Systems Microbiolo38

Systems Microbiolo38 - this problem ° Some organisms...

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Systems Microbiology ° Viable count o This is the more common method – dilute sample many times over o Demonstration: Prof. Schauer displays samples of test tubes with successive dilutions – each test tube is progressively less cloudy. o Then you plate the resulting tubes and wait for colonies to appear o You want to count a plate with between 30 and 300 cells ° Otherwise the error becomes too high o Demonstration: Prof. Schauer displays agar plates resulting from each successive dilution o This kind of evaluation is difficult for slow-growing bacteria – you have to leave the plate to grow for up to a month. o This method doesn’t work for bacteria that can’t make colonies ° These bacteria might be viable, but clump (you can use detergents to try to fix
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Unformatted text preview: this problem) ° Some organisms don’t separate, but come in chains o Plating methods ° Sometimes putting the agar on top is useful, because it stops the bacteria from moving around ° Turbidity as an indirect measure o Light scattering off of organisms o Depends on morphology of organisms – larger organisms scatter more light o You can quantify organisms by measuring the light scattering ° Photometers ° This is advantageous because you can still keep using the sample ° Chemostat culture o Instrument called a chemostat – bioreactor of sorts – you grow bacteria in it o Open system o Number of bacteria and rate of growth are kept constant o It enables you to control both the bacterial concentration and the doubling time....
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