Multiple Choice Questions PDF
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This document contains multiple choice questions about microbiology, including bacterial growth and microbial contamination. The summary also highlights that the questions are on topics concerning microorganisms and their growth.
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1. **Bacterial growth refers to:** - an increase in the number of cells. **(Correct Answer)** - the occurrence of mitosis. - the time required for one cell to divide into two. - the occurrence of binary fission. 2. **Which is an example of a micronutrient?** - vita...
1. **Bacterial growth refers to:** - an increase in the number of cells. **(Correct Answer)** - the occurrence of mitosis. - the time required for one cell to divide into two. - the occurrence of binary fission. 2. **Which is an example of a micronutrient?** - vitamin B12 - iron **(Correct Answer)** - inorganic phosphorus - arginine 3. **All microorganisms require:** - phosphorus, aluminum, and sodium. - calcium, potassium, and magnesium. - carbon, iron, and sodium. - phosphorus, nitrogen, and sulfur. **(Correct Answer)** . **Microbial growth is generally described as an increase in cell number rather than the 4 expansion in size of an individual microbial cell.** - True **(Correct Answer)** - False . **A medium containing known substances in precise amounts is known as a ________ 5 media.** - complex - natural - selective - defined **(Correct Answer)** 6. **Selective medium differs from differential medium because:** - selective medium permits growth of a particular microbial type while differential medium is used to distinguish between types of organisms. **(Correct Answer)** - differential medium differentiates pathogens from nonpathogens while selective medium grows only pathogens. - selective medium permits growth of more organisms than differential medium. - differential medium contains growth inhibitors while selective medium does not. 7. **Microbial contamination is prevented by the:** - use of the quadrant streak method. - use of cultures containing special nutrients. - spread-plate method. - use of aseptic technique. **(Correct Answer)** . **To ensure growth of a newly discovered bacterium with unknown nutritional 8 requirements, it would be best to begin with a ________ medium rather than a ________ medium.** - minimal / complex - complex / minimal **(Correct Answer)** - selective / complex - selective / differential . **A selective medium is used to suppress the growth of some bacteria in order to facilitate 9 the growth of other bacteria.** - True **(Correct Answer)** - False 0. **A complex medium is one that has been completely made in the laboratory and the 1 concentration of all the nutrients is known.** - True - False **(Correct Answer)** 1. **Which of the following methods used to enumerate cells often requires specialized 1 staining to observe non-pigmented bacteria?** - spread-plating - microscopy **(Correct Answer)** - spread-plating, turbidity, and microscopy - spectrophotometry/turbidity 2. **Direct microscopic counting of cells is an accurate method for estimating the number of 1 viable cells in a sample.** - True - False **(Correct Answer)** 3. **When attempting to determine viable cell counts of a heat-sensitive bacterial isolate, 1 which cell counting method should be avoided?** - pour-plate method **(Correct Answer)** - live staining and direct counting with a microscope - both spread- and pour-plate methods - spread-plate method 14. **The number of colonies obtained in a plate count does NOT depend on the:** - incubation time. - size of the colonies. **(Correct Answer)** - type of culture medium. - inoculum volume. 15. **Serial dilutions are generally made:** - when the appropriate viable count is unknown. - to reach a suitable dilution while minimizing error. - based on powers of 10, although other serial dilution factors are possible. - All of these answer choices apply. **(Correct Answer)** 6. **When viable cell concentrations are too high to count on an agar plate, it is common to 1 use larger sized plates to increase the surface area for counting the colonies.** - True - False **(Correct Answer)** 17. **The time interval required for the formation of two cells from one is called the:** - generation time. **(Correct Answer)** - growth rate. - division rate. - growth time. 18. **The time between inoculation and the beginning of growth is usually called the:** - log phase. - lag phase. **(Correct Answer)** - decline phase. - dormant phase. 19. **Which of the following statements is FALSE?** - Bacteria typically divide by binary fission, producing two daughter cells. - The generation time of bacteria may vary from species to species. - In the death phase, bacterial growth may cease as a result of oxygen and nutrient depletion. - In the lag phase, cell death exceeds cell division. **(Correct Answer)** 20. **Which choice best illustrates what occurs in the stationary phase of bacterial growth?** - cryptic growth, where the number of new cells equals the number of dying cells **(Correct Answer)** - unbalanced growth, where the number of dead cells increases while the number of new cells decreases - cryptic growth, where the number of dead cells decreases while the number of new cells increases - balanced growth, where the number of dead cells equals the number of new cells 1. **The lag phase does NOT occur if an exponentially growing culture is transferred into a 2 nutrient-rich medium with the same components and growth conditions as the previous medium.