Why is a thick smear undesirable?
Why is a thick smear undesirable?
A very thick smear diminishes the amount of light that can pass through, thus making it difficult to visualize the morphology of single cells. Smears typically require only a small amount of bacterial culture. An effective smear appears as a thin whitish layer or film after heat-fixing.
Why are smears air dried?
Overlapping organisms are hard to identify and diminishes the amount of light that can pass through and makes it difficult to visualize the morphology of single cells. Why is it essential that smears be air-dried? It may prevent the organisms from being fixed to the slide and wash away during staining process.
Why should you be careful not to overheat the smear?
* Overheat will denature and rupture the cell wall. * Excess water on the slides will boil during fixation. Why should you be careful not to overheat the smear during the heat-fixing process? basic dyes with positive charge bind to negative charge cells.
What would happen if you didn’t heat fix a smear before performing the direct stain?
What would happen if you didn’t heat-fix a smear before 1 point performing the direct stain? This is an unacceptable protocol; the cells will not be adhered tightly to the slide and will wash off during staining.
What heat fix means?
Heat fixation is a technique used in organism staining that is able to kill organisms, adhere them to the slides being used, and alter them so they can take on the stains being used. This process kills the organism on the slide, and ensures it stays in place on the slide.
What are the three reasons for the heat fixing step when preparing bacterial smears?
Discuss the reasons for heat fixing bacterial smears prior to staining.
- To kill bacteria on slide;
- to make dye penetrate cells;
- to coagulate proteins of cells thus making cells stick to slide.
Why is the size more accurate in a negative stain?
Why is the size more accurate in a negative stain than in a simple stain? Because it’s not subjected to heat fixing or other harsh chemicals- ensuring that cell-size does not change or be distorted by the stain. Air-drying helps keep the size as well.