McMaster University

BIO 2EE3

CHAPTER 6

1)Which one of the following elements is considered a microelement, usually required in minute amounts in microbiological media?

1. 1. Manganese
   2. Iron
   3. Magnesium
   4. Potassium
   5. Phosphate

2. A heterotroph is an organism that uses                    as a source of                       
   1. Carbon dioxide; carbon
   2. Sunlight; energy
   3. Organic compounds; carbon
   4. Organic compounds; energy
   5. Inorganic compounds; energy

3. What is nitrogen fixation?
   1. The release of an amino group from an amino acid for assimilation
   2. The reduction of dinitrogen to ammonia for assimilation
   3. The oxidation of ammonia to nitrate for assimilation
   4. The reduction of nitrate to dinitrogen for assimilation
   5. The oxidation of nitrate to ammonia for assimilation

4. What is the most common solidifying agent used in microbiological media?
   1. Gelatin
   2. Polycrylamide
   3. Alginate
   4. Agar
   5. Silica

5. Term for a bacterium that doesn’t use oxygen for growth, but will grow in the presence of oxygen
   1. Facultative anaerobe
   2. Facultative aerobe
   3. Aerotolerant anaerobe
   4. Anaerobe
   5. Aerobe

6. What is the term for microbes that grow optimally at a pH below 5.5?
   1. Acidophiles
   2. Barophiles
   3. Psychrophiles
   4. Halophiles
   5. Alkalophiles

7. In the environment, one microorganism often provides a nutrient for another microbe that is unable to synthesize the nutrient by itself. What is this type of relationship called?
   1. Syntrophy
   2. Prototrophy
   3. Oligotrophy
   4. Auxotrophy
   5. Eutrophy

8. Which of these methods can be used to obtain a viable cell count?
   1. Turbidity measurement
   2. Plate counts of serial dilutions
   3. Counting chamber direct count
   4. Optical density
   5. Loop dilution

9. If a cell culture contains 400 cells/ml at time = 0 and it has a generation time of 30 minutes, how many cells (cells/ml) will be present after 2 hours of incubation?
   1. 1200 cells/mL
   2. 1600 cells/mL
   3. 2400 cells/mL
   4. 3200 cells/mL
   5. 6400 cells/mL

10. How long would it take a culture of E. coli with a starting cell density of 1 X 10⁵ cells/ ml to reach a cell density of 1 X 10⁸ cells/ml if it had a generation time of 30 minutes
    1. 3 hours
    2. 4 hours
    3. 5 hours
    4. 6 hours
    5. 7 hours

11. During steady state growth in a chemostat, the growth rate of the cells is equivalent to
    1. The cell yield
    2. The generation time
    3. The nutrient concentration
    4. The flow rate
    5. The dilution rate

12. Many pharmaceutical products are heat sensitive so they are sterilized
    1. By ionizing radiation
    2. By freezing
    3. With ozone gas
    4. With chlorine gas
    5. By ultraviolet radiation

13. Many disinfectants are strong oxidizing agents and disrupt many cellular functions. Which of these is an example of an oxidizing agent?
    1. Carbolic acid
    2. Phenol
    3. Isopropanol
    4. Chlorine bleach
    5. Triclosan

14. What is the function of siderophores?
    1. Transporting proteins out of the cell
    2. Moving potassium into the cell for osmotic regulation
    3. Binding glucose for transport into the cell
    4. Binding iron for transport into the cell
    5. Transporting waste products out of the cell

15. A phototroph is an organism that uses                       as a source of                       
    1. Inorganic compounds; energy
    2. Carbon dioxide; carbon
    3. Organic compounds; energy
    4. Sunlight; energy
    5. Organic compounds; carbon

16. What is the most abundant form of nitrogen in the biosphere?
    1. Nitrite
    2. Nitrous oxide
    3. Ammonia
    4. Nitrate
    5. Dinitrogen

