Alex Brooks demonstrates aseptic techniques
Bacteria Lab Report
Introduction &
Hypothesis
Bacteria are a specific kind of prokaryotic organisms that are very versatile and can survive in a wide range of environments. Due to rapid mutations, bacteria can be found virtually anywhere. In his textbook, Campbell Biology, Reece et. al. states that bacteria present in three distinct shapes: coccus (spherical), bacillus (rod-shaped), and spirillum (p. 557). Many people are unaware of the impact that bacteria has on our everyday lives. While it is easy to consider pathogenic (disease-causing) bacteria, many bacteria are not only beneficial to human life but also essential to life. Probiotic bacteria provide positive health effects to the host. To learn more about techniques involved in studying bacteria, we took a culture from a fingertip of a student’s unwashed hands and a culture after a thorough hand washing. We hypothesized that the plate inoculated with a clean fingertip would present with fewer bacterial colonies than those inoculated with an unwashed fingertip.
Bacteria are a specific kind of prokaryotic organisms that are very versatile and can survive in a wide range of environments. Due to rapid mutations, bacteria can be found virtually anywhere. In his textbook, Campbell Biology, Reece et. al. states that bacteria present in three distinct shapes: coccus (spherical), bacillus (rod-shaped), and spirillum (p. 557). Many people are unaware of the impact that bacteria has on our everyday lives. While it is easy to consider pathogenic (disease-causing) bacteria, many bacteria are not only beneficial to human life but also essential to life. Probiotic bacteria provide positive health effects to the host. To learn more about techniques involved in studying bacteria, we took a culture from a fingertip of a student’s unwashed hands and a culture after a thorough hand washing. We hypothesized that the plate inoculated with a clean fingertip would present with fewer bacterial colonies than those inoculated with an unwashed fingertip.
Materials & Methods
After becoming familiarized with the techniques used to culture bacteria, we set out to test our hypothesis. First, we gently rubbed one fingertip in a sterilized agar plate using caution to avoid contamination from the air while the lid was open. Then, we washed our hands and repeated the procedure with a separate agar plate. Both agar plates were sealed with Parafilm to prevent contamination. They were then inserted in an incubator for 48 hours at 38°C with the lids facing down to prevent condensation from contaminating the culture.
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After becoming familiarized with the techniques used to culture bacteria, we set out to test our hypothesis. First, we gently rubbed one fingertip in a sterilized agar plate using caution to avoid contamination from the air while the lid was open. Then, we washed our hands and repeated the procedure with a separate agar plate. Both agar plates were sealed with Parafilm to prevent contamination. They were then inserted in an incubator for 48 hours at 38°C with the lids facing down to prevent condensation from contaminating the culture.
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Results
Both plates were examined carefully after a 48 hour incubation period. Although the difference between the unwashed and washed cultures was not remarkable, there was a slight reduction in the number of bacterial colonies present on the plates that were inoculated with our clean hands. There were 3 distinct bacterial colonies in the agar plates created after hand washing compared to 4 bacterial colonies on the agar plates inoculated with unwashed hands.
Discussion & Analysis
This simple experiment not only demonstrates the importance of hand washing but also highlights the necessity of using aseptic techniques when studying bacteria in a lab. Had the plates been left open during inoculation, bacteria present in the air and other surfaces could have contaminated the culture producing incorrect experimental data. Although great care was taken to avoid contamination of the sterile agar plates, both students dried their hands with non-sterile hand towels prior to inoculating the second agar plate. This could have been the cause for more bacteria than expected on the washed agar plate.
References
Bacteria Parasites Remedies. (n.d.).HealTone. Retrieved May 6, 2012, from http://www.healtone.com/categories/-Parasites%252bBacteria/Reece, J.B., Urry L.A., Cain, M.L., Wasserman, S.A., Minorksy, P.V., & Jackson, R. B. (2011) Campbell Biology. Boston: Benjamin Cummings.
Both plates were examined carefully after a 48 hour incubation period. Although the difference between the unwashed and washed cultures was not remarkable, there was a slight reduction in the number of bacterial colonies present on the plates that were inoculated with our clean hands. There were 3 distinct bacterial colonies in the agar plates created after hand washing compared to 4 bacterial colonies on the agar plates inoculated with unwashed hands.
Discussion & Analysis
This simple experiment not only demonstrates the importance of hand washing but also highlights the necessity of using aseptic techniques when studying bacteria in a lab. Had the plates been left open during inoculation, bacteria present in the air and other surfaces could have contaminated the culture producing incorrect experimental data. Although great care was taken to avoid contamination of the sterile agar plates, both students dried their hands with non-sterile hand towels prior to inoculating the second agar plate. This could have been the cause for more bacteria than expected on the washed agar plate.
References
Bacteria Parasites Remedies. (n.d.).HealTone. Retrieved May 6, 2012, from http://www.healtone.com/categories/-Parasites%252bBacteria/Reece, J.B., Urry L.A., Cain, M.L., Wasserman, S.A., Minorksy, P.V., & Jackson, R. B. (2011) Campbell Biology. Boston: Benjamin Cummings.