Question 1

Which of the following microscopes operates based on the absorption of light at one wavelength and its emission at a longer wavelength?

Accepted Answer

Fluorescent microscopes operate based on the principle of absorbing light at one wavelength and emitting it at a longer wavelength, which is a characteristic feature of fluorescence. This allows for the visualization of structures or molecules within a sample that have been tagged with fluorescent dyes.

Question 2

Heterotrophic organisms derive their energy from oxidation of

Accepted Answer

Heterotrophic organisms derive their energy from the oxidation of organic molecules, as they cannot synthesize their own food and must rely on other organisms or organic substances for nutrition.

Question 3

The flagellar arrangement of Vibrio cholerae, as seen in the image provided, can be described as
 Source: CDC and Dr. William A. Clark

Accepted Answer

A

Question 4

When creating a bacterial growth curve, what data is necessary?

Accepted Answer

To create a bacterial growth curve, it is essential to know the number of living cells to plot the growth phases and the doubling time to understand how quickly the population is increasing. This information allows for the calculation of growth rates and the plotting of the curve over time.

Question 5

Organisms with fimbriae can be more pathogenic because it allows them to

Accepted Answer

Fimbriae are hair-like structures that allow bacteria to adhere to surfaces, including body tissues, enhancing their ability to colonize and cause infection.

Question 6

Which of the following cell wall components is shared by both gram-positive and gram-negative organisms?

Accepted Answer

Peptidoglycan is a component of the cell wall that is found in both gram-positive and gram-negative bacteria, serving as a structural molecule that gives the cell wall its rigidity.

Question 7

A microbiology student has walking pneumonia due to Mycoplasma pneumoniae. He decides to self-medicate with the leftover penicillin tablets he had from his last case of Streptococcus pyogenes. What is the fault in his thought process?

Accepted Answer

Mycoplasma pneumoniae lacks a cell wall, which is the target of penicillin's action. Penicillin inhibits cell wall synthesis, but since M. pneumoniae does not have a cell wall, the antibiotic is ineffective against it.

Question 8

A technologist inoculates a chocolate agar with a stock culture of Neisseria gonorrhoeae. She forgets to subculture the organism at 48 hours. At 72 hours, she realizes her mistake and subcultures the organism to a new chocolate agar. At 24 hours, the subculture is not growing. On a growth curve, the organism is displaying the

Accepted Answer

The organism is likely in the death phase because it did not grow when subcultured after being left for an extended period (72 hours) without subculturing. Neisseria gonorrhoeae, being a fastidious organism, requires timely subculturing to sustain viability. The lack of growth indicates that the cells were likely dying or dead by the time of subculturing.

Question 9

Bacteria use metabolic pathways to create ATP for power much like gasoline. Which of the following pathways does not directly generate ATP as a by-product?

Accepted Answer

The Pentose-phosphate cycle (also known as the phosphogluconate pathway or hexose monophosphate shunt) is primarily involved in producing NADPH and pentoses, not directly in the generation of ATP.

Question 10

E. coli is capable of using both respiration and fermentation. To produce the maximum amount of ATP, it should use

Accepted Answer

Oxidation of glucose through aerobic respiration is the most efficient way for E. coli to produce ATP, as it fully breaks down glucose into CO2 and H2O, yielding significantly more ATP compared to fermentation or anaerobic pathways.

Question 11

The vanA gene causes vancomycin resistance in Enterococcus species. This gene can be passed to other organisms, such as methicillin-resistant Staphylococcus aureus, by all of the following means except

Accepted Answer

The correct term for the genetic element that can facilitate the transfer of genes, including antibiotic resistance genes, between bacteria is "transposons," not "transporons." Transformation, conjugation, and transduction are all mechanisms by which bacteria can acquire new genetic material, including antibiotic resistance genes like vanA.

Question 12

An organism that can grow in an environment with an alkaline pH, high salt concentration, and at a temperature of 0°C is described as

Accepted Answer

An organism that thrives in an alkaline environment is alkaliphilic, in high salt concentrations is halophilic, and at low temperatures (0°C) is psychrophilic.

Question 13

Saline, rather than fresh water, is used to prepare smears of bacteria for Gram stain because

Accepted Answer

Fresh water has a lower solute concentration compared to the bacterial cell, leading to water influx into the cell due to osmosis, causing the cell to swell and potentially burst. This can interfere with the staining process and the integrity of the bacterial cells.

Question 14

Lipid A is located

Accepted Answer

Lipid A is a component of lipopolysaccharides (LPS), which are found in the outer membrane of gram-negative bacteria. It is not associated with gram-positive organisms, porin proteins, or the cytoplasmic membrane.

Question 15

Binary fission determines an organism's

Accepted Answer

Binary fission is a method of asexual reproduction that results in the replication of the parent organism into two daughter organisms, essentially determining the generation or doubling time of the organism.

Question 16

In times of plenty, bacteria are able to store various substances within the cell (carbohydrate, ATP, or lipid reserves) by means of

Accepted Answer

Inclusion bodies are the storage form for various substances within bacterial cells, such as carbohydrates, ATP, or lipids, especially during times of nutrient abundance. These are granules found in the cytoplasm of the cell, serving as a reserve of key nutrients.

Question 17

Which metabolic pathway is the primary means of glucose metabolism by E. coli?

Accepted Answer

The Embden-Meyerhof-Parnas pathway, also known as glycolysis, is the primary pathway for glucose metabolism in E. coli, converting glucose to pyruvate.

Question 18

Mutants that cannot grow on defined minimal medium without some nutritional additive are known as

Accepted Answer

Auxotrophs are mutants that have lost the ability to synthesize one or more compounds necessary for their growth and therefore require those compounds to be added to their growth medium.

Question 19

DNA sequences within a single cell that are able to jump to different locations within a chromosome are called

Accepted Answer

Transposons, also known as "jumping genes," are DNA sequences that can move or "jump" from one location in the genome to another, which can affect the function of genes at the new location.

Question 20

What is the toxic portion of the lipopolysaccharide component of gram-negative cell walls?

Accepted Answer

Lipid A is the toxic component of lipopolysaccharides (LPS) in the outer membrane of gram-negative bacteria, responsible for the endotoxic effects.

Quiz 3: The Bacterial Cell