Table of Contents
- 1 What happens if you mix eosin and methylene blue?
- 2 What will the outcome be if you used an acidic dye to stain a smear?
- 3 What is smear how it is formed for bacterial staining?
- 4 Does E coli grow on eosin methylene blue agar plates?
- 5 What are some consequences of not leaving a stain on a smear long enough?
- 6 What are the staining methods?
- 7 How does heating the bacterial Smear during a Zn stain promote?
- 8 How are crystal violet and safranin used in micro lab?
What happens if you mix eosin and methylene blue?
Eosin Y and methylene blue are pH indicator dyes which combine to form a dark purple precipitate at low pH; they also serve to inhibit the growth of most Gram positive organisms.
What will the outcome be if you used an acidic dye to stain a smear?
Acidic: Have negatively charged ion (anionic) and are therefore repelled by the charge of the bacterial suface and can’t permeate the cell. The dye will stain the background and leave the microbe transparent. Decolorizing Agent- Acid Alcohol- Removes the color from cells without the waxy cell wall.
What happens when you stain bacteria?
A Gram stain is colored purple. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive.
What is smear how it is formed for bacterial staining?
A bacterial smear is simply that—a small amount of culture spread in a very thin film on the surface of the slide. To prevent the bacteria from washing away during the staining steps, the smear may be chemically or physically “fixed” to the surface of the slide.
Does E coli grow on eosin methylene blue agar plates?
It also contains the carbohydrate lactose, which allows differentiation of gram-negative bacteria based on their ability to ferment lactose. Quadrant 1: Growth on the plate indicates the organism, Escherichia coli, is not inhibited by eosin and methylene blue and is a gram-negative bacterium.
What organisms grow on eosin methylene blue agar?
Result Interpretation on EMB Agar
| Organisms | Growth |
|---|---|
| Escherichia coli | Blue-black bulls eye; may have green metallic sheen |
| Pseudomonas aeruginosa | Colorless |
| Enterobacter aerogenes | Good growth; pink, without sheen |
| Klebsiella pneumoniae | Pink, mucoid colonies |
What are some consequences of not leaving a stain on a smear long enough?
What are some consequences of not leaving a stain a smear long enough (under-staining)? Some consequences of under-staining are that the cells may lose their stain when washed with water or alcohol. This would make it difficult to identify the cell under the microscope.
What are the staining methods?
Types of Staining Techniques
| Sr. No. | Staining Technique |
|---|---|
| 1. | Simple (Monochrome) |
| 2. | Negative (Relief) |
| 3 | Gram |
| 4 | Acid fast (Ziehl-Neelsen technique) |
How to predict the effect of a Gram stain?
The smears background would turn out red while the cells would turn out blue. Predict the effect on Gram-positive & Gram-negative cells of the following “mistakes” made when performing a Gram stain. Consider each mistake independently. A. Failure to add the iodine. B. Failure to apply the decolorizer.
How does heating the bacterial Smear during a Zn stain promote?
How does heating the bacterial smear during a ZN stain promote entry of carbolfuchsin into the acid-fast cell wall? Heating melts the mycolic acid and allows the stain to penetrate the cell walls. Why do you suppose the acid-fast stain is not as widely used as the Gram stain?
How are crystal violet and safranin used in micro lab?
Both crystal violet and safranin are basic stains and may be used to do simple stains on Gram-positive and Gram-negative cells. This being the case, explain how they end up staining Gram-positive and Gram-negative cells differently in the Gram stain.
How does the Zn smear promote the entry of carbolfuchsin?
In fact, most cells, prokaryotic and eukaryotic are gram negative. How does heating the bacterial smear during a ZN stain promote entry of carbolfuchsin into the acid-fast cell wall? Heating melts the mycolic acid and allows the stain to penetrate the cell walls.