L3 Microbial Metabolism PDF

L3: Microbial metabolism BIO-440 Jan 21, 2025 By Dr. Anny Cárdenas Assistant Professor, Department of Biology 1 Content Topic 1: Introduction to metabolism: Metabolic classification of microorganisms Topic 2: Chemoorganotrophs: Glucose oxidation vs f...

L3: Microbial metabolism BIO-440 Jan 21, 2025 By Dr. Anny Cárdenas Assistant Professor, Department of Biology 1 Content Topic 1: Introduction to metabolism: Metabolic classification of microorganisms Topic 2: Chemoorganotrophs: Glucose oxidation vs fermentation Topic 3: Electron transport and metabolic diversity: anaerobic respiration and examples of chemolithotrophy Topic 4: Anabolic reactions: autotrophy Life begins with microbial metabolism Bacteria 3.5-2.7 billions and years ago archaea Brock 16th edition, ©Pearson Microbial life has a common set of requirements in termsofmetabolis 3 Source of 1 energy Water 2 4 Source of Source of carbon electrons Metabolism: series of biochemical reactions needed to sustain life to big smallsubstrates rea smalltobigsubstrates Catabolism: biochemical reactions to drive Anabolism: biochemical reactions to drive the synthesis of ATP (exergonic) the biosynthesis of cellular material Brock 16th edition, ©Pearson Redox reactions: series of biochemical reactions needed to sustain life nvong.si i Iaminded Gain of e- Loss of e- Gain of e- Brock 16th edition, ©Pearson Reducing power/potential: is the ability to donate electrons during electron transfer reactions (redox reactions) Oxidation of glucose to CO2 Test glucose electrofonors Brock 16th edition, ©Pearson Electron transfer reactions Redox reactions can be understood in terms of reduction potential, which measures the affinity of a substance for electrons. Electron transfer reactions Strongest electron donors Strongest electron acceptors elections receive Electron transfer reactions The greater the difference in reduction potential between electron donor and electron acceptor, the greater the free energy released. Electron transfer reactions  Electron carriers The NAD+/NADH pair has a reduction potential of -0.32 V  Metabolic classes of microbes plants Electron source Organisms that obtain Organisms that obtain their electrons from their electrons from organic molecules are inorganic molecules are called called chemolithotrophs chemoorganotrophs Brock 16th edition, ©Pearson Metabolic classes of microbes Classification of metabolic types based on carbon sources Carbon source anomans Heterotrophs Autotrophs use moan obtain carbon for carbon dioxide (CO2) biosynthesis of as its carbon source to molecules from an build biomass organic compound  heterotroph Chemorgano What metabolic classification is given to an organism that requires organic substrates for its carbon source to grow and develop, and obtains energy and electrons from the decomposition of organic compounds? What metabolic classification is given to an organism that requires light for energy, inorganic substrates as electron sources and CO2 as carbon source? autotroph Photolitho  Chromatium autotrophs typesof Photolitho What metabolic classification is given to an organism that requires light for energy, inorganic substrates as electron sources and CO2 as carbon source? Chemoorganotrophs: use organic molecules to fuel metabolism Fermentation: is a form of anaerobic catabolism in which organic compounds both donate electrons and accept electrons, and redox balance is achieved without the need for external electron acceptors. Respiration: is a form of aerobic or anaerobic catabolism in which an electron donor, organic or inorganic*, is oxidized using an external electron acceptor such as O2(aerobic) or some other compound (anaerobic)  Chemoorganotrophs: use glucose to fuel metabolism Glycolysis: glucose is oxidized to pyruvate Glyceraldehyde 3-phosphate 2 ATPPut interaction Stage 1 reaction redox Stage 2 trans S nosphate  Chemoorganotrophs: use glucose to fuel metabolism Glycolysis: glucose is oxidized to pyruvate Glyceraldehyde 3-phosphate Stage 1 Stage 2 NET YIELD: 2 ATP, 2 molecules of NADH, 2 molecules of pyruvate The Citric Acid Cycle (Krebs cycle): cyclical series of reactions resulting in the conversion of three molecules of CO2 The Citric Acid Cycle (Krebs cycle): cyclical series of reactions resulting in the conversion of three molecules of CO2 NET YIELD: 1 ATP, 4 molecules of NADH, 1 molecule of FADH2 and 3 molecules of CO2 per Acetyl-CoA Fermentation Substrate-level phosphorylation occurs when a phosphate group is transferred from a high-energy substrate to ADP. Results in the production of ATP Butyric acid fermentation by Clostridium butyricum AcetylCoA redugdfate Butyrate Gut barrier integrity usedforguthealth Anti-inflammatory effects antiinflammatory Modulate low pH  Chemotrophs Organotrophs: Use glycolysis and fermentation Use respiration Jelection teapot Respiration: process in which chemical energy from redox reactions is conserved by using electron transport reactions to pump protons (or other ions) across a membrane. Electrons are transferred from reduced donors to external electron acceptors Electron transport takes place within the cytoplasmic membrane*, culminating in the reduction of an external electron acceptor and the formation of an electrochemical gradient across the membrane.  outoffell Electrons from NADH and FADH2 are passes through complexes I-IV in cell The transferred through a series of carriers, such as flavoproteins, quinones, iron-sulfur proteins, and cytochromes. Energy from electron transfer is used to pump protons (H⁺) across the plasma membrane, creating a proton gradient. hightoo'Entiations The proton gradient drives ATP synthase to produce ATP outside membrane F1 F0 aᵗhhne to  typicallycytochrome The final acceptor depends on the organism and environment: Aerobic conditions: Oxygen is the terminal acceptor, forming water. Anaerobic conditions: Other molecules like nitrate, sulfate, or fumarate serve as acceptors. Energetics in fermentation and aerobic respiration Electron transport chain and metabolic diversity Anaerobic respiration in E. coli (facultative anaerobe) Aerobic Anaerobic in the presence of nitrate Nitrate reduction (first step of denitrification) Chemolithotrophy: inorganic compounds are the source of electrons First step in chemolithotrophic metabolisms begin with the oxidation of an inorganic electron donor and with the electrons entering an electron transport chain. thatcan enzymes Membrane Hydrogenase that splits H2 Ralstonia eutropha uses H2 as electron donor Soluble Hydrogenase reduces NAD+ Phototrophy: light energy is used instead of chemical reactions to drive electron flow and generate proton motive force Oxygenic photosynthesis: oxygen is produced from the oxidation of water finalaccepterElections Anoxygenic photosynthesis: oxygen is not produced. As a consequence, there is only photosystem I waternot 9198 Phototrophy: light energy is used instead of chemical reactions to drive electron flow and generate proton motive force Autotrophy: source of carbon is CO2 Calvin cycle: series of biosynthetic reactions by which some organisms convert CO2 into organic compounds Mainly present in photosynthetic, most chemolithotrophic bacteria, and a few archaea. The key enzyme complex of Calvin cycle is Rubisco. It consists of 16 polypeptides with 8 active sites where CO2 is fixed automorsphric CO2 Calvin cycle Nitrogen fixation is the process by which certain Bacteria and Archaea convert atmospheric nitrogen (N 2) into ammonia (NH3) Catalyzed by the enzymatic complex nitrogenase. Nitrogenase consists of two proteins, dinitrogenase and dinitrogenase reductase Iron–molybdenum cofactor (FeMo-co) Both proteins contain iron, and dinitrogenase contains molybdenum as well  fromglycolysis Nitrogen fixation coming Dinitrogenase reductase receives electrons from Flavodoxin (Fdx) and then transferers them to Dinitrogenease that catalyzes the reaction using ATP  Nitrogen fixation Azotobacter vinelandii produces slime to protect cells from O2 Cyanobacterium Anabaena showing a single heterocyst (green). The heterocyst is a thick-walled differentiated cell that specializes in nitrogen fixation and protects nitrogenase from O2 inactivation. nation Questions? 46