Agar Lab Report

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Bacterium growth on various agar plates


The purpose of this experiment is to show different agar plates inhibit or enable growth of different organisms. Some varieties of media enable the grow of a wide range of organisms such as nutrient agar. Other media are selective which means they contain specific nutrients to encourage the growth of certain organisms. This means other organisms will die due to the selective nutrients such as high concentration of salt which will cause plasmolysis. Differential organisms require different nutrients which show it is fairly easy to isolate and identify organisms by using selective media. Differentiation media are also used by taking advantage of whether an organism produces acid or not. MacConkey agar is an example of a differential media which will enable the organism to express a colour depending on whether it produces acid. This agar contains a pH indicator which can provide more information on the type of bacteria that is growing on the agar.

Method A more detailed method is provided in the 280.201 Industrial Microbiology lab manual. However, the basic steps of carrying out this experiment are as follows:
• Five agar plates are provided including:
1. Nutrient agar
2. Mannitol Salt agar
3. Eosin-methylene blue agar
4. MacConkey agar
5. KF Streptococcal agar
• Divide the agar plates into quarters and name each quarter with the four different cultures provided which include:
1. Escherichia coli
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