# 6.2: Procedure

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Your instructor will show you an example of a simple dichotomous key using geometric shapes (see below). The key is based on looking for features that distinguish one shape from another. Similarly, unknown bacteria can be identified by looking for tests that distinguish one type of bacteria from another based on their different properties. Dichotomous keys for bacterial unknowns are based on Gram reactions, morphologies and metabolic assays like the ones you have learned in lab. Once you understand the concept of developing a dichotomous key, you will design your own keys that will allow you to identify your particular unknowns based on these characteristics. There are many ways to make a useful key, so your key may not resemble those made by other students.

Note

Although additional staining can sometimes be used as part of a dichotomous key, you will be only using the metabolic tests for this exercise.