Lab #10

Lab Report #10, Part 1: Fill in the following chart. The page numbers in red refer to the Leboffe Lab Manual; the Slide numbers in red refer to the Biochemicals for Unknown Identification.ppt Powerpoint file

Test

Substrate

Enzyme

What does a positive test look

What does a negative test look

like? (After adding test reagents)

like? (After adding test reagents)

Methyl Red Test:

Glucose

Glucose

fermentation

Enzymes

p. 243, Slide 30 ff

Vogues-Proskauer

Glucose

Glucose

Test:

fermentation

Enzymes

p. 243, Slide 33 ff

Urease Test

p. 289, Slide 41 ff

Carbohydrate

Glucose (for

Glucose

Utilization and

fermentation)

fermentation

Hydrogen Sulfide

Enzymes

Production as

Detected by Triple

Sucrose (for

Sucrose

Sugar Iron (TSI)

fermentation)

fermentation

Agar

Enzymes

Lactose (for

Lactose

fermentation)

fermentation

Enzymes

Sodium

Sulfate reducing

p. 301, Slide 38 ff

thiosulfate (for

Enzymes

H2S production)

Practice Unknown: ___
E. coli
___________

Lab Report 10-Virtual Practice Unknown, Part 2

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 performed on the graded unknown.

Prior to beginning this lab worksheet, please look at the unknown presentation (available through the Canvas portal) as well as the following video from the Community College at Baltimore:

Enterotube: https://youtu.be/2_S986lk6s0,

Answer the following questions:

1. What is one advantage of using an Enterotube (a rapid identification method) over individual biochemical test tubes?

2. Which type of bacteria are often identified using the Enteropluri test? (Choose one)

A. Gram positive Staphylococcus

B. Gram positive bacillus

C. Gram negative enteric bacteria

D. Acid fast Mycobacteria

Complete the following data tables with test observations and conclusions from experiments performed on your microbial unknown. Please use complete sentences; don’t 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. Methyl red (left) and Vogues Proskauer (right) test results for Escherichia coli.

Test Condition

Observation

Conclusions

Methyl-Red Test
-MRVP broth

(Color of broth after adding methyl red reagent?)

(Glucose fermented to acid?)

Vogues-Proskauer Test
– MRVP broth

(Color of liquid layer after adding VP reagents?)

(Glucose fermented to neutral end products?)

Figure 2. Urease test results for Escherichia coli.

Test Condition

Observation

Conclusions

Presence of Urease
– Urea broth or agar

(Color of media?)

(Urease present?)

Figure 3. TSI slant test result for Escherichia coli.

Test Condition

Observation

Conclusions

Triple Sugar Iron (TSI) Slant (be sure to mention H2S production!)
-TSI slant

(Color of slant and butt? Breaks/gaps in agar?)

(Which carbohydrates (if any) are fermented? Is gas produced? Is hydrogen sulfide made?)