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GROWTH OF MICROORGANISMS

GROWTH OF MICROORGANISMS. Nutritional Classification. Based upon energy and carbon sources Energy source- electron donors Phototrophs (light nourishment) Photosynthesis. Electron Donors. Chemotrophs Oxidation Reduction Breaking & forming bonds. Carbon Source. Autotrophs (self)

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GROWTH OF MICROORGANISMS

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  1. GROWTH OF MICROORGANISMS

  2. Nutritional Classification • Based upon energy and carbon sources • Energy source- electron donors • Phototrophs (light nourishment) • Photosynthesis

  3. Electron Donors • Chemotrophs • Oxidation • Reduction • Breaking & forming bonds

  4. Carbon Source • Autotrophs (self) • Heterotrophs ( different) • Combination of terms

  5. Photoautotrophs • Energy(electrons) source-light • Carbon source-CO2 • Green & purple Sulfur bacteria

  6. Photoheterotrophs • Energy source-light • Carbon source –organic cpds • Green & purple non Sulfur bacteria

  7. Chemoautotrophs • Energy source is oxidation -reduction reactions • Carbon source • Nitrifying bacteria

  8. Chemoheterotrophs • Energy & carbon source • Remove electrons from H in organic cpds • Final electron acceptor is oxygen • Final electron acceptor is organic cpd

  9. Physical Requirements for Growth • Temperature-range • Psychrophiles • Psychrotrophs

  10. Temperature • Mesophiles-25-40C • Thermophiles-50-60C • Hyperthermophiles

  11. Determination of Range • Maximum temperature • Minimum temperature • Optimum temperature is closer to max

  12. pH • Measures acidity or alkalinity • Bacteria grow best at slightly alkaline pH • Add buffers to bacterial cultures • Molds & yeasts lower pH

  13. Osmotic Pressure • Microbes need water to grow • Use salt/sugar to preserve food • Obligate halophiles • Facultative halophiles

  14. Chemical Requirements for Growth • Carbon source-50% of dry weight of cell • Nitrogen source-amino acids, nucleic acids

  15. Minerals • Trace elements • Small amounts of Fe, Zn, Cu, Co etc. • Macronutrients-S & P • Water-medium for chemical reactions

  16. Other Growth Requirements • Growth factors-essential nutrients • E. coli needs no growth factors

  17. Other Growth Requirements • Buffers • A solidifying agent

  18. Agar Advantages • Few organisms degrade it • Liquefies at 100 C • Liquid until 40-50 C • Lab-keep liquid at 50 C • Once solidified, heat to 100 C • Gelatin • Nutrient for some organisms • Liquefies at 35-37 C

  19. Oxygen Requirements • Aerobes • Use molecular oxygen for respiration • Superoxide free radicals (O. -) • Superoxide dismutase- must have • H2O2 is toxic

  20. Oxygen Requirements • Facultative anaerobes

  21. Oxygen Requirements • Obligate anaerobes

  22. Oxygen Requirements • Aerotolerants • Microaerophiles

  23. Growth of Bacterial Population • Binary fission or budding • Generation time-doubling time

  24. Growth Curve • Lag phase-preparing to grow • Log phase • Stationary phase-growth ceases • Death Phase

  25. Growth of a Colony • Mass of cells –pure culture • Some colonies are distinct • Mixture of cells in different phases of growth

  26. Growth of a Colony • Location within colony determines access to oxygen • Surface cells fully aerobic • E. coli obtain energy aerobic respiration • Embedded cells in center-anaerobic

  27. Biofilms • In nature, microbes in liquid environment • Cells imbedded in extracellular slime • Excreted by cells • Type of defense mechanism

  28. Biofilms • Quorum sensing • Important role in infections • Soaps & disinfectants

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