Answer :
The question is about the preparation of smear slides, which is a common technique used in microbiology to prepare samples for viewing under a microscope. The key difference in preparing smear samples from solid media as opposed to liquid media involves how the cells are transferred to the microscope slide.
When preparing smear cells from a solid media:
- Dispersal in Water (Option A): Cells from a solid media, like agar plates, are not already in suspension. Therefore, a loopful of cells is typically taken and dispersed in a loopful of distilled water placed onto the microscope slide. This helps in making a uniform smear, which is essential for good microscopic examination.
Here is a step-by-step process for preparing a smear from solid media:
- Step 1: A loopful of distilled water is placed onto the center of a clean microscope slide.
- Step 2: Using an inoculating loop, a small amount of culture is scraped from the solid media.
- Step 3: This sample is then mixed into the water on the slide to create a thin, even layer.
- Step 4: The slide is then allowed to air dry completely.
- Step 5: Finally, the smear is heat-fixed by passing it through a flame gently, so the cells stick to the slide and are ready for staining.
Unlike suspensions from liquid media, where cells are already present in the fluid and can be placed directly on the slide, solid media requires an additional step (dispersal in water) to ensure the cells are spread thinly enough for viewing. Therefore, the correct option is A: dispersed in a loopful of distilled water onto the microscopic slide.
