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Metabolism of  organic  matter
 

Metabolism of organic matter

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    Metabolism of  organic  matter Metabolism of organic matter Presentation Transcript

    • METABOLISM OF ORGANIC ANDINORGANIC MATTER Gunjan Mehta Deptt. of Biotechnology, Virani Science College, Rajkot
    • Metabolism of Organic matter1. Fermentation 2. Respiration 1. Fermentation:“Special kind of redox reaction in which both electrondonors and acceptors are organic in nature”. Internally generated organic compounds such as pyruvic acid can serve as electron acceptor when external electron acceptor is absent. Reduced compounds produced during such reactions are secreted in extracellular. Fermentation yields less amount of ATP molecules than respiration, as in fermentation reaction organic compounds can’t be fully oxidized to CO2 & H2O.
    • Fermentation In Fermentation, the organic compounds are simply rearranged into a form containing less energy than the organic substrate. Fermentation generate few ATPs per molecule of substrate than respiration, hence more substrate molecules should be metabolize during it. ATP synthesis during fermentation is substrate level phosphorylation and remains largely restricted to amount formed during glycolysis. Chemiosmotic synthesis and oxidative phosphorylation of ATP don’t occur in fermentation.
    • Fermentation
    • Respiration “Biochemical process in which organic compound serve as electron donor while external compound serve as terminal electron acceptor”.
    • Aerobic Respiration When O2 serve as terminal electron acceptor.
    • Anaerobic respiration Instead of O2 other inorganic compound serve as terminal electron acceptor. Anaerobic Terminal Product Example Metabolism Electron acceptor Anaerobic Fe3+, S Fe2+, Denitrifiers, respiration H2S Sulfur reducers etc Denitrification NO3-, NO2- NO2, Paracoccus N2O, N2 denitrifucans Sulfate SO42- H2S Desulfovibrio reduction desulfuricans Methanogenes CO2 CH4 Methanococccus
    • Aerobic Vs Anaerobic respiration Aerobic respiration is very imp process in bioremediation as various organic compounds will be fully oxidized and converted to inorganic minerals. In bacteria this procedure involves enzymes capable of adding O2. 1. Monooxygenase- one O2 molecule 2. Dioxygenase- two O2 molecule Anaerobic respiration: Carried out by obligatory anaerobes and facultative anaerobes. O2 will be given preference.
    • Fermentation vs Respiration Respiration is more efficient than fermentation because of following reasons… 1. The difference in reducing potential between the primary electron donor and terminal electron acceptor is high. 2. In respiration complete oxidation of organic matter will occur compared to fermentation where incomplete oxidation will occur.
    • Metabolism of Inorganic matter 1. Nitrate reduction 2. Sulfate reduction 3. Lithotrophy: a) Hydrogen bacteria b) Sulfur bacteria Mainly followed during anaerobic respiration by Nitrate reducing bacteria, Sulfate reducing bacteria and many other lithotrophic bacteria. These metabolic pathways are the most integral parts of Biogeochemical cycles.
    • Nitrate reduction/ Denitrification Nitrate reduction takes place through both assimilatory and dissimilatory cellular functions. Assimilatory denitrification: nitrate is reduced to ammonia, which then serves as a nitrogen source for cell synthesis. Thus, nitrogen is removed from the liquid stream by incorporating it into cytoplasmic material. Dissimilatory denitrification: nitrate serves as the electron acceptor in energy metabolism and is converted to various gaseous end products but principally molecular nitrogen, N2, which is then stripped from the liquid stream. A relatively small fraction of the nitrogen is removed through assimilation. Dissimilatory denitrification is, therfore, the primary means by which nitrogen
    • Nitrate reduction A carbon source is also essential as electron donor for denitrification to take place.. Denitrification releases nitrogen which escapes as an inert gas to the atmosphere while oxygen released stays dissolved in the liquid and thus reduces the oxygen input needed into the system. Each molecule of nitrogen needs 4 molecules of oxygen during nitrification but releases back 2.5 molecules in denitrification. Thus, theoretically, 62.5% of the oxygen used is released back in denitrification.
    • Assimilatory denitrification Nitrate is reduced to ammonia, which then serves as a nitrogen source for cell synthesis. Thus, nitrogen is removed from the liquid stream by incorporating it into cytoplasmic material.
    • Assimilatory denitrification
    • Assimilatory denitrification Since oxidation state of nitrogen in nitrate is +5 and in ammonia it is -3. Total 8 e- must be transferred to nitrate in order to reduce it to ammonia.
