Bacteria Quiz
Questions: 16 · 10 minutes
1. A bacterium transfers a plasmid directly to another bacterium through cell-to-cell contact. What process has occurred?
Transduction
Endospore germination
Binary fission
Conjugation
2. Milk kept in a refrigerator generally spoils more slowly than milk left on a warm counter. What best explains this difference?
Warm temperatures turn bacteria into viruses.
Refrigeration instantly kills every bacterium in the milk.
Cold temperatures remove all nutrients that bacteria require.
Low temperature slows the metabolism and reproduction of many spoilage bacteria.
3. Several people become ill after eating food containing a toxin that bacteria produced before the food was eaten. What does this illustrate?
Illness can occur only if living bacteria enter the bloodstream.
Bacterial products in food can cause illness even when tissue invasion is not the main mechanism.
All bacterial toxins are destroyed immediately at room temperature.
Foodborne illness is always caused by viruses rather than bacteria.
4. A patient has a viral respiratory infection. Why would an antibiotic that blocks bacterial ribosomes usually not treat it?
Viruses are too small for any medicine to affect.
Viruses neutralize every antibiotic before it reaches infected cells.
Viruses do not possess the bacterial ribosomes targeted by the drug.
Antibiotics work only outside the human body.
5. Which statement best reflects the role of bacteria in the human microbiome?
Every bacterium living on the body causes disease.
Many resident bacteria coexist with humans and can contribute to processes such as digestion or competition with pathogens.
Human health requires eliminating all resident bacteria.
The microbiome remains identical throughout a person's life.
6. What is the main function of a bacterial endospore?
Helping the bacterium persist through harsh conditions in a dormant, resistant form
Serving as the bacterium's normal method of sexual reproduction
Allowing the cell to capture prey with a membrane-bound organ
Producing energy through photosynthesis in all bacterial species
7. A student presses an unwashed fingertip onto one nutrient plate and a washed fingertip onto another. Fewer colonies grow on the second plate. Which conclusion is best supported?
Soap permanently sterilized the student's entire hand.
Every colony on the first plate represented a harmful species.
Handwashing reduced the number of culturable bacteria transferred under these conditions.
The washed fingertip contained no microorganisms of any kind.
8. What is the usual process by which one bacterial cell produces two daughter cells?
Binary fission
Budding from a multicellular embryo
Fusion of two parent cells
Meiosis
9. During yogurt production, certain bacteria make the mixture more acidic. What activity is primarily responsible?
Fermenting milk sugars and producing lactic acid
Using light energy to produce oxygen
Converting proteins directly into atmospheric nitrogen
Removing every water molecule from the milk
10. Why do many Gram-positive bacteria retain the purple dye during Gram staining?
They have an outer membrane rich in lipopolysaccharide.
They have a thick peptidoglycan layer that traps the dye complex.
They lack a cell wall, allowing dye to enter the cytoplasm freely.
They produce pigments that permanently turn the stain purple.
11. A bacterial population includes a few cells with a mutation that provides resistance to an antibiotic. What is most likely after repeated exposure to that antibiotic?
Resistant cells are more likely to survive and contribute offspring to later generations.
The antibiotic causes all resistant cells to lose the mutation.
Susceptible cells reproduce faster because the drug supplies nutrients.
Every bacterium deliberately changes its genes to survive.
12. Which characteristic distinguishes bacterial cells from eukaryotic cells?
Their cell membrane is made entirely of cellulose.
They contain no genetic material.
They always consist of multiple specialized cells.
Their DNA is not enclosed within a membrane-bound nucleus.
13. A bacterium grows in both oxygen-rich and oxygen-free environments, although its energy pathways differ. How is it best described?
An obligate aerobe
An obligate intracellular virus
A facultative anaerobe
A photosynthetic eukaryote
14. A microscope shows bacterial cells moving through liquid using long, whip-like structures. Which structures most likely produce this movement?
Capsules
Ribosomes
Plasmids
Flagella
15. Legume plants often grow well in nitrogen-poor soil when certain bacteria live in their root nodules. What do these bacteria provide?
They create sunlight for the plant's leaves.
They convert atmospheric nitrogen into compounds that can enter biological nutrient cycles.
They convert all soil minerals into glucose.
They replace the plant's need for water.
16. Before transferring a bacterial culture, a student disinfects the work surface and uses sterile tools. What is the main purpose of these steps?
To make all bacterial species visible without staining
To guarantee that the target bacteria reproduce faster
To reduce unwanted microbial contamination of the culture and workspace
To convert harmful bacteria into harmless species