A close inspection of colonies of micrococcus sp on

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A close Inspection of Colonies of Micrococcus sp. on YGC Agar shows that there is no Zone of Clearing round each of these Colonies, as is the Case with Staphylococcus sp. This is because Micrococcus sp. does not produce sufficient Amounts of Acid to change the pH of the Agar and dissolve the Calcium Carbonate. Micrococcus sp. -- like Staphyloccus sp. -- is Catalase Positive. Our Micrococcus luteus does not form the eponymous (L= on [the] name) Clusters that define Staphyloccus sp. and our Micrococcus luteus , unlike our Staphyloccus epidermidis does not produce a Zone of Clearing around Colonies when growing on YGC Agar. ___________________________________________________________ “I have something here for you. Your father wanted you to have this when you were old enough, but your uncle wouldn't allow it. He feared you might follow old Obi-Wan on some damn fool idealistic crusade like your father did.” What is it?’ Your father's light saber. This is the weapon of a Jedi Knight. Not as clumsy or random as a blaster; an elegant weapon for a more civilized age. For over a thousand generations, the Jedi Knights were the guardians of peace and justice in the Old Republic. Before the dark times... before the Empire.” © 1977 Lucasfilm, Ltd.
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Lab 1 Page 16 Staphylococcus epidermidis (Atlas Page 158) Staphylococcus epidermidis (“Staph epi”) is a Gram Positive Facultative Aerobe found on Human Skin. As the Name implies, they are spherical Cocci (G= berries) . The Colonies are White. Staphylococcus epidermidis is on YGC Medium. The Calcium Carbonate is responsible for the White Chocolate Appearance. When Staphylococcus grows on our Yeast-Glucose-Calcium Carbonate (YGC) Medium it secretes Acids that allow the Calcium Carbonate to go back into Solution, forming clear Zones -- they look dark -- around each Colony. If you look at a Colony growing near the Side of the Petri Plate, you’ll note that the Zone of Clearing forms a Half-Dome underneath each Colony. Staphylococcus is a major Bacterial Species on Human Skin, which allows us to do Direct Isolations. Samples are usually obtained from moist or oily areas such as the Sides of the Nose or behind the Ears. Such a “Patient” Sample can then be directly streaked onto a Yeast Extract, Glucose, Calcium Carbonate Agar (YGC Agar). The Yeast Extract and Glucose serve as the Nutritional Base and the Calcium Carbonate -- insoluble at the pH of the Medium -- will dissolve in the Presence of Acids secreted by growing Staphylococcus . The Result will be a Zone of Clearing around each smooth, round Staphylococcus Colony on YGC Agar. White Colonies surrounded by a Zone of Clearing on YGC Agar are usually (but not always) Staphylococcus epidermidis , a Non-Pathogenic Species. One of the Reasons Staphylococcus epidermidis in not Pathogenic is that it does not produce Beta Hemolysins. So Staphylococcus epidermidis grown on Blood Agar will not produce any Hemolysis.
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