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Observing Chemotaxis in Using Soft Agar Assays in an Undergraduate Microbiology Laboratory

    Author: Cindy R. DeLoney-Marino1
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    Affiliations: 1: Department of Biology, University of Southern Indiana, Evansville, IN 47712
    AUTHOR AND ARTICLE INFORMATION AUTHOR AND ARTICLE INFORMATION
    • Published 02 December 2013
    • Corresponding author. Mailing address: Department of Biology, University of Southern Indiana, 8600 University Boulevard, Evansville, IN 47712. Phone: 812-461-5373. Fax: 812-465-1052. E-mail: crdeloney@usi.edu.
    • ©2013 Author(s). Published by the American Society for Microbiology.
    Source: J. Microbiol. Biol. Educ. December 2013 vol. 14 no. 2 271-272. doi:10.1128/jmbe.v14i2.625
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    Abstract:

    Chemotaxis, the directed movement of cells towards or away from a chemical, is both an exciting and complicated behavior observed in many bacterial species. Attempting to adequately visualize or demonstrate the chemotaxic response of bacteria in the classroom is difficult at best, with good models to illustrate the concept lacking. The BSL-1 marine bacterium (a.k.a. ) is easy to culture, making it an ideal candidate for experiments in an undergraduate microbiology course. A number of chemoattractants for have been identified, including a variety of sugars, nucleosides, and amino acids (1, 2). Below presents how the soft agar-based chemotaxis assay can be implemented in the undergraduate laboratory. As bacterial cells migrate towards one or more attractants in soft agar, students can directly observe the chemotaxic behavior of without the need to learn complicated techniques or use specialized equipment. Once the bands of bacterial cells are observed, the migration can then be disrupted by the addition of excess attractant to the soft agar, thereby visualizing what happens once cells are no longer in a gradient of attractant. In addition, soft agar plates lacking attractants can be used to visualize the random movements of bacterial cells that are non-chemotaxing. These exercises can be used in the microbiology laboratory to help students understand the complex behavior of bacterial chemotaxis.

Key Concept Ranking

Aliivibrio fischeri
0.5681818
Vibrio fischeri
0.5681818
Aliivibrio fischeri
0.5681818
Marine Bacteria
0.49291387
Bacterial Movement
0.4839181
Culture Media
0.46293867
0.5681818

References & Citations

1. Brennan CA, DeLoney-Marino CR, Mandel MJ 2013 Chemoreceptor VfcA mediates amino acid chemotaxis in Vibrio fischeri Appl Environ Microbiol 79 1889 1896 10.1128/AEM.03794-12 23315744 3592237 http://dx.doi.org/10.1128/AEM.03794-12
2. DeLoney-Marino CR, Wolfe AJ, Visick KL 2003 Chemoattraction of Vibrio fischeri to serine, nucleosides and N-acetylneuraminic acid, a component of squid light organ mucus Appl. Environ. Microbiol. 69 7527 7530 10.1128/AEM.69.12.7527-7530.2003 14660408 310003 http://dx.doi.org/10.1128/AEM.69.12.7527-7530.2003
3. Pruss BM, Nelms JM, Park C, Wolfe AJ 1994 Mutations in NADH:ubiquinone oxidoreductase of Escherichia coli affect growth on mixed amino acids J. Bacteriol 176 2143 2150 8157582 205332
4. Wolfe AJ, Berg HC 1989 Migration of bacteria in semisolid agar Proc Nat Acad Sci USA 86 6973 6977 10.1073/pnas.86.18.6973 2674941 297974 http://dx.doi.org/10.1073/pnas.86.18.6973
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/content/journal/jmbe/10.1128/jmbe.v14i2.625
2013-12-02
2017-09-25

Abstract:

Chemotaxis, the directed movement of cells towards or away from a chemical, is both an exciting and complicated behavior observed in many bacterial species. Attempting to adequately visualize or demonstrate the chemotaxic response of bacteria in the classroom is difficult at best, with good models to illustrate the concept lacking. The BSL-1 marine bacterium (a.k.a. ) is easy to culture, making it an ideal candidate for experiments in an undergraduate microbiology course. A number of chemoattractants for have been identified, including a variety of sugars, nucleosides, and amino acids (1, 2). Below presents how the soft agar-based chemotaxis assay can be implemented in the undergraduate laboratory. As bacterial cells migrate towards one or more attractants in soft agar, students can directly observe the chemotaxic behavior of without the need to learn complicated techniques or use specialized equipment. Once the bands of bacterial cells are observed, the migration can then be disrupted by the addition of excess attractant to the soft agar, thereby visualizing what happens once cells are no longer in a gradient of attractant. In addition, soft agar plates lacking attractants can be used to visualize the random movements of bacterial cells that are non-chemotaxing. These exercises can be used in the microbiology laboratory to help students understand the complex behavior of bacterial chemotaxis.

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FIGURE 1.

(A) 10 μl of log-phase was dropped onto the center of SWT soft agar and incubated at 28°C for approximately 3.5 h. Both an inner and outer band of bacterial cells migrating towards attractants in the agar can be observed (indicated by arrows). (B) Bacterial cells inoculated onto MM-M soft agar containing 1 mM glucose migrate out in a single band. (C) Migration can be perturbed by dropping 10 μl of excess attractant (2 M serine, indicated by the arrow) outside the migrating band(s). (D) Random migration of bacterial cells in MM-M lacking an attractant.

Source: J. Microbiol. Biol. Educ. December 2013 vol. 14 no. 2 271-272. doi:10.1128/jmbe.v14i2.625
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