2420 Practical 2 Quizzes

If nitrite is missing from an incubated culture tube of nitrate broth, the bacteria did not produce nitrate reductase. True False

False

In the catalase test, you must make sure that your culture is 48 hours old or you could get a false negative.

False

It is recommended that the coagulase test be checked for results within 48-72 hours because coagulation can revert to liquid within this time. True False

False

When testing for cytochrome C oxidase, using oxidase droppers, one looks for the development of a deep purple color within 20 minutes. True False

False

In TSI agar ________ reacts with iron sulfate to form a visible black precipitate. a. urease b. cytochrome oxidase c. cysteine desulfurase d. hydrogen sulfide

Hydrogen Sulfide

Upon addition of zinc to a nitrate broth culture, a red color developed. Is this a positive or negative test for nitrate reduction? a. positive b. negative

Negative

The coagulase test is diagnostic for a. Staphylococcus epidermidis b. Staphylococcus aureus c. Bacillus subtilis d. Enterococcus faecalis

Staphylococcus aureus

In the oxidase test, why is it important that the results of the test be read within 30 seconds upon application of the reagent?

The reagent can oxidize spontaneously resulting in a false positive.

Because gelatin melts at 28oC, an uninoculated control should be incubated with an inoculated stab to verify that any liquefaction is not temperature-related. True False

True

By using nitrate reductase, some facultative anaerobic bacteria can substitute nitrate for oxygen as the final electron acceptor in oxidative phosphorylation. True False

True

Denitrification is the multi-step conversioin of nitrate to nitrogen gas. True False

True

Gelatinases are exoenzymes which hydrolyze gelatin into its component amino acids so they can be transported into the cell and metabolized. True False

True

If a reaction occurs between the inoculating loop and hydrogen peroxide, the resulting false positive would be due to poor specificity of the test system . True False

True

The urease test is important for distinguishing Proteus from other enteric bacteria like E. coli, and the intestinal pathogens Salmonella and Shigella. True False

True

Which of the following is true of the enzyme catalase?

all of the above

A positive result in the catalase test is indicated by a. bubbles upon addition of hydrogen peroxide b. an acidic pH c. A color change to red d. a visible bubble in the durham tube

bubbles upon addition of hydrogen peroxide

In the nitrate reduction test, zinc powder a. converts nitrite to nitrate b. catalyzes the conversion of nitrate to nitrite c. is a chromogenic reducing agent d. stabilizes the pH

catalyzes the conversion of nitrate to nitrite

Catalase is an enzyme that functions to

convert hydrogen peroxide into water and gaseous oxygen

The presence of gas in the Durham tube in a nitrate reduction test indicates that the organism a. has reduced nitrate to ammonia b. has reduced nitrate to nitrite c. has performed denitrification d. has fermented nitrogen

has performed denitrification

Amylase removes____________ from starch and 1,6-glucosidase removes ____________ from starch. a. branched polymers of glucose; individual glucoses b. individual glucoses; branched polymers of glucose c. individual glucoses; individual glucoses d. amylose; amylopectin

individual glucoses; branched polymers of glucose

When testing for starch hydrolysis, you cover the starch plate with: a. iodine b. hydrogen peroxide c. urease d. none of these

iodine

Which of the following is not true of amylase? a. it is found in saliva b. it catalyzes the reaction: 2H2O2 -> 2 H2O + O2 c. it catalyzes the reaction: Starch + H2O à Glucose + Maltose d. it is a exoenzyme

it catalyzes the reaction: 2H2O2 -> 2 H2O + O2

The oxidase test will yield positive results for organisms that

possess cytochrome c oxidase

Which of the following is not true of cytochrome c oxidase? a.is the final link in the electron transport chain . b.passes electrons to O 2 to form water. c.produced by members of the family Enterobacteriaceae. d.produced by Pseudomonas.

produced by members of the family Enterobacteriaceae.

A positive result in the oxidase test will appear as

purple on the swab

Cysteine desulfurase a. strips the sulfhydryl & amino groups from cysteine b. hydrolyzes starch c. is the final link in the ETS that provides ATP d. is an oxygen reductase

strips the sulfhydryl & amino groups from cysteine

Which of the following is not true of the test for urease production? a. urea broth contains phenol red indicator b. urea is converted to ammonia and carbon dioxide by urease c. sulfanilic acid and dimethyl-2- naphthyl-amine reagents are used. d. all of the above are true

sulfanilic acid and dimethyl-2- naphthyl-amine reagents are used.

Coagulase production can give a pathogenic organism an advantage during infection because it allows the microbe to a. penetrate deeper into tissues b. escape from being trapped in blood clots c. be more motile in the host blood d. surround itself with fibrin to prevent phagocytosis

surround itself with fibrin to prevent phagocytosis

The pH indicator in urea broth turns from yellow to hot pink when urease is produced. This is in response to: a. ammonia b. an increase in pH c. a decrease in pH d. a & b e. a & c

A & B

The slide coagulase test assays for a. liquefaction b. hemolysis c. free coagulase d. bound coagulase

Bound Catalase