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Microbial Metabolism Metabolism of Rumen 1 Microbial Metabolism Metabolism of Rumen Microorganisms Ching-Tsan Huang (黃慶璨) Office: Agronomy Building, Room 111 Tel: (02) 33664454

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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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    Digestive Tract of Ruminants 瘤胃




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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


    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


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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

  • 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.


    Anaerobic Food Chains


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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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    Rumen High Fermentibility Carbohydrate

    Blood tissue


    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



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    N and P Flow Dynamics

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    RUMEN-UP RUmen Metabolism Enhanced by Naturally Using Plants

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