Overview
This lecture explains the steps and purpose of a simple staining procedure in microbiology, focusing on visualization and preparation techniques for bacterial cells.
Purpose of Simple Staining
- A simple stain uses only one dye, known as a chromophore.
- Direct staining involves a positively charged dye coloring negatively charged bacterial cells.
- Simple stains help visualize clear, small bacterial cells, revealing size, shape, and arrangement.
Slide Preparation Steps
- Prepare a bacterial smear and allow it to completely air dry before fixing.
- Heat fix the smear by quickly passing the slide through a flame two or three times.
Staining Procedure
- Cover the smear with methylene blue dye for 30–60 seconds.
- Use five or six drops to fully cover the smear; adjust amount and time as needed for your reagents.
- Rinse the slide gently with distilled water, aiming above the smear so water flows over it.
Drying and Observation
- Gently blot the slide dry; do not wipe.
- Ensure the slide is fully dry before examining under a microscope.
- Cell types observed depend on the culture used for the smear.
Post-Observation Steps
- After observation, gently blot oil from the slide and store in a slide box.
Key Terms & Definitions
- Simple stain — A staining technique using a single dye to color cells.
- Chromophore — The colored part of a dye molecule.
- Direct stain — Staining method where the dye colors the cells directly.
- Methylene blue — A common basic dye used in simple staining.
Action Items / Next Steps
- Practice preparing and staining bacterial smears as described.
- Ensure all slides are dry before microscopic examination.
- Clean and store slides properly after use.