Culturing microorganisms Flashcards
Describe how bacteria can be grown in a lab
Culture medium
What does a culture medium contain?
Carbohydrates
Minerals
Proteins
Vitamins
Give examples of a culture medium
Nutrient broth solution
Solid agar jelly
Describe how to make an agar plate
Hot agar jelly is poured into a shallow round plastic dish called a petri dish
When the jelly is cooled, inoculating loops are used to transfer the microorganisms to the culture medium. Alternatively a sterile dropping pipette and spreader can be used
Microorganisms replicate
What temperature are the cultures kept at in schools?
Below 25 degrees
So harmful pathogens do not develop
What temperature are the cultures kept at in industrial use?
Higher temperatures so they grow rapidly
Describe how the effect of antibiotics on bacterial growth is investigated?
Place paper discs soaked in different types or concentrations of antibiotics on the agar place that has an even covering of bacteria - leave space between each disc
Use a control - paper disc not soaked in any antibiotic- soak in sterile water instead
Leave the plate for 48hrs in 25 degrees
What is an inhibition zone?
Where the bacteria have died and can not grow `
The more effective the antibiotic, the …
Larger the inhibition zone
How will you reduce the contamination by unwanted microorganisms in the experiment?
Petri dishes and culture mediums must be sterilised before use (heat to high temperature)
If an inoculating loop is used it should be sterilised by passing it through a hot flame
Lid should be lightly taped on the petri dish to stop air and microorganisms getting in
Petri dish should be stored upside down to stop drops of condensation falling onto the agar surface
How do you calculate the area of the inhibition zone?
area = pi r squared
