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Cover Your Cough! A Short and Simple Activity to Demonstrate the Antimicrobial Effect of Desiccation

    Author: Jennifer Cook Easterwood1
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    Affiliations: 1: Department of Biology, Queens University of Charlotte, Charlotte, NC 28274
    AUTHOR AND ARTICLE INFORMATION AUTHOR AND ARTICLE INFORMATION
    • Published 02 December 2013
    • Corresponding author. Mailing address: Department of Biology, Queens University of Charlotte, 1900 Selwyn Ave., Charlotte, NC 28274. Phone: 704-337-2261. Fax: 704-337-2325. E-mail: easterwj@queens.edu.
    • ©2013 Author(s). Published by the American Society for Microbiology.
    Source: J. Microbiol. Biol. Educ. December 2013 vol. 14 no. 2 263-264. doi:10.1128/jmbe.v14i2.602
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    Abstract:

    Many undergraduate microbiology laboratory manuals include exercises demonstrating the antimicrobial effects of physical agents, such as UV light and heat, and chemical agents, such as disinfectants and antibiotics (3, 4). There is, however, a lack of exercises examining the effects of desiccation on bacterial growth and survival. This particular form of antimicrobial control is especially relevant today with an increased emphasis on coughing and sneezing into one’s sleeve or a tissue, where microbes will not contaminate hands and will eventually desiccate and die (2). Desiccation can have bacteriostatic or bactericidal effects depending on the species, the material on which the organism has desiccated, and the length of time. The absence of water can damage many cellular components, including enzymes, nucleic acids, and cell membranes (1). However, many prokaryotes have some degree of resistance to desiccation, with Escherichia coli surviving around 24 hours and Bacillus species surviving upwards of 300 years, though these numbers can vary due to a number of confounding factors (5). Some of these factors include the method by which desiccation occurred, whether desiccation occurred in a natural or laboratory situation, and the species itself (5). To address the effects of desiccation on bacterial growth and survival, a short, simple exercise was developed. By inoculating various materials with bacterial cultures and allowing them to air-dry for 24 hours, students can visualize the effects of desiccation by analyzing the growth, or lack thereof, when organisms are transferred to nutrient agar plates. This exercise has been used in a health professions microbiology course as well as a microbiology course for biology and biochemistry majors. It is short enough to be conducted during a standard lecture period or during a longer laboratory period in conjunction with other experiments demonstrating the effectiveness of physical agents on microbial growth

Key Concept Ranking

Nutrient Agar
0.6666667
Nutrient Broth
0.625
Escherichia coli
0.5833333
Bacterial Growth
0.54364324
0.6666667

References & Citations

1. Billi D, Potts M 2002 Life and death of dried prokaryotes Res Microbiol 153 7 12 10.1016/S0923-2508(01)01279-7 11881900 http://dx.doi.org/10.1016/S0923-2508(01)01279-7
2. Centers for Disease Control and Prevention 2010 Cover your cough [Online.] http://www.cdc.gov/flu/protect/covercough.htm
3. Johnson TR, Case CL 2013 Laboratory experiments in microbiology 10th ed Benjamin Cummings San Francisco, CA
4. Leboffe MJ, Pierce BE 2012 Brief microbiology laboratory theory and application 2nd ed Morton Publishing Englewood, CO
5. Potts M 1994 Desiccation tolerance of prokaryotes Microbiol Rev 58 755 805 7854254 372989
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/content/journal/jmbe/10.1128/jmbe.v14i2.602
2013-12-02
2017-11-19

Abstract:

Many undergraduate microbiology laboratory manuals include exercises demonstrating the antimicrobial effects of physical agents, such as UV light and heat, and chemical agents, such as disinfectants and antibiotics (3, 4). There is, however, a lack of exercises examining the effects of desiccation on bacterial growth and survival. This particular form of antimicrobial control is especially relevant today with an increased emphasis on coughing and sneezing into one’s sleeve or a tissue, where microbes will not contaminate hands and will eventually desiccate and die (2). Desiccation can have bacteriostatic or bactericidal effects depending on the species, the material on which the organism has desiccated, and the length of time. The absence of water can damage many cellular components, including enzymes, nucleic acids, and cell membranes (1). However, many prokaryotes have some degree of resistance to desiccation, with Escherichia coli surviving around 24 hours and Bacillus species surviving upwards of 300 years, though these numbers can vary due to a number of confounding factors (5). Some of these factors include the method by which desiccation occurred, whether desiccation occurred in a natural or laboratory situation, and the species itself (5). To address the effects of desiccation on bacterial growth and survival, a short, simple exercise was developed. By inoculating various materials with bacterial cultures and allowing them to air-dry for 24 hours, students can visualize the effects of desiccation by analyzing the growth, or lack thereof, when organisms are transferred to nutrient agar plates. This exercise has been used in a health professions microbiology course as well as a microbiology course for biology and biochemistry majors. It is short enough to be conducted during a standard lecture period or during a longer laboratory period in conjunction with other experiments demonstrating the effectiveness of physical agents on microbial growth

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Figures

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FIGURE 1.

Materials used to demonstrate desiccation.

Source: J. Microbiol. Biol. Educ. December 2013 vol. 14 no. 2 263-264. doi:10.1128/jmbe.v14i2.602
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FIGURE 2.

Results of desiccation tolerance of and on doorknobs.

Source: J. Microbiol. Biol. Educ. December 2013 vol. 14 no. 2 263-264. doi:10.1128/jmbe.v14i2.602
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