3. One gram of soil was suspended in 9 ml saline and thoroughly mixed. From this suspension, 4 serial, 1:10 dilutions were made. 200 hundred microliters of each of the last four serial dilutions were used for spread plating on TY media, resulting in 5600 colonies, 412 colonies, 54 colonies and 8 colonies. What do you calculate as the bacterial concentration in the soil? (For your information 1 gram = 1 ml)

3. One gram of soil was suspended in 9 ml saline and thoroughly mixed. From this suspension, 4 serial, 1:10 dilutions were made. 200 hundred microliters of each of the last four serial dilutions were used for spread plating on TY media, resulting in 5600 colonies, 412 colonies, 54 colonies and 8 colonies. What do you calculate as the bacterial concentration in the soil? (For your information 1 gram = 1 ml)

An Illustrated Guide To Vet Med Term

4th Edition

ISBN:9781305465763

Author:ROMICH

Publisher:ROMICH

Chapter16: Testing Testing

Section: Chapter Questions

Problem 3MC

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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 work
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.
15. Agar is used for solidifying culture media because: it does not affect the growth of bacteria it does not add to the nutritive properties of the medium the melting and solidifying points of agar solution are not the same all of the above
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 above
1. 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?
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?
1.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. Which of the following is NOT true of spread plating method? A. the maximum inoculum allowed is 1.0 ml B. spreading of the inoculum is done using a disinfected glass L-rod C. A pre-solidified medium is required prior to inoculation of the sample. D. A and B 2. Plates inoculated with bacteria are inverted during incubation to: A. prevent contamination B. limit the colony growth C. A and B D. A and C E. All of the above F. None of the above
1. What is the most common sterilization technique used in laboratories? 2. List at least 5 procedures of the aseptic technique and describe its uses. 3. Why is Gram stain one of the most important and widely used stains in bacteriology? 4. Explain the Gram staining technique in chronological order. Indicate the reagent used and the time of usage on each reagent.
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 suspension
1) would you describe the contents of the soil-inoculated broth as being a “pure culture”? Why or why not? 2) How did the uninoculated broth differ in appearance from the broths inoculated with E. Coli and M. Luteus? And then how could you tell if a supposedly sterile, uninoculated broth was contaminated? Please explain in detail and highlight the important parts cuz I am confused and need help! Thanks
6a. A sample is given to you that contains 6 million cells per ml. You must make a series of serial dilutions in order to get a countable number on a plate to prove that there are indeed 6 million cells per ml. The plate that you eventually put a sample of bacteria on must have between 10 and 100 colonies for ease of counting. What dilutions do you make to get this many colonies on a plate? How many colonies do you have on that plate? Show what dilutions you make (Write exactly how much liquid you move into each test tube and how much liquid was in the test tube, ex. Move 1 ml of culture into 9 ml of water – 10x dilution). Don’t forget to tell me how much liquid you eventually put on your plate. (If you want to draw something out, you could draw then take a picture of it with your phone and submit the image along with the worksheet). 6b. Do the same problem as in 6a, but now you have to do it in 3 test tubes or less. What dilutions do you do now? please use drawings to help…