Microbiology Lab Homework: Biochemical Test Answers

If you inoculated a triple iron-sugar slant with Shigella, a glucose fermenter, your results should be what?

A good test for distinguishing among groups within the Enterobacters is the triple sugar-iron (TSI) test.

The black precipitate that is found in the buttt of a TSI agar slant inoculated with Salmonella indicates what?

A gap in the buttt of the agar of a TSI agar slant after 24 hours of growth indicates liquefaction by extracellular enzymes.

In the TSI test, sodium thiosulfate acts as a substrate for the measure of what reaction?

A bacterial species may produce H2S but not turn the buttt yellow.

The triple sugar-iron agar medium contains lactose, sucrose, glucose, sodium thiosulfate, and ferrous sulfate.

A specimen was inoculated onto the Triple Sugar Iron (TSI) medium pictured here.
http://media.pearsoncmg.com/bc/bc_0mastering/microbiology/coaching_activities/tsi_07.jpg
The bacterium is unable to ferment lactose and/or sucrose.
The bacterium is able to ferment glucose.
The bacteria is Gram-positive.
The pH of the agar decreased following incubation.
Hydrogen sulfide (H2S) was produced.

A specimen was inoculated onto the Triple Sugar Iron (TSI) medium pictured here.
http://media.pearsoncmg.com/bc/bc_0mastering/microbiology/coaching_activities/tsi_05.jpg
The bacterium is able to ferment glucose.
The bacterium is able to ferment lactose and/or sucrose.
The bacteria is Gram-positive.
The pH of the agar increased following incubation.
Hydrogen sulfide (H2S) was produced.
To conduct this test the slant must be streaked.
To conduct this test the butt of the tube should be stabbed.

A Catalase test was done on an unknown specimen. Observe the pictured result and answer the following question.

http://session.masteringmicrobiology.com/problemAsset/1556556/1/catalase_test_03.jpg

Select ALL appropriate statements regarding the pictured Catalase test result.

The organism can convert hydrogen peroxide to water and oxygen.
The organism does not produce catalase.
The organism produces catalase.
The organism can convert hydrogen peroxide to hydrogen sulfide.
The organism is probably a strict anaerobe.

A Catalase test was done on an unknown specimen. Observe the pictured result and answer the following question.
http://media.pearsoncmg.com/bc/bc_0mastering/microbiology/coaching_activities/catalase_test_03.jpg
Select ALL appropriate statements regarding the pictured Catalase test result.
The catalase test can be used to identify genus and species of a test organism.
The image shows a negative test result.
The image shows a positive test result.
The organism tested is probably an aerobe or a facultative anaerobe.
The organism tested is protected against oxygen radicals.

Two different bacterial samples, A and B, were tested with an Oxidase dry slide. This is a picture of the test results.

http://session.masteringmicrobiology.com/problemAsset/1556554/1/Oxidase_dry_slide_02.jpg

Select ALL appropriate statements regarding the pictured Oxidase test results.

Specimen A fermented cytochrome oxidase.
Specimen A produces cytochrome oxidase.
Specimen A does not produce cytochrome oxidase.
Specimen B fermented cytochrome oxidase.
Specimen B produces cytochrome oxidase.
Specimen B does not produce cytochrome oxidase.

Two different bacterial samples, A and B, were tested with an Oxidase dry slide. This is a picture of the test results.
http://media.pearsoncmg.com/bc/bc_0mastering/microbiology/coaching_activities/oxidase_dry_slide_02.jpg
Select ALL appropriate statements regarding the pictured Oxidase test results.
Specimen A shows a negative result
Specimen A shows a positive result
Specimen A is not a pathogen
Specimen B shows a negative result
Specimen B shows a positive result
Specimen B most likely has a respiratory chain that uses oxygen as a final electron acceptor.

A Catalase test was done on an unknown specimen. Observe the pictured result and answer the following question.
Select ALL appropriate statements regarding the pictured Catalase test result.

Two different bacterial samples, A and B, were tested with an Oxidase dry slide. This is a picture of the test results.
Select ALL appropriate statements regarding the pictured Oxidase test results.

Catalase breaks down which compound into water and oxygen gas?

When you add hydrogen peroxide to a cut, if the bacteria in the cut cannot produce catalase, they will most likely be killed.

In the catalase test, if possible, you should not test colonies from a blood agar plate because they may give a false positive due to the erythrocytes having catalase activity.

You are testing enteric bacteria for catalase activity and some of the bacteria begin bubbling immediately upon addition of the H2O2, while others may take a few minutes before some weak bubbling occurs. Are these late, weak bubbles the result of a positive catalase test?

The catalase test should have the same result whether the bacteria are on a slant, on a nutrient agar plate, or have been transferred to a glass slide.

Superoxide dismutase degrades toxic superoxides into __________.

Which bacterial groups will have the enzyme catalase?

Only prokaryotic cells have the enzyme catalase

If a bacterial species is aerobic, it uses oxygen as its final electron acceptor and must have which enzyme?

The oxidase test determines if a bacterial species has a means of dealing with hydrogen peroxide.

Reduction of the oxidase reagent p-aminodimethylaniline is due to which oxidase enzyme?

The action of cyanide is to irreversibly inhibit cytochrome oxidases from operating. How would this affect an oxidase test?

The plate method of the oxidase test is more accurate than the filter paper method.

The oxidase reagent p-aminodimethylaniline was prepared 4 months in advance and has developed a blue coloration. Upon adding it to your plate cultures, you see that the colonies immediately turn blue in color also. Does this mean the bacteria are oxidase-positive? Why or why not?

In the oxidase test, incubating bacteria for 10 minutes after the addition of the oxidase reagent in order to see a color change is too long and should be considered a false positive.