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