How do chemical stains enhance the usefulness of light microscopes in microbiology?

• A. They sterilize the specimen to prevent contamination during observation.
• B. They increase the contrast between microbial cells and their background, making structures more visible.
• C. They magnify the specimen beyond the optical limits of the microscope.
• D. They convert light microscopes into electron microscopes for higher resolution.

Answer: (B)

Verified step by step guidance

1. Understand that light microscopes rely on differences in light absorption or refraction to visualize specimens, but many microbial cells are nearly transparent and lack natural contrast.
2. Recognize that chemical stains are dyes that bind to specific components of microbial cells, such as cell walls, membranes, or nucleic acids, thereby altering their optical properties.
3. Know that by binding to cellular structures, stains increase the difference in light absorption or color between the cells and the surrounding medium, which enhances contrast.
4. Realize that enhanced contrast allows for clearer visualization of microbial morphology and internal structures under the light microscope, facilitating identification and study.
5. Conclude that chemical stains do not sterilize specimens, magnify beyond optical limits, or convert light microscopes into electron microscopes; their primary role is to improve contrast for better visibility.