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Microbial Nutrition Cell metabolism

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Presentation on theme: "Microbial Nutrition Cell metabolism"— Presentation transcript:

1 Microbial Nutrition Cell 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 % Nucleic acid 13-34% Lipid % Also monomers, intermediates and inorganic ions

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

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

6 Defined / Complex Media
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


11 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)

12 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)


14 Glycolysis

15 Substrate-level phosphorylation

16 Fermentation products
Need to regenerate NAD+ Reduce pyruvic acid

17 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





22 Summary Nutrients Energy production Macronutrients/micronutrients
Defined/complex media Cell membranes Energy production Different modes

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

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