EBIO 3400 1st Edition Lecture 11Outline of Last Lecture I. Importance of growth Outline of Current Lecture II. Aerobic respiration/anaerobic respirationIII. Fermentation IV. How is ATP generated in fermenting microbes?V. Primary and secondary metabolismVI. Secondary metabolismCurrent LectureI. Aerobic respiration/anaerobic respirationA. Aerobic electron acceptor: Oxygen- Aerobic electron donor: waterB. Anaerobic electron acceptors: NO3, SO4, CO2, Fe (3+)- Anaerobic electron donors: NO, N2O, H2S, CH4, Fe (2+)C. Denitrification: Nitrogen goes from terrestrial and from oceanic back into the atmosphere - e acceptor: NO3- Reduced products: NO, N2O, N2D. Sulfate reduction- e acceptor: SO4- Reduced products: CH4E. Iron reduction- e acceptor: Fe (3+)- Reduced products: Fe (2+)F. Methanogensis- e acceptor: carbon dioxide - Reduced products: methane Note: The order in which e- acceptors are used in nature depends on the energy yield from them- O2 NO3 Fe (3+) SO4- Yield of energy goes down from oxygen then to the other electron acceptors- Less ATP per glucose as you go down: energy differenceThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- CO2 lousy electron acceptor, grow slowly in methanogens but live anaerobically so no other source besides CO2 because everything else has been used upII. Fermentation * Internally balanced oxidation-reduction reactionRegeneration of NAD+- Different from respiration because No e- transport system- Still all driven by movement of electrons (usually via regeneration of NAD+ as electron shuttle)- Regeneration of NAD+ without an e- transport system- Sugars are broken down to pyruvate using many - Different pathways in microbes (e.gEmbden-Meyerhoff Pathway (glycolysis, Entner-Doudoroff Pathway, Pentose-phosphate Pathway) - Simple fermentation: Some kind of substrate (sugar) being oxidized to some kind of product (A) passing electrons to NAD------Need to recycle electrons so dump them back on organic molecule and passed to another organic molecule but more reducedIII. How is ATP generated in fermenting microbes- Making ATP without an e- transport chain or ATPases…- Substrate-level phosphorylation: Phosphate group coming from organic molecule to make ATP and pyruvate as end product. ADP ATP (after being phosphorylated) - The generation of energy without electron transport systemsWhy does fermentation yield so little ATP?1) The carbon compounds are only partially oxidized2) The reduction potentials between primary electron donor and electron acceptor are smallChaim Weizmann- Figured out how to use Clostridium acetobutylicum to manufacture butanol from the fermentation of molasses and grain- Some Clostridium spp. ferment amino acids using the Stickland reaction: one amino acid is oxidized …another is the electron acceptor to restore NAD+- This organism live in nutrient rich environments where a lot of proteins are being brokendown----Bottom of ocean, pond- Many bacteria can biosynthesize all of their biomass from simple molecules (e.g. nitrate, phosphate, glucose etc)…..e.g. E. coli, Pseudomonas sp. Streptomycetes, can grow in media containing only a carbon compound and six inorganic salts…. - Extreme example some methanotrophs: eat methane, really good energy sources- CH4 protein polysaccharides, nucleic acids, co-factors (vitamins)- Others are more “fastidious” and require the presence of exogenous amino acids and other organic compounds, e.g. many pathogens and symbionts are fastidious- e.g. Some Neisseria spp. can only be grown in the lab in the presence of all 20 amino acids and 7 vitaminsIV. Primary and secondary metabolismA. “Primary Metabolism”= relates to the growth phaseB. Secondary Metabolism = metabolic pathways that are not involved in growth of cells take place when cells have stopped growing (e.gproduction of antibiotics by bacteria and fungi)Figure …. primary and secondary metabolic products (metabolites).- Production of Bacitracin by Bacillus licheniformis prior to endospore formation- Organisms stored glycogen in cytoplasm to carry out secondary metabolism getting ready for dormancy- End of Log phase is brought about by: Exhaustion of limiting nutrient or build up of toxins (e.g. alcohol in yeast culturesV. Secondary metabolism- Non-growth related metabolism, usually turned on by nutrient limitation or other stress that limits growth….1) Antibiotics2) Spore production for survival and dispersal3) Nutrient acquisition: a. Siderophores for iron
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