Methanogens are archaea that obtain energy through the anaerobic synthesis of methane from carbon dioxide, hydrogen, or organic compounds like acetate. They are strict anaerobes that thrive in environments rich in organic matter like the rumen, wetlands, and sediments. Chemolithotrophs are prokaryotes that obtain energy from the oxidation of reduced inorganic compounds like hydrogen, ammonia, and sulfide while fixing inorganic carbon. They generate ATP through oxidative phosphorylation using electrons from inorganic molecules in their electron transport chain rather than organic nutrients. Methanogens and chemolithotrophs play important ecological roles in biogeochemical cycling through the removal and fixation of compounds.

1. PRESENTED BY --
M. NOONNY KHUMAN(17/BBT/05) SOHENA LASKA
ASHISH P. MAHANTA(17/BBT/60) TAHMINA MAZUMD

2. Contents
What are chemolithotrophs
Chemolithotrophy definition
Chemolithotrophy metabolism
II. Chemolithotrophy
I. Methanogens
What are Methanogens
Pathway for methane synthesis
III. Conclusion
IV. Reference

3. Methanogens

4. WHAT ARE METHANOGENS
•Strict anaerobes
•Obtain energy by converting CO2 , H2 ,
formate , methanol , acetate & other compounds
either methane or methane & CO2 .
•Ability to produce methane anaerobically.
•Autotrophic when growing on CO2 & H2 .
•Largest group of Archaea .
•Methanogens thrive in anoxic environment rich in
organic matter. The rumen and intestinal system of
animals , freshwater and marine sediment , swamps
and marches hotsprings , anoxic sludge digester and
anaerobic protozoa.

5. SIGNIFICANCE –
Energy source for heat and electricity .
Fuel.
ORDERS --
Based on overall shape , 16SrRNA sequence , cell wall
chemistry and structure , membrane lipids and other
features , methanogens can be divided into 5 orders –
i. Methanobacteriales
ii. Methanococcales
iii. Methanomicrobiales
iv. Methanosarcinales
v. Methanopyrales

6. MethanopyralesMethanosarcinales
Methanobacteriales Methanococcales

7. Unit co-factors of METHANOGENS -
i. H4MPT (Tetrahydromethanopterin)
ii. MFR (Methanofuran)
iii. Co-enzyme M(2 mercaptoethane sulphonic acid)
iv. Co enzyme F420 & F430
Pathways of Methane production –
i. Hydrogenotrophic
ii. Acetoclastic
iii. Methylotrophic

8. PATHWAY FOR METHANE SYSTHESIS FROM CO2 :-
CHOMFR- Formyl methanofuran CH3SCOM- Methyl sulphur coenzymeM
COM- 2marcaptoethane sulphonic acid or coenzymeM
H4MPT- Tetra hydroxy methanofuran / methanopterin
HSHTP- Marcaptoheptanoy theorenine phosphate
Co – factors – Methanopterin (MPT) , Methanofuran ( MFR)

9. Chemolithotrophy

10. • Certain groups of prokaryotes ,
obtain their energy from the oxidation of reduced
inorganic compounds such as sulfide, ammonia and
hydrogen, and use carbon dioxide as carbon
source. These organisms are
called chemolithotrophs or chemoautotrophs.
• The term "chemolithotrophy" refers to a cell’s
acquisition of energy from the oxidation of inorganic
compounds, also known as electron donors.
WHAT ARE CHEMOLITHOTROPHS

11. • Chemolithotrophs generate ATP through oxidative
phosphorylation.
• Organisms thrive in specific environments.
• Do not require external carbon source.
• These microbes obtain electrons for the electron
transport chain from the oxidation of inorganic
molecules rather than NADH generated by the
oxidation of organic nutrients.
• Much less energy is available from oxidation of
inorganic molecules than from the complete
oxidation of glucose to Co2

16. Chemolithotrophy
Metabolism

18. Conclusion
• Methanogens are responsible for the production of
methane in ruminants.
• Methanogens play a vital ecological role in anaerobic
environments by removing excess hydrogen and
fermentation products produced by other forms of
anaerobic respiration.
 Lithotrophs participate in many geological processes,
such as the formation of soil and the biogeochemical
cycling of carbon, nitrogen and other elements.
Lithotrophs also associate with the modern day issue of
acid mine drainage. Lithotrophs may be present in a
variety of environments, including deep terrestrial
subsurfaces, soils, mines and in endolith communities.

20. References
•http://www.els.net/WileyCDA/ElsArticle/refId-
a0021153.html
•https://openoregonstate.pressbooks.pub/microbiol
ogy/chapter/chemolithotrophy-nitrogen-
metabolism/
https://study.com/academy/lesson/methanogens-
definition-classification-examples.html
•https://en.wikipedia.org/wiki/Methanogen
•https://en.wikipedia.org/wiki/Hydrogen_oxidizing_b
acteria

22. 1. Methanogenic bacteria are Archaea that are –
a. Strict anaerobes that obtain energy through the synthesis of methane
b. Strict anaerobes that obtain energy through the consumption of methane
c. Strict aerobes that energy through the synthesis of methane
2. Which of the following have been suggested to be among the first living
organism to have developed ?
a. Methanococcus
b. Methanopyrales
c. Methylococcus
d. NOTA
3. Chemotrophs –
a. Are all heterotrophs
b. Are all autotrophs
c. NOTA
d. Maybe heterotrophs or autotrophs

23. 4. Microorganisms are classified into phototrophs and chemotrophs on the
basis of –
a. Carbon source
b. Energy source
c. Electron source
d. Nutrients
5. Chemotrophs obtain energy from organic or inorganic compounds by –
a. Oxidation b. Reduction c. Oxidoreduction d. Hydrolysis
6. Chemolithotrophic autotrophs include –
a. Sulphur oxidizing bacteria c. Nitrifying bacteria
b. Hydrogen bacteria d. All of the above
7. The microorganism which can use organic compounds as the sole energy,
carbon and electron sources are –
a. Photolithotrophic autotrophs
b. Chemoorganotrophic heterotrophs
c. Chemolithotrophic autotrophs
d. Photoorganotrophs