In the process of chemical fixation during microbiological staining, how does alcohol act to fix bacterial cells?

• A. Alcohol denatures bacterial proteins, causing them to coagulate and adhere to the slide.
• B. Alcohol stains the bacteria by binding to their lipids.
• C. Alcohol dissolves the bacterial cell wall, allowing the cell contents to spread on the slide.
• D. Alcohol reacts with bacterial DNA, making it visible under the microscope.

Answer: (A)

Verified step by step guidance

1. Understand the purpose of chemical fixation in microbiological staining, which is to preserve the structure of bacterial cells and attach them firmly to the slide to prevent loss during staining and washing.
2. Recognize that alcohol is commonly used as a chemical fixative because of its ability to interact with bacterial cell components.
3. Recall that alcohol acts primarily by denaturing proteins. This means it disrupts the three-dimensional structure of bacterial proteins, causing them to unfold and coagulate.
4. Understand that this coagulation of proteins causes the bacterial cells to become fixed, meaning they adhere tightly to the slide surface and maintain their shape during subsequent staining steps.
5. Note that alcohol does not primarily stain bacteria, dissolve the cell wall, or react with DNA in this context; its main role is protein denaturation leading to fixation.