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  1. nutrition
    process by which chemical substances (nutrients) are acquired from the environment and used for cellular activities
  2. essential nutrients
    must be provided to an organism
  3. Two categories of essential nutrients

    micronutrients or trace elements
  4. macronutrients
    • required in large quantities; play principal roles in cell structure and metabolism 
    • •proteins, carbohydrates
  5. micronutrients or trace elements
    –required in small amounts; involved in enzyme function and maintenance of protein structure

    •manganese, zinc, nickel
  6. Microbial Growth
    •Increase in cell number

    •Populations increase at very rapid rates

    • •Colonies of bacteria contain billions
    • of cells

    •Method of growth:  Binary fission

    •Typical growth rates: 20-30 minutes
  7. Bacterial Growth Rates
    • Each new fission cycle increases the population by a factor of 2 – exponential or logarithmic
    • growth.
  8. Generation, or doubling time
    Time required for a complete fission cycle 

    • Each new fission cycle increases the population by a factor of 2 – exponential or logarithmic
    • growth.
  9. Generation time
    • Time required for population to double

    • Typical generation time: 20 min
  10. Equation for calculating population size over time
    N^ƒ = (N^i)2^n

    N^ƒ  is total number of cells in the population.

    N^i is starting number of cells.

    Exponent n denotes generation time.

    2^n number of cells in that generation
  11. Lag phase
    Cells are not dividing

    They are getting use to the environment

    They are preparing
  12. Log phase
    Cells are metabolically active

    Vulnerable to antibiotics and radiation

    Cells are dividing
  13. Stationary phase
    Number of cells and number of live cells are equal
  14. Death phase
    Number of dead cells is greater than number of live cells
  15. Measuring Bacterial Growth: Direct Chamber
    Counting Chamber: the slide has a grid

    Cheap and fast to use
  16. Viable Count
    –Plate count method - counts colonies, 12 hours; gives an accurate estimate of the number of viable cells


    –Most probable number (MPN)
  17. Which method would give you the highest
    estimate, a direct count or viable count?
  18. Minimum temperature
    • lowest temperature that permits a microbe’s growth and metabolism
  19. Maximum temperature
    • highest temperature that permits a microbe’s growth and metabolism
  20. Optimum temperature
    • promotes the fastest rate of growth and metabolism
  21. Psychrophiles
    1.optimum temperature below 15oC; capable of growth at 0oC
  22. Mesophiles
    1.optimum temperature 20o-40oC; most human pathogens
  23. Thermophiles
    1.optimum temperature greater than 45oC
Card Set:
2015-03-14 16:42:58
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