Mastering Quiz: 4B Microscopy and Staining

After you add crystal violet and rinse the slide, what should be your next step? a. Add Gram's iodine. b. Add safranin. c. Add decolorizing agent. d. Observe on microscope.

a. Add Gram's iodine.

Why is visualization not sufficient to properly identify bacteria? a. Bacteria have a limited set of shapes and many unrelated bacteria share the same shape. b. Identification is only needed in clinical specimens. c. Many unrelated bacteria can share the same shape. d. Not all bacteria can be seen with a light microscope. e. Bacteria have a limited set of shapes.

a. Bacteria have a limited set of shapes and many unrelated bacteria share the same shape.

What can you conclude about the Gram stained specimen? Based on your observation of this Gram stained specimen, select ALL appropriate statements. a. It can be ruled out that this specimen is taxonomically found in the Staphylococcus genus. b. The pictured bacterium is Gram positive c. The pictured bacteria are diplococci d. The pictured bacteria have a staph arrangement e. The pictured bacteria have strep arrangement f. The pictured bacteria are most likely non-acid fast. g. The pictured bacteria produce lipopolysaccharide (LPS), also known as endotoxin.

a. It can be ruled out that this specimen is taxonomically found in the Staphylococcus genus. c. The pictured bacteria are diplococci f. The pictured bacteria are most likely non-acid fast. g. The pictured bacteria produce lipopolysaccharide (LPS), also known as endotoxin.

https://mediaplayer.pearsoncmg.com/assets/secs-microbio-amin-dichotomous-practice Why is the unknown in this example not Pseudomonas? a. It ferments lactose. b. It can tolerate oxygen. c. It is a Gram-negative cell. d. It is a rod-shaped cell.

a. It ferments lactose.

What happens to the Gram-positive cell wall during decolorization? a. The decolorizing agent dehydrates the peptidoglycan. b. The decolorizer breaks apart the peptidoglycan. c. The decolorizing agent dissolves the outer membrane. d. The decolorizing agent forms a complex with the peptidoglycan.

a. The decolorizing agent dehydrates the peptidoglycan.

https://mediaplayer.pearsoncmg.com/assets/secs-microbio-amin-dichotomous-practice How is fermentation of lactose detected? a. The drop in pH turns the indicator dye yellow. b. The cells form a black precipitant. c. The acetoin produced turns the medium pink. d. The medium become turbid when exposed to air.

a. The drop in pH turns the indicator dye yellow.

What can you conclude about the pictured specimen? Based on your observation of this stained specimen, select ALL appropriate statements. a. The pictured bacteria are cocci b. The pictured bacteria are bacilli c. This is a picture of a Gram stained specimen d. The bacteria would not have been heat fixed in the preparation of this slide e. This is a picture of a negative stained specimen

a. The pictured bacteria are cocci d. The bacteria would not have been heat fixed in the preparation of this slide e. This is a picture of a negative stained specimen

https://mediaplayer.pearsoncmg.com/assets/secs-microbio-amin-dichotomous-practice How many questions are needed in this dichotomous key to determine if the unknown is Bacteroides? a. Three b. Four c. Two d. Five

a. Three

How many answers are there to a question in a dichotomous key flowchart? a. Two b. Three c. Any number of answers are possible. d. Four

a. Two

Mycoplasma pneumoniae is a bacterium that lacks a cell wall. It causes atypical pneumonia. Which antibiotic would be most effective in treating this infection, and why? a. ciprofloxacin, because it inhibits an enzyme necessary for bacterial DNA replication b. cloxacillin, because it is a penicillin that resists the activity of penicillin-degrading enzymes c. penicillin, because it inhibits the enzyme that cross-links peptidoglycan d. vancomycin, because it binds and blocks the terminal two amino acids on the short peptide attached to NAM

a. ciprofloxacin, because it inhibits an enzyme necessary for bacterial DNA replication

Which of the following groups of organisms belongs in the domain Eukarya? a. protozoa b. bacteria c. archaea d. viruses

a. protozoa

After Gram's iodine is added and then rinsed, what is the next step in the Gram stain procedure? a. Add crystal violet. b. Add decolorizing agent. c. Add safranin. d. Blot the slide dry.

b. Add decolorizing agent.

If you FORGOT to do the decolorizing step, what colors would the Gram-positive and Gram-negative cells be when viewed at the end of the procedure? a. Gram-positive cells would be purple, and Gram-negative cells would be colorless. b. All would be purple. c. Gram-positive cells would be purple, and Gram-negative cells would be pink. d. All would be pink.

b. All would be purple.

Ciprofloxacin (Cipro) is an antibiotic that inhibits bacterial DNA replication. It enters cells by diffusion. Many cells resist the action of Cipro by expressing a membrane protein that pumps the antibiotic out the cell. What does the Cipro-resistance protein have in common with porins? a. Both are enzymes. b. Both are transport proteins. c. Both are structural proteins. d. Both are defensive proteins.

b. Both are transport proteins.

The first question in this dichotomous key addresses a. bacterial morphology. b. Gram stain differences. c. metabolic characteristics. d. oxygen tolerance.

b. Gram stain differences.

https://mediaplayer.pearsoncmg.com/assets/secs-microbio-amin-dichotomous-practice How would the results be different if this organism was Salmonella? a. It would not ferment lactose. b. It would produce hydrogen sulfide. c. It would not tolerate oxygen. d. It would be a rod.

b. It would produce hydrogen sulfide.

As bacterial cells age, their peptidoglycan begins to break apart. What would be the effect on decolorization? a. Old Gram-negative cells will not be decolorized. b. Old Gram-positive cells will be decolorized. c. All cells will decolorize. d. Age will not affect decolorization.

b. Old Gram-positive cells will be decolorized.