** - True **(Correct Answer)** - False 2. **The rate of exponential growth varies greatly according to bacterial species and 2 bioavailable nutrients.** - True **(Correct Answer)** - False 3. **In both the lag and stationary phase, there is no net increase or decrease in viable 2 cells.** - True **(Correct Answer)** - False 24. **The death phase applies to individual cells rather than populations.** - True - False **(Correct Answer)** 5. **A bacterial cell in nutrient broth with a generation time of 15 minutes will produce 16 2 cells in 2 hours.** - True - False **(Correct Answer)** 26. **Cell density in a chemostat is controlled by:** - the concentration of the limiting nutrient. - the size of the initial inoculum. - the dilution factor. - the concentration of the limiting nutrient and the dilution factor. **(Correct Answer)** . **By controlling the concentration of nutrients continuously added to a chemostat, cells 1 can constantly be maintained at the:** - **a.** lag growth phase - **b.** stationary growth phase - **c.** exponential growth phase - **d.** death growth phase - **Correct Answer:** **c. exponential growth phase** . **A closed system, used for bacterial growth, where nothing is added and nothing is 2 removed is called:** - **a.** a chemostat - **b.** a lag culture - **c.** a continuous culture - **d.** a batch culture - **Correct Answer:** **d. batch culture** 3. **Bacteria that are able to grow in humans and cause disease would be classified as:** - **a.** hyperthermophiles - **b.** psychrophiles - **c.** thermophiles - **d.** mesophiles - **Correct Answer:** **d. mesophiles** 4. **Most mesophilic organisms can grow in a temperature range of:** - **a.** 50-65°C - **b.** 20-45°C - **c.** 10-20°C - **d.** 0-15°C - **Correct Answer:** **b. 20-45°C** . **The optimal growth temperature of a bacterium is most closely related to the optimal 5 temperature for:** - **a.** DNA replication - **b.** mRNA attachment to ribosomes - **c.** enzyme function - **d.** transcription of DNA - **Correct Answer:** **c. enzyme function** . **Cultures of a bacterial species were incubated on the shelf of a refrigerator (5°C), on a 6 lab benchtop (25°C), on the shelf of a 37°C incubator, and on the shelf of a 50°C incubator. After incubation, there was no growth at 37°C or 50°C, slight growth on the benchtop, and abundant growth at refrigeration. What term could be used for this species?** - **a.** anaerobe - **b.** halophile - **c.** mesophile - **d.** psychrophile - **Correct Answer:** **d. psychrophile** . **A bacterium whose optimal growth temperature is 35°C would be classified as a 7 thermophile.** - **True** - **False** - **Correct Answer:** **False** (it would be classified as a mesophile) . **The optimum growth temperature for an organism is typically closer to its minimum 8 temperature rather than the maximum temperature.** - **True** - **False** - **Correct Answer:** **False** . **Relative to enzymes in mesophilic microorganisms, which of the following is NOT 9 characteristic of enzymes in psychrophiles?** - **a.** fewer hydrogen bonds - **b.** fewer ionic bonds - **c.** decreased alpha helix content - **d.** decreased beta sheet content - **Correct Answer:** **d. decreased beta sheet content** 1. **A microbe growing in a refrigerator is likely:** - A) psychrophilic. - B) psychrotolerant or psychrophilic. - C) mesophilic. - D) hyperthermophilic. - **Correct Answer:** B) psychrotolerant or psychrophilic. 2. **Some microbes can grow in boiling water.** - A) True - B) False - **Correct Answer:** A) True . **Taq polymerase was isolated from a thermophile and is used in the polymerase chain 3 reaction (PCR) technique because it does not become inactivated at high temperatures.** - A) True - B) False - **Correct Answer:** A) True 4. **Irreversible cell damage is more likely to occur at low rather than high temperatures.** - A) True - B) False - **Correct Answer:** B) False 5. **Many fungi and bacteria grow best at pH 5 or below.** - A) True - B) False - **Correct Answer:** A) True 6. **The optimal pH for growth of an organism refers to its intracellular environment.** - A) True - B) False - **Correct Answer:** B) False . **Based on studies with obligate acidophiles, high concentrations of hydrogen ions are 7 required for their membrane stability.** - A) True - B) False - **Correct Answer:** A) True . **The ratio of the vapor pressure of the air in equilibrium with a substance to the vapor 8 pressure of pure water is known as:** - A) vapor activity. - B) water activity. - C) positive water balance. - D) osmosis. - **Correct Answer:** B) water activity. 9. **Organisms able to live in environments with high sugar concentrations are:** - A) osmophiles. - B) halotolerant. - C) anaerobic fermenting bacteria. - D) xerophiles. - **Correct Answer:** A) osmophiles. 10. **When water activity is low, an organism must:** - A) increase its internal solute concentration. - B) increase its external solute concentration. - C) decrease its internal solute concentration. - D) decrease its external solute concentration. - **Correct Answer:** A) increase its internal solute concentration. 1. **A halotolerant facultative anaerobe would grow BEST in which of the following 1 environments?** - A) oxygen depleted saline - B) oxygenated saline - C) oxygenated non-saline - D) oxygen depleted non-saline - **Corrected Answer:** C) oxygenated non-saline.
