B5.3 - Growing Bacteria In The Lab (Finished) Flashcards
Where can an uncontaminated culture of microorganisms be grown?
Sterilised Petri dishes and agar.
How do you make sure the culture remains uncontaminated?
Sterilise the inoculating loop before use and fix the lid of the Petri dish to prevent unwanted microorganisms getting in
Why are growing uncontaminated cultures needed?
For investigating the action of disinfectants and antibiotics
What temperature should cultures be grown at and why?
25°C to reduce likelihood of pathogens growing that might be harmful to humans
What is a culture medium?
A liquid or gel containing nutrients
Where can contamination come from?
Skin, air, soil
How is an agar filled petri dish prepared?
Hot agar gel is poured into a Petri dish and left to cool and set
Appart from in agar gel where else can micro-organisms be cultured?
Microorganisms can also be cultured in a flask of sterile nutrient broth solution
Why do you need uncontaminated cultures?
To investigate the effects of antibiotics, temp etc on the culture you are interested in, infection will produce incorrect results
What is the risk when growing bacteria?
There is a risk that a mutation may occur producing a dangerous pathogen when culturing bacteria
How do you prepare a petri dish of microorganisms?
1) steralise inoculating loop by heating it until red hot in the flame of a bunsen and letting it cool
2) Dip the loop into a suspension of bacteria and make zigzag streaks across agar. Replace lid quickly
3) Fix the lid of the petri dish with tape to prevent contamination
4) label and store upside down
Why should you not seal the petri dish all the way around?
As oxygen needs to get in to prevent harmful anaerobic bacteria from growing
Why should you store the petri dish upside down?
To stop condensation falling onto the agar surface
What is an autoclave used for?
An autoclave is used for sterilising equipment using steam and high pressure
