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1. Should you see signs of microbial growth in a sterile medium if you allow it to incubate for several days? Explain your answer.

2. Do you think there were any deficiencies in your aseptic technique, and if so, can you identify them? Explain your answer. If there were no deficiencies in your aseptic technique, identify at least one potential way through which contamination could occur while working with cultures.

3. Which was most challenging for you in terms of aseptic technique: transfer from broth to broth, broth to slant, or broth to plate? Explain your answer.

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Related questions

For Microbiology, I am doing a lab and am stuck on two of thequestions. It is 1-4 Common Aseptic Transfers and InoculationMethods.

1) Which medium was most difficult for you to transfer from?Which medium was most difficult for you to inoculate? Explain yourdifficulties. (Note: there are no current answers to thesequestions, but based on your evaluation of personalexperiences)

2) Did you get growth on/in the sterile NB and NA slant tubesyou practiced with? If so, where did you see it and what might havebeen its source(s)?

purplegnat545

Considering the cultures to be used for inoculating each medium in this exercise, how many microbial types should you expect to see in/on each medium?

Select one:

a. 3

b. 0

c. 1

d. Several

e. 2

Which of the following is common to minimize airborne contamination?

Select one:

a. Make someone else do the experiment

b. Perform the experiment in a windy room

c. Keep a microscope nearby

d. Breathing in sample

e. Hold open tubes at an angle

How can a hot sterile flame loop be cooled quickly to use in the next streak?

Select one:

a. Put in sterile portion of agar plate

b. Blow on it

c. Stick the loop in ice

d. Set the loop on the lab bench

e. Pour tap water on the loop

True or false: Most colonies can been seen without aid (naked eye), and most single cells cannot be seen without a microscope.

Select one:

True

False

An isolated, single colony forms after incubation of a:

Select one:

a. Virus (viral particle arrangement in some cases)

b. Single cell (cell arrangement in some cases)

c. Sterile agar plate

d. Sterile flame loop

e. Liquid mixed culture

These are commonly used for growing stock cultures that can be refrigerated for several weeks:

Select one:

a. Broth tubes

b. Cotton swabs

c. Gym socks

d. Agar slants

e. Petri dishes

Beginning at the base of the slant surface and gently moving the loop back and forth as you withdraw is called:

Select one:

a. Slant mixing

b. Fishtail inoculation

c. Zig-zag streaking

d. Squirrel inoculation

e. Quadrant streaking

If you are going to mix a broth culture prior to transfer, what is a safe way to do this without special equipment?

Select one:

a. Tap the tube with your fingers

b. Vortex it

c. Use a inoculating loop

d. Stick the tube in the outer cone

What is the primary purpose of the streak plate method?

Select one:

a. Quantify CFUs

b. Isolate an individual colony

c. Quantify the cell count of a mixed culture

d. Inoculate a culture on a plate

e. Confirm the identity of an unknown genus

Please answer questions at the end.

In this lab, you will add different volumes of âcell-free supernatantâ (CFS) to fresh cultures of V. harveyi and observe bioluminescence. The CFS is prepared by culturing V. harveyi in liquid medium overnight, then separating the cells from the supernatant by centrifugation.

MATERIALS â¢ overnight culture of V. harveyi in AB medium â¢ fresh AB medium â¢ 1 microcentrifuge tube â¢ 3 glass culture tubes

PROCEDURE

1. This experiment will be performed with your lab group. Label the microcentrifuge tube and 3 glass cultures tubes with your group number. Also, label the 3 glass culture tubes as follows: âMedia only,â âCells+fresh media,â and âCells+CFS.â

2. Using aseptic technique, pipet different volumes of fresh AB medium into the glass tubes as follows: 1 mL in the âMedia onlyâ tube, 800 ul in the âCells+fresh mediaâ tube, and 500 ul in the âCells+CFSâ tube.

3. Pipet 500 ul of the overnight culture into a microcentrifuge tube and centrifuge at maximum speed (>13,000 x g) for 5 min to pellet the cells.

4. After centrifugation is complete, transfer 300 ul of the cell free supernatant (CFS) from the microfuge tube to the glass tube labeled âCells+CFSâ. Be careful to avoid the cell pellet.

5. Remove the remaining supernatant from the microfuge tube using a micropipette and discard as culture waste.

6. Add 500 ul of fresh AB medium to the cell pellet in the microfuge tube and pipet up and down to resuspend until no clumps are visible.

7. Add 200 ul of the cell suspension to the âCells+fresh mediaâ tube and 200 ul of the cell suspension to the âCells+CFSâ tube. Note the time.

8. Place the 2 glass tubes containing cells in the 30 degree incubator/shaker.

9. After 1 hour and 2 hours, observe your tubes next to the âMedia onlyâ tube in a dark room. You will need to let your eyes adjust for at least 30 seconds (count to 30 slowly in the dark) before you can evaluate whether the cultures are luminescent or not. Also, make sure you try swirling the tubes in the darkroom and observe the tubes for a minute after you have stopped swirling. After the observation at the 1 hour time point, put your tubes back in the incubator shaker until the 2 hour time point.

10. Note your observations. At the end of the lab, place your tubes in the tube waste.

Questions

1. What were the expected results? Explain the rationale of the experiment. If you didnât obtain the expected results, hypothesize why not and describe how the experiment could be improved.

2. What are differences between luminescence and fluorescence?

3. Why do V. harveyi cultures glow more brightly when swirled vigorously? Be specific.

4. Imagine you have a mutant V. harveyi strain that canât synthesize autoinducer and another mutant V. harveyi strain that makes a defective luciferase. If you streaked both strains near (but not touching) each other on the same plate, would you expect to see light produced? If so, by which strain, where, and why?

5. You have two identical tubes of wild-type V. harveyi (with the same cell concentration in each tube) in fresh media. To one tube, you add CFS from a light-producing V. fischeri culture, and to the other tube you add an equal volume of fresh media. If both tubes of V. harveyi have the same light production, what can you conclude? Explain.

6. Many biomedical research labs study quorum sensing in V. fischeri or V. harveyi. How is studying light production in marine bacteria relevant to human health? List at least 3 different examples.

7. Why do you think it is important for bacteria to be able to control the expression of some genes based on the number of individuals present?