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 ConsiderationspH
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.