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MIBO 3500L Final Exam with complete solutions
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MIBO 3500L Final Exam with complete solutions
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MIBO 3500L Final Exam with complete solutionsCulture - Answer -A nutrient medium growing one or more species of microorganisms
Pure culture (anexic) - Answer -When a culture contains only one species of microorganism
-Simplifies experimental design and interpretation of results
-Must be made up of individual cells of a single genetic makeup (genotype)
-A colony is usually derived from a single cell and thus can be used to inoculate medium
and generate this
Wire (platinum) inoculating loop - Answer -Used to transfer microbes from one culture medium to another, expedites sterilization and inoculation processes because:
-Conducts heat extremely well
-Cools just as rapidly as it acquires heat
Plastic inoculating loop - Answer -Used to transfer microbes from one culture medium to
another
-Not flamed before use
-Pre-sterilized and disposable
Inoculating wooden stick - Answer -Used to transfer microbes from one culture medium to another
-Pre-sterilized
-Reusable
-Not flamed before use
TSBYE tube inoculations - Answer -1. Hold sterilized transfer instrument (either loop or stick) in your dominant hand
2. Hold the bacterial culture in your non-dominant hand
3. Remove the cap of the bacterial culture without touching your transfer instrument to anything
-One way to do this is to curl the little finger of your dominant hand around the cap and twist it off
4. Dip the transfer instrument into the bacterial culture, then remove the instrument and replace the cap on the culture tube -Work carefully but quickly; the longer the tube is open the higher the risk of contamination from airborne microbes...only uncap the tube when you are ready to use it
5. While still holding the transfer instrument, place the bacterial culture back in the test tube rack and pick up the TSBYE tube
6. Remove the lid of the TSBYE tube the same way you did in step 4
7. Dip the transfer instrument containing bacteria into the TSBYE tube, then remove the instrument and replace the cap on the tube
-This will inoculate the TSBYE medium with the bacteria from the transfer instrument
8. Set the newly inoculated TSBYE tube back in the test tube rack and discard your transfer instrument in the appropriate waste container
9. Inoculate your second tube as a "mock control" (no bacteria)
10. Your TA will inoculate your tubes at 37°C for 24 hours then store them for you to view next class
11. Observe the TSBYE tubes for turbidity (cloudiness), which is an indication of bacterial growth
TSAYE slant inoculations (EXERCISE 1.4 - Culture Transfer Techniques) - Answer -1. Hold sterilized transfer instrument (either loop or stick) in your dominant hand
2. Hold the bacterial culture in your non-dominant hand
3. Remove the cap of the bacterial culture without touching your transfer instrument to anything
-One way to do this is to curl the little finger of your dominant hand around the cap and twist it off
4. Dip the transfer instrument into the bacterial culture, then remove the instrument and replace the cap on the culture tube
-Work carefully but quickly; the longer the tube is open the higher the risk of contamination from airborne microbes...only uncap the tube when you are ready to use it
5. While still holding the transfer instrument, place the bacterial culture back in the test tube rack
6. Pick up the TSAYE slant with your non-dominant hand and remove the lid the same way you did in step 4
7. Place the transfer instrument flat against the agar and gently move the instrument in a zigzag motion up the slant from bottom to top
8. Set the newly inoculated TSAYE slant back in the test tube rack and discard your transfer instrument in the appropriate waste container
9. Inoculate your second slant as a "mock control" (no bacteria)
10. Your TA will inoculate your tubes at 37°C for 24 hours then store them for you to view next class
11. Observe the TSAYE slants for a thick film of bacteria on the surface of the slant
Describe one advantage/disadvantage of using TSBYE versus TSAYE slant to grow organisms. - Answer -There is much less room for error when transferring the culture
-Simply dip and stir the culture into the broth -With TSAYE, a certain technique and more attention to detail are required as too harsh
of a streak can puncture the agar and compromise culture growth
Streaking for isolation - Answer --A sterile loop is used to spread the cells out on a solid surface, usually agar, to create single colonies from a population of cells
-The individual single cells will grow and divide, each forming a single visible colony
-Ensures that growth of each of the starting cells yields a colony isolated from all others
-Allows one to separate microbes from one another in a mixed culture
Not all microbes are pathogenic - Answer -Less than 1% are pathogenic
- Humans can greatly benefit from microbes(antibiotics, fertilizers, pharmaceuticals and bioremediation)
- Microbes drive the cycles of many chemical elements critical to live on Earth (e.g. C, N, S, P,O, etc)
Streaking for isolation procedure (EXERCISE 1.5 - Streaking for isolation) - Answer -1. Label the bottom of a Petri dish with your name, the microbe, the date, and the medium (TSAYE)
2. Sterilize your loop or select a pre-sterilized loop/wooden stick
3. Using aseptic technique, dip the sterile loop/stick into the pure bacterial culture you were given
4. With your plate on the bench top, lift the lid on one side enough to allow you to transfer the liquid on the loop/stick onto one quadrant of the agar surface; spread a modest amount of culture in a small patch
5. Using a NEW stick, pass through the patch once and streak a small area nearby
6. Using another NEW stick, pass through the previous streak and streak a larger area; usually the greatest number of single colonies will be here, which is why it's useful to make this one the largest
7. With one last NEW stick, pass through the previous streak, and streak using the remaining surface of the plate
8. Incubate your plates inverted at 37°C; the plates will be removed after 24-48 hours and kept for you to view at the next lab meeting
9. Repeat steps 4-7 with the mixed culture
Microbial diversity in the laboratory (pt. 1) procedure (EXERCISE 1.6 - Observing and enumerating microbes in the environment) - Answer -1. Use a Sharpie to label the edge of the underside of the TSAYE plate with your name, date, and media (writing on the edge gives more space to observe your colony morphology later)
2. Draw a line down the center of the underside to break the plate into two halves
3. Use a sterilized cotton swab to swab an area of the laboratory of your choosing (wet the swab with saline if you choose a dry area as this will increase the likelihood of getting microbes onto the swab)
4. Lightly zig-zag the swab onto one half of the plate, almost completely covering it to produce a growth streak
5. Use a Sharpie to label this half with the area you swabbed from
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