Organelles, granules, and bacterial endospores are best observed using which type of microscope?

• A. Scanning electron microscope
• B. Fluorescence microscope
• C. Phase-contrast microscope
• D. Bright-field microscope

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the characteristics of each microscope type listed in the problem. For example, a scanning electron microscope (SEM) provides detailed 3D images of the surface of specimens but is not typically used for observing internal structures like organelles or endospores within bacteria.
2. Step 2: Recognize that a fluorescence microscope uses fluorescent dyes to highlight specific components within cells, which is useful for certain cellular structures but requires staining and may not be ideal for observing unstained organelles or endospores.
3. Step 3: Consider the bright-field microscope, which is the most common type and uses light passing through the specimen. However, it often lacks the contrast needed to clearly see transparent structures like organelles or endospores without special staining.
4. Step 4: Learn that the phase-contrast microscope enhances contrast in transparent and unstained specimens by converting phase shifts in light passing through the specimen into brightness changes in the image. This makes it especially useful for observing organelles, granules, and bacterial endospores in living cells without staining.
5. Step 5: Conclude that because phase-contrast microscopy allows visualization of internal structures in live, unstained bacterial cells by enhancing contrast, it is the best choice for observing organelles, granules, and bacterial endospores.