Question

3) You are given an unknown Gram+ bacterium and told that it forms endospore. You perform an endospore staining procedure on a culture of this organisms that has been incubated at an appropriate temperature for double its usual growth time(to induce adverse conditions).

b) What would you expect to see in a Gram stain of the same organism?

- I answered "there will not be any staining to this bacteria because endospores are resistant to gram staining" is this correct??

Answer 1

Answer: Endospores are dormant forms of bacteria and are produced by Gram positive bacteria , in response to adverse environmental conditions. Mature endospores are highly resistant to environmental conditions such as heat and chemicals and thus endospore coat is highly resistant to staining , a special method called ENDOSOPRE STAINING was developed which uses heat treatment and usage of malachite green and a counter stain , where endospore will take Green color and cells will take pink color of counterstain. In this case, since you are using Gram Staining technique which is very mild technique as compared to endospore staining technique, endospore would not pick any stain and will be observed colorless under microscope

you are correct in that, endospore would not take up any of Gram stains as endospore themselves are resistant to the Gram Stain process, but the bacterial cells which carry the endospore will be stained purple and endospore will be seen as clear oval or spherical area within the stained bacteria under microscope.