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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.

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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). ...read more.


The amount of growth ranges from abundant (++++) to none (-). MEDIUM MICROORGANISM GROWTH DESCRIPTION TSA Escherichia Coli Enterobacter Aerogenes Staphylococcus Epidermidis Streptococcus Faecalis ++++ ++++ ++++ ++++ White to beige White to beige White to beige White to beige EMB Escherichia Coli Enterobacter Aerogenes Staphylococcus Epidermidis Streptococcus Faecalis ++++ ++++ - - Green metallic sheen Pink mucoid; dark centre No growth No growth KF Escherichia Coli Enterobacter Aerogenes Staphylococcus Epidermidis Streptococcus Faecalis - - - +++ No growth No growth No growth Pink to red colonies Discussion: After completing the experiment, we can note that each medium used produced different results. The results showcase the differences between enriched, differential and selective media. The enriched media, TSA, had growth for all four different cultures. In this experiment, TSA acted as a growth medium because the most common and even fastidious forms will grow on this medium. TSA is also known as Soybean-Casein Digest agar (Dickson, 2002). It can be considered a defined medium because it can be easily replicated. ...read more.


The KF media, being a selective media, promotes growth of only one type of organism and discourages the growth of any others (Madigan et al, 2012). It makes sense that the medium was selective in producing the growth for its own relative organism. In conclusion, enriched, differential and selective mediums produced different growth results for each culture. The enriched media, Tryptic Soy Agar, produced identical looking growth observations for all four organisms. The differential media, EMB, showcased the difference in gram positive and gram-negative medias by turning them different colours; pink for E. Aerogenes and green for E.Coli respectively. Lastly, the selective medium, KF, promoted the growth of one culture, Streptococcus Faecalis, and discouraged the other cultures. Resources: Department of Biology, 2012, Biology 240 Fundamentals of Microbiology Laboratory Manual. University of Waterloo. pp. 45-47. Dickson, J. (2002) ?MadSci? Faculty, Microbiology, Iowa State University. Oct 2012. < http://www.madsci.org/posts/archives/2000- 02/951527342.Mi.r.html> HiMedia. ?Technical Data: KF Streptococcal Agar Base? Oct 2012. < Himedialabs.com/TD/M248.pdf> Madigan, Martinko, Stahl, Clark. 2012. Brock Biology of Microorganisms, 13th Ed. Benjamin Cummings. San Francisco. Pp. 884-888 Liu, S. (2005) ?Science Buddies: All About Agar?. Oct 2012. <http://www.sciencebuddies.org/science-fair projects/project_ideas/MicroBio_Agar.shtml> Wellesley College BISC 209 Microbiology (2010) ?OpenWetWare? Oct 2012. < http://openwetware.org/wiki/BISC209:_Selective,and/or_Differential,_and/or_Enriched_media> ...read more.

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