3.A bacterial culture was diluted and results from duplicate plates were obtained as indicated below. What was thenumber of colony forming units/mL of the original culture?Dilution used for plating10-210-310410-510⁰10-710-84.5.Amount plated0.1 mL0.1 mL0.1 mL0.1 mL0.1 mL0.1 mL0.1 mLColony counts after incubation(Results from duplicate plates)Too many to countToo many to count341 41399 17527 : 297:20:0Ten grams of hamburger were added to 90 mL of sterile buffer. This was mixed well in a blender. One-tenth of amL of this slurry was added to 9.9 mL of sterile buffer. After thorough mixing, this suspension was further dilutedby successive 1/100 and 1/10 dilutions. One-tenth of a mL of this final solution was plated onto Plate Count agar.After incubation 145 colonies were present. How many colony-forming units were present in the total 10 gramsample of hamburger?Devise a serial dilution scheme to prepare a 10-5 dilution on a plate using the least number of sterile water dilutiontubes.Devise a serial dilution scheme to prepare 1/10, 1/30 and 1/90 dilutions of a disinfectant.

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3. A bacterial culture was diluted and results from duplicate plates were obtained as indicated below. What was the number of colony forming units/mL of the original culture? Dilution used for plating 10-² 10-3 104 10-5 10-6 10-7 10-8 Amount plated 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL Colony counts after incubation (Results from duplicate plates) Too many to count Too many to count 341 413 99 175 27 29 7:2 0:0

3. A bacterial culture was diluted and results from duplicate plates were obtained as indicated below. What was the number of colony forming units/mL of the original culture? Dilution used for plating 10-² 10-3 104 10-5 10-6 10-7 10-8 Amount plated 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL Colony counts after incubation (Results from duplicate plates) Too many to count Too many to count 341 413 99 175 27 29 7:2 0:0

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter26: Prokaryotes: Bacteria And Archaea

Section: Chapter Questions

Problem 8TYK

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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)
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. You are given a 1 gram soil sample of unknown bacterial load. After doing 10-fold serial dilutions of the soil in sterile water, 100 uL volumes are taken from each dilution for preparation of pour plates. Following incubation, you are observing the growth of the plate prepared from the 10-8 plate. You divide the plate into two equal parts and count 46 colonies in each half.a) What was the dilution factor?b) How many total colonies were on the plate?c) Was your count valid?d) How many bacteria were present in the soil sample?
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?
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. What is the statistically significant number range of colonies that may be counted on a Petri dish (for the pour plate method)? 2. Scientific Notation. Fill in the missing information. a) 4.5 x 109 = _______ b) 50 x 107 = _______ c) 2300 x 1010 = _______ d) 0.54 x 108 = _______ 3. You wish to determine viable counts on a culture of Bacillus subtilis. You begin by pipetting 1 ml of culture into 99 ml of sterile water. After mixing the dilution well you make a series of 4 further dilutions of 10-1 each. From the three most dilute samples, you prepare three pour plates using 1 ml in each. After incubation you find the plate counts of the plates are 16, 245 and 890 respectively. a) Show the dilution scheme. b) What is the estimated viable count (cells/ml) in the original culture?
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.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.
2.1The number of bacteria in the samples need to be quantified. The laboratory uses a specificprotocol where the dilution factor on the spread plates must be:10-6; 10-7; 10-8Describe how you would prepare the required dilution series using the least amount of dilutionwater. 2.2 Calculate the amount of bacteria in the sample from the following results (show the steps in the calculation): Dilution factor Count10-6 27110-7 3510-8 21
8. 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.
An inoculum of 106 bacterial cells was introduced into a flask of culture medium and growth monitored. No change was seen for 18 minutes (the lag phase), then growth occurred rapidly. After a further 87 minutes, the population had increased to 5.08 × 107 cells. What is the doubling time of the culture? Show your solution. (The 87-minute period is after the lag phase.)
A serial dilution of a bacterial culture yields the following number of colonies. Which plate(s) should be used to determine the original cell density? Plate A Plate B Plate C Plate D Plate E Dilution Factor 10-5 10-6 10-7 10-8 10-9 # of Colonies Too many to count 850 456 80 14 Group of answer choices All of these choices A & B D & E E None of these choices A B & C D B C & D C