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Unformatted text preview: DIRECT MEASUREMENT OF MICROBIAL GROWTH Liquid cultures are usually used and population numbers are recorded as the number of cells per milliliter of the culture medium. Usually numbers in a very small sample are counted and then the number per milliliter (ml) is calculated. To get the small sample, a series of dilutions is performed. This is done because bacterial numbers are usually so large that actually counting all the bacteria in 1 ml is difficult or impossible. The original sample is usually diluted by taking 1 ml from it and putting it into sterile liquid--either 1 ml into 9 ml (which gives a 1:10 dilution) or 1 ml into 99 ml (which gives a 1:100 dilution). If necessary, the first dilution can be mixed and then 1 ml of this transferred to 9 or 99 ml again, and so on. When a "countable" dilution is achieved, the original number per ml 9 or 99 ml again, and so on....
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This note was uploaded on 01/23/2012 for the course MCB MCB2010 taught by Professor Smith during the Fall '09 term at Broward College.
- Fall '09