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12 Cards in this Set
- Front
- Back
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Generation Time
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aka doubling time-the time required for a population of cells to double
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Calculating Generation Time
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Because of this geometric progression, there is a direct, predictable relationship between the number of cells in a culture initially and the number there after a period of exponential growth
N(f) = N(i)2 n power |
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Limits to Growth
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Lack of nutrients, build up of wastes
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Lag Phase
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Period after inoculation of a culture before growth begins
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Exponential Phase
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period of exponential growth
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Stationary Phase
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period in which growth ceases
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Death Phase
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Period in which cells die off
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How do we measure growth?
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Total cells count-direct microscopic counts; direct count
Viable Counts-plate count; colony count (spread plate method) Measurements of cell mass and turbidity |
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Measurements of Cell Mass and Turbidity
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Cell Mass-centrifuge organisms and weigh them (dried)
Turbidity: measure cloudiness of a cell suspension by light scattering (spectophotometer) Cell number or turbidity are proportional (if you know one, you can figure out the other) |
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Effect of environmental factors on microorganisms
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Important to distinguish between effects on viability and effects on growth (including reproduction)
Important factors: temp, pH, water availability, oxygen |
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Effects of Temp. on Growth Rate
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Each microorganism has a minimum, maximum, and optimum growth rate
Organisms can be classified by temperature |
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Effects of pH
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Acidophiles & Alkilophiles
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