Methanothermobacter thermautotrophicus

A Microbial Biorealm page on the genus Methanothermobacter thermautotrophicus

Classification

Higher order taxa

Cellular organisms; Archaea; Euryarchaeota; Methanobacteria;Methanobacteriales; Methanobacteriaceae; Methanothermobacter

Species

NCBI: Taxonomy

Genus: Methanothermobacter

Species: Thermautotrophicus

Description and significance

Methanothermobacter thermautotrophicus is a methanogenic, Gram-positive microorganism consisting of pseudomurein (3). Pseudomurein is also known as peptidoglycan which is a major component of the cell wall of some archaebacteria that is only chemically different but structurally and morphologically the same as bacteria peptidoglycan. A certain strain of Methanothermobacter thermautotrophicus called Methanothermobacter thermautotrophicus str. Delta H which the genome was completely sequenced by Oscient Pharmaceuticals Corporation/Ohio State University, is anaerobic (does not need oxygen), nonmotile (not capable of movement on the microorganism level, methane (CH3) producing archeon. The growth of this organism occurs between the pH of around 7. This strain can be found in thermophilic, anaerobic areas such as sewage slude digestors and was discovered and isolated from sewage sludge in 1971 in Urbana, Illinois. (7)

Methanothermobacter thermautotrophicus is used in research purposes in order to better understand the evolution of archeabacteria. It is assumed that archeabacteria and bacteria evolved in parallel. For example, a protein with nuclease-ATPase activity, Nar71 was isolated from ‘’methanothermobacter thermautotrophicus cell extracts as part of an archaeal DNA-repair system.(9) Another finding was the use of the horizontal gene transfer which was evidence of divergence that occurred and which help better understand the ancestry of Methanothermobacter thermautotrophicus to other lineages.

http://www.ncbi.nlm.nih.gov/sutils/static/GP_IMAGE/Diversity.jpg

Genome structure

The 1,751,377-bp sequence of the archeaon, Methanobacter thermautotrophicus str. Delta H, has been completely sequenced by Genome Therapeutics Corporation through the process of gene shotgun sequencing. This strain is the only currently mapped out genome of the species. It contains 1921 genes and has a length of 1,751,377 nt. Also, this strain contains 48 structural RNAs and the bacteria consists of a circular topology. (7)

Methanothermobacter thermautotrophicus grows and gains energy through the conversion of hydrogen and carbon dioxide to methane. It was discovered that Methanothermobacter thermoautotrophicus has archaea-sepcfic cell walls called pseudomurein which is similar to how peptidoglycan of eubacteria work. Methanothermobacter thermautotrophicus is thermophillic with an optimal growth temperature of 65-70 degrees Celsius.

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?

Cell structure and metabolism

A closely related species to M. thermautotrophicus is M. thermautotrophicum which has an interesting feature. This archaeabacteria has the ability to produce energy productively by using H2 to reduce carbon dioxide molecules into methane and synthesizes all of its cellular components from gaseous subtrates including N2 or NH4, and other inorganic salts. Through this way, M. thermoautotrophicum produces its energy and thus is a very energy efficient archaeabacteria. (7)

Through the use of M. thermautotrophicus cell-free homogenates, the production of archaeal ether-type glycolipids was researched. Glycolipids provide energy and serve as markers for cellular recognition. It is a crucial part to the archaeabacteria M. thermautotrophicus in biosynthesis. (4)

Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.

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

The methanogenic potential in a high temperature natural gas fields in Japan produce biogenic methane. Biogenic methane (produced by methanogens such as M. thermautotrophicus) and thermogenic methane (produced by thermochemical degradation of organic matter) are almost indistinguishable in their characteristics as methane. Recent experiments were done in Japan to better understand the production of biogenic methane. Through the use of 16s rRNA gene libraries and culture-based methods water samples were made to better understand the production of biogenic methane. Although the great majority of methane deposits are thermogenic, the ability to manipulate biogenic methane will help produce oil organically. (10)

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

Current Research

1. In vitro Biosynthesis of Ether-type Glycolipids in the Methanoarchaeon Methanothermobacter thermautotrophicus.

The biosynthesis of archaeal ether-type glycolipids was investigated in vitro using Methanothermobacter thermautotrophicus cell-free homogenates. The sole sugar moiety of glycolipids and phosphoglycolipids of the organism is the beta-D-glucosyl-(1->6)-D-glucosyl (gentiobiosyl) unit. The enzyme activities of archaeol:UDP-glucose beta-glucosyltransferase (monoglucosylarchaeol synthase, MGA synthase) and monoglucosylarchaeol:UDP-glucose beta-1,6-glucosyltransferase (diglucosylarchaeol synthase, DGA synthase) were found in the methanoarchaeon. The synthesis of DGA is probably a two-step glucosylation: (i) archaeol + UDP-glucose -> MGA + UDP; and (ii) MGA + UDP-glucose -> DGA + UDP. Both enzymes required the addition of K(+) ions and archaetidylinositol for their activities. Ten mM MgCl2 stimulated DGA synthase, in contrast to MGA synthase, which did not require Mg(2+). It was likely that the activities of MGA synthesis and DGA synthesis were carried out by different proteins because of the Mg(2+) requirement and their cellular localization. MGA synthase and DGA synthase can be distinguished in cell extracts greatly enriched for each activity by demonstrating differing Mg(2+) requirements of each enzyme. MGA synthase preferred a lipid-substrate with the sn-2,3 stereostructure of the glycerol backbone on which two saturated isoprenoid chains are bound at the sn-2 and sn-3 positions. A lipid-substrate with unsaturated isoprenoid chains or sn-1,2-dialkylglycerol configuration exhibited low activity. Tetraether type caldarchaetidylinositol was also actively glucosylated by the homogenates to form monoglucosyl caldarchaetidylinositol and small amount of diglucosyl caldarchaetidylinositol. The addition of Mg(2+) increased the formation of diglucosyl caldarchaetidylinositol. This suggested that the same enzyme set synthesized the sole sugar moiety of diether type glycolipids and tetraether type phosphoglycolipids.

2. Spontaneous Mutants in trpY and Mutational Analysis of the TrpY Archaeal Transcription Regulator.

Over 90% of Methanothermobacter thermautotrophicus mutants isolated as spontaneously resistant to 5-methyl tryptophan (5MT) had mutations in trpY. Most were single base pair substitutions that identified separate DNA- and tryptophan-binding regions in TrpY. In vivo and in vitro studies revealed that DNA binding was sufficient for TrpY repression of trpY transcription but that TrpY must bind DNA and tryptophan to assemble a complex that represses trpEGCFBAD.

3. Isolation and characterization of an amiloride-resistant mutant of Methanothermobacter thermautotrophicus possessing a defective Na+/H+ antiport.

A spontaneous mutant of Methanothermobacter thermautotrophicus resistant to the Na+/H+ antiporter inhibitor amiloride was isolated. The Na+/H+ exchanger activity in the mutant cells was remarkably decreased in comparison with wild-type cells. Methanogenesis rates in the mutant strain were higher than wild-type cells and resistant to the inhibitory effect of 2 mM amiloride. In contrast, methanogenesis in wild-type cells was completely inhibited by the same amiloride concentration. ATP synthesis driven by methanogenic electron transport or by an electrogenic potassium efflux in the presence of sodium ions was significantly enhanced in the mutant cells. ATP synthesis driven by potassium diffusion potential was profoundly inhibited in wild-type cells by the presence of uncoupler 3,3',4',5- tetrachlorosalicylanilide and sodium ions, whereas c. 50% inhibition was observed in the mutant cells under the same conditions.