Lab Report 9–Virtual Practice Unknown
In this lab, you will work independently to record the data for various biochemical tests. Note that the practice unknown biochemical tests are the same identification tests that will be performed for your unknown organism report.
Prior to beginning this lab worksheet, please look at the Biochemicals for Unknown Identifiction.pptx presentation (available through the Canvas portal) as well as the following videos (linked below):
1. Carbohydrate fermentation broths: https://youtu.be/vJcL9f52Zuk
2. Catalase: https://youtu.be/C_p8iA2TlfM
Answer the following questions:
1. What is the purpose of the Durham tube in a carbohydrate fermentation broth?
2. What are the bubbles that are formed during the Catalase reaction? Choose one:
a. Carbon dioxide c. Hydrogen sulfide gas
b. Oxygen d. Methane gas
Complete the following data tables with test observations and conclusions from the figures below. Please use complete sentences; dont just state positive or negative for the conclusions or you will be marked off. Note: When filling out an observation, describe what you see (i.e. lactose fermentation media has turned yellow and there is air present in the inverted Durham tube). When filling out a conclusion, describe what you can learn from your observation (i.e. the unknown is capable of fermenting lactose to an acid and a gas).
Figure 1. Citrate test result for Escherichia coli. Figure 2. Catalase test result for Escherichia coli.
Test Condition
Observation
Conclusions
Citrate Utilization
– Citrate slant or citrate compartment in Enterotube II
(Color of media? Growth?)
(Citrate utilized as carbon source?)
Presence of Catalase
-TSA slant
(Bubbles after adding hydrogen peroxide?)
(Catalase present?)
Figure 3. Glucose fermentation (left) and lactose fermentation (right) test results for Escherichia coli.
Test Condition
Observation
Conclusions
Glucose Fermentation
· Carbohydrate fermentation tube
(Color of media? Gas in Durham tube?)
(Glucose fermented to acid and/or gas?)
Lactose Fermentation
· Carbohydrate fermentation tube
(Color of media? Gas in Durham tube?)
(Lactose fermented to acid and/or gas?)
Figure 4. Sucrose fermentation test result for Escherichia coli. Figure 6. Indole test result for Escherichia coli.
Figure 5. Gelatinase test result for Escherichia coli. Figure 7. Oxidase dry slide test result for Escherichia coli.
Test Condition
Observation
Conclusions
Sucrose Fermentation (as evidenced in sucrose fermentation broth)
(Color of broth? Gas in Durham tube?)
(Sucrose fermented to acid and/or gas?)
Presence of
Gelatinase
-Gelatin deep
(Liquification?)
(Gelatinase present?)
Indole Production (Presence of Tryptophanase)
– SIM media
(Color of reagent layer after adding Kovacs reagent?)
(Tryptophanase present?)
Oxidase test
– Oxidase dry slide with culture taken from TSA plate/slant
