Laboratory Experiments in Microbiology (12th Edition) (What's New in Microbiology)
12th Edition
ISBN: 9780134605203
Author: Ted R. Johnson, Christine L. Case
Publisher: PEARSON
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Chapter 22, Problem 2CT
Assume that a DRT value for autoclaving a culture is 1.5 minutes. How long would it take to kill all the cells if
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The solution containing bacterial spores is heated in an autoclave. When the autoclave has reached a constant temperature of 121 °C, there are still 106 spores/ml. The specific death constant for bacterial spores at 121 ° C is 11.62 min-1. How long should the heating be continued at a constant temperature so that there are 1 spores/ml left?
Enter the answer in minutes to three decimal places.
In an experiment to calculate the decimal reduction time for an Escherichia coli culture, viable cells were exposed to a constant temperature of 80°C for a set amount of time. After exposure, the remaining number of surviving cells were counted. Based on Table 1, what is the decimal reduction time?Table 1. Decimal Reduction Time for E. coli Heated to 80°C
Total time of exposure (minutes):
Number of Microbial Cells Present:
0
100
1
80
3
50
4
42
6.5
26
13
10
21
0
There are two cultures of yeast cells in the pictures, one has been incubated for 6 hours and one has been incubated for 24 hours. After a 10x dilution by taking 100µl of each culture and adding it to 900 µl water in a microcentrifuge tube and 100µl sample from the tube was taken to view in the counting chamber.
a) Count the total number of yeast cells for each culture respectively
b) Calculate the concentration and density of yeast cells for each culture respectively
Chapter 22 Solutions
Laboratory Experiments in Microbiology (12th Edition) (What's New in Microbiology)
Ch. 22 - Prob. 1QCh. 22 - Prob. 2QCh. 22 - Give an example of a nonlaboratory use of each of...Ch. 22 - Define the term pasteurization. What is the...Ch. 22 - Explain why fungi and Bacillus sometimes grow...Ch. 22 - Assume that a DRT value for autoclaving a culture...Ch. 22 - Indicators are used in autoclaving to ensure that...Ch. 22 - A biological indicator used in autoclaving is a...Ch. 22 - The source of Legionella causing...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- You just finished plating your electroporatio products on your YPD-Zeocin plate and you think you did everything perfectly but you come back the folloeing week and have zero colonies. Which of the following could be the reason for the absence of colonies? A) You centrifuged your electroporated cells for 30 sec at 16,000 rpm instead of 4,000 rpm before plating them B) You added sorbitol+YPD to your cells thirty minutes after pulsing your cells C) The Zeocin had not been added to the plates when they were made. D) All of the above E) Both a and b onlyarrow_forwardWhat would the final concentration of a bacteria culture be if 2.7 x 106 cells/ml were diluted 8.2 x 10-2? What would the initial concentration of a bacteria culture be if the final concentration was 3.7 x 102 cells/ml and the total dilution was 4.6 x 10-4?arrow_forwardThe culture you are working has a doubling time of 2 hours and a cell density of 3 x 106 cells per mL. For your experiment, you first dilute the culture 100 fold. Assuming that there is no lab phase and that the cells remain in exponential growth the entire time, what is the cell density (cells/mL) after 10 hours?arrow_forward
- (b) A Food material containing Bacillus stearothermophilus PS1518 as an indicator organism ts subjected to heat sterilization at 121 C. Calculate the time required to reduce the organism to one tenth of the original number. Fo value for the organism is 4 minutes and the decimal reduction time , D, at 116°C is 40 minutes. Assume operation is at constant temperature of 121°C. HINT Fo = -To 10 dt Where Fo = equivalent exposure time at 121°C of the actual exposure time at a variable temperature To = the reference temperature =121 C, z=10 = number ofC necessary for10fold increase in Farrow_forwardAssume that you are adding 300 microliters of 1% substrate solution per well in a 24-well plate. If we can order 5 milligrams of fibronectin for $871.00, how much would it cost to have enough to use every well of the 24-well culture plate?arrow_forwardA culture of S. cerevisea has an overnight OD of 2.3 (1.0 OD is approx 1.0x107 cells/ml) You will be plating 100µl onto agar and want the final count of colonies on the plate to be around 300 colonies. How much of the 2.3 OD culture must you use to get a 500µl subdilution (with sterile water), so that you have diluted enough to get approx 300 colonies per 100ularrow_forward
- During the heat shock step, a student accidentally heated the cells at 42°C for 5 minutes. Only a few colonies were found on the agar plates at the end of the experiment. Explain the results.arrow_forwardIf 0.1 ml of a 1 * 10−6 dilution plate contains 56 colonies, calculate thenumber of cells per ml of the original culturearrow_forwardA culture with approximately 4x105 cells/mL were incubated. After 10 hours, the number of cells had increased to 5x109. a) How long was the generation time in minutes?b) How many generations have occurred?arrow_forward
- Why should agar media be completely dissolved before they are dispensed in tubes and plates? What are the bases for pegging the temperature at 1210C for 15-30 minutes during moist heat sterilization and 1800C for two (2) hours using dry heat sterilization? Can you sterilize culture media using dry heat sterilization? Why is that so? You will notice in the videos shown, the cotton plug is not used. What is role of cotton plug in media prep, sterilization and culture of microorganisms? Instead of using cotton plug, plastic screw-cap is used, can you substitute this for the former? Is it technically acceptable in microbiology?arrow_forwardThe PD# of your culture is 165. You plated 3745 cells per well. You have recovered 12,655 cells. What's the new PD#?arrow_forwardA culture is incubated for 10 hours. 1 hours after inoculation it reached the exponential growth phase. At this time point the cell density was 1x10^4 cells/ml. 5 hours after inoculation (still during the exponential growth phase) the cell density was 1x10^7 cells. Calculate K and g(t). The growth constant (k) is minute. (round to 3 decimal points) The generation time (gt) is minutes. (round to whole number)arrow_forward
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