Methanogenic ArchaebacteriA

7/30/2019 Methanogenic ArchaebacteriA

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Sabyasachi Dasgupta

BTB/10/010


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They are the Oldest living Organisms that came into being 3.7

million years ago when Earth was not quite pleasant


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They Have a 3 Layered (Gramve ) or 2 layered(Gram +ve) Cell wall

They dont have any membrane bound organelles like mitochondria or

lysosomes

They have DNA spread into the cytoplasm condensed in an area called

Nucleoid

They have Small packets of DNA

called Plasmids

They have 16s rRNA Subunit

Have Pilli, Fimbriae and Flagella

Can thrive through extremes of

conditions


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Ms Residence


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CO2

H2Formate

Fermentation

CH4

CO2

+

Hence M family is

referred to as

Methanogens

because they

produce Methane.


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Group I

Group II

Group III

Methanobacteriu

m

Methanobrevibac

ter

Methanococcus

Methanospirilliu

m

Methanosarcina


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Genus: Methanobacterium Genus: Methanobrevibacter


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Mr. Methanobacterium byrantii

of

genus Methanobacterium


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Most Chemically Complex Cell wallamong Group I members

Tough and rigid composed of

Pseudomurein

Lacks D-Amino acids that is present

in the peptidoglycan of eubacteria

Resembles those of Gram +veBacteria and hence gives the +ve

result for Gram Reaction

It is Thick and Homogenous


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C20 diether

C40tetra

ether


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Morphologically rodshaped and filamentous32 50% G+C Stain +ve in GramReactionUses H2 + CO2 andformate asMethanogenic Substrates.


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Structure of Pseudomurein

Tough and rigid 3 layer cell wall.

Lacks D-Amino acids that is present

in the peptidoglycan of eubacteria

Resembles those of Gram +veBacteria and hence gives the +ve

result for Gram Reaction

It is Thick and Homogenous

Pseudomurein is present in the

innermost layer. The chemical

composition of the outer layers is

not yet known.


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C20 diether

C40tetra

ether


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27 32% G+C Stain +ve in Gram

ReactionUses H2 + CO2 only asMethanogenic Substrates. Straight or circular rodshapedMethanobrevibacter smithii.


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Flexible single layered cell wall

Its entirely made up of Proteins

Resembles those of Gram -ve

Bacteria and hence gives theve

strain result for Gram Reaction

It is Homogenous

Traces of Glucosamine is present


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C20 diether is the only component present as lipids in methanococcus


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30 32% G+C Stain +ve in GramReactionUses H2 + CO2 andformate asMethanogenic Substrates. Shaped as irregularshaped spheres (cocci)


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Group III

Genus Methanospirillium Genus Methanosarcina


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PPlug,

SSheath,

WCell wall,

AM Amorphous Matrix

It has the most complex

Cell Wall among theMethanogens

Two layered Cell Wall

Outer Wall made of

protein resistant toproteases and

detergents(SDS)

Sheath envelopes the

cells in a helical

trichome

Inner Layer is electron rich

Polar flagella may be present at both ends

allowing limited movements


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C20 diether

C40tetra

ether


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45 47% G+C Stain -ve in Gram

ReactionUses H2 + CO2 andFormate as

Methanogenic SubstrateCurved Rod or Spiralshaped


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Single thick and rigid Cell Wall

Made of heteropolysaccharides

which consists of galactosamine,

neutral sugars and muramic acids.

The Cell wall is acidic in Nature

Dont posses Envelope but cell wall is

laminar

Some contain a methanochondroitin

covering exterior to the S-Layer and

is sometimes called matrix.

The matrix plays an important role in

cell adhesion


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C20 diether is the only component present as lipids in methanococcus


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38 51% G+C Stain +ve in GramReactionUses H2 + CO2 ,CH3OH, Methylamineand Acetate as

Methanogenic SubstrateObserved as IrregularSpherical packets

M h


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MethanogenesisIt is the process of formation of Methane (CH4) by Methanogenic Bacteria from

substrates such as :i) H2

ii) CO2iii) Methanol

iv) Acetate

v) Formate etc.

With the help of Various Co-Factors and Co-Enzymes such as:

i) F420

ii) Coenzyme B

iii) Coenzyme M

iv) Methanofuran

v) Methanopterin

Two complex pathways exist that can be somewhat simplified as:

CO2 + 4 H2 CH4 + 2H2O

CH3COOH CH4 + CO2

M P


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Methanogenesis Pathway

Cofactor abbreviations:

1) Tetrahydromethanopterin

(H4MPT)

2) MethanopterinMPT

3) MethanofuranMFR

4) 2-mercaptoethanesulfonic

acid or coenzyme M

(CoM).


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The mechanism Relating Methanogenesis to ATP synthesis is still undiscovered

Classical Electron Transport chain is not involved

Energy Conservation is though to be mediated by a Chemiosmotic Membrane Potential

On collapsing the potential ATP concentration diminishes rapidly

Energy Yielding Reactions Performed by the Methanogens:

4H2 + HCO3- + H+ CH4 + 3H2O -33

4HCOO- + 4H+ CH4 + 3CO2 + 2H2O -35

4CH3OH 3CH2 + CO2 + H2O -76

4CH3NH3+ + 3H2O 3CH4 + 4NH4

+ + HCO3- + H+ -75

CH3COO- + H+ CH4 + CO2 -9

Reaction G (kcal/Mole)


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Out

InIn

Out

Cell Membrane2e-Hydrogenase

F420(Reduced)

F420(Oxidized)

2H+

H2

2H+


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In addition to oxidation of H2 coupled with the

reduction of CO2 methanogens are capable ofusing elemental sulfur as the electron acceptor

This process is called Sulphur Reduction

Methanogens belonging to Groups I and II cease

Methanogenesis when exposed to a sulphur

gradient and grown in its presence.

Group III methanogens continue Methanogenesis

simultaneously along with Sulphur Reduction

CO2 is their sole Carbon source and are hence

autotrophs

They are highly reducing in nature


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Actions of the M makes us do this but CH4

Can be very efficient and useful as a biofuel and waste treatment


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(Workplace of the M. Family)

Heating Coil

What does he do

In here???

Mr. Methanospirillium hungarii

Stays & Works

in here


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Street Lights

Runs on CH4

VolkswagenCH4 run vehicle

Mirant Kendall Regeneration Station


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Bibliography


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Bibliography

Textual References for this presentation on Ms Family has been collected from: i) Microbiology Lansing M. Prescottii) Wikipedia www.wikipedia.org

Visual and Photographic References have been taken from:i) www.wadsworth.org/resnres/bios/macario/ii) www.corbisimages.com
http://www.wikipedia.org/http://www.wikipedia.org/


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Methanogenic ArchaebacteriA