Microbiology Chapter 6

1) In one hospital, Pseudomonas aeruginosa serotype 10 infected the biliary tract of 10 percent of 1300 patients who underwent gastrointestinal endoscopic procedures. After each use, endoscopes were washed with an automatic reprocessor that flushed detergent and glutaraldehyde through the endoscopes, followed by a tap water rinse. P. aeruginosa 10 was not isolated from the detergent, glutaraldehyde, or tap water. What was the source of the infections?

2) The addition of which of the following to a culture medium will neutralize acids?

3) Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt? A) thermophiles B) anaerobes C) psychrophiles D) hyperthermophiles E) facultative halophiles

in Figure 6.1, which line shows the growth of an obligate aerobe incubated anaerobically? Select one: a. a b. b c. c

5) In Figure 6.3, which tube shows the expected growth pattern for a microaerophile?

6) In Figure 6.1 ,which line best depicts an obligate anaerobe in the presence of O2? Select one: a. a b. b c. c

A sample of milk is tested for its bacterial content in a plate count assay. A one-milliliter sample of the milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in a pour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample contained A) 54 cells. B) 540 cells. C) 5400 cells. D) 54,000 cells. E) 540,000 cells.

A culture medium consisting of agar, peptone and beef heart extract is a/an: a) selective medium. b) chemically defined medium. c) differential medium. d) complex medium. e) enrichment medium.

9) Which of the following is NOT a direct method to measure microbial growth?

The term aerotolerant anaerobe refers to an organism that: a. Is killed by oxygen. b. Uses oxygen or grows without oxygen. c. Doesn't use oxygen, but tolerates it. d. Prefers to grow without oxygen. e. Requires less oxygen than is present in air.

11) In Figure 6.3, which tube shows the expected growth pattern for a facultative anaerobe?

12) The data in Table 6.2 indicate that S. aureus is a(n)

13) In Figure 6.1, which line best depicts a facultative anaerobe in the absence of O2? a. a b. b c. c

If cells are grown in media containing amino acids labeled with radioactive nitrogen (¹⁵N), most of radioactivity will be found in the cells' A) DNA. B) proteins. C) phospholipids. D) DNA and proteins. E) DNA and phospholipids

15) Figure 6.2 shows a typical bacterial growth curve with the x-axis indicating the log of the number of bacteria and the y-axis indicating time in culture. In the figure, which sections of the graph illustrate a logarithmic change in cell numbers? A) a and c B) b and d C) a and b D) c and d E) a and d

16) Most bacteria grow best at pH

17) An experiment began with 4 cells and ended with 128 cells. How many generations did the cells go through?

18) Most fungi grow best at pH

19) Pathogenic bacteria isolated from the respiratory or intestinal tracts of humans are A) capnophiles that grow best in carbon dioxide incubators. B) facultative anaerobes that require reducing media for growth. C) strict aerobes that grow best in candle jars. D) capnophiles that prefer highly oxygenated growth conditions. E) strict aerobes that grow best in reducing media.

20) Three cells with generation times of 60 minutes are inoculated into a culture medium. How many cells are there after 5 hours?

Figure 6.2 shows a typical bacterial growth curve with the x-axis indicating the log of the number of bacteria and the y-axis indicating time in culture. In the figure, which section (or sections) shows a growth phase where the number of cells dying equals the number of cells dividing? A) a B) b C) c D) d E) a and c

22) Most bacteria reproduce by

The biosafety level (BSL) for a clinical microbiology laboratory working with potentially airborne pathogens, such as tuberculosis bacteria, is A) BSL-1. B) BSL-2. C) BSL-3. D) BSL-4.

The biosafety level (BSL) for most introductory microbiology laboratories is A) BSL-1. B) BSL-2. C) BSL-3. D) BSL-4.

