Question

A dichotomous key was made to distinguish between various endospore forming bacteria. Why would Gram staining not be the best choice to use first in the dichotomous key?

Answer 1

Endospore forming Bacteria is the one which is characterized by its ability to form thick walled structures called as endospores. These structures are found under harsh environmental conditions to protect the bacterial cell from desiccation and heat. They are a means of perennation.

To create a dichotomous key to differentiate between various endospore forming bacteria, we have two choices, the bacteria which does not form endospore and the bacteria which forms endospore. The bacteria which forms endospore can be further divided into three categories on the basis of location of endospore, Central endospore, Terminal endospore and subterminal endospore.

To create this key, we may also use the term bacteria showing affinity for malachite green dye and bacteria not showing affinity for malachite green dye. This is because, malachite green dye is used to stain endospores in bacteria. Absence of endospores will lead to no staining of bacteria by malachite Green.

This is the process to create a dichotomous key to distinguish between endospore forming bacteria. But we cannot use Gram staining as the First Choice in this key. This is because Gram staining and endospore formation are two different concepts. A Gram Positive Bacteria may or may not show the presence of endospore and a Gram Negative bacteria may or may not show the presence of endospore.

The endospore forming bacteria are mainly bacillus and clostridium species, both of which are Gram Positive Bacteria. But this is a generalization. The formation of endospore by a bacterium depends mainly on the environment it lives in.

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