Experiment 1

Question 1

What are the 2 lab methods to get a pure culture ?

Answer 1

Streak plate and pour plate

Question 2

What are the steps to a streak plate ?

Answer 2

1. Sterilize the loop in the Bunsen burned by putting the loop in the fire until it’s red . Allow to cool
2. Pick an isolated colony from the agar plate culture and spread it over the first quadrant in back and fourth motion.
3. Flame the loop again and allow it to cool. After, go back to the area you just streaked and extend four streaks at a 90 degree angle.
4. Flame the loop again and repeat the procedure turning the plate 90 degrees again.
5. Repeat the procedure one more time but this time you are doing the last streak at an angle.

Question 3

What are the steps to a pour

plate ?

Answer 3

1. Add specimen to the center of the petridish.
2. Get some sterile molten agar from the water bath.
3. Hold the tube in your hand, remove the cap, flame the neck of the tube.
4. Lift the lid of the petri dish slightly and pour the sterile molten agar into the petri dish and cover the lid.
5. Gently rotate the dish to mix the culture and the medium thoroughly.

Question 4

What are the 3 different types of lab Media used?

Answer 4

Basic media

Selective media

Differential media

Question 5

Basic media

Answer 5

contain essential components to growth. Is not selective and can be used to grow a wide variety of microbial types that do not have special growth requirements. Ex: Nutrient Agar and Tryptic Soy Agar.

Question 6

Differential media

Answer 6

has a component (i.e. a carbohydrate) that can be used by some organisms and not by others. Also an indicator that demonstrates any change in its component

-Lactose in Eosin Methylene Blue (EMB) [Lactose fermenters produce a green sheen]

Question 7

Selective media

Answer 7

has a component that can suppress the growth of some organisms and not others.

Example: the 7.5% Manitol Salt Agar (MSA) [Only Salt-loving organisms or Halophiles can grow on this]

Question 8

Nutrient agar

Answer 8

basic media

Question 9

MSA (mannitol salt agar)

Answer 9

clear red color

Question 10

EMB Plate

Answer 10

Blood plate

Question 11

Carbohydrate fermentation tubes (glucose, lactose, sucrose)

Answer 11

carbohydrates (sugars) fermented by some bacteria to produce acid alcohol or gas.

A=yellow ferments carbohydrate inulin

N=Red no fermentation

G=Air bubble in Durham tube and fermentation.

Question 12

SIM

Answer 12

Sulfide=blacken medium. If organisms can break down sulfur turns black.

Indole=turns pink. If organisms can break down tryptophan turns pink. The presence of indole can be detected by adding a chemical solution Kovac’s reagent to the culture.

Motility=growth away from the line of inoculation. All Staphylococci non-motility

Question 13

Urea

Answer 13

TUBE

Question 14

Phenylalanine

Answer 14

after incubation a full pipette of ferric chloride is added to the slant.
Green= (+) for Deaminase
Ex: E. Coli (-) and P vulgaris (+)

Question 15

Starch plates

Answer 15

agar plate. One or two drops of iodine is used.

Clear= (+) for hydrolysis
Dark= (-) for hydrolysis

Question 16

Catalase test

Answer 16

ydrogen peroxide is needed. All Staphylococci are catalase (+)

Bubbles= (+)

All Staphylococci are catalase positive