SCIENCE TEST

of 4 of the large
ng lactose broth
t tubes (all concubated
at 37°C
es were examas
yellow. If no
red. If CO 2 was
the top of the
e broth
CO 2
−
+
−
− −
28. In Experiment 1, which of the bacterial species fermented
lactose?
For a F. sugar Species to be B fermented, only it must produce acid alone, or acid and CO2. Under the
G. Species C only
heading H. Species “Lactose B and broth” Species in Table D only1,
we see that acid and CO2 were produced by species
B, and J. acid Species alone C and was Species produced D only by species D.
29. 29. Suppose Suppose that that in Experiment in Experiment 2 both 2 Species both B Species and Species B and C had been added to a large test tube
Species C had been added to a large test tube contain-
containing
ing sucrose
sucrose
broth
broth and
and
to
to
a large
a large
test
test
tube
tube
containing
containing
lactose broth. Which of the following would
most likely lactose depict broth. the results? Which of the following would most
likely depict the results?
Answer: C.
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Comparing Table 1 and Table 2, we see that when two species are combined, they
perform the fermentation they can do on their own plus any synergistic fermentation. For
example, from Table 1 we see that species C ferments sucrose by producing both acid
and CO2, and species D ferments lactose by producing both acid and CO2. In Table 2, we
see that together they ferment both sucrose and lactose by producing both acid and CO2. There is a similar relationship between B and C, so we expect a similar result.
30. Suppose a scientist isolates a bacterial species that is 1 of the 4 species used in Experiment 1. She adds
the species to sucrose broth and observes that neither acid nor CO2 is produced. She then adds the species
to lactose broth and observes that both acid and CO2 are produced. Based on the results of Experiment 1,
the species is most likely:
F. Species A.
G. Species B.
H. Species C.
J. Species D.
Answer: G.
Sucrose broth Lactose broth
acid CO 2 acid CO 2
A. – – + +
B. + + – –
C. + + + +
D. – – – –
From Table 1, we see that there are three species that produce neither acid nor CO 2 in a
sucrose broth when they are alone in the broth: species A, species B and species D. Of
these, only species B produces both acid and CO 2 in a lactose broth.
31. What is the evidence from Experiments 1 and 2 that Species C and Species D acted synergistically in
Experiment 2?
A. No acid was produced when each species was alone in the sucrose broth, but acid was produced
when the 2 species were together in the sucrose broth.
B. No acid was produced when each species was alone in the lactose broth, but acid was produced
when the 2 species were together in the sucrose broth.
C. No CO2 was produced when each species was alone in the sucrose broth, but CO2 was produced
when the 2 species were together in the sucrose broth.
D. No CO2 was produced when each species was alone in the lactose broth, but CO2 was produced
when the 2 species were together in the lactose broth.