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Lecture 4 - Growth and Nutrition

# Lecture 4 - Growth and Nutrition - Microbial Growth and...

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1 Microbial Growth and Nutrition Microbial population growth Bacteria reproduce via binary fission. Doubling time may be as short as 20-30 minutes. Population will increase geometrically or exponentially as long as environment remains favorable. Fig. 7.13 See pp. 204-209.

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2 Exponential Growth of Bacteria The time it takes for the population to double in number is called the generation time or doubling time. N f =(N i )2 n N f = total number of cells in population N i = the number of cells at starting time n = the number of generations 2 n = number of cells in generation n
3 Example: How many Staphylococcus aureus cells could be present in a sandwich after 4 hours if the initial population was 10 cells and the generation time is 20 minutes? N f = (10)2 12 = 10 X 4,096 = 40,960 Typical bacterial growth curve Fig. 7.15

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4 Methods of counting bacteria • Direct observations in a microscope • Turbidity measurement of liquid cultures • Colony counting following dilution plating • Particle counters and flow cytometers • Detecting cell products
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Lecture 4 - Growth and Nutrition - Microbial Growth and...

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