What is the hallmark of dichotomous keys? a. They are open-ended questions. b. They consist of a series of paired statements, in which only one statement of each pair applies to a given organism. c. They only relate to biochemical processes of the cell. d. They only relate to the shape of the cell.

b. They consist of a series of paired statements, in which only one statement of each pair applies to a given organism.

You performed the Gram stain. You are expecting to find purple Gram-positive cocci and pink Gram-negative bacilli. Instead, you observe purple cocci but don't seem to see any bacilli. How could you explain this? a. You forgot the crystal violet step. b. You forgot the safranin step. c. You forgot the decolorizing step. d. You forgot the Gram's iodine step.

b. You forgot the safranin step.

Tetracycline is an antibiotic that inhibits protein synthesis by bacterial ribosomes. It enters cells by diffusion. Many cells resist the action of tetracycline by making a membrane protein that pumps tetracycline out of the cell. What type of membrane transport does this resistance mechanism represent? a. facilitated diffusion b. active transport c. osmosis d. group translocation

b. active transport

How could penicillin-sensitive Streptococcus grow in the presence of penicillin? a. by growth in a hypotonic environment b. by growth in an isotonic environment c. by growth in a hypertonic environment d. Penicillin-sensitive Streptococcus could not grow in the presence of penicillin.

b. by growth in an isotonic environment

Cindy was diagnosed with a rapid strep test. What kind of test is this? a. staining b. serological c. nucleic acid analysis d. biochemical

b. serological

How does safranin affect Gram-positive cells? a. Safranin cannot pass through the outer membrane. b. Safranin penetrates cell walls and causes the walls to become pink. c. Safranin penetrates the cell wall, but is masked by the darker crystal violet stain. d. Safranin does not penetrate Gram-positive cell walls.

c. Safranin penetrates the cell wall, but is masked by the darker crystal violet stain.

What happens to the Gram-negative cell wall during decolorization? a. The decolorizing agent breaks apart the peptidoglycan. b. The decolorizing agent forms a complex with the lipopolysaccharide in the outer membrane. c. The decolorizing agent dissolves the outer membrane. d. The decolorizing agent forms a complex with the peptidoglycan.

c. The decolorizing agent dissolves the outer membrane.

What can you conclude about the pictured bacteria? Based on your observation of this stained specimen, select ALL appropriate statements. a. The indicated structure is used for reproduction b. The pictured bacteria are cocci c. The indicated structure is an endospore d. The indicated structure is a nucleus e. If a Gram stain was performed on this bacterium within 24 hrs of a fresh culture, it would most likely be Gram-positive. f. The pictured bacteria are bacilli g. The indicated structure is a vacuole

c. The indicated structure is an endospore e. If a Gram stain was performed on this bacterium within 24 hrs of a fresh culture, it would most likely be Gram-positive. f. The pictured bacteria are bacilli

What can you conclude about the Acid-Fast stained specimen? Based on your observation of this acid-fast stained specimen, select ALL appropriate statements. a. The pictured bacteria probably produce lipopolysaccharide (LPS), also known as endotoxin. b. The pictured bacteria is probably Gram-negative c. The pictured bacteria are acid-fast d. This bacteria probably makes endospores e. The pictured bacteria are non-acid-fast f. The pictured bacteria are possibly a type of mycobacteria g. The pictured bacteria have mycolic acid in their cell walls

c. The pictured bacteria are acid-fast f. The pictured bacteria are possibly a type of mycobacteria g. The pictured bacteria have mycolic acid in their cell walls

Why are flowcharts useful for dichotomous keys? a. They provide a map to the answer. b. They allow the researcher to get the answer without having to do many tests. c. They allow the researcher to visualize relationships between different bacteria.

c. They allow the researcher to visualize relationships between different bacteria.

You performed the Gram stain on a smear. You are expecting to find purple Gram-positive bacilli and pink Gram-negative cocci. Instead, you observe pink bacilli and pink cocci. Which of the following is NOT a possible explanation for this unusual result? a. You decolorized too much. b. You skipped the Gram's iodine step. c. You skipped the safranin step. d. You skipped the crystal violet step.

c. You skipped the safranin step.

Many Gram-negative bacteria are naturally resistant to penicillin. Which of the following would make them more susceptible to penicillin? a. synthesizing a thicker layer of peptidoglycan b. producing a penicillin-degrading enzyme c. producing a porin with a more permissive channel d. producing a NAM-to-NAM cross-linking enzyme to which penicillin cannot bind

c. producing a porin with a more permissive channel

What is the best procedure for decolorization? a. Add water until run-off is clear. b. Cover the smear with decolorizing agent for 30 seconds. c. Rinse the smear with decolorizing agent until the smear has no more color. d. Add decolorizing agent until run-off is clear.

d. Add decolorizing agent until run-off is clear.

After you add crystal violet to the slide, what should be your next step? a. Decolorize. b. Add Gram's iodine. c. Add safranin. d. Rinse with distilled water.

d. Rinse with distilled water.

https://mediaplayer.pearsoncmg.com/assets/secs-microbio-amin-dichotomous-practice What test result indicates that the unknown can utilize citrate as its sole carbon source? a. The culture becomes turbid. b. It turns the medium black. c. The medium turns pink. d. The medium turns blue.

d. The medium turns blue.

Biochemical tests _________________. a. are the most effective way to determine bacterial shape b. are visualized using microscopes c. are used to determine rate of growth d. are the main methods used to identify unknown bacteria

d. are the main methods used to identify unknown bacteria