Answer :
Final answer:
The number of questions to identify Streptococcus via a dichotomous key can't be specified without the key. The dichotomous key narrows down options based on characteristics like cell shape and biochemical tests until reaching the genus Streptococcus.
Explanation:
The exact number of questions needed to identify a bacterium of the genus Streptococcus using a dichotomous key cannot be determined without access to the specific key being referenced.
Generally, a dichotomous key works by posing a series of questions that lead to two possible answers - a process of elimination based on observable characteristics such as cell shape (cocci or bacilli), Gram reaction (positive or negative), and other biochemical tests.
By following the key, based on questions related to colony morphology, Gram reaction, staining properties, and physiological tests, you gradually narrow down to the genus or species in question.
As you move through the key, with each choice made, you eliminate other possible bacteria until you arrive at the genus Streptococcus.
For example, if the key first asks you to differentiate based on the cell shape and Streptococcus is classified as cocci, then you would follow the branch of the key designated for cocci.
Following subsequent branches might include tests for oxygen tolerance, hemolysis on blood agar, or other specific biochemical tests. Ultimately, the number of questions answered is contingent on the complexity of the key and the number of differentiating characteristics that need to be considered.
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