Microbiology lab report on Escherichia coli and Staphylococcus aureus.

Essay by soliedejoyCollege, UndergraduateA+, September 2008

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Microbiology Lab ReportPractica #1BTC307LAmber AmelingmeierThursday, September 18, 2008OBJECTIVESIn this lab experiment two different types of bacteria, Escherichia coli and Staphylococcus aureus, were grown singly and mixed on four different types of agar in order to observe the varying morphologies within the colonies. Resulting data was analyzed to provide understanding of the use of differing culture media and conditions for bacterial growth.

RESULTSFour different agar types were used in this experiment. The first (Nutrient) allowed for growth of both E. coli and S. aureus. The second agar used (MKL) inhibited the growth of S. aureus but allowed the growth of E. coli. The third (ASH) yielded growth of both bacterial species. The fourth (Mannitol) was found to inhibit growth of E. coli (Table 1).

Table 1. Indication of growth within the four types of agar. G = growth, NG = no growth.

E. coliS. aureusMixed cultureNutrientGGGMKLGNGGASHGGGMannitolNGGGChanges in color within the sampled cultures were also noted.

No changes occurred within the Nutrient agar. The MKL agar exhibited a color change with E. coli and the mixed culture. The agar changed from red to purple, and a noticeable border was present surrounding the colonies that exhibited growth on the dish. The ASH agar did not yield a color change. The Mannitol agar exhibited a change with S. aureus and the mixed culture, but no change with E. coli (Table 2).

Table 2. Indication of color change within the four types of agar.

E. coliS. aureusMixed cultureNutrientTransparentTransparentTransparentMKLRed to PurpleRedRed to PurpleASHRedRedRedMannitolRedRed to YellowRed to YellowCONCLUSIONS AND DISCUSSIONTwo noticeable changes occurred during this experiment. First, two of the twelve inoculated Petri dishes yielded no growth. In order to explain these occurrences, we must first examine the differing properties of the types of agar used. Nutrient agar is enriched to allow growth of a wide...