microbial metabolism metabolism of rumen …cthuang.bst.ntu.edu.tw/microbialmetabolism/mm9-ppt.pdf1...

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Microbial MetabolismMetabolism of Rumen MicroorganismsChing-Tsan Huang (黃慶璨)Office: Agronomy Building, Room 111Tel: (02) 33664454E-mail: cthuang@ntu.edu.tw

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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. Rumination4. Release of fermentation gases

(CH4 and CO2)Conditions:Ox-red potential = -250 ~ -450 mVpH 5.8 ~ 6.8Temperature = 39 ~ 41oCOsmolarity 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 TractDiagram 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

CaecumLarge intestine

RectumAnus

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 HostNeocallimastix N. frontalis

=N. variabilis=N. patricarumN. hurleyensis

SheepSheep

Piromyces P. communisP. maeP. dombonicaP. spiralisP. minutusP. citroniiP. rhizinflatusP. polycephalus

SheepHorseElephantKatjang goatSika deerPonySaharian assWater buffalo

Orpinomyces O. joyonii=O. bovis=N. joyoniiO. interalaris

SheepWater buffalo

Anaeromyces A. elegansA. mucronatus

CowSheep

Caecomyces(Sphaeromonas)

C. communisC. equi

SheepHorse

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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HydrogenosomesExist in different anaerobic eucaryotic organisms:

Parasitic protozoaFree-living ciliatesRumen ciliatesAnaerobic fungi

Membrane-surrounded organellesEnergy-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 HydrogenosomesKey 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:ferredoxinoxidoreductase;

2. NAD-dependent malate dehydrogenase (decarboxylating);

3. NADH:ferredoxinoxidoreductase activity of the 51-kDa (Tvh-47) and 24-kDa (Tvh-22) catalytic flavoproteincomponent of complex I;

4. ferredoxin-dependent Fe-hydrogenase;

5. hypothetical NAD-dependent 65-kDa Fe-hydrogenase;

6. acetate:succinate CoA-transferase;

7. succinate thiokinaseNature 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 bacteriahydrolyze 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 CO2to CH4 using H2 produced by other bacteria, and they also cleave acetate to CH4and 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

RumenHigh Fermentibility Carbohydrate

Blood tissue

Feces

Fate of Carbohydrates in Ruminants

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Food Energy

DigestibleEnergy

Metabolisable Energy

FaecalEnergy

MethaneEnergy

UrineEnergy

Energy forProduction

Energy forMaintenance

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-UPRUmen Metabolism Enhanced by Naturally Using Plants