Microbiology, 2021

364 9 • Review Questions
18. In which environment are you most likely to
encounter an acidophile?
A. human blood at pH 7.2
B. a hot vent at pH 1.5
C. human intestine at pH 8.5
D. milk at pH 6.5
19. A soup container was forgotten in the
refrigerator and shows contamination. The
contaminants are probably which of the
following?
A. thermophiles
B. acidophiles
C. mesophiles
D. psychrotrophs
20. Bacteria isolated from a hot tub at 39 °C are
probably which of the following?
A. thermophiles
B. psychrotrophs
C. mesophiles
D. hyperthermophiles
21. In which environment are you most likely to
encounter a hyperthermophile?
A. hot tub
B. warm ocean water in Florida
C. hydrothermal vent at the bottom of the
ocean
D. human body
22. Which of the following environments would
harbor psychrophiles?
A. mountain lake with a water temperature of
12 °C
B. contaminated plates left in a 35 °C
incubator
C. yogurt cultured at room temperature
D. salt pond in the desert with a daytime
temperature of 34 °C
23. Which of the following is the reason jams and
dried meats often do not require refrigeration to
prevent spoilage?
A. low pH
B. toxic alkaline chemicals
C. naturally occurring antibiotics
D. low water activity
24. Bacteria living in salt marshes are most likely
which of the following?
A. acidophiles
B. barophiles
C. halotolerant
D. thermophiles
25. EMB agar is a medium used in the identification
and isolation of pathogenic bacteria. It contains
digested meat proteins as a source of organic
nutrients. Two indicator dyes, eosin and
methylene blue, inhibit the growth of grampositive
bacteria and distinguish between
lactose fermenting and nonlactose fermenting
organisms. Lactose fermenters form metallic
green or deep purple colonies, whereas the
nonlactose fermenters form completely
colorless colonies. EMB agar is an example of
which of the following?
A. a selective medium only
B. a differential medium only
C. a selective medium and a chemically
defined medium
D. a selective medium, a differential medium,
and a complex medium
26. Haemophilus influenzae must be grown on
chocolate agar, which is blood agar treated with
heat to release growth factors in the medium. H.
influenzae is described as ________.
A. an acidophile
B. a thermophile
C. an obligate anaerobe
D. fastidious
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