Laboratory Activity to Effectively Teach Introductory Geomicrobiology Concepts to Non-Geology Majors †
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Authors:
Massimiliano Marvasi1,*,
Yarely C. Davila-Vazquez2,
Lilliam Casillas Martinez2
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Published 02 December 2013
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Supplemental materials available at
http://jmbe.asm.org During our experiment we trained students in making Standard B4. The experience was successful but it was very time consuming. Consequently, during the preparation of the manuscript we decided to exclude this part, suggesting the instructor prepare the media for the students. - *Corresponding author. Mailing address: Soil and Water Science Department, University of Florida, 2033 Mowry Road – Room 330E, PO Box 103610, Gainesville, FL 32610-3610. Phone: 352-273-8195. Fax: 352-273-5645. E-mail: [email protected].
- ©2013 Author(s). Published by the American Society for Microbiology.
Abstract:
We have designed a three-week experiment that can complement any microbiology course, to teach main geomicrobiology concepts for non-geology majors. One of the most difficult concepts for non-geology majors to comprehend is how bacteria serve as a platform for different mineralization reactions. In our three-week laboratory practice, students learn the main principles and conditions required for an induced bacterial mineralization. Upon completion of the laboratory experience, students will: 1) learn how microbial-induced mineralization (such as calcium carbonate formation) is affected by differential media and growth conditions; 2) understand how bacterial physiology affects any induced in situ or in vitro mineralization; 3) comprehend how growing conditions and bacterial physiologies interrelate, resulting in differential crystal formation. The teaching-learning process was assessed using a pre-/posttest with an increase from 26% to 76% in the number of positive answers from the students. We also measured the students’ proficiency while conducting specific technical tasks, revealing no major difficulties while conducting the experiments. A final questionnaire was provided with satisfactory evaluations from the students regarding the organization and content of the practices. 84–86% of the students agreed that the exercises improved their knowledge in geomicrobiology and would like to attend similar laboratories in the future. Such response is the best indicator that the laboratory practice can be implemented in any undergraduate/graduate microbiology course to effectively teach basic geomicrobiology concepts to non-geology majors.
References & Citations
Supplemental Material
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- Appendix 1: Procedures for B4 media preparation and inoculation of the strains for the Geomicrobiology laboratory practice
- Appendix 2: Student laboratory handout and answer key
- Appendix 3: Reporting card
- Appendix 4: Pre- and post-activity assessment and answer key
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Abstract:
We have designed a three-week experiment that can complement any microbiology course, to teach main geomicrobiology concepts for non-geology majors. One of the most difficult concepts for non-geology majors to comprehend is how bacteria serve as a platform for different mineralization reactions. In our three-week laboratory practice, students learn the main principles and conditions required for an induced bacterial mineralization. Upon completion of the laboratory experience, students will: 1) learn how microbial-induced mineralization (such as calcium carbonate formation) is affected by differential media and growth conditions; 2) understand how bacterial physiology affects any induced in situ or in vitro mineralization; 3) comprehend how growing conditions and bacterial physiologies interrelate, resulting in differential crystal formation. The teaching-learning process was assessed using a pre-/posttest with an increase from 26% to 76% in the number of positive answers from the students. We also measured the students’ proficiency while conducting specific technical tasks, revealing no major difficulties while conducting the experiments. A final questionnaire was provided with satisfactory evaluations from the students regarding the organization and content of the practices. 84–86% of the students agreed that the exercises improved their knowledge in geomicrobiology and would like to attend similar laboratories in the future. Such response is the best indicator that the laboratory practice can be implemented in any undergraduate/graduate microbiology course to effectively teach basic geomicrobiology concepts to non-geology majors.

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Author and Article Information
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Published 02 December 2013
-
Supplemental materials available at
http://jmbe.asm.org During our experiment we trained students in making Standard B4. The experience was successful but it was very time consuming. Consequently, during the preparation of the manuscript we decided to exclude this part, suggesting the instructor prepare the media for the students. - *Corresponding author. Mailing address: Soil and Water Science Department, University of Florida, 2033 Mowry Road – Room 330E, PO Box 103610, Gainesville, FL 32610-3610. Phone: 352-273-8195. Fax: 352-273-5645. E-mail: [email protected].
- ©2013 Author(s). Published by the American Society for Microbiology.
Figures
Example of workflow of the experiments conducted over the three-week period to introduce main geomicrobiology concepts. Week 1. Characterization of soil microorganisms based on Gram type, morphology and pigmentation. Unique morphotypes were streaked on different B4 media. Week 2. An example is provided of possible results: strain A is grown on both Standard B4 and Buffered B4. When strain A is grown on Standard B4 it can modify the pH by itself, inducing alkalization and fostering precipitation. Below, when the same strain is grown on a buffered acidic environment (Buffered B4), the precipitation does not occur. A similar but opposite example is shown for strain B. Students discriminated between acid/alkaline conditions and presence or absence of crystal precipitation. Week 3. Crystals and their matrices were collected from the biofilms and analyzed using the optical microscope.

