rp6

Question 1

examples of aseptic techniques that could be used

Answer 1

wash hands with soap and disenfect surfaces to kill microbes
sterilise pipette and boil agar to prevent contamination
flame neck of bottle of bacteria to kill microbes
bunsen burner close - upward current of air draws air borne microbes away
lift lid of petri dish slighty so microbes dont enter

Question 2

method to investigate effect of antimicrobial substance on microbial growth

Answer 2

prep area using aseptic technqiues
use sterile pipette to transfer bacteria from broth to agar plate using aseptic technqiues

Question 3

why is it important to maintain pure culture of bacteria

Answer 3

bacteria may outcompete bacteria being investigated or could be harmful to humans

Question 4

why hold lid with 2 pieces of tape instead of sealing completely

Answer 4

allows oxygen in so prevents growth of anaerobic bacteria which are more likely to be pathogenic

Question 5

why use paper discs with water and no antimicrobial agent

Answer 5

acts as control
ensures antimicrobial prevented growth not paper disc

Question 6

why incubate upside down

Answer 6

condensation drips onto lid rather than agar surface

Question 7

what if irregular inhibition zones

Answer 7

repeat reading at different positions and calculate a mean

Question 8

why not use higher antimicrobial conc

Answer 8

mire bacteria killed so clear zones may overlap

Question 9

why incubate at 25 or less

Answer 9

below human body temp so prevents growth of pathogens

Question 10

explain presence and absence of clear zones

Answer 10

clear zones mean antimicrobial diffuses out of disk into agar inhibiting growth of bacteria
larger clear zones means more bacteria killed so more effective antimicrobial
no clear zones means if antibiotic used bacteria may be resistant or antibiotic may not be effective against specific bacteria