Lab6ReportCH

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Santa Fe College *

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2000

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Chemistry

Date

Feb 20, 2024

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docx

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2

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Name(s) : Lab 6 Report : UTILIZATION/FERMENTATION OF CARBOHYDRATE, PROTEIN CATABOLISM, AND RESPIRATION TEST IN BACTERIA 1) Record of your observation of grown cultures: Test performed S. aureus E. coli Simmons slant Simmons slant tube remains green: Negative test One Simmons slant test tube tested positive and the other Simmons slant test tube tested negative. H 2 S test H 2 S test tube did not change H 2 S had a positive test in which the medium had a black ferric sulfide precipitate. H 2 O 2 test H 2 O 2 test had a minimal reaction with some bubbles: Negative test H 2 O 2 test produced more bubbles quickly: Positive test 2) 2) Do you have the same results with your lab partners since you worked on the same original culture and your media were prepared from the same batch? What reasons you might think contributed to the differences: Yes, we all had the same results. Only one of the two E. coli slant test tubes changed colors, while the other test tube did not. 3) What caused the Simmons slant to turn blue? Bacteria that survive inoculation utilize the citrate present in the agar and covert ammonium phosphate to ammonium and ammonium hydroxide. The increase in pH then causes color change in the bromothymol blue indicator, causing the medium to change from green (neutral) to a deep blue color (alkaline). 4) What caused the positive deep to turn black? When hydrogen sulfide (H 2 S) is detected, ferric sulfide, a black precipitate, is formed. Any blackening of the medium is an indication of sulfur reduction and a positive test. The absence of the black color in the medium indicates a negative reaction.
5) What caused the bubbles released in H 2 O 2 test? This test is used to identify organisms that produce the enzyme, catalase. This enzyme breaks down hydrogen peroxide ( H 2 O 2 ) into water and oxygen gas. The bubble resulting from production of oxygen gas. 6) What did you learn from this practice related to bacterial metabolism bacterial growth?
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