Question

1. What color are endospores following the spore stain? What is the purpose of using safranin?

2. What is meant by "vegetative cell" when performing the endospore stain?

3. Why is it important to use older cultures when performing the endospore stain?

4. What is the color of the capsule following the capsule stain?

5. What are the potential medical implications if the medical micro lab identifies a spore-forming bacterium from a patient specimen?

6. What is the purpose of inoculating two organisms when testing for motility?

7. How do you determine if the organism that has been cultured is motile?

8. Name one other method that could be used to determine motility.

Answer 1

1.] On following the spore stain, Endospores will appear green in color in Schaeffer-Dulton Technique, while it will be red in colour in Dorner's Method of Endospore Staining Technique.

Safranin in this endospore staining technique acts as counter stain (produces a contrasting background to distinct endospore from vegetative cell). The purpose of this counter stain is to stain the vegetative cells that lost the primary stain.

2.] When performing the endospore stain, a vegetative cell is the normal bacterium that grows and multiplies in favorable environmental conditions-  sufficient nutrients, optimal temperature and moisture, etc. Vegetative cells on extreme environmental conditions undergo sporulation to form endospores. Vegetative cells easily lose the primary stain when washed with water; they undergo pink or reddish color with intake of counter stain safranin.

3.] It is important to use older cultures when performing the endospore stain because older bacteria (culture) are under greater nutritional stress (as the spores are not produced until starvation of about 72 hrs), so there will be presence of more endospores.

4.]  The main purpose of capsule stain is to distinguish capsular material from the bacterial cell. The color of the capsule following the capsule stain in India Ink Method will be clear against a dark background as it takes no stain; while in Anthony's Stain Method, the capsule will take light violet color.