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Nutrient agar is enriched to allow growth of a wide variety of bacterial cultures, thus it was expected that both of the cultures used would exhibit growth on the nutrient agar. McCracken agar (MAKE) is selective for certain types of bacteria and is known to inhibit growth of Gram-positive microorganisms. S. Erasures is Gram-positive, thus we saw no growth in the MAKE Petri dish inoculated with S. Erasures. The human blood agar (ASH) is nutrient-rich and exhibits a favorable growth environment for many bacterial species, and thus allowed growth of both E. Coli and S. Erasures.

Manitoba’ agar has a high concentration of NCAA which inhibits most bacterial groups. Staphylococcus species, however, are able to grow in these conditions and S. Erasures was present in the Imitation Petri dish (Banana 2005). The second change that occurred during this experiment was the change in color of the agar, which was noted to occur within four of the inoculated dishes. These color change occurrences are indicative of pH changes within the agar dishes. The MAKE agar is both selective and differential, and is thus is able to identify lactose degradation due to the presence of a pH indicator.

When a lactose-positive colony such as E. Coli is inoculated on the agar, the decrease in pH yields a change in color on the agar and the presence of a noticeable border surrounding the bacterial colonies. The Imitation agar, like MUG also can be used as a differential agar. The color changes on the Imitation agar are indicative of acid metabolic wastes produced by the fermentation of Imitation by Staphylococci bacteria. This fermentation causes the agar to change from red to allow, which is what occurred in the dishes containing S. Erasures (Gјenter et al, 1998). QUESTIONS. A.

The needle is flamed before inoculation in order to prevent cross contamination of bacteria on the medium and after to kill the bacteria collected for the culture. B. Alt is important to hold the cap of the tube in your hand, and angled downwards, because microbial contamination can occur if the cap is exposed to another surface or the open air. C. The needle must be cooled before the inoculation because if not, the heated needle can kill the bacterial sample you are trying to collect. . Enriched media are those that have been supplemented with nutrients to allow for growth of a wide variety of microorganisms.

Differential or isolation media are those that are used for differentiating or isolating particular bacterial groups based upon their metabolic properties, and do so by the addition of specific indicator compounds. Selective or inhibitory media allow for, or inhibit, specific bacterial groups based upon the addition of distinct components to the media. Transport media are used in the transportation of bacterial cultures, and contain monuments that assist in the deterrence of growth during the transportation period (Madding et al, 2005).

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