In taxonomy, Methanobacterium is a genus of the Methanobacteriaceae. Contrary to their name, they are not exactly a bacterial species as they belong to the archaea and have the distinguishing biopolymer, peptidoglycan, missing from their cell membranes. Methanobacterium are nonmotile and live without oxygen. Some members of this genus can use formate to reduce methane; others live exclusively through the reduction of carbon dioxide with hydrogen. They are ubiquitous in some hot, low-oxygen environments, such as anaerobic digestors, their wastewater, and hot springs.
Scientific name: Methanobacterium
Methanobacterium are methane-producing archaebacteria. They are generally known as methanogens. A genus of firmly anaerobic bacteria that reduce CO using molecular hydrogen, H2, to give methane. They demonstrate a number of features that distinguish them from other bacteria, and are now classified as a separate cluster, the Archaebacteria. Methanobacteria are found in the anaerobic sediment at the underneath of ponds and marshes (hence marsh gas is the common name for methane) and as fraction of the microflora of the rumen in cattle and anyother herbivorous mammals (Brock et al.).
The species within the genus Methanobacterium differ widely in length and filaments are common. Cell walls emerge to be Gram positive, but are composed of pseudomurein rather than peptidoglycan. They are non-motile and flagella are missing. Metabolism is strictly anaerobic and H2 or formates are used as an electron donor. All species develop with H2 and CO2 as a substrate for methanogenesis. Cells are mesophillic or thermophillic. All species not succeed to grow under aerobic conditions and mainly are acid tolerant (will grow at pH less than 5). There are 12 species of genus Methanobacterium and they are isolated from aneraobic digestors, sewage sludge, manure, groundwater, and development water of oil-bearing rocks (Prescott et al.).
Species belonging to the genus Methanobacterium are hydrogenotrophic methanogens, which utilise H2/CO2 and sometimes formate and alcohols as substrates for growth and methane production . Growth occurs under strictly anaerobic conditions and most species are able to grow autotrophically. The morphology of Methanobacterium in pure culture varies widely between the species, as cells may be short to long, curved or straight rods, which can occur singly, in pairs, chains or as long filaments. Cells may also form large aggregates.
Examples of Methanobacterium Species:
1) Methanobacterium bryantii
2) Methanobacterium formicum
2) Methanobacterium thermoautotrophicum
Methanobacterium thermoautotrophicum is a methane producing micro-organism (methanogen) that was usually isolated from the municipal waste-treatment facility in Champaign, Illinois, USA. Methanogens are considered one of the most diverse groups in the archaea domain, with over 50 species, each with its own unique characteristics. Fortunately, they all have a few things in common. They are obligate anaerobes, so they live in places without oxygen. Oxygen actually harms them and sometimes kills them.
|Staining||Gram stain results are variable|
|Morphology||Curved, crooked to straight rods, long to filamentous, about 0.5- 1.0 um in width.|
|Specialized structures||Endospores not formed.. Cells produce fimbriae|
|Oxygen||Very strictly anaerobic|
|Temperature||Optimum growth temperatures are 37-45`C for mesophilic species and 55`C or greater for thermophiles.|
|Requires||Ammonia is the sole nitrogen source, and sulfide may serve as sulfur source.|
|Unique features||Energy metabolism by reduction of CO2 to CH4 electron donors are limited to H2, formate and CO (Kluyver and Schnellen 1947).|