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Dear Blog and Blog Readers,
Last week:
We made several plates to test different qualities of our bacteria:
Here are the results of the following tests:
Thioglycolate:
Since there was pink at the top and throughout this indicated that the bacteria uses oxygen but can not use oxygen as well this bacteria is facultative.
DNASE:
This test is to see if this bacteria secretes DNase which hydrolyzes linkages between nucleotides in DNA. Therefore, if the bacteria secretes this enzyme, the DNA will be left in small fragments. For this test to be positive a clear zone after 1N HCL was flooded onto the plate. On our plate there was no clear area and therefore this test was negative and S does not secrete DNase.
EMB:
EMB is a selective medium that inhibits gram-positive bacteria, is used for identifying enteric bacilli, and is a differential medium used to distinguish between those that ferment lactose and/or sucrose and those that don't. If the bacteria ferment lactose then they will produce acid which will cause the dyes to get into the colonies. This results in dark blue colonies. When acid production is lower pink colonies will result. Since we had bacteria growing the bacteria is gram negative and since it is pink is slightly ferments lactose and sucrose.
MacConkey Agar:
This plate is used to distinguish between gram negative and positive bacteria. Our bacteria is growing and therefore our bacteria is gram negative since it inhibits gram positive bacteria. When the color is red or pink it indicates that the bacteria ferments lactose, which it is evident that S does ferment lactose from this test.
Mannitol Salt Agar:
Mannitol Salt Agar tests is the bacteria is a halophile (able to live in very salty environments). S did not grow at all and therefore is not a halophile and the test is negative
Phenylethyl Alcohol Agar:
The PEA Agar tests inhibits gram negative bacteria and our bacteria didn't grow, therefore our bacteria is gram negative.
Blood Agar Plate:
Here, there is beta hemolysis which indicates partial hemolysis because there is a greenish hue around the colony.
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