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Microbial Metabolism
Metabolism of Rumen
Microorganisms
Ching-Tsan Huang (黃慶璨)
Office: Agronomy Building, Room 111
Tel: (02) 33664454
E-mail: [email protected]
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Ruminants
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Digestive Tract of Ruminants
瘤胃
蜂巢胃
重瓣胃
皺胃
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1. Mastication and wetting of plant
feed
2. Supply of HCO3- and H2O (from
saliva and drinking)
3. Rumination
4. Release of fermentation gases
(CH4 and CO2)
Conditions:
Ox-red potential = -250 ~ -450 mV
pH 5.8 ~ 6.8
Temperature = 39 ~ 41oC
Osmolarity 400 mOsmol kg-1
Dry matter 10 ~ 18 %
Organisms: (g-1 rumen digesta)
Bacteria 1010 ~ 1011
Protozoa 105 ~ 106
Fungi 105 (thallus-forming units)
Fermentation products:
Acetate, Propionate, Butyrate,
CO2, CH4
MouthRumen-
reticulum
Digestive Tract
Diagram of Ruminants
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1. Selection of small plant particles and microbial
cells for transport to rest of digestive tract.
2. Absorption of liquids.
Gastric digestion – acid hydrolysis of
microbial biomass and some plant tissue.
Further microbial fermentation
Feces formation and removal of feces
containing viable bacteria and anaerobic fungi.
Used by animal tissues for energy,
biosynthetic reactions, and growth
Omasum
Abomasum-small intestine
Caecum
Large intestine
Rectum
Anus
Ruminant Digestive system
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Redox Potential of Microbial Growth
Anaerobic respiration
Aerobic respiration
Bacillus spp.
Escherichia coli
Clostridium spp.
Rumen microbes
Sulfate reducing bacteria
Methanogenic bacteria
+ 250 mV
0 mV
- 220 mV
- 250 mV
- 200 mV
ORP
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Genera Species Host
Neocallimastix N. frontalis
=N. variabilis
=N. patricarum
N. hurleyensis
Sheep
Sheep
Piromyces P. communis
P. mae
P. dombonica
P. spiralis
P. minutus
P. citronii
P. rhizinflatus
P. polycephalus
Sheep
Horse
Elephant
Katjang goat
Sika deer
Pony
Saharian ass
Water buffalo
Orpinomyces O. joyonii
=O. bovis
=N. joyonii
O. interalaris
Sheep
Water buffalo
Anaeromyces A. elegans
A. mucronatus
Cow
Sheep
Caecomyces
(Sphaeromonas)
C. communis
C. equi
Sheep
Horse
Cyllamyces C. aberensis Cow
Rumen fungi
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Mitochondrial Respiratory Complex
http://hobab.fc2web.com/sub4-mitochondria.htm
Organelles of mitochondrial origin.
Müller M et al. Microbiol. Mol. Biol. Rev. 2012;76:444-495
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Hydrogenosomes
Exist in different anaerobic eucaryotic organisms:
Parasitic protozoa
Free-living ciliates
Rumen ciliates
Anaerobic fungi
Membrane-surrounded organelles
Energy-generating organelles
They enable the organisms to perform an oxidative
metabolism following the initial glycolytic pathway
They produce molecular hydrogen by oxidizing pyruvate
or malate under anoxic conditions
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Biochemistry of Hydrogenosomes
Key enzymes of the hydrogenosome
• pyruvate:ferredoxin oxidoreductase
• hydrogenase
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Mitochondria Shared Hydrogenosomes
Pyruvate-DH
complex Malic enzyme Pyruvate:ferredoxin
TCA cycle Succinate thiokinase Oxidoreductase
Cytochrome
oxidase Adenylate kinase Hydrogenase
F0F1ATPase [2Fe-2S] ferredoxin
cardiolipin ATP-ADP exchange
Hydrogenosomes vs Mitochondria
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Biochemical Reaction in Rumens
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1. pyruvate:ferredoxin
oxidoreductase;
2. NAD-dependent malate
dehydrogenase
(decarboxylating);
3. NADH:ferredoxin
oxidoreductase activity
of the 51-kDa (Tvh-47)
and 24-kDa (Tvh-22)
catalytic flavoprotein
component of complex I;
4. ferredoxin-dependent
Fe-hydrogenase;
5. hypothetical NAD-
dependent 65-kDa Fe-
hydrogenase;
6. acetate:succinate CoA-
transferase;
7. succinate thiokinase
Nature 432, 618-622 (2 December 2004)
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Metabolism of VFA in
ruminants in relation to
the availability of ATP
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All organic material is
metabolized to methane
via a few methanogenic
substrates: CO2 + H2,
acetate, formate,
methanol, and
methylamines.
Methanogenesis:
Anaerobic Food Chains
Methanogenesis
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(Mackie et al.,1991)
Three-stage for
complete anaerobic
degradation
Fermentative bacteria
hydrolyze and ferment
carbohydrates, proteins,
lipids and other
macromolecules.
These compounds are
degraded by a second
group of bacteria called the
obligate H2-producing
acetogenic microbes.
Methanogens reduce CO2
to CH4 using H2 produced
by other bacteria, and they
also cleave acetate to CH4
and CO2.
Reconstruction of C1A hydrogenosome from genomic data.
Youssef N H et al. Appl. Environ. Microbiol. 2013;79:4620-
4634
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http://210.105.65.2/information/images/ohp_08.gif
Rumen
High
Fermentibility
Carbohydrate
Blood tissue
Feces
Fate of Carbohydrates in Ruminants
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Food Energy
Digestible
Energy
Metabolisable Energy
Faecal
Energy
Methane
Energy
Urine
Energy
Energy for
Production
Energy for
Maintenance
0.35-0.89
0.81
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N and P Flow Dynamics
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http://www3.unileon.es/dp/dp1/EUROPA/rumup.html
RUMEN-UP
RUmen Metabolism Enhanced by Naturally Using Plants
