Microbial Metabolism Lecture Notes PDF

5 Microbial Metabolism Learning Objective 5-7 Compare and contrast aerobic, anaerobic respiration and fermentation. 5-8 Provide an example of the use of biochemical test to identify bacteria in the laboratory. 5-9 Summarize energy production in cells 5-10 Describe the major type...

5 Microbial Metabolism Learning Objective 5-7 Compare and contrast aerobic, anaerobic respiration and fermentation. 5-8 Provide an example of the use of biochemical test to identify bacteria in the laboratory. 5-9 Summarize energy production in cells 5-10 Describe the major types of anabolism and their relationship to catabolism. Anaerobic Respiration The final electron acceptor in the electron transport chain is NOT O2 Yields less energy than aerobic respiration Electron Acceptor Products NO3– NO2–, N2 + H2O SO4– H2S + H2O CO32 – CH4 + H2O Fermentation Releases energy from the oxidation of organic molecules Does not require oxygen Does not use the Krebs cycle or ETC Uses an organic molecule as the final electron acceptor Produces only small amounts of ATP  Lactic acid Alcohol fermentation: fermentation: produces lactic acid produces Homolactic ethanol + CO2 fermentation: produces Glucose is oxidized to lactic acid only Heterolactic pyruvic acid; pyruvic fermentation: produces acid is converted to lactic acid and other acetaldehyde and compounds CO2; NADH reduces Glucose is oxidized to acetaldehyde to pyruvic acid, which is ethanol then reduced by NADH Fermentation Figure 5.18b Fermentation. Biochemical Tests and Bacterial Identification Fermentation test: bacteria that catabolize carbohydrate or protein produce acid, causing the pH indicator to change color Oxidase test: identifies bacteria that have cytochrome oxidase (e.g., Pseudomonas) protein + a carbohydrate mannitol +a pH indicator in tubes Microorganism No S. epidermidis S. aureus E. coli Results (-) mannitol (-) mannitol (+) mannitol (+) Products Acid Acid and gas Figure 5.11 An Overview of Respiration and Fermentation. Protein Catabolism (proteases and peptidases) Extracellular proteases Protein Amino acids Deamination, decarboxylation, dehydrogenation, desulfurization Organic acid Krebs cycle Lipid Catabolism Figure 5.21 Catabolism of various organic food molecules. Photosynthesis Light-dependent (light) reactions: conversion of light energy into chemical energy (ATP and NADPH) Light-independent (dark) reactions: ATP and NADPH are used to reduce CO2 to sugar (carbon fixation) via the Calvin-Benson cycle Oxygenic:  Figure 5.25a Photophosphorylation. Electron transport chain Light Excited electrons (2 e–) Electron carrier In Photosystem I Cyclic photophosphorylation Metabolic Diversity among Organisms Phototrophs use light energy Chlorophyll ETC Chlorophyll oxidized ADP + P ATP Photoautotrophs use energy in the Calvin-Benson cycle to fix CO2 to sugar Oxygenic: produces O2 Anoxygenic: does not produce O2 Photoheterotrophs use organic compounds as sources of carbon Chemoautotrophs Use energy from inorganic chemicals; CO2 as carbon source Energy is used in the Calvin-Benson cycle to fix CO2 Chemoheterotrophs Use energy and carbon from organic chemicals Glucose NAD+ ETC Pyruvic acid NADH ADP + P ATP  Metabolic Diversity among Organisms Nutritional Type Energy Source Carbon Source Example Photoautotroph Light CO2 Oxygenic: Cyanobacteria, plants Anoxygenic: Green bacteria, purple bacteria Photoheterotroph Light Organic Green bacteria, purple compounds nonsulfur bacteria Chemoautotroph Inorganic CO2 Iron-oxidizing bacteria Chemical Chemoheterotroph Chemical Organic Fermentative bacteria compounds Animals, protozoa, fungi, bacteria Metabolic Pathways of Energy Use Figure 5.29 The biosynthesis of polysaccharides. ADPG: adenosine diphosphoglucose UDPG: uridine diphosphoglucose UDPNAc: UDP-N-acetylglucosamine Figure 5.30 The biosynthesis of simple lipids. Figure 5.31a The biosynthesis of amino acids. Intermediates in the Krebs cycle An amino acid An amino acid Figure 5.32 The biosynthesis of purine and pyrimidine nucleotides. The Integration of Metabolism Amphibolic pathways: metabolic pathways that function in both anabolism and catabolism Many pathways function simultaneously with common intermediates Figure 5.33 The integration of metabolism.