MCB 100 Introductory Microbiology March 1 2019 Chapter

MCB 100 Introductory Microbiology March 1, 2019 Chapter 5 - Microbial Metabolism

Glycolysis and Krebs Cycle Redox Reactions Summarized C 6 H 12 O 6 + 6 H 2 O + 10 NAD+ + 2 FAD 6 CO 2 + 10(NADH + H+) + 2 FADH 2 (cell has gained 4 ATPs)

Redox Reactions of the Electron Transport Chain Summarized 10(NADH + H+) + 2 FADH 2 + 6 O 2 12 H 2 O + 10 NAD+ + 2 FAD Aerobic Respiration of Glucose C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O

Glucose Catabolism by Aerobic vs. Anaerobic Respiration Glycolysis, Pyruvate Dehydrogenase Reaction and Krebs Cycle C 6 H 12 O 6+6 H 2 O+10 NAD++2 FAD 6 CO 2+10(NADH + H+)+2 FADH 2 In aerobic respiration an ETC is used to make a PMF. 2 NADH + 2 H+ + O 2 2 NAD+ + 2 H 2 O In anaerobic respiration an ETC is used to make a PMF. NADH + H+ + NO 3 - NAD+ + H 2 O + NO 2 -

Anaerobic Respiration Choose the FALSE statement. A. Anaerobic respiration is a form of metabolism that is used by animals and plants as well as by some bacteria. B. In anaerobic respiration, most of the ATP is made by a membrane-bound ATP synthase that uses a proton motive force gradient. C. In anaerobic respiration the terminal electron acceptor is an oxidized mineral such as nitrate or sulfate. D. In anaerobic respiration the proton motive force gradient is created by the reactions of a membranebound electron transport chain.

Anaerobic Respiration Choose the FALSE statement. A. Anaerobic respiration is a form of metabolism that is used by animals and plants as well as by some bacteria. FALSE anaerobic respiration is not seen in animals or plants B. In anaerobic respiration, most of the ATP is made by a membrane-bound ATP synthase that uses a proton motive force gradient. C. In anaerobic respiration the terminal electron acceptor is an oxidized mineral such as nitrate or sulfate. D. In anaerobic respiration the proton motive force gradient is created by the reactions of a membranebound electron transport chain.

Alternatives to Aerobic Respiration (Seen in Chemoheterotrophic Microorganisms) Fermentation food source = organic matter (sugars etc. ) final oxidizing agent = an organic compound Major means of ATP production: substrate level phosphorylation

Anaerobic Chemohetrotrophic Metabolism Fermentation - ATP is generated by Substrate Level Phosphorylation - terminal electron acceptors are organic compounds - anaerobic - does not require light - does not require an oxidized mineral - inefficient, extracts only a fraction of the potential energy in the food molecules examples: LACTIC ACID FERMENTATION ETHANOL FERMENTATION Yield: 2 ATPs per glucose consumed For more about fermentation see pages 146 – 149, esp. figures 5. 21 and 5. 22.

Examples of Fermentation Products Lactic Acid Made by a variety of bacteria including Lactobacilli and Lactococcus that are used in cheese and yogurt production and Streptococcus that play a role in tooth decay. Ethanol Made by bacteria and fungi, especially yeasts. Carbon Dioxide Made by many bacteria and fungi as a by product of ethanol formation. Acetic Acid Made in the mixed acid fermentation by many bacteria and made by Acetobacter and Gluconobacter strains that are used to produce vinegar. Vinegar production is a two step process: first, yeast are used anaerobically to produce ethanol from sugar in the apple juice, then, Gluconobacter and Acetobacter species are used aerobically to partially oxidize the ethanol to acetic acid. Gluconobacter and Acetobacter carry out a form of incomplete aerobic respiratory metabolism, they use oxygen, but they don’t fully oxidize the ethanol. Propionic Acid This three carbon fatty acid is found in small amounts in Swiss cheese. Butyric Acid, Acetone, Isopropanol, Butyraldehyde A variety of 3 – 4 carbon organic solvents are produced by various anaerobic bacteria, especially in the genus Clostridium. Some of these solvents are used for cleaning agents, paint thinners and solvents for the production of munitions. 2, 3 -Butanediol Made by many species of bacteria, detected by the Vogues-Proskaur test.

Aerobic Respiration, Anaerobic Respiration and Fermentation ATP can be made in the absence of non-combined oxygen (O 2) by the reactions of: A. B. C. D. E. fermentation only aerobic respiration only anaerobic respiration only both fermentation and aerobic respiration both anaerobic respiration and fermentation

Alternatives to Aerobic Respiration (Seen in Autotrophic Microorganisms) Photosynthesis carbon source = carbon dioxide or carbonate (CO 2 fixation by the Calvin cycle, the dark reactions of photosynthesis) Major means of ATP production: Light Reactions of Photosynthesis ETC & PMF

PHOTOAUTOTROPHY (aka photosynthesis) (energy from light, carbon from CO 2) - Oxygenic Photosynthesis: 6 CO 2 + 6 H 2 O + light C 6 H 12 O 6 + 6 O 2 - Anoxygenic Photosynthesis: 6 CO 2 + 12 H 2 S + light C 6 H 12 O 6 + 12 S 0 + 6 H 2 O

Photosynthesis – The Light Reactions Generates ATP and NADPH ATP is used as a source of energy needed to convert carbon dioxide to sugar NADPH is used as a reducing reagent

Photosynthesis – Dark Reactions: The Calvin cycle is used for fixation of carbon in both photoautotrophic and chemoautotrophic organisms. Making sugar from CO 2 requires ATP (energy) and NADPH (reducing power).

