MCB 3020C Microbiology Lab UCF
Exam 3 Newest With Questions And
Answers 2026/2027 Graded A
KIA:Sulfur Reaction - ANSWER>-Reduction of sulfur produces H2S, which combines with iron in the media to form
black precipitate (ferrous sulfide).
-Ferrous sulfide precipitate will obscure color in the bottom of the tube.
-H2S will only form as a byproduct of sulfur reduction in an acidic environment
Peptides for energy - ANSWER>bacteria can catabolize polypeptides and perform respiration
deamination - ANSWER>removes amino group
-in phenylalanine slant, it tests for an enzyme that removes the amino group from phenylalanine, through
deamination
, Decarboxylation - ANSWER>-an enzyme removes the carboxy group from the amino acid, releasing CO2 , and the
corresponding amine, which increase the pH of the media
Desulfhydrase - ANSWER>removes hydrogen sulfide H2S from the amino acids that contain sulfur, such as the
amino acid cysteine and methionine
Methyl Red Test - ANSWER>Tests for: mixed acid fermentation pathway
Products:stable acids that came from the breaking down of glycolysis to pyruvate.
Indicator: Methyl red
Positive test: pH<4.4 = remain vibrate red color
Negative tests: pH 4.4-6.2=orange color& pH>6.2 = yellow
Voges-Proskauer Test - ANSWER>Tests for: organisms that produce 2,3-butanediol as a final product through the
fermentation of glucose
Exam 3 Newest With Questions And
Answers 2026/2027 Graded A
KIA:Sulfur Reaction - ANSWER>-Reduction of sulfur produces H2S, which combines with iron in the media to form
black precipitate (ferrous sulfide).
-Ferrous sulfide precipitate will obscure color in the bottom of the tube.
-H2S will only form as a byproduct of sulfur reduction in an acidic environment
Peptides for energy - ANSWER>bacteria can catabolize polypeptides and perform respiration
deamination - ANSWER>removes amino group
-in phenylalanine slant, it tests for an enzyme that removes the amino group from phenylalanine, through
deamination
, Decarboxylation - ANSWER>-an enzyme removes the carboxy group from the amino acid, releasing CO2 , and the
corresponding amine, which increase the pH of the media
Desulfhydrase - ANSWER>removes hydrogen sulfide H2S from the amino acids that contain sulfur, such as the
amino acid cysteine and methionine
Methyl Red Test - ANSWER>Tests for: mixed acid fermentation pathway
Products:stable acids that came from the breaking down of glycolysis to pyruvate.
Indicator: Methyl red
Positive test: pH<4.4 = remain vibrate red color
Negative tests: pH 4.4-6.2=orange color& pH>6.2 = yellow
Voges-Proskauer Test - ANSWER>Tests for: organisms that produce 2,3-butanediol as a final product through the
fermentation of glucose
