In the process of preparing a bacterial smear for staining, what is the primary purpose of heat fixing the sample?

• A. To enhance the color intensity of the stain
• B. To prevent the formation of endospores
• C. To sterilize the staining reagents
• D. To kill the bacteria and adhere them to the slide

Answer: (D)

Verified step by step guidance

1. Understand that heat fixing is a step in preparing bacterial smears before staining, which involves briefly passing the slide through a flame or applying gentle heat.
2. Recognize that the main goals of heat fixing are to kill the bacteria, which makes the sample safer to handle, and to make the bacterial cells stick firmly to the glass slide so they do not wash off during staining.
3. Note that heat fixing does not enhance the color intensity of the stain directly; staining intensity depends more on the type of stain and staining procedure.
4. Understand that heat fixing does not prevent the formation of endospores, as endospore formation is a biological process within bacteria, not affected by heat fixing at this stage.
5. Acknowledge that heat fixing does not sterilize the staining reagents; sterilization of reagents is done separately through other methods.