Biochemical Tests

Question 1

What does the MacConkey Agar Test determine?

Answer 1

whether or not bacteria can ferment lactose to lactic acid

Question 2

What does the MacConkey Agar Test promote the growth of?

Answer 2

gram negative bacteria

Question 3

When does bacteria turn hot pink in the MacConkey Agar Test?

Answer 3

when bacteria can ferment lactose into lactic acid

Question 4

What kind of colonies exhibit no colour change in the MacConkey Agar Test?

Answer 4

non-lactose fermenting colonies

Question 5

What does the starch agar test determine?

Answer 5

some bacteria perform starch (amylose) hydrolysis via amylase

Question 6

What does amylase break starch down into in the starch agar test?

Answer 6

glucose (monosaccharide) and disaccharides for catabolism

Question 7

What happens if bacteria doesn’t have amylase in starch agar test?

Answer 7

starch isn’t broken down in plate and starch stays

Question 8

What colour does iodide case remaining starch to turn in starch agar test?

Answer 8

dark purple

Question 9

What does dark purple colour mean in starch agar test?

Answer 9

amylase negative

Question 10

What does a clearing mean in starch agar test?

Answer 10

amylase positive

Question 11

What does gram staining identify?

Answer 11

unknown species of bacteria

Question 12

What is the motility test?

Answer 12

thinner agar used to allow mobile bacteria to move through agar

Question 13

What does the motility test determine?

Answer 13

whether bacteria can move

Question 14

What does a straight red line mean in the motility test?

Answer 14

negative test
bacteria weren’t able to move

Question 15

What does a completely red agar mean in the motility test?

Answer 15

positive test
bacteria were able to move throughout agar

Question 16

What percentage of sheep blood is in the hemolysis test?

Answer 16

5%

Question 17

What does the presence of beta hemolysin mean in hemolysis test?

Answer 17

complete hemolysis with transparency
bright yellow

Question 18

What does the presence of alpha hemolysin mean in hemolysis test?

Answer 18

partial hemolysis without transparency
dull yellow

Question 19

What does the presence of gamma hemolysin mean in the hemolysis test?

Answer 19

no hemolysis
gray colour

Question 20

What does the catalase test determine?

Answer 20

if organism is catalase positive it can break down hydrogen peroxide into water in oxygen

Question 21

What does a positive catalase test result in?

Answer 21

bubbles

Question 22

What does a negative catalase test result in?

Answer 22

no bubbles