Laboratory Experiments in Microbiology (11th Edition)
11th Edition
ISBN: 9780321994936
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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Chapter 22 Solutions
Laboratory Experiments in Microbiology (11th Edition)
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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- starting with four bacterial cells per milliliter in a rich nutrient medium, with a 1-hour lag phase and a 30-minute generation time, how many cells will there be in 1 ml of this culture after 10 hours?arrow_forwardIn 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 0arrow_forwardThere 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 respectivelyarrow_forward
- The 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_forwardYou 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_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_forwardA culture of S. cerevisea has an overnight OD of 4.5 (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 4.5 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_forwardA strep culture is sampled at two points in time, 1 hour and 10 minutes apart. 3.2 x 105 cells/ml are found in the first sample, and 1.8 x 107 cells/ml in the second sample. What was the generation or doubling time (in minutes)?arrow_forward
- If 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_forwardWhy 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_forward
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cell culture and growth media for Microbiology; Author: Scientist Cindy;https://www.youtube.com/watch?v=EjnQ3peWRek;License: Standard YouTube License, CC-BY