Photosynthesis Which one of the following statements is TRUE? A. Carbon dioxide is converted to organic substances by the reactions of the Calvin cycle. B. Carbon dioxide is converted to organic substances by the light reactions of photosynthesis. C. The reactions of the Calvin cycle require the presence of non-combined oxygen (O 2). D. The production of ATP by the light reactions of photosynthesis is done by substrate-level phosphorylation. E. Reactions of the Calvin cycle require photons of light.

Alternatives to Aerobic Respiration (Seen in Chemoautotrophic Microorganisms) Aerobic & Anaerobic Chemoautotrophs carbon source = carbon dioxide or carbonate (CO 2 fixation by reactions that are similar to those of the Calvin cycle, the dark reactions of photosynthesis) Major means of ATP production: Inorganic Chemical Reactions involving an ETC & PMF

CHEMOAUTOTROPHY (energy from inorganic redox reaction, carbon from CO 2) - Ammonia oxidation: - Nitrite oxidation: - Iron reduction: - Sulfate reduction: - Sulfide Oxidation: - Methanogenesis: NH 3 + 1. 5 O 2 HNO 2 + H 2 O HNO 2 + 0. 5 O 2 HNO 3 2 Fe+2 + ½ O 2 + 2 H+ 2 Fe+3 + H 2 O 2 Fe+3 + H 2 2 Fe+2 + 2 H+ H 2 SO 4 + 4 H 2 H 2 S + 4 H 2 O H 2 S + 2 O 2 H 2 SO 4 CO 2 + 4 H 2 CH 4 + 2 H 2 O Chemoautotrophic metabolism requires some reduced compound plus some oxidized compound as starting materials for a redox reaction that yields energy so ATP and NADPH can be made. The Calvin cycle is used to assimilate CO 2.

Electron Transport Systems from Chemoautotrophic Bacteria The Electron Transport System in Sulfide Oxidizing Bacteria Energy Production in Nitrosomonas: Oxidation of Ammonia to Nitrite from: Timothy Paustian University of Wisconsin-Madison

Another Example of Chemolithotrophic Metabolism Hydrogen Sulfide Oxidation Some species of bacteria in the genera Thiobacillus, Rhodopseudomonas and Beggiatoa, can use H 2 S as the reducing reagent in chemoheterotrophic energy production. The overall chemical reaction is: H 2 S + 2 O 2 H 2 SO 4 Deep Ocean Volcanic Vent An electron transport chain is involved in a series of redox reactions. ATP is made by using the proton gradient that is generated by the electron transport chain. This type of metabolism is very important in deep sea thermal vent communities. The hot water from the volcanic vent contains H 2 S, which is used as fuel by chemoheterotrophic bacteria. The bacteria act as the lowest rung of the food chain in thermal vent ecosystem. Tube worms depend on sulfide oxidizing bacteria

Chemoautotrophy Which one of the following statements about chemolithotrophy (chemoautotrophy) is FALSE? A. Many chemoautotrophs can survive and grow in the absence of light. B. The chemolithotrophic microorganism can't make ATP unless it can acquire a certain mix of inorganic substances that can produce a favorable redox reaction. C. Chemoautotrophs can make ATP using energy from photons of visible light but they require some organic compounds as nutrients in order to grow. D. A chemoautotroph does not need an organic source of carbon such as sugar or amino acids. E. All chemoautotrophs are either Bacteria or Archaea.

Other Interesting Chemoautotrophic Bacteria - Hydrogen Oxidizing Bacteria Aerobic: H 2 + O 2 H 2 O example: Alcaligenes eutrophus, this bacterium can fix carbon dioxide using a Ru. Bis. Co-type enzyme (Calvin cycle) if grown on methanol in N-limiting conditions, it produces polyhydroxybutyrate. (which is a biodegradable plastic) Anaerobic: H 2 + NO 3 - H 2 O + NO 2 example: Paracoccus denitrificans called hydrogen-oxidizing denitrifying bacteria - Methanotrophic Bacteria Methanotrophs use CH 4 as a carbon and energy source, aerobically. Methane is oxidized to methanol and then to formaldehyde, which can be assimilated by some species of bacteria to provide carbon. In methanotrophs, formaldehyde can be oxidized to carbon-dioxide. The redox reactions yield a PMF which can be used to make ATP.

More Metabolic Pathways Entner-Doudoroff Pathway - an alternative way of converting one glucose to two pyruvates - requires only 1 ATP per glucose to get the reactions started - yields a profit of 1 ATP per glucose to 2 pyruvates Gluconeogenesis - reverse of glycolysis, synthesis of sugar from pyruvate - requires input of 6 ATPs to convert two pyruvates to one glucose - many of the reactions are just reversed glycolysis reactions - two of the irreversible glycolysis reactions are bypassed Pentose-phosphate Pathway Synthesis of amino acids from glycolysis & Krebs cycle intermediates Synthesis of glycolysis & Krebs cycle intermediates from amino acids Synthesis and Degradation of Fatty Acids Alcohol Metabolism