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Microbio Lab 1 pt 2
| Question | Answer |
|---|---|
| What is the objective of the aseptic technique? | To maintain axenic (pure) cultures, to avoid contamination |
| Describe the method for handling the cap of a test tube while transferring cultures: tube to tube, tube to plate | Between inoculations, caps should remain on test tubes at all times. When removing cap, hold it between your pinky and palm/ Do not lay cap on work area |
| Why should the plate remain inverted when working with a culture grown on an agar plate? | To avoid contamination/ So condensations doesn't leak onto the culture |
| What should be done if living material is spilled? | Cover the involved area with disinfectant and notify the instructor immediately |
| What characteristics are generally noted when observing a specimen prepared with a simple stain? | Cellular morphology, arrangement, endospores |
| What is a differential stain? What is the most widely used? | Involves the application of two or more reagents, imparting color to a cell or its parts/ Gram stain |
| Describe the appearance of a Gram + organism on a slide and a Gram - | Gram+ appear blue or violet after decolorization by alcohol/ Gram- appear pink or red and have an outer membrane with a high lipid content |
| List and describe the steps in smear preparation pt1 | Wash slide with soap & dry/ label slide with a permanent marker with organism initials/ prepare smear from agar/ loop of water on slide, flame loop |
| List and describe the steps in smear preparation pt2 | get small amount of culture and mix with water until cloudy/ spread to a dime size and allow to air dry/ flame loop/ heat-fix bacteria to slide/ allow slide to cool |
| Briefly describe the procedure for heat fixation | Pass slide 2-3 times through flame. This stops all enzymatic activity within the cell and has an adhesive effect |
| Two reasons heat-fixation is used in smear preparation | Keeps cell structure from being destroyed by enzymes/ Makes cells adherent to the slide |
| List and describe the steps used in the preparation of a Gram stain. | prepare a bacterial smear to be stained/ cover smear with crystal violet and let stand for 1 min/ rinse slide/ cover with iodine for 1 min/ rinse/ use alcohol until clear/ rinse/ use safranin for 2 min/ rinse and blot dry on bibulous paper |
| Briefly describe the general function of each step of gram staining. | 1 the cell wals of both Gram+ and - bacteria affix crystal violet/ Iodine forms large crystals within the dye to be deposited into the peptidoglycan layer/ Alcohol decolorized gram- bacteria/ Safranin counterstains gram - bacteria |
| Describe the technique for the isolation of a pure culture from a mixed culture | |
| List and describe five basic features require for the complete identification of a microbe (pg. 29-30) | Morphological: Shape, size, grouping, Gram reaction |
| List and describe five basic features require for the complete identification of a microbe (pg. 29-30) | Colonial: Form, elevation, margin, optical, color |
| List and describe five basic features require for the complete identification of a microbe (pg. 29-30) | Biochemical: Presence or absence of enzymes, detected by growth or chemical tests |
| List and describe five basic features require for the complete identification of a microbe (pg. 29-30) | Antigenic structure: antibodies are mixed with unknown to determine if the unknow has antigens to antibodies, strains can be identified |
| List and describe five basic features require for the complete identification of a microbe (pg. 29-30) | Virulence of Pathogens: Identified by animal or plant inoculation/ organisms are examined for clinical aspects of the disease |
| List and describe the five colonial characteristics of bacteria | Form: shape of colony/ Elevation: colony above agar/ Margin: edges of colony/ Optical characteristics: light interaction with colony/ Color |
| Describe the streak plate technique for the isolation of pure cultures | Flame loop/ cool loop in media after each flame/ Use loop to obtain a small amount of inoculum/ smear on top quadrant to line/ flame loop/ smear from previous line to bottom quadrant & line/ flame loop/ smear on last quadrant/ flame loop |
| Be able to recognize the common shapes and arrangements of bacteria | |
| Explain possible errors in Gram staining | Vigorous decolorization could cause all cells to loose primary stain/ The age of bacterial culture may affect the results of gram staining |
Created by:
Clinton Perdue
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