Microbial Nutrition Cell metabolism

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Microbial NutritionCell metabolism
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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

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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

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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

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Micronutrients

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

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Defined / Complex Media

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

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Other Culturing Considerations

• pH
• Oxygen concentration
• Temperature
• Light / carbon dioxide (phototrophic organisms)

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Role of Oxygen in Nutrition

• Obligate aerobes require O2
• Obligate anaerobes O2 is toxic
• Facultative anaerobes
• Microaerophilic organisms

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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

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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)

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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)

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Glycolysis
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Substrate-level phosphorylation
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Fermentation products

• Need to regenerate NAD
• Reduce pyruvic acid

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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

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Summary

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

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