A Study On Nutrient Agar

1078 WordsOct 23, 20155 Pages
Nutrient Agar To observe the colony morphology, the original unknown culture was streaked for isolation on nutrient agar using the quadrant streaking technique, inverted, and incubated at 37° C for 48 hours. This allowed for observation of the colony morphology. Separation of Gram-positive and Gram-negative The original unknown culture was streaked for isolation on Columbia CNA agar and MacConkey agar using a quadrant streak, inverted, and placed in a 37° C incubator for 48 hours. CNA agar contains a mix of colistin and nalidixic acid, as well as sheep blood. If there is poor or no growth on CNA agar, then the organism was inhibited by colistin and nalidixic acid and is Gram-negative. However if there is good growth, the organism was not inhibited by colistin and nalidixic acid, and is Gram-positive. MacConkey agar contains bile salts and crystal violet. If there is poor growth or no growth, the organism was inhibited by crystal violet and/or bile, and is Gram-positive. If there is good growth, the organism was not inhibited by crystal violet or bile, and is Gram-negative. Gram Stain This protocol was performed once using the culture on the Columbia CNA agar, and once using the culture on the MacConkey agar. The Gram stain uses crystal violet as a primary stain, ethanol-acetone as a negative stain, and safranin as a counterstain. A small amount of the culture was heat-fixed to a glass microscope slide. The culture was flooded with methylene blue, and allowed to sit for one
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