17. Which one of the following is NOT a physical factor that affects the growth rate of cells?
    1. Pressure
    2. Nutrient concentration
    3. Light intensity
    4. Radiation
    5. Temperature

18. What term applies to a microbe that can synthesize all of its cellular constituents from a simple carbon source and inorganic salts?
    1. Heterotroph
    2. Chemotroph
    3. Auxotroph
    4. Autotroph
    5. Phototroph

19. Term for microbes that grow optimally at a pH above 8.5
    1. Barophiles
    2. Halophiles
    3. Psychrophiles
    4. Acidophiles
    5. Alkalophiles

20. Enrichment media that contains starch as the sole carbon source is encouraging the growth of microbes that produce                                
    1. The enzyme cellulose
    2. All 20 amino acids
    3. Glucose
    4. The enzyme amylase
    5. All required vitamins

21. What would you use to measure the optical density of a bacterial culture?
    1. The plate count method
    2. A flow cytometer
    3. A Petroff-Hauser counting chamber
    4. A spectrophotometer
    5. A microscope

22. The plate count method was used to estimate the number of bacteria in a culture over time. Serial dilutions were made of culture samples at various time points. A 0.1 ml portion of the

10^-6 dilution was spread over the surface of a nutrient agar plate for each time point. The plates were incubated for 24 hrs and the colony forming units (CFU) were counted on each plate. A total of 45 colonies were counted on the plate for the 30 minute time point. What was the cell population for this time point?

1. 45 x 10⁴ CFU/mL
2. 45 x 10⁵ CFU/mL
3. 45 x 10⁶ CFU/mL
4. 45 x 10⁷ CFU/mL
5. 45 x 10⁸ CFU/mL

23. Fresh media is inoculated with an actively growing Escherichia coli culture. You measure the optical density (OD) at the time of inoculation and record a value of 0.05) Two hours later you take another reading and record a optical density of 0.2) What is the generation time for your culture?
    1. 30 minutes
    2. 40 minutes
    3. 50 minutes
    4. 60 minutes
    5. Cannot determine from information given

24. What is a chemostat?
    1. A system used for the continuous culture of microbial cells
    2. A nutrient that is able to control the growth rate of a bacterial culture
    3. The maximum growth rate that can be obtained for a useable substrate
    4. A batch culture that uses a defined medium for growth
    5. A chemical used as a substrate for growth of microbial cells

25. Alcohols like ethanol and isopropanol are commonly used as antiseptics because they are very effective at reducing the bacterial load. What is their mode of action?
    1. Inhibiting protein synthesis
    2. Inhibiting transcription
    3. Disruption of peptidoglycan
    4. Disrupting the plasma membrane
    5. Inhibiting DNA replication

26. What is the best definition of an antiseptic?
    1. A physical agent that is used to sterilize hospital equipment
    2. An antibiotic that is applied to living tissue
    3. A physical agent that is used on human tissue to inhibit microbial growth
    4. A chemical agent that is applied to living tissue to kill and inhibit microbes
    5. A chemical agent that is applied to hospital equipment to kill or inhibit microbes

27. An autotroph is an organism that uses                     as a source of                    
    1. Sunlight; energy
    2. Carbon dioxide; carbon
    3. Organic compounds; carbon
    4. Inorganic compounds; energy
    5. Organic compounds; energy

28. The enzyme catalase is used to detoxify which harmful oxygen species?
    1. Hydrogen peroxide
    2. Hydroxyl radical
    3. Ozone
    4. Singlet oxygen
    5. Superoxide

29. If you had an E. coli culture with a starting cell density of 1 X 10⁶ cells/ml and it had a generation time of 40 minutes, what would be the cell density after incubation for 6 hours?
    1. 3 x 10⁸ cells/mL
    2. 5.1 x 10⁸ cells/mL
    3. 6.3 x 10⁸ cells/mL
    4. 9.4 x 10⁸ cells/mL
    5. 1 x 10⁹ cells/mL