Microbiology fact file Flashcards
what is the independent variable
plant extracts
how do you vary the independent variable
mint, garlic and lemon
what is the dependent variable
zone of inhibition area
how do you measure the dependent variable
measure the diameter of the zone of inhibition and calculate the area for each disc
use a ruler to measure
what organism variables should be controlled
age of plant/bacteria
species of bacteria - E.coli
what environmental variable should be controlled
temperature - incubator set to 25 degrees for 24 hours
what procedural variables should be controlled
volume of plant extract used - 20 micro litres using a micropipette
volume of bacteria solution used - 1cm3 using a graduated pipette
concentration of ethanol used to soak each plant extract in
diameter of paper disks used - 5mm
incubation time - 24 hours
what repeats should be carried out and how many times
5 repeats for each plant extract and calculate the mean results for each plant extract
how is the investigation made reliable
repeat 5x for each plant extract to identify any anomalous results
how is the investigation made valid
control variables
using aseptic technique
use ethanol as a negative control - since each plant extract was soaked in ethanol
how is the investigation made safe
aseptic technique
flame test tube bottle necks to sterilise them
use virkon as a disinfectant spray as a disinfectant
use autoclave after to sterilise equipment
what is the method
- prepare plate by using aseptic technique and mix sterile agar with 1cm3 of E.coli and pour into plate and allow to set
- soak microbiology discs that are 5mm with 20 micro litres, using a micropipette, of plant extract and one with ethanol and allow to dry
- secure plate lid with two pieces of tape
- incubate for 24 hours at 25 degrees
- measure diameter of zones of inhibition and calculate area for each plant/disk
- repeat experiment 5x for each plant extract and calculate the mean