) In Figure 6.1, which line best depicts a psychrotroph incubated at 0°C? A) a B) b C) c

4) In Figure 6.1, which line best illustrates the growth of a facultative anaerobe incubated aerobically? A) a B) b C) c

5) Which of the following is an advantage of the standard plate count? A) can readily count cells that form aggregates B) determines the number of viable cells C) can be performed on very dilute samples, such as lake water D) provides immediate results E) can be used to count heat-sensitive bacteria

6) Which of the following is an advantage of the direct microscopic count? A) can readily count organisms that are motile B) can easily distinguish live from dead cells C) requires no incubation time D) sample volume is unknown E) requires a large number of cells Answer: C

18) Thirty-six colonies grew in nutrient agar from 1.0 ml of undiluted sample in a standard plate count. How many cells were in the original sample? A) 4 B) 9 C) 18 D) 36 E) 72

25) Which of the following is an example of a metabolic activity that could be used to measure microbial growth?

24) Which enzyme catalyzes the reaction: 2H2O2 → 2H2O + O2? Which enzyme catalyzes the reaction: 2H2O2 2H2O + O2? A) Peroxidase B) Oxidase C) Superoxide dismutase D) Catalase

Patients with indwelling catheters are susceptible to infections because Select one: a. Injected solutions are contaminated. b. Their immune systems are weakened. c. Infections can be transmitted from other people. d. Biofilms develop on catheters. e. Bacteria cause infections.

Salts and sugars work to preserve foods by creating a A) Depletion of nutrients. B) Hypotonic environment. C) Hypertonic environment. D) Lower osmotic pressure. E) Lower pH.

34) Which of the following is the best definition of generation time?

36) Which enzyme catalyzes the reaction: O2- + O2- + 2H+ → H2O2 + O2? Which enzyme catalyzes the reaction: O2- + O2- + 2H+ → H2O2 + O2? A) Catalase B) Oxidase C) Peroxidase D) Superoxide dismutase

37) Which of the following elements is NOT correctly matched with its cellular function?

39) Which enzyme catalyzes the reaction: H2O2 + 2H+ → 2H2O? A) Catalase B) Oxidase C) Peroxidase D) Superoxide dismutase

39) Assume you inoculated 100 cells into 100 ml of nutrient broth. You then inoculated 100 cells of the same species into 200 ml of nutrient broth. After incubation for 24 hours, you should have

40) For the three types of media in Table 6.1, which medium (or media) is/are chemically defined?

41) During which growth phase will gram-positive bacteria be most susceptible to penicillin? During which growth phase will gram-positive bacteria be most susceptible to penicillin? A) death phase B) stationary phase C) lag phase D) log phase E) The culture is equally susceptible during all phases.

Which of the following pairs is mismatched? A) hyperthermophiles — growth at 85°C B) psychrotroph — growth at 0°C C) psychrophile — growth at 15°C D) thermophile — growth at 37°C E) mesophile — growth at 25°C

43) Which of the following is an organic growth factor?

44) A culture medium on which only gram-positive organisms grow and a yellow halo surrounds

45) The source of nutrients in nutrient agar is

46) An isolated colony on a streak plate contains millions or billions of identical cells.

47) In performing a ten-fold dilutions series from a sample containing 10,000 bacteria per milliliter, the fourth tube in the dilution series will have 10 cells per milliliter.

48) Laboratory cultivation of obligate anaerobes requires reducing media or special growth chambers filled with inert gases.

49) Nitrogen-fixing bacteria, such as cyanobacteria, can use atmospheric nitrogen (N2) for their nitrogen source.

50) Bacterial growth refers to an increase in the numbers of cells in a bacterial culture.

51) Agar is used as a solidifying agent in microbiological media since few bacteria can degrade it.

52)Pure cultures can easily be obtained on streak plates, even if the desired bacteria are present in very low concentrations.

53) Turbidity is an indirect measurement of bacterial growth that can be measured using a spectrophotometer.

54) Filtration methods are used to count bacteria present in very low concentrations, such as in lakes and streams.

55) Most pathogenic bacteria are thermophiles.