Culturing Microorganisms

What is the name given to the process that is used by bacteria to reproduce?

Binary Fission

How quickly can bacteria reproduce in ideal conditions?

every 20 minutes

Name the two mediums that can be used in the lab to culture bacteria

• nutrient broth

• agar gel plate

Describe how an uncontaminated culture of bacteria can be prepared using aseptic techniques

1. Sterislise petri dish, nutrient broth and agar

2. Pass an inoculating loop through a Bunsen burner to sterilize it

3. After transferring the bacteria, the lid of the ptri dish should be lightly taped on

4. Store the petri dish upside down

5. Store it at 25 degrees or lower

Why is the Petri dish sealed with two pieces of adhesive tape?

• to seal the lid

• to allow oxygen to diffuse into the petri dish

What nutrients are found in a culture medium

• water

• glucose

• amino acids

• minerals

what are the ‘dots’ of bacteria grown on agar jelly known as?

a colony (colonies)

Why can’t schools grow bacteria at 37 degrees celsius?

harmful pathogens could grow

What is the name of the clear area around the filter paper discs on the plate?

zone of inhibition

How could the area of the zone of inhibition be calculated?

Measure the diameter of the inhibition zone

Divide by 2 to get the radius

Use the equation

πr2

why must petri dishes and culture be sterilised before use?

• to kill any unwanted microorganisms

• to prevent contamination

why should the petri dish be placed upside down?

to stop drops of condensation falling into the agar surface and disrupting the colonies

why should you open a sterile agar plate next to a Bunsen flame?

the flame kills the bacteria