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- 4. All the following can be autoclaved EXCEPT: a) Biological material b) Glass ware c) Radioactive material d) Broth and gel media for growing bacteria5. The autoclave raises the atmospheric pressure to _____ : a) 10 psi b) 15 psi c) 20 k joules d) 25 watts6. In the experiment with serial dilutions, the plates which should be used for the final count for colonies should have a range of _______ CFU in order to have a reliable estimate: a) <10 b)10-15 c) 15-20 d) none of the above1.What advantage(s) does the pour plate method have over the streak-plate method? 2.Why is the loop flamed before it is placed in a culture tube? Why is it flamed after completing the inoculation? 3.Before inoculating and pouring molten nutrient agar into a plate, why must the agar first be cooled to 50° C? 4.Explain why plates should be inverted during incubation. 5.Explain why plates should be inverted during incubation.1. What is the hazard of the spattering tendency in heating a wire loop with specimens over a flame? 2. Why is heat a highly effective sterilizing agent?3. Which of the three methods of heat sterilization is the most appropriate and practical to use in sterilizing antibiotic solutions? (Direct flame, Dry heat, Moist heat)
- 4) You are interested in the total bacterial load of the bat guano. In order to determine this, you go back to your original broth culture and prepare a dilution series. You then spread 100 ml of each dilution onto 3 separate plates. You obtain the following results: Plate 1, 10 -1 dilution: 362 colonies Plate 2, 10 -3 dilution: 76 colonies Plate 3, 10 -5 dilution: 8 colonies. Based on your results, calculate the CFUs/ml in your original broth culture. show your work1. The Petri Dish method is used in microbiology to raise bacteria in: a) rapid growth b) pure culture c) septic environment d) all of the above 2. What is the difference between antiseptic and sanitization? 3. In order to prevent any kind of contamination the medium must be _________ before placing it in the Petri dish. a) lyophilized b) pasteurized c) autoclaved d) distilled1. Sally Monella found 344 bacterial colonies on one of her plates. She had prepared this plate after a serial dilution of a culture of Yersinia pestis. She had pipetted 1 ml sample of diluted Yersinia pestis from a tube with the overall dilution factor of 106 into a plate and covered it with agar. She used this plate to calculate the concentration in cells/ml of a bacterial culture. a) How many organisms were in the original culture? b) Were her results valid? Why or why not?
- You prepared 10-7, 10-8, and 10-9 dilutions of a bacterial suspension in sterile saline. Then you plated 0.15mL if each dilution onto each of 3 plates of nutrient agar. After incubation, the colonies were way too numerous to counton the plates prepared from the 10-7 dilution. The plates from the 10-8 dilution had 355, 360, and 350 colonies. The platesfrom the 10-9 dilution had 115, 117, and 118 colonies. Determine the concentration of colony forming units (cfu/mL) inthe original bacterial suspension8. The time of the incubation for the serial dilution experiment should be ___ hrs.: a) 12 b) 24 c) 48 d) one week 9. The autoclave temperature must be at least ___ : a) 100 oC b) 100 oF c) 121.6 oC d) 121.6 oF 10. The use of the autoclave ensures: a) the death of all bacteria b) the death of all bacterial spores c) all of the above d) none of the above.4. You used 1mL of a river water sample at a 10-3 dilution and added this to an agar plate. After incubation, you count 60 colonies. How many colony forming units (CFUs) are present? Show your work.
- 1. A plate with a final dilution factor of 107 produced 210 colonies. a) What was the original concentration in the sample? b) If you were to dilute the original sample with a dilution factor of 108, how many colonies would you count on the plate? c) If you were to dilute the original sample with a dilution factor of 106, how many colonies would you count on the plate? 2. Sally Monella found 344 bacterial colonies on one of her plates. She had prepared this plate after a serial dilution of a culture of Yersinia pestis. She had pipetted 1 ml sample of diluted Yersinia pestis from a tube with the overall dilution factor of 106 into a plate and covered it with agar. She used this plate to calculate the concentration in cells/ml of a bacterial culture. a) How many organisms were in the original culture? b) Were her results valid? Why or why not?The Petri Dish method is used in microbiology to raise bacteria in: a) rapid growth b) pure culture c) septic environment d) all of the above 2. What is the difference between antiseptic and sanitization?3. In order to prevent any kind of contamination the medium must be _________ before placing it in the Petri dish. a) lyophilized b) pasteurized c) autoclaved d) distille2. You use tubes to test aerotolerance of bacteria. From your samples you have 3 results: A. Bacteria growing on the surface. B. Bacteria growing throughout the tube, the agar shows cracks. C. Bacteria growing about 5 mm below the surface. Please interpret each bacterial result. (Give the bacteria an oxygen classification, explain what classification means and interpret the cracks in the agar.)