2. Mendosicutes are uneven gram stained
“methanogenic bacteria’ ’now called as methanogens
and are classed as Achaea bacteria
3. Methanogens are relatively diverse group of archaea
and prokaryotic organism that can be found in various
anoxic habits
Methanogenic archaea are a very diverse group and
some strains can grow under extreme conditions .like
exteme high or low temperature.
Methanogenic are coccoid or bacilli shape
There are over 50 described species of methanogens.
They are mostly anaerobic organisms that cannot
function in aerobic conditions.
4. Methanogens lack peptidoglycan, a polymer that is
found in the cell wall of bacteria. Some methanogens
have cell wall composed of psedopeptidoglycan.
Other methanogens do not, but have at least one
paracrystaline array (s – layer)made of proteins that fit
together like jigsaw puzzle.
Methanogenic bacteria are considered a critical group
of bacteria, because of their polygenetic diversity and
the only of hydrocarbon methane. They require anoxia
and highly reduced conditions for growth.
These bacteria use co2 or methyl group as terminal
electron acceptor and produce methane as their
catabolic end product.
5. Habitat:
• They are found in diverse habitat which are associated
with decomposition of organic matter ,bogs, anaerobic
digesters ,aquatic sediments, hydrothermal submarine
vents and geothermal springs.
• In animals, they are found in rumens of herbivores,
mammalian intestines, human oral cavity, guts of
insects.
6. Methanogenis is the production of CH4 from either
co2 plus H2 or from methylated organic compounds.
Process of methanogensis was first demonstrated over
200 years ago by Alessandro volta.
The process is strictly anaerobic.
A variety of unique co- enzymes are involved in
metanogenesis.
7. Complex organic compounds cannot be utilized by
methanogens.
They use only C1 compound and only C2 compounds
.Acetate .
There are two nutritional groups of methanogens.s
• Obligate chemolithotrophic methanogens that grow
with CO2 plus H2 according to equation
CO2 +4H4 4CO2 + 4H2
• Some of these organisms live with the quasi –
chemolithotrophic substrates HCOOH and CO
4HCOOH 4CO2 +4H2
CO2 +4H4 CH4 +2H2O
8. Methylotrophic methanogens that grow with methyl
group containing substrates for example Methanol,
acetate
CH3COOH CH4 + CH2
• Organisms such as Methanosarcina barkeri grown on
methanol. Here, fourth of the substrate has to be
oxidized to CO2 for reducing power generation.
CH3OH + H2O CO2 + 6H
3CH3OH + 6H 3CH4 + 3H2O
4CH3 3CH4 +
CO2+2H2O
9. Group 2 organisms produce methane directly from
methyl groups and not via CO2
Obligate chemolithotropic methanogens do not
contain cytochromes which are present in
methanogens
10. The first two novel co enzymes discovered in
methanogens are co-enzyme M and F420
Co-enzyme M is a simple chemical compound. Its
reactive group is merecepot which can be methylated
and methyl co-enzyme M is the ultimate a precursor of
methane.
Co-enzyme F420 is adeazaflavin, it is a redox carrier
and its role is analogous to that of ferrodoxin in other
anaerobes.
Its functions as electron acceptor of hydrogenise and
as electron donor in several reduction reactions.
11.
12. Formation of methane from bicarbonate
• The four steps leading to formation of methane of
methane bicarbonate are as follows
HCO3 + H2 HCOO + H20
HCOO + H2 + H CH2O + H2O
CH2O + H2 CH3OH
CH3OH + H2 CH4 + H2O
HCO3 + H + 4H2 CH4 + 3H20
13. Formation of methane from Acetate
• Methanosarcina barkeri is a classic and
representative species for those methanogenic
bacteria that utilize acetate, methanol and
methylamine as substrate.
• Formation of methane from acetate is a
oxidoreduction process.
• First CO and methyl co-enzyme M are produced
which is precursor of methane. CO2 is also
produced.
14. Formation of methane from Methanol and Methylamine
Methanogenesis of methanol and methylamine can be
subdivided into two process
• Oxidation of one fourth of the methyl groups to CO2.
• Reduction of three fourth of methyl groups into CH4.
• A methanol coenzyme M and trim ethylamine coenzyme M
methyltransferase have been characterized.
• The methyl group is first transferred to the protein bound 5
hydroxy benzimidazolycobamide.
• Methyl groups transfer further proceeds to coenzyme M.
15. Methanogens are widely used in anaerobic digesters to
treat wastewater as well as aqueous organic pollutants.
Industries have selected methanogens for there ability
to perform biomethanation during wastewater
decomposition there by rendering the process
sustainable and cost – effective.
16. Decomposers used in sewage treatment.
Use methane gas as biofuel.
Contribute in global warming.
Can oxidize iron.
Can form symbiotic relation with certain bacteria.
