Lecture - Bacterial Growth

Lecture - Bacterial Growth - Goal of the bacterium is to...

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Goal of the bacterium is to become bacteria – Stan Falkow
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Growth Kinetics: Doubling time Death Kinetics: D or Z values
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Bacterial Growth Know your enemy: Metabolic requirements Optimum growth Inhibitory conditions Antibiotic sensitivity Mutations
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Growth Measurement Tools Direct microscopic counts Colony plate counts Turbidity Biotechnology (PCR, reporter genes, biosensors)
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Direct microscopic count (DMC) Hemocytometer Membrane filters Stained Cells Advantages: Fast, Simple, cheap No cultivation Disadvantages: Viability? Inaccurate: limited sample, not species-specific
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Direct Microscopic Count (DMC) Estimate cell numbers Need > 105 CFU/ml Fluorescent dyes differentiate between live and dead cells
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Standard Plate Counts 1. Serial dilutions of sample: 1 ml into 9 ml broth/PBS 1. Spread or pour plate (100 l or 1/10 ml) 1. Count colonies (CFU=25-300) 1. Multiply by dilution factor: 45 x 105 or 4.5 x 106 1:10 10-4 1:100 10-3 10-5 10-2 10-3 10-4 10-5 10-6 6 45 750 750 45 6
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Turbidity Spectrophotometer: measures optical density or light scatter Dependent on wavelength (bacteria at A600) Absorbance = 1/O.D. =Proportional to cell number Pure culture or water samples (not foods) Calibrate with DMC or plate counts
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td = Doubling time or generation time (Time required for one division) μ = specific growth rate td = ln2/ μ = 0.693/ μ μ(Δ t ) = 2.3 log10(N/ N0 ) μ=2.3 (logN - log N0) “Microbiology is the only science where multiplication and division are the same thing” – source unknown
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Exponential Growth: Final number of bacteria = N Initial number of bacteria = N0 Total # divisions = n N=N0 2n N=N0 e μt [ e = limit of (1+1/n)n]
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This note was uploaded on 09/25/2010 for the course FOS 4222 taught by Professor Rodrick during the Spring '08 term at University of Florida.

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Lecture - Bacterial Growth - Goal of the bacterium is to...

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