anaerobicJenN - Introduction to the Enrichment Culture A...

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Introduction to the Enrichment Culture A critical variable in enriching for organisms is the energy source phototrophs use light as an energy source chemotropism use chemical reactions as an energy source They are almost always oxidation-reduction reactions The electron donor/acceptor pair is usually the master varialbe in enrichment cultures organotrophs have an organic electron donor lithotrophsb have an inorganic electron donor Oxygen is a powerful electron acceptor and oxidation of essentially all organic and most inorganic electron donors is favorable under aerobic conditions Under anaerobic conditions: inorganic compounds (nitrate, sulfate, CO2) serve as electron acceptors Most anaerobic respiration processes are much less favorable fermentation use an organic compound as both the electron donor and acceptor Besides electron donor/acceptor there are other nutritional needs that must be met in the growth medium carbon source , in the case of most media with an organic elctron donor (like glucose) the electron donor is also the carbon source If CO2 is the only C-source available this will select for autotrophs to fix their own carbon All organisms also require sources of N, P, and S, major and trace metal nutrients Enrichment cultures are tried in a defined medium containing only mineral nutrients and the electron donor/acceptor which provides strong selection for the desired organism Some organisms require organic nutrients (vitamins or amino acids) and if the initial plan fails then we will have to add vitamin solution or a small amount of a complex nutrient (yeast extract) Habitat simulation is when you make an organisms feel “at home” to culture it acidophiles favor low pH thermophiles favor high temperatures selective agents such as adding bacterial inhibitors (penicillin or revamping) will favor eukaryotes Adding cycloheximide will inhibit eukaryotes and favor bacterial growth
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This note was uploaded on 09/30/2011 for the course BIOMI 3910 at Cornell.

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anaerobicJenN - Introduction to the Enrichment Culture A...

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