other Methanococcus species, Methanococcus maripaludis is a nitrogen fixing species. Energy is generated via metabolic processes of this archaeabacteria. This species is strictly anaerobic, meaning it can live in the absence of oxygen. Methane is the final product of the anaerobic metabolic processes of Methanogenesis maripaludis.
“Methane formation occurs only under strictly anaerobic conditions” (5). Because of this, methanogenesis occurs only in environments that are anoxic, meaning environments that are abnormally low in or lacking oxygen. Archaea, in comparison to Eukaryotes, are able to grow under extreme conditions such as high temperature and high salt environments. Methanococcus is commonly found in geothermal habitats such as thermal vents. Methanococcus maripaludis is found in salt-marsh sediment on the southeastern coast of the United States.
Application to Biotechnology
As previously stated, methane is the final product of the anaerobic metabolic processes of Methanococcus maripaludis. This species is a commonly used archaeabacteria in laboratories for several reasons. A couple of reasons why it is popular model is because of the fact that is capable of rapid growth and it plates for single colonies with high efficiency. Another reason is because it has a relatively simple genome. Furthermore, this species has a large set of genetic tools. Integrative and expression vectors as well as positive and negative genetic selection are a few of the genetic tools for Methanococcus maripaludis.
Currently, Methanococcus maripaludis is being studied for its mechanism of regulation nitrogen. Specifically, research is being done on the activity nitrogenase, a a nitrogen fixer in Methanococcus maripaludis. Also, research groups such as the John Leigh Lab of the University of Washington are studying hydrogen, the electron donor in the metabolic process involved in the production of methane, and its effects on regulating mRNA and protein levels in this species. Furthermore, since Methanococcus maripaludis already has a wide set of genetic tools, genetic tool development is another aspect of this species that is being studied. Research groups are looking into other ways that this species can be helpful in genetic studies.
1. Dawes, Edwin. Microbial Energetics. New York: Blackie. 1986
2. Whitman et al. 1997. Development of genetic approaches for the methane-producing archaeabacterium Methanococcus maripaluis. Biofactors, Volume 6, Number 1: 37-46. http://www.ingentaconnect.com/content/ios/bio/1997/00000006/00000001/bio29;jsessionid=3ko9jad5p7srd.alice?format=print
3. John Leigh Lab. University of Washington Department of Microbiology. http://faculty.washington.edu/leighj/mm.html
4. Moat et al. Microbial Physiology, 4th edition. New York: Wiley-Liss. 2002
5. Brock et al. Biology of Microorganisms, 7th edition. New Jersey. 1994
Edited by Allen De Leon, student of Rachel Larsen at UCSD.