Required Practical 6 Aseptic Technique

Question 1

Suggest why aseptic technique is necessary

Answer 1

• prevent contamination of cultures from environment which could nullify investigation - environment not contaminated by potentially hazardous microorganisms

Question 2

Suggest a potential risk of working with non-pathogenic bacteria

Answer 2

Could mutate into a disease-causing strain

Question 3

Suggest why agar plate is labelled on underside

Answer 3

• lid could get lost| - culture is inverted during incubation so easier to identify is underside is labelled

Question 4

Suggest why the neck of bottle containing culture is flamed

Answer 4

• produces a convection current away from opening| - prevent entry of microorganisms

Question 5

Suggest why lid of agar plate is lifted at an angle facing Bunsen burner

Answer 5

• creates a convection current upwards from plate| - prevents microorganisms from air contaminating plate

Question 6

Suggest why an inoculating loop is preferred to a plastic spreader

Answer 6

• plastic spreader cannot be flamed like an inoculating loop since there is risk of breakage - must be dipped in ethanol and passed quickly though flame

Question 7

Give ways in which aseptic conditions are maintained

Answer 7

• bench sprayed with disinfectant - sterile pipette and spreader used - Bunsen burner to flame inoculating loop and neck of bottle containing culture - lid of agar plate lifted slightly and towards Bunsen burner

Question 8

Suggest why two pieces of adhesive tape are used to seal agar plate as oppose to sealing around it

Answer 8

• allows free passage of air| - normal growth (rather than promoting growth of anaerobic bacteria)

Question 9

Suggest why cultures are not incubated above 30 degrees Celsius

Answer 9

Reduces risk of growing microbes that are pathogens to humans

Question 10

Suggest why inhibition zones are measured with the plate upside down

Answer 10

Clearer observations due to condensation on lid

Question 11

Suggest why agar plates are incubated upside down

Answer 11

Prevents droplets of moisture which form during incubation falling on culture