Unit 9 Flashcards
What is the purpose of bacteria producing different enzymes for carbohydrate utilization?
A) To defend against antibiotics.
B) To utilize the energy in various carbohydrates.
C) To build cellular structures.
D) To communicate with other bacteria.
B) To utilize the energy in various carbohydrates.
Explanation: Bacteria produce different enzymes to break down various carbohydrates because each type of carbohydrate requires specific catalysis for its utilization. These enzymes enable bacteria to access the energy stored in the chemical bonds of these carbohydrates.
True or False: Polysaccharides like starch and cellulose are simpler for bacteria to utilize than monosaccharides like glucose.
A) True
B) False
B) False
Explanation: Polysaccharides like starch and cellulose are complex carbohydrates composed of long chains of monosaccharide units. They are more complex and typically require more effort for bacteria to break down than simple sugars like monosaccharides.
In the lab, observing the growth of bacteria on media that requires fermentation indicates the ability of the organism to ferment __________ to grow.
carbohydrates
Explanation: Fermentation-based media are designed to test the ability of bacteria to ferment carbohydrates as a means of energy production when oxygen is not available for aerobic respiration.
What is the main energy source provided by glycolysis for the organisms?
A) NADH
B) ATP
C) Glucose
D) NAD+
B) ATP
Explanation: Glycolysis is a metabolic pathway that converts glucose into pyruvate, releasing energy that is captured in the form of ATP (adenosine triphosphate), the main energy currency of the cell.
True or False: The purpose of fermentation in bacteria is to produce ATP as the main energy source.
A) True
B) False
B) False
Explanation: The primary purpose of fermentation is not to produce ATP but to recycle NAD+ from NADH, which is necessary for glycolysis to continue in the absence of oxygen. While a small amount of ATP is produced during glycolysis, fermentation itself does not produce additional ATP.
Fermentation allows bacteria to recycle __________, which is needed for glycolysis.
NAD+
Explanation: Fermentation is a metabolic process that converts NADH back into NAD+, ensuring a continuous supply of NAD+ for glycolysis, which is essential for ATP production under anaerobic conditions.
What term is used to describe normal, non-pathogenic, lactose-fermenting gut bacteria?
A) Enterics
B) Coliforms
C) Non-coliforms
D) Pathogens
B) Coliforms
Explanation: Coliforms are the non-pathogenic bacteria in the gut that can ferment lactose. They are considered indicators of fecal contamination in water supplies because they should not be present in drinking water.
True or False: MacConkey’s agar is both selective for Gram-positive bacteria and differential.
A) True
B) False
B) False
Explanation: MacConkey’s agar is selective for Gram-negative bacteria due to the presence of crystal violet and bile salts which inhibit the growth of Gram-positive bacteria. It is also differential based on the ability of bacteria to ferment lactose.
If a Gram(-) bacterium cannot ferment lactose, its growth on MacConkey’s agar will appear _______.
clear or slightly purple
Explanation: Gram-negative bacteria that cannot ferment lactose will not produce acid, and therefore, the pH indicator, neutral red, will not turn fuchsia. The growth will appear clear or take on the slight purple hue from the crystal violet in the medium.
What does the Triple Sugar Iron (TSI) agar test assess?
A) The ability to ferment only lactose
B) The ability to ferment only glucose
C) The ability to ferment glucose, sucrose, and lactose
D) The production of catalase enzyme
C) The ability to ferment glucose, sucrose, and lactose
Explanation: TSI agar is a differential medium that tests a bacterium’s ability to ferment three different sugars: glucose, sucrose, and lactose. It contains phenol red as a pH indicator to detect acid production from fermentation.
True or False: In the TSI agar test, the butt and the slant of the tube are assessed independently to determine H2S production.
A) True
B) False
B) False
Explanation: While the butt and slant of the TSI agar tube are assessed independently for sugar fermentation, H2S production is indicated by the blackening of the medium, which can occur throughout the tube due to the presence of H2S reacting with ferrous sulfate.
In carbohydrate fermentation tubes, the presence of CO2 is detected using a/an _______ tube.
Durham
Explanation: A Durham tube is an inverted small tube placed inside the fermentation tube to trap any CO2 gas that may be produced as a byproduct of carbohydrate fermentation.
What does the Methyl-Red test in the MR-VP series assess?
A) Alcohol waste production
B) Acid waste production
C) The ability to ferment lactose
D) The ability to reduce nitrate
B) Acid waste production
Explanation: The Methyl-Red test in the MR-VP series is used to detect the production of mixed acids from glucose fermentation. If acidic waste products have been produced, the addition of methyl red will turn the medium red.
True or False: The VP test in the MR-VP series is used to determine the production of alcohol waste products.
A) True
B) False
A) True
Explanation: The VP test, part of the MR-VP series, is used to detect the presence of neutral end products, such as acetoin, from glucose fermentation. Barritt’s Reagents VP-A and VP-B are added to see if a red color develops, indicating alcohol waste products.
What does a yellow butt indicate in a glucose fermentation test?
A) The bacteria can produce hydrogen sulfide (H2S).
B) The bacteria can ferment glucose.
C) The bacteria can ferment lactose.
D) The bacteria produce carbon dioxide (CO2) only.
B) The bacteria can ferment glucose.
Explanation: A yellow color in the butt of the test tube indicates an acidic condition due to the fermentation of glucose, meaning the bacteria can ferment glucose.
