Question

QUESTION 1

1. Why do non-fermenters form white/colorless colonies on MacConkey agar?

   		a. They breakdown mannitol
   		b. They are gram positive
   		c. They are coliform
   		d. They do not breakdown lactose
   		e. They are fecal coliform

5 points   

QUESTION 2

1. Bacteria that can breakdown (ferment) lactose would show this result.

   		a. Yellow color change on a mannitol salt agar
   		b. Yellow color change on a lactose phenol red broth tube
   		c. Green/brown color change on blood agar
   		d. Red color on a lactose phenol red broth tube
   		e. None of the above

5 points   

QUESTION 3

1. What results would you see if Staphylococcus epidermidis was grown MSA agar?

   		a. Clear colonies
   		b. Red colonies
   		c. The plate would turn yellow
   		d. No growth would occur
   		e. Growth on the plate with no color change (plate remains red)

5 points   

QUESTION 4

1. The lid is removed from the petri dish in the UV experiment because

   		a. It prevents bacteria from growing on the surface.
   		b. It serves as a control
   		c. The lid would absorb or block UV light
   		d. It prevents condensation from forming on the surface
   		e. Allows for oxygen so the bacteria can grow

5 points   

QUESTION 5

1. If the transmittance reading is 80%, which of the following is correct?

   		a. 80% of the light is blocked by the sample
   		b. The population would be low
   		c. The population would be high
   		d. The sample would be very turbid
   		e. None of the above

5 points   

QUESTION 6

1. Which of the choices is the same value as 5.0 x 107

   		a. 0.005 x 105
   		b. 50.0 x 109
   		c. 50.0 x 108
   		d. .05 x 109
   		e. 500.0 x 104

5 points   

QUESTION 7

1. What is the cell concentration of the sample, if the following dilutions were performed?

   There are 4 tubes with each containing 9 ml of sterile water. 1 ml was transferred from the sample to each of the tubes by a serial dilution. 1 ml from the 3th tube was plated and 20 colonies (CFU) grew.

   		a. 2.00 x102 cfu/ml
   		b. 2.00x103 cfu/ml
   		c. 2.00x104 cfu/ml
   		d. 2.00x105 cfu/ml
   		e. 2.00x106 cfu/ml

5 points   

QUESTION 8

1. The presence of dark purple colonies with a metallic green sheen on EMB agar indicates.

   		a. Staphylococcus epidermidis
   		b. Escherichia coli
   		c. Klebsiella aerogenes
   		d. Bacillus subtilis
   		e. Geobacillus stearothermophilus

5 points   

QUESTION 9

1. The Durham tube detects for the presence of

   		a. Acids
   		b. Base
   		c. Hemolysins
   		d. Gas
   		e. enzymes

5 points   

QUESTION 10

1. A bacterial colony growing on a blood agar plate exhibits a clear zone around the colony. What does this indicate?

   		a. Antibiotic resistance
   		b. Alpha hemolysin
   		c. Beta hemolysin
   		d. Gamma hemolysin
   		e. Antibiotic susceptibility

5 points   

QUESTION 11

1. The presence of E. coli in drinking water indicates

   		a. Fecal contamination
   		b. Possible fecal contamination
   		c. That it is from a free-living source
   		d. Presence of fecal pathogens
   		e. None of the above

5 points   

QUESTION 12

1. Staphylococcus aureus growing on mannitol salt agar plate would show this result.

   		a. Purple colonies
   		b. Red colonies
   		c. Clear colonies
   		d. The plate appears yellow
   		e. The plate appears red

5 points   

QUESTION 13

1. A broad spectrum is

   		a. An antibiotic that works only on gram positives
   		b. An antibiotic that works equally well on gram positives and gram negatives
   		c. Is a disinfect that kills all bacteria
   		d. A chemical that causes thymine dimers

5 points (Extra Credit)   

QUESTION 14

1. A cell count showed these results. What is the cell concentration in cells/ml?

   First counting square- (20 clear cells 10 blue cells)

   Second counting square- (15 clear cells 5 blue cells)

   Third counting square- (30 clear cells 15 blue cells)

   Fourth counting square- (10 clear cells 5 blue cells)

   Fifth counting square- (15 clear cells 10 blue cells).

   The cell count was prepared using ½ sample ½ dye.

   		a. 1.8x104 cells/ml
   		b. 3.6x105 cells/ml
   		c. 9.0x104 cells/ml
   		d. 1.8x105 cells/ml
   		e. 3.6x104 cells/ml

5 points   

QUESTION 15

1. In the UV Radiation on Bacterial Growth lab, which of the following is correct?

   		a. The unexposed side of the plate contain no growth
   		b. Petri dish with lids were exposed to UV light
   		c. E.coli showed growth after the longest exposure
   		d. D. radiodurans showed growth after the longest exposure
   		e. No difference in growth between E.coli and D. radiodurans

5 points   

QUESTION 16

1. If a zone of inhibition is large, the following statement is true.

   		a. The antibiotic concentration is high in the zone of inhibition.
   		b. The antibiotic concentration is low in the zone of inhibition.
   		c. The antibiotic is bacteriostatic.
   		d. The antibiotic is bactericidal.
   		e. The bacteria are resistant to the antibiotic.

5 points   

QUESTION 17

1. If an agar plate (media) is made containing lactose as the only source of nutrient and methylene blue dye, which of the following bacteria would grow?

   		a. Bacillus subtilis
   		b. Staphylococcus epidermidis
   		c. Marine bacteria
   		d. Escherichia coli
   		e. Deinococcus radiodurans

5 points   

QUESTION 18

1. In the direct counting experiment, yeast cells that are living

   		a. Are stained blue because of the dye
   		b. Do not clump together
   		c. Remain clear after the addition of the dye
   		d. Are stained purple because of crystal violet
   		e. Will float to the top of the tube

5 points   

QUESTION 19

1. A bacteria is able to grow after a one hour exposure to UV light. What is the most likely explanation?

   		a. Thymine dimmers are not formed
   		b. The bacteria are gram positive
   		c. The bacteria are gram negative
   		d. Repair mechanisms are very efficient at fixing thymine dimmers
   		e. Repair mechanisms are very efficient at fixing mismatch repairs

5 points   

QUESTION 20

1. How does NaCl in mannitol salt agar kill organism?

   		a. It reduces pH
   		b. Cl ions can kill
   		c. It causes an organism to lose water
   		d. It causes organism to gain water and burst
   		e. It prevents enzymes from working

5 points   

QUESTION 21

1. Purple/blue bacterial colonies grew on Coliscan Easygel plates. These colonies are

   		a. E. coli
   		b. K. aerogenes
   		c. B. subtilis
   		d. S. epidermidis
   		e. S. aureus

5 points   

Click Save and Submit to save and submit. Click Save All Answers to save all answers.

Answer 1

Answer 1: They do not breakdown lactose.

The gram negative enteric bacteria grow in MacConkey agar is differentiated by their ability to ferment the lactose.

Answer 2: e: none of the above

If the lactose is fermented by the bacteria then the production of acid will drop the pH of the media causing color change of neutral red indicator to pink.

Answer 3: Red colonies.

As staphylococcus epidermisis donot ferment mannitol it will show a red zone around the colonies.

Answer 4: athe lid will absorb or block UV light.

UV light do not penetrate even thin layer of plastic or glass.