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Definition
| Solutions consisting of a solvent (Water or ethanol) and a colored molecule (often a benzene derivative), the chromagen |
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Definition
| Colored molecule used in a stain |
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Definition
| The portion of the chromogen that gives it it s color |
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Definition
| Is the charged portion of a chromogen and allows it to act as a dye through ionic or covalent bonds between the chromogen and the cell. |
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Definition
Where the auxochrome becomes positively charged as a result of picking up a hydrogen ion or losing a hydroxide ion.
EX: methylene blue, crystal violet, safranin |
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Definition
| Kills the bacteria, makes them adhere to the slide, and coagulates cytoplasmic proteins to make them more visible |
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Term
| How long do you stain with crystal violet? |
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Definition
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Term
| How long do you stain with safranin? |
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Definition
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Term
| How long do you stain with methylene blue? |
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Definition
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Term
| Why is the gram stain so important? |
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Definition
| Allow microbiologists to detect differences between organisms or parts of the same organism. Most commonly used differential stain in bacteriology. |
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Definition
| Differential stain in which a decolorization step occurs between the application of two basic stains. |
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Term
| Primary Stain in gram staining |
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Definition
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Term
| Why is iodine added to the gram stain? |
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Definition
| Iodine is added as a mordant to enhance crystal violet staining by forming a crystal violet-iodine complex. |
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Definition
| Most critical step in gram stain, Gram- cells are decolorized by the solution where as gram+ are not. Gram - are then colorized by the counterstain. |
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Term
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Definition
| Coloring of gram- cells after decolorization. Uses safranin. |
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Term
| What color are gram - cells? |
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Definition
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Term
| What color are gram+ cells? |
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Definition
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Term
| What is the ability to resist decolorization based on? |
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Definition
| The different wall construction of gram+/- cells. |
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Term
| Why are gram- cells incapable of retaining crystal violet stain? |
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Definition
| Because gram- cells have a higher lipid content and a thinner peptidoglycan layer than gram+, the alcohol/acetone in the decolorizer extracts the lipid, making the gram- wall more porous and incapable of retaining the complex, thereby decolorizing it. |
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| Why are gram+ cell less susceptible to decolorization? |
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Definition
| The thicker peptidoglycan and greater degree of cross-linking traps the crystal violet-iodine complex. |
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| What is the most crucial step in gram staining? |
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Definition
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Definition
| Leaving the alcohol on too long and getting reddish gram+ cells. |
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Definition
| Produces purple gram- cells. |
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Term
| What are some possibilities of gram stain inconsistency? |
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Definition
| Poor decolorization, prep of the emulsion, age of culture, nonbacterial elements. |
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Term
| How does the age of a culture affect gram staining? |
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Definition
| Older cultures may lose their ability to resist decolorization and give an artificial result |
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Term
| In addition to gram reaction what else does the gram stain reveal? |
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Definition
| Determination of cell morphology, size, and arrangement. |
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