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Micro LABquiz #3
Exercises 5, 7, 3, 4
| Question | Answer |
|---|---|
| Fixed | to kill bacteria & stick to slide |
| Simple Stain | Uses only one stain; To determine cell shape, size, and arrangement |
| Direct Stain | Stains the bacteria |
| Negative Stain | Stains the background only |
| Basic Stain | Chromophore is a (+) ion |
| Acidic Stain | Chromophore is a (-) ion |
| Heat Fixing | Too much heat, denatures bacterial enzymes & causes autolysis of the cells |
| Gram Stain | differential stain that allows classification of Gram(+) or Gram(-) |
| Primary Stain (1) | Crystal Violet (CV) |
| Mordant (2) | Iodine (I) |
| Decolorizing Agent (3) | Alcohol (washes out primary stain of GM-) |
| Secondary Stain/Counterstain (4) | Safranin (turns GM- red) |
| Gram Positive | Multiple layers of Peptidoglycan in cell wall; Alcohol dehydrates cells walls and holds in CV-I |
| Gram Negative | Thin layer of Peptidoglycan surrounded by thick outer lipid layer; Alcohol dissolves outer lipid layer & CV-I wash out through Peptidoglycan layer |
| Why will Gram+ cells more than 24hrs old stain gram negative? | As bacteria die, cell walls degrade and do not retain primary stain |
| Which step can be omitted without affecting determination of the Gram reaction? | Safranin |
| What would happen if you performed a gram stain on human cells? | The primary stain would wash out because they do not have CELL WALLS |
| Chemically Defined Medium | Exact chemical composition is known |
| Complex Media | Chemical composition varies from batch to batch |
| Nutrient Broth | liquid complex medium |
| Nutrient Agar | Peptone, Beef Extract, NaCl, Agar, Distilled Water |
| Agar | An extract from marine red algae; Remains solid & few microbes can eat it |
| Steam Sterilization | Autoclaving, uses steam under pressure |
| Petri Plates | provide large surface area for growing and observing colonies |
| Inoculated | intentionally introduced to keep alive and study growth |
| Incubation Period | inoculated bacteria increase in number during |
| Turbid | cloudy |
| Colony | population of cells that arise from a single bacterial cell |
| Colony-Forming Unit (CFU) | group of the same microbes attached to one another |
| Flocculent | clumps of microbial cells |
| Pellicle | membrane across the surface (typically broth) |
| Sediment | microbial cells settled at the bottom of tube |
| Contaminants | unwanted microbes |
| Aseptic Technique | used to exclude contaminants |
| Broth Cultures | provide large # of bacteria in a small space; easily transported |
| Agar Slants | provide solid growth surface, easier to store & transport (VS petri plates) |
| Agar Deeps | grow bacteria that require LESS oxygen; test for motility (motile bacteria grow away from stab line) |
Created by:
kwright0005
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