The objective of this lab was to determine if different cultures would successfully grow on diverse agar medias and to distinguish the appearance of growth on the mediums.

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        The objective of this lab was to determine if different cultures would successfully grow on diverse agar medias and to distinguish the appearance of growth on the mediums. The experiment involved three different types of growth medias - selective, differential and enriched. The experiment also involved four broth cultures - Escherichia Coli, Enterobacter Aerogenes, Staphylococcus Epidermidis and Streptococcus Faecalis.

Selective media was a growth medium that enhanced and inhibited the growth of certain organisms due to an added media component (Madigan et al., 2012). The selective medium used in this experiment was KF Streptococcal Agar.

Differential media allowed the identification of microorganisms based on observable properties (Madigan et al., 2012). In this experiment, the differential media used was Eosin Methylene Blue (EMB) Agar. The methylene blue in EMB inhibited the growth of gram-positive bacteria and only allowed gram-negative organisms to be grown. EMB had a pH of 7.2 and used lactose and sucrose for energy. (Madigan et al., 2012)

Enriched media allowed metabolically fastidious organisms to be grown because of the added specific growth factors (Madigan et al., 2012). The Tryptic Soy Agar was used as the enriched media in this experiment. TSA was mainly used as a control for growth medium. It was also used to observe colony morphology, to develop a pure culture and to achieve adequate growth for further testing (Liu, 2005)

In this experiment, we transferred the four liquid broth cultures onto each of the Agar plates using a sterile cotton swab. We dipped the swab into the broth once and created a stroke, 2 cm long, on each of the agar plates in a specific order. We started with the least enriched media, EMB (differentiable), and ended with the most enriched media, TSA (enriched); with KF being swabbed in between.

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Materials and Methods

Please refer to Department of Biology, 2012, Biology 240 Fundamentals of Microbiology Laboratory Manual, Experiment 10: Selective, Differential and Enriched Media, pp. 45-47.

Results

Table 1: Growth On Distinctive Mediums

Table 1 summarizes the amount and description of growth of each microorganism on the different agar plates. The amount of growth ranges from abundant (++++) to none (-).

Table 2: Ideal Results For Growth On Distinctive Mediums

Table 2 summarizes the expected results for the amount of growth of ...

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