Microbiology: Principles and Explorations
9th Edition
ISBN: 9781118743164
Author: Jacquelyn G. Black, Laura J. Black
Publisher: WILEY
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Chapter 6, Problem 21SQ
Summary Introduction
Introduction: Plate count techniques are mainly based on bacterial cell reproduction on the agar plates. It is a traditional method, and it is used for probiotic product quality assurance.
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A sample of Earth Alive Soil Activator was diluted by transferring 1 gram into a 9 ml dilution blank (tube A) and then serially diluted five (5) more times by transferring 1 ml of a previous dilution into a tube of 9 ml of sterile water. After making these serial dilutions, 2 ml samples were taken from tubes D, E, and F, added into empty petri dishes, and molten PCA was poured into each petri dish. Tubes A, B, and C were heated in a 80˚C water bath for 30 minutes, 2 ml samples of these tubes were added into empty petri dishes, and molten PCA was poured into each petri dish. These plates were allowed to solidify, and they were incubated at 35˚C for 48 hours. After the incubation period, you counted CFUs on all 6 plates. The results of your CFU counts are contained in table 1.
Table 1. CFU counts for 3 plates from the heated dilutions (A-C) and the 3 plates from the non-heated dilutions (D-F)
# CFUs
Not heated
Heated
A
--
400
B
--
45
C
--
6
D
350
--
E
31
--
F
2
--…
a) What is the dilution factor if you add a 1ml aliquot of a specimen to 99ml of diluent?
b)How to make 500ml of a 1:250 dilution?
In this experiment, a culture was serially diluted to the concentrations below. Each plate was plated with 0.25mL of the dilution. Using the most diluted plate, what is the correct concentration of the original culture?
A) 2.0 X 10^-3 cells/mL
B) 2.0 X 10^5 cells/mL
C) 4.0 X 10^5 cells/mL
D) 5.0 X 10^4 cells/mL
Chapter 6 Solutions
Microbiology: Principles and Explorations
Ch. 6 - What are the differences between the lag phase and...Ch. 6 - How does logarithmic rate of increase differ from...Ch. 6 - Prob. 1.3SCCh. 6 - Why does a direct microscopic count of bacteria...Ch. 6 - What does the ending -phile mean? Distinguish...Ch. 6 - What enzymes do most obligate anaerobes lack? How...Ch. 6 - Prob. 2.3SCCh. 6 - Prob. 3.1SCCh. 6 - Distinguish between the various kinds of media:...Ch. 6 - What is the purpose of a stock culture? Why is it...
Ch. 6 - Prob. 1CCSCh. 6 - Exactly 100 bacteria with a generation time of 30...Ch. 6 - In the above example, do you think that the number...Ch. 6 - Prob. 3CTQCh. 6 - Prob. 1SQCh. 6 - Match the following growth phase terms to their...Ch. 6 - Which of the following is the best definition of...Ch. 6 - Prob. 4SQCh. 6 - The most probable number (MPN) technique is a...Ch. 6 - Match the terms with their definitions:Ch. 6 - Prob. 7SQCh. 6 - Why do foods containing a high concentration of...Ch. 6 - Some bacteria have complex nutritional...Ch. 6 - Prob. 10SQCh. 6 - Which type of cell will shift to aerobic...Ch. 6 - Which of the following statements about endospores...Ch. 6 - Prob. 13SQCh. 6 - Blood agar is often used to observe changes in the...Ch. 6 - A bacterial medium that contains 20 grams of beef...Ch. 6 - MacConkey agar contains the dye, crystal violet,...Ch. 6 - Prob. 17SQCh. 6 - What are the purposes of carrying out the streak...Ch. 6 - Prob. 19SQCh. 6 - During quorum sensing, bacteria sense their...Ch. 6 - Prob. 21SQCh. 6 - Identify the position of each of the following on...
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- - What is a pure culture? - Describe the procedure for making a streak plate from a clinical specimen (like a urine culture). - What is the desired outcome (result) of a streak plate? - Clinically, why is it important to make a pure culture from a clinical specimen? What do you do next in order to treat the patient?arrow_forwardA culture of E. coli is diluted as follows:(1) 65mL are added to 435mL of water.(2) 10uL from (1) are then added to 9.99mL of water.(3) A 10-3 dilution is made from tube # (2).(4) 100uL from (3) are plated for a pour plate and incubated. There were 34 colonies counted on one quarter of the plate following incubation. a) What was the overall dilution?b) How many cfu/mL were present in the original culture?c) How many milliliters of water is needed to make a 10-3 dilution using 1000 uL from the original culture?arrow_forwardYou have found that the D-value (decimal reduction value) of an antimicrobial agent to be 4 minutes when the agent was exposed to a bacterial culture having an initial total viable cel1 count of 10° CFU/mL. After 4 minutes upon addition of the antimicrobial agent, what would have been the total viable count of the culture in this experiment? A) O 10° CFU/mL B) O 10$ CFU/mL C) O 10° CFU/mL D) O 10' CFU/mLarrow_forward
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