Biology - Culturing Microorganisms (Triple content)

What do bacteria need to grow in a culture medium?

Carbohydrates, minerals, proteins, and vitamins are required for bacteria to grow.

What are nutrient broth and agar jelly?

They are culture mediums. Bacteria grow on agar jelly forming visible colonies or spreading evenly.

Why are school lab cultures incubated at 25°C?

This prevents the growth of harmful pathogens, which are more likely to grow at higher temperature

How can you test antibiotics on bacterial growth?

Place paper discs soaked in antibiotics on an agar plate. Bacteria-resistant strains continue to grow, and non-resistant strains die, forming an inhibition zone.

What is an inhibition zone?

It is the clear area around an antibiotic disc where bacteria have died.

What is a control in antibiotic testing?

A control disc is soaked in sterile water to compare results and confirm that any bacterial growth changes are due to the antibiotic.

Why must Petri dishes and equipment be sterilised before use?

To prevent contamination from unwanted microorganisms that could affect results.

How should Petri dishes be stored?

Store them upside down to prevent condensation from dripping onto the agar which will disrupt the colonies.

How can you compare the effectiveness of antibiotics?

Measure the size of inhibition zones around each disc. Larger zones indicate more effective antibiotics.

How do you calculate the area of an inhibition zone?

Use the formula of the area of a circle: A = πr², where r is the radius of the inhibition zone