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FIGURE 1.
Example of workflow of the experiments conducted over the three-week period to introduce main geomicrobiology concepts. Week 1. Characterization of soil microorganisms based on Gram type, morphology and pigmentation. Unique morphotypes were streaked on different B4 media. Week 2. An example is provided of possible results: strain A is grown on both Standard B4 and Buffered B4. When strain A is grown on Standard B4 it can modify the pH by itself, inducing alkalization and fostering precipitation. Below, when the same strain is grown on a buffered acidic environment (Buffered B4), the precipitation does not occur. A similar but opposite example is shown for strain B. Students discriminated between acid/alkaline conditions and presence or absence of crystal precipitation. Week 3. Crystals and their matrices were collected from the biofilms and analyzed using the optical microscope.
Box-and-wisher plot showing the median of 25th to 75th percentile of positive responses in the pre- and posttests to assess student learning in geomicrobiology after the three-week laboratory experiment.

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FIGURE 3.
Box-and-wisher plot showing the median of 25th to 75th percentile of positive responses in the pre- and posttests to assess student learning in geomicrobiology after the three-week laboratory experiment.
Assessment for student performance. The scale ranges from very good ( 5 ), to good ( 3 ), to poor ( 1 ). Tasks assigned: (A) The student is able to prepare the B4 medium as instructed * . (B) The student uses aseptic techniques to streak the isolates on B4 media plates. (C) The student can discriminate among alkaline (red) and acidic (yellow) conditions in the B4 media plates. (D) The student is able to associate acidic conditions on B4 plates with impairment of crystal formation. (E) The student discriminates among different crystal morphologies using the microscope. (F) The student is able to visualize the EPS matrix using the microscope. (G) The student properly identifies the crystals on the biofilm.

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FIGURE 4.
Assessment for student performance. The scale ranges from very good ( 5 ), to good ( 3 ), to poor ( 1 ). Tasks assigned: (A) The student is able to prepare the B4 medium as instructed * . (B) The student uses aseptic techniques to streak the isolates on B4 media plates. (C) The student can discriminate among alkaline (red) and acidic (yellow) conditions in the B4 media plates. (D) The student is able to associate acidic conditions on B4 plates with impairment of crystal formation. (E) The student discriminates among different crystal morphologies using the microscope. (F) The student is able to visualize the EPS matrix using the microscope. (G) The student properly identifies the crystals on the biofilm.
Main findings reported after the three-week laboratory experience to introduce geomicrobiology concepts. On panels A and B, two different morphotypes were grown on standard B4 plates with Phenol Red as indicator and incubated for 7 days at 40°C. Biofilms in panel A were alkaline (see red coloration, indicative of pH ≥ 8.2 with an arrow indicating the crystals). In panel B, we show a strain with a more acidic metabolism and, consequently, no crystals were formed (yellow, indicative of pH ≤ 6.4). Panels C and D demonstrate the observation of CaCO3 crystals (see arrows) with the stereomicroscope (magnification 4X). Panels E and F show examples of CaCO3 crystals observed with the optical microscope (magnification 100X). Panel G shows the matrix stained with crystal violet associated with the carbonate crystals that are progressively dissolved after 0.1 N HCl treatments.

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FIGURE 2.
Main findings reported after the three-week laboratory experience to introduce geomicrobiology concepts. On panels A and B, two different morphotypes were grown on standard B4 plates with Phenol Red as indicator and incubated for 7 days at 40°C. Biofilms in panel A were alkaline (see red coloration, indicative of pH ≥ 8.2 with an arrow indicating the crystals). In panel B, we show a strain with a more acidic metabolism and, consequently, no crystals were formed (yellow, indicative of pH ≤ 6.4). Panels C and D demonstrate the observation of CaCO3 crystals (see arrows) with the stereomicroscope (magnification 4X). Panels E and F show examples of CaCO3 crystals observed with the optical microscope (magnification 100X). Panel G shows the matrix stained with crystal violet associated with the carbonate crystals that are progressively dissolved after 0.1 N HCl treatments.