Required Practical 6- Effect of antimicrobial substances

Question 1

Control experiment?

Answer 1

Well with no amylase solution (distilled water instead)

Question 2

Why is sample incubated at 25°C

Answer 2

Because incubating at 37°C (human body temperature) could enable pathogens to grow that are harmful to humans

Question 3

Inhibition zone

Answer 3

Clear circle around antibiotics

Question 4

What does zone tell you?

Answer 4

Larger inhibition zone= killed more bacteria= antibiotic works better
Little/ no inhibition zone= bacteria are resistant, antibiotic not killed by it= not effective

Question 5

What are the control variables?

Answer 5

-size of holes: use same cork borer to cut holes
-volume of enzyme: add exactly 2 drops in each well, using pipette

Question 6

Aspetic techniques?

Answer 6

-wipe surfaces down with antibacterial wipes before & after experiment
-use Bunsen burner in work space so convection currents draw microbes away from culture
-flame wire hoop
-flame neck of bottle- prevent bacteria entering
-keep vessels containing bacteria open for minimum amount of time

Question 7

How can you spread bacteria evenly?

Answer 7

Using sterileinoculating loop

Question 8

How should you tape the lid on?

Answer 8

Lightly- taping the entire dish prevents oxygen entering so promotes growth of more harmful anaerobic bacteria

Question 9

Why are agar plates upside down?

Answer 9

-clearer observation of inhibition zones due to condensation on lid- measure zones
-prevents drops of moisture formed during incubation dropping on culture

Question 10

Why are aseptic techniques necessary?

Answer 10

-prevent contamination of cultures from environment
-Environment not contaminated by potentially hazardous microorganisms

Question 11

Potential risk of using non-pathogenic bacteria?

Answer 11

-could mutate into disease-causing strain