Catherine Smith
Name: ___________________________ Hoa Nhu Le / BIOL 3132-03 (13985–1pm)
TA/Lab Period: ____________________________________
Lab 8 Handout
Lab 8 Parts 1 and 2
Lab 8 Part 1 Biochemical Tests II Exercises 5-6, 5-7, 5-11, 5-12
1) The following shows results of three di erent unknown
bacterial strains grown on nitrate broth for the purpose of
tes ng for nitrate reduc on; an uninoculated control tube
was also included. Following 24 hour incuba on of the
cultures at 37⁰C, nitrate reduc on reagents A and B were
added to each culture tube, including the control tube.
Based on this result, zinc powder was added to tubes 1 (the
control), 2, and 4. Record your observa ons/interpreta ons
in the table below. Refer to Table
5-7 in your lab manual (p. 269)
when recording results. NOTE:
gas produc on was not tested in
this analysis, so you do not need
to record anything for this in the
table.
Results
Organism Color Interpretations
After Reagents After Zinc
No change Negative nitrate test → no nitrate
Control (clear/ Red reduction (Zinc turned nitrate to
translucent) nitrite)
No change Negative nitrate test → no nitrate
Tube 2 Unknown (clear/ Red reduction (Zinc turned nitrate to
translucent) nitrite)
Orange-Red (no
Positive nitrate test → nitrate
Tube 3 Unknown Orange-Red additional color
reduction (to nitrite) occurred
change)
No change
Positive nitrate test → nitrate was
Tube 4 Unknown (clear/ Yellow
reduced beyond nitrite
translucent)
1
This study source was downloaded by 100000846043569 from CourseHero.com on 05-07-2022 12:42:13 GMT -05:00
https://www.coursehero.com/file/98073304/Lab-8-Handountpdf/
ti ti ti ti ffti ti ti
, a. According to your data in the table above, which unknowns are positive for
nitrate reduction, whether to nitrite or beyond?
Unknown 3 reduced nitrate to nitrite
Unknown 4 reduced nitrate beyond nitrite
b. If you had checked for gas production in this analysis and saw bubbles like this
for unknown 4 after 24 hour incubation, how would you interpret this? Would be
necessary to add reagents, A & B to this tube?
If the organism is not a fermenter, then this confirms that nitrate what
reduced to nitrogen gas (N2). It is not necessary to add reagents A & B
since this confirms that nitrate reduction occurred.
2) Answer the questions below referring to the citrate test and urea test,
respectively.
a. The following shows results of two bacterial strains grown
on Citrate Agar. Record your observations/interpretations
of these cultures in the table below. Refer to Table 5-8 in
your lab manual (p. 275) when recording results.
1: uninoculated control
2: Salmonella typhimurium
3: Salmonella typhi
Organism Color Result +/– Interpretation
Control Green – Citrate is not utilized
Serratia Citrate is utilized (as sole carbon
Blue +
typhimurium source)
Small amount of blue color → citrate is
Serratia typhi Blue-Green +
utilized
b. The following shows results of two bacterial strains,
Serratia marcescens and Providencia stuartii, grown
on Urea broth. Record your observations and
interpretations of these cultures in the table below.
Refer to Table 5-13 in your lab manual (p. 301) when
recording results.
2
This study source was downloaded by 100000846043569 from CourseHero.com on 05-07-2022 12:42:13 GMT -05:00
https://www.coursehero.com/file/98073304/Lab-8-Handountpdf/
Name: ___________________________ Hoa Nhu Le / BIOL 3132-03 (13985–1pm)
TA/Lab Period: ____________________________________
Lab 8 Handout
Lab 8 Parts 1 and 2
Lab 8 Part 1 Biochemical Tests II Exercises 5-6, 5-7, 5-11, 5-12
1) The following shows results of three di erent unknown
bacterial strains grown on nitrate broth for the purpose of
tes ng for nitrate reduc on; an uninoculated control tube
was also included. Following 24 hour incuba on of the
cultures at 37⁰C, nitrate reduc on reagents A and B were
added to each culture tube, including the control tube.
Based on this result, zinc powder was added to tubes 1 (the
control), 2, and 4. Record your observa ons/interpreta ons
in the table below. Refer to Table
5-7 in your lab manual (p. 269)
when recording results. NOTE:
gas produc on was not tested in
this analysis, so you do not need
to record anything for this in the
table.
Results
Organism Color Interpretations
After Reagents After Zinc
No change Negative nitrate test → no nitrate
Control (clear/ Red reduction (Zinc turned nitrate to
translucent) nitrite)
No change Negative nitrate test → no nitrate
Tube 2 Unknown (clear/ Red reduction (Zinc turned nitrate to
translucent) nitrite)
Orange-Red (no
Positive nitrate test → nitrate
Tube 3 Unknown Orange-Red additional color
reduction (to nitrite) occurred
change)
No change
Positive nitrate test → nitrate was
Tube 4 Unknown (clear/ Yellow
reduced beyond nitrite
translucent)
1
This study source was downloaded by 100000846043569 from CourseHero.com on 05-07-2022 12:42:13 GMT -05:00
https://www.coursehero.com/file/98073304/Lab-8-Handountpdf/
ti ti ti ti ffti ti ti
, a. According to your data in the table above, which unknowns are positive for
nitrate reduction, whether to nitrite or beyond?
Unknown 3 reduced nitrate to nitrite
Unknown 4 reduced nitrate beyond nitrite
b. If you had checked for gas production in this analysis and saw bubbles like this
for unknown 4 after 24 hour incubation, how would you interpret this? Would be
necessary to add reagents, A & B to this tube?
If the organism is not a fermenter, then this confirms that nitrate what
reduced to nitrogen gas (N2). It is not necessary to add reagents A & B
since this confirms that nitrate reduction occurred.
2) Answer the questions below referring to the citrate test and urea test,
respectively.
a. The following shows results of two bacterial strains grown
on Citrate Agar. Record your observations/interpretations
of these cultures in the table below. Refer to Table 5-8 in
your lab manual (p. 275) when recording results.
1: uninoculated control
2: Salmonella typhimurium
3: Salmonella typhi
Organism Color Result +/– Interpretation
Control Green – Citrate is not utilized
Serratia Citrate is utilized (as sole carbon
Blue +
typhimurium source)
Small amount of blue color → citrate is
Serratia typhi Blue-Green +
utilized
b. The following shows results of two bacterial strains,
Serratia marcescens and Providencia stuartii, grown
on Urea broth. Record your observations and
interpretations of these cultures in the table below.
Refer to Table 5-13 in your lab manual (p. 301) when
recording results.
2
This study source was downloaded by 100000846043569 from CourseHero.com on 05-07-2022 12:42:13 GMT -05:00
https://www.coursehero.com/file/98073304/Lab-8-Handountpdf/
