DONETask 2

Topics: Bacteria, Microbiology, Agar plate, Growth medium / Pages: 2 (661 words) / Published: May 5th, 2015
A. Describe the difference between an obligate and facultative aerobe.
An obligate aerobe is a microorganism that must have oxygen for growth and will grow at the top of the test tube. A facultative aerobe prefers oxygen but it is not necessary for growth. Many of these microorganisms will grow at the top of the tube, but will also be dispersed throughout as well.
B. Discuss the temperature requirements of the organisms (you grew) in this lab.
Both Staphylococcus epidermis and Lactobacillus acidophilus are mesophiles. Mesophiles grow best between 25- 45 degrees Celsius (Alonzo, n.d.). In this experiment both bacteria have grown easily at a maintained room temperature of 26 Celsius.
C. Discuss under what conditions you would want to control the growth of microbes.
To minimize risk of contamination with unwanted microorganisms, aseptic technique was employed during collection. This includes hand washing with bactericidal soap, cleaning area with an “all-purpose” germicide, and prior sterilization of media and refrigeration upon receipt. My eight-year-old son, fresh from baseball practice, unwashed and teeming with microbes, was the source of Staphylococcus epidermis culture. I disinfected our working area, washed my hands, readied our working material, with aseptic technique swabbed his antecubital area with a sterile swab, placed directly in the nutrient broth test tube without (further) contamination, loosely recapped and racked above the refrigerator for incubation. The Lactobacillus acidophilus culture was similarly done. After cleaning my area and preparing the necessary material, I washed my hands, opened the L. acidophilus capsule and transferred the contents into the MRS media test tube. The culture was recapped without contamination, inverted to mix, cap loosened, and racked above the refrigerator.
D. Discuss the basic forms of culture media.
All media are prepared in a sterile fashion.
Nutrient broth is liquid, containing various material as



References: Alonzo, Cynthia. (n.d.). Aseptic Technique & Culture Microbes. In Microbiology – MLT1 (pp. 84-99) Englewood, CO: Hands-On Labs, Inc. Betsy, T., & Keogh, J. (2005). Microbiology Demystified. Blacklick, OH, USA: McGraw-Hill Professional Publishing. Retrieved from http://www.ebrary.com

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