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Mico lab quiz 2
MICRO
| Question | Answer |
|---|---|
| What is the most common differential stain | Gram stain |
| Gram stain | 1st test run on a specimen brought into a lab |
| What is a gram stain used for | To distinguish between a gram + cell and a gram - cell |
| Why gram + purple | Thick peptidoglycan cell wall, holds tight to crystal violet after iodine sets the stain |
| Why gram - pink | Thin cell wall and LPS outer membrane, cell takes in color of secondary stain-- safranin |
| Theoretically could you use any color for your primary and counter stain as long as their not the same color | Yes it would be best if the primary stain was darker; counter stain lighter |
| Capsules are | Mucoid polysaccharide or polypeptide layers-- repel most stains |
| Why are capsules important | Increase virulence by resisting phagocytosis |
| How is a capsule stain different | Use a negative staining process, acidic stain, capsule is colorless |
| Acidic stain | Background (Congo red) |
| Basic stain | Cell (manevals stain) |
| Capsule is colorless | White clearing around stain |
| Why a no heat fixation step durning a capsule stain | Causes cells to shrink, leaves and artificial white layer around cell, mix cells with serum or albumin--makes cells adhere to slide |
| What does a endospore stain do for us | Differential stain used to detect endospores |
| Endospores | Dormant form of a bacterium, allows it to survive poor environment, cell will form spores when requirements for life are unavailable ie: nutrients, oxygen, water |
| What does the endospore staining process help | Helps us to identify bacterial species because location and shape of spores is unique |
| Where can the location of the spores be | Center, terminal, subterminal |
| Shape of the spore | Spherical, oval |
| What does the steam do durning a endospore stain | Drives green stain into spores |
| What happens for the cells to stain pink durning an endospore stain | Green washes out of cell durning decolonization(water), and cells take on counter stain |
| The 5 day culture will have | A lot more spores (green) |
| What bacteria was used for the 2 day and 5 day endospore stain | Bacillus subtilis culture |
| What bacteria was used for the capsule stain | Klebsiella pneumoniae |
| What bacteria was used for the gram + gram stain | Staphylococcus epidermidis |
| What bacteria was used for the gram - gram stain | Escherichia coli |
| Failure to add the iodine in gram stain | Crystal violet will wash off of gram +. Both + and - will be pink |
| Failure to apply the decolorizer in gram stain | Decolorizer- removes primary stain in gram -. No decolorizer means the crystal violet retained by gram -. Both + and - will be purple |
| Failure to apply the safranin in gram stain | No counter stain. + will be purple - will be colorless |
| Reversal of crystal violet and safranin stains in gram stain | Safranin washed out of gram - cells. Counter stain is darker than primary stain so both gram + and - will be purple |
| If you saw eukaryotic cells on your gum line, they were most likely your own epithelial cells. Are you gram + or harm -. What is it about your cell structure that would allow you to predict this result | Cells act like gram - cells. Epithelial cells have a plasma membrane and no cell wall |
| Why does this excerise call for 5 day old culture of Bacillus | 5 day old culture is dying off, lacking in nutrients, which triggers sporulation |
| Spores do not stain easily. Perhaps you have seen them as untainted white objects inside bacillus species in other standing procedures. If they are visible as untainted objects in other stains, of what use is the endospore stain | A. Identify spores. B. Rule out spore- like structures including inclusions, vacuoles |
Created by:
Khuller