Experiment 19: extracellular enzymes

Question 1

Amylase does what

Answer 1

hydrolyzes strach; releasing free glucose

Question 2

DNase does what

Answer 2

hydrolyzed DNA; releasing free nucleotides

Question 3

Collagenase does what?

Answer 3

its a specific protease that hydrolyzes gelatin (which comes from collagen); releasing free amino acids

Question 4

Caseinase does what

Answer 4

its a specific protease that hydrolyzes casein protein (found in milk protein); releasing free amino acids

Question 5

Lipase does what?

Answer 5

hydrolyzes the breakdown of tributyrin

Question 6

Which test is this? and it it postive or negative? how can you tell?

Answer 6

It’s the lipid hydrolysis test.

• the colonies that are blue-tinged are positive for lipase and positive for tributyrin hydrolysis
• the colony on the right corder is not blue-tinged so it is negative for lipase and negative for tributyrin hydrolysis

Question 7

Which test is this? is it positive or negative? how do you know?

Answer 7

its the DNA hydrolysis test, the left side is positive for hydrolysis the right side is negative for DNase

• if there is a clear area surronding the growth it is positive and has hydrolyzed the DNA
• if the area around the growth is still green the organism is negative for DNA hydrolysis

Question 8

Which test is this? which side is positive/ negative? how do you know?

Answer 8

This is the starch hydrolysis test, the right side is positive the left side is negative

• clearing = positive for starch hydrolysis
• purple around growth = negative for starch hydrolysis

Question 9

Which test is this? which side is positive/ negative? how do you know?

Answer 9

this test is the gelatin hydrolysis

• if its liquid it’s collagenase positive
• if it’s solid it collagenase negative

Question 10

Which test is this? How do you read this?

Answer 10

This is the mannitol salt agar plate..if there is growth it must be a salt tolerant Staphylococcus species

• if there is no growth the organism is inhibited by the salt
• if there is growth and the medium turned yellow it means the mannitol fermented and is a pathogenic staphylococcus species
• if there is growth and the medium did not turn yellow it means the mannitol did not ferment and is a non-pathogenic Staphylococcus species

Question 11

Which test is this?

Answer 11

mannintol salt agar plate

Question 12

Which test is this? which side is positive/ negative? how do you know?

Answer 12

the left side is coagulated which means it must be a pathogenic S. aureus

• the left side did not coagulate which means it’s not S. aureus

Question 13

Which test is this? which side is positive, which side is negative?

Answer 13

• this is the Novobicin test
• the left side is susceptible
• the right side is resistant
• greatr than 16mm (susceptible), less than 16 mm is resistant

Question 14

Which test is this? which side is negative or postive?

Answer 14

Catalalase test the top is positive the bottom is negative