Question 1

Which of the following best describes the function of phenol red in the Phenol Red Sugar Broth test?

Accepted Answer

It is a pH indicator that turns yellow in acidic conditions.

Question 2

A student observes a phenol red glucose broth tube that is yellow with a bubble in the Durham tube. How should this result be recorded?

Accepted Answer

$$A/G$$

Question 3

In the Triple Sugar Iron Agar (TSI) test, what does a black precipitate in the butt of the tube indicate?

Accepted Answer

Production of hydrogen sulfide ($$H_2S)$$

Question 4

Which enzyme is responsible for the hydrolysis of starch in the starch hydrolysis test?

Accepted Answer

Amylase

Question 5

A positive methyl red test is indicated by which color after adding methyl red reagent?

Accepted Answer

Red

Question 6

Which of the following is the correct equation for the catalase reaction?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 7

In the citrate utilization test, a positive result is indicated by which color change?

Accepted Answer

Green to blue

Question 8

Which of the following best describes a psychrophile?

Accepted Answer

An organism that grows best at low temperatures ($$0^\circ C to$$ $$20^\circ C)$$

Question 9

During the nitrate reduction test, what does it mean if the tube remains colorless after adding reagents A and B, but turns red after adding zinc?

Accepted Answer

Nitrate was not reduced

Question 10

Which of the following is a real-life application of the Kirby-Bauer method?

Accepted Answer

Measuring the effectiveness of antibiotics against specific bacteria

Question 11

What is the main difference between direct and indirect ELISA tests?

Accepted Answer

Direct ELISA detects antigens, indirect ELISA detects antibodies

Question 12

Which of the following best describes a biofilm?

Accepted Answer

A complex community of microorganisms attached to a surface and embedded in a self-produced matrix

Question 13

In the SIM medium, what does a red color after adding Kovac's reagent indicate?

Accepted Answer

Positive for indole production

Question 14

Which enzyme is responsible for the hydrolysis of urea in the urea hydrolysis test?

Accepted Answer

Urease

Question 15

A positive oxidase test is indicated by which color change?

Accepted Answer

Colorless to blue-purple

Question 16

Which of the following is a disadvantage of bacterial conjugation in a clinical setting?

Accepted Answer

It increases the risk of antibiotic resistance spreading among bacteria.

Question 17

In the litmus milk test, what does a pink color indicate?

Accepted Answer

Acid production due to lactose fermentation

Question 18

Which of the following best describes the role of Durham tubes in carbohydrate fermentation tests?

Accepted Answer

They collect gas produced during fermentation.

Question 19

Which of the following is the correct sequence of reagents added in the nitrate reduction test?

Accepted Answer

Nitrate reagent A, nitrate reagent B, zinc

Question 20

A patient’s urine sample is tested using latex agglutination and shows visible clumping. What does this indicate?

Accepted Answer

A positive result for the target antigen or antibody

Microbiology Lab Final Exam Review: Biochemical Tests and Microbial Physiology

Study Guide - Practice Questions