    • Dissimilatory denitrification In dissimilatory denitrification, nitrate serves as the electron acceptor in energy metabolism and is converted to various gaseous end products but principally molecular nitrogen, N2, which is then stripped from the liquid stream. Dissimilatory denitrification is the primary means by which nitrogen removal is achieved.
    • Dissimilatory denitrification
    • Dissimilatory denitrification Nitrogenous oxides, principally NO3-, NO2- are used as terminal electron acceptor in the absence of O2 and reduced molecular nitrogen N2 during microbial metabolism. Enzymes for denitrification procedure are oxygen sensitive and works under anaerobic condition. All denitrifying organisms are facultative anaerobes such as Pseudomonas and Alcaligens. Achromobacter, Vibrio, Flavobacterium
    • Sulfate reduction SO42-( most oxidized form of S) can be used as terminal electron acceptor by a specialized group of microbes which are known as Sulfur reducing bacteria…. SO42- first reduced to sulfite(SO3- ) and then to sulfide(H2S) or S2- and then incorporated into Cysteine. The oxidation level of S in SO42- is (+6) and in sulfide it is (-2), so total 8 electrons are required to reduce SO42- to S2-. Gram +ve: Desulfotomaculum Gram –ve: Desulfovibrio
    • Assimilatory sulfate reduction Adenosine-PO2-PO2-PO3+ SO42- -PPi ATP sulfurylase Adenosine- PO3 –SO3 Adenosine phosphosulfate (APS)/ AMP-SO2 APS phosphorylase Phosphoadenosine phosphosulfate/ SO3- -AMP- SO2 -AMP-3’-P PAPS reductase SO3-2
    • Assimilatory sulfate reduction SO3-2 3NADPH3NADP Sulfite reductase H2S +O- acetyl serine -acetate acetyl serine sulfhydrilase L- Cysteine
    • Assimilatory sulfate reduction
    • Assimilatory sulfate reduction There is sound thermodynamic reason behind the formation of APS, which is AMP derivative of sulfate. The reduction potential of sulfate can be increased by attaching AMP, which makes it a better electron acceptor than free sulfate. Formation of PAPS: The reductant is sulfhydryl protein called thioridoxin, which accepts e- from NADPH. 3 ATP molecules are used: a. 2 ATP for PAPS
    • Dissimilatory sulfate reduction Dissimilation of sulfate is very rare as it yields less amount of energy than any alternative e- donor as nitrate or oxygen. Since energy influences growth and metabolism of these SRBs, it shows slow growth.
    • Comparative pathways
    • Lithotrophy The study of metabolism of organism using reduced inorganic material is called lithotrophy. CO2- Lithoautotrophs(Most of) H2, NH3, H2S, NO2, Fe+2, CO- Lithotrophs(Some) Consist of one of the major class of autolithotrophs and very important for it.
    • Classification of lithotrophs 1. Hydrogen bacteria:e- donor e- Final Example acceptor Product H2 O2 H2O Alkaligens eutrophus Sulfur oxidizing bacteria: e- e- Final Example donor acceptor Product H2S, O2 SO42- Thiobacillus thioxidans, S2-, Baggiatoa
    • Classification of lithotrophs 3. Iron oxidizing bacteria e- e- Final Exampledonor acceptor Product Fe+3 O2 SO42- Thiobacillus thioxidans, 4. Nitrogen oxidizing bacteriaa. Ammonia oxidizing: e- e- Final Exampledonor acceptor ProductNH4+ O2 N2O, NO-, Nitrosomonas eutropy 2 3-
    • Classification of lithotrophs 3. Iron oxidizing bacteria e- e- Final Exampledonor acceptor Product Fe+3 O2 SO42- Thiobacillus thioxidans, 4. Nitrogen oxidizing bacteriaa. Ammonia oxidizing: e- e- Final Exampledonor acceptor ProductNH4+ O2 N2O, NO-, Nitrosomonas eutropy 2 3-
    • Classification of lithotrophs b. Nitrite oxidizing: e- e- Final Exampledonor acceptor Product NO2- O2 NO3- Nitrobacter winograsky 5. Methanogens e- e- Final Exampledonor acceptor Product H2 CO2, CH4 Methanococcus spp Acetate, Methyl
    • Classification of lithotrophs 6. Methylotrophs e- e- Final Exampledonor acceptor Product CH4 CO2 Organic Methylococcus compound
    • Hydrogen bacteria Facultative lithotrophs Also known as hydrogen oxidizing bacteria capable of utilizing H2 as source of energy. Majority of these bacteria are aerobic capable of utilizing O2 as terminal e- acceptor. However they are not purely dependent on H2 as energy source but are capable of utilizing other organic sources. That’s why it is facultative lithotrophs. CO2+ 2H2[CH2O]n+H2O
    • Sulfur oxidizing bacteria It includes….1. Photosynthetic sulfur oxidizers: Green sulfur bacteria & purple sulfur bacteria2. Non- Photosynthetic sulfur oxidizers: colourless sulfur bacteria such as Baggiatoa, Thiothrix Almost all are gram –ve e- donors for SOBs: H2S, S2-, S2O3 Comprises physiologically diverse group of bacteria:1. Obligatory autotrophs(CO2- sole C source)2. Facultative heterotrophs(Mixotrophic) Eg:
    • Sulfur oxidizing bacteria On the basis of pH requirement:1. Neutrophile: pH= 7.02. Acidophile: pH= 1- 5 (Thiobacillus thioxidans) S2-/ H2S [S]- linear polysulfate Sulfur oxidase/ sulfite oxidase SO32- APS APS SO42-
    • Sulfur oxidizing bacteria Few sulfur oxidizing bacteria are archaebacteria such as Sulfolobus. Lives on sulfur rich spring- hot spring in temperature range upto 90º C and pH=1. H2S+2CO2 SO42- + 2H+ S+ H2O+O2  SO42-+ 2H+ S2O3+ H2O+2O2 SO42- + 2H+