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Microbial Nutrition Cell metabolism

Microbial Nutrition Cell metabolism. Nutritional Categories of Microorganisms. Microorganisms are often grouped according to the sources of energy they use: Phototrophs use light as an energy source Photosynthesis Chemotrophs use chemicals as energy sources Chemoorganotroph

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Microbial Nutrition Cell metabolism

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  1. Microbial NutritionCell metabolism

  2. Nutritional Categories of Microorganisms • Microorganisms are often grouped according to the sources of energy they use: • Phototrophs use light as an energy source • Photosynthesis • Chemotrophs use chemicals as energy sources • Chemoorganotroph • Chemolithotroph

  3. Biochemical Components of Cells • Water: 80 % of wet weight • Dry weight • Protein 40-70 % • Nucleic acid 13-34% • Lipid 10-15 % • Also monomers, intermediates and inorganic ions

  4. Macronutrients • Cells make proteins, nucleic acids and lipids • Macronutrients • macromolecules, metabolism • C, H, O, N, S, P, K, Mg, Fe • Sources • Organic compounds • Inorganic salts

  5. Micronutrients • Elements needed in trace quantities • Co, Cu, Mn, Zn, V • Enzymes • tap water • Growth factors • Organic compounds • Vitamins

  6. Defined / Complex Media • Defined • Prepared with precise amounts of chemicals • Known composition • Complex • Exact composition unknown • Digests of beef, soybean, yeast

  7. Other Culturing Considerations • pH • Oxygen concentration • Temperature • Light / carbon dioxide (phototrophic organisms)

  8. Role of Oxygen in Nutrition • Obligate aerobes – require O2 • Obligate anaerobes – O2 is toxic • Facultative anaerobes • Microaerophilic organisms

  9. Transport of Nutrients into the Cell • Nutrients are obtained from the environment • Many of the nutrients are polar • Cannot diffuse across the cell membrane • Proteins embedded in the membrane • Transport against a concentration gradient - active transport

  10. Bioenergetics • Living cells require energy for growth, biosynthesis, reproduction and transport • Energy needed to drive the biochemical reactions of cells is stored and transferred via adenosine triphosphate (ATP)

  11. Fermentation and Respiration • Chemoorganotrophs obtain their energy from oxidation of organic compounds • loss of electrons/removal of hydrogen • Fermentation • No terminal electron acceptor • Respiration • Terminal electron acceptor (e.g. O2)

  12. Glycolysis

  13. Substrate-level phosphorylation

  14. Fermentation products • Need to regenerate NAD+ • Reduce pyruvic acid

  15. Oxidative phosphorylation • Occurs in respiration (aerobic and anaerobic) • Proton motive force • Electrons from NADH are passed along an electron transport chain • Protons are pumped across membrane • Electrochemical gradient • Drives ATP synthesis from ADP and Pi

  16. Summary • Nutrients • Macronutrients/micronutrients • Defined/complex media • Cell membranes • Energy production • Different modes

  17. Further reading Madigan MT, JM Martinko, J Parker, 2000. Brock Biology of Microorganisms, 9th Edition. Chapters 3 and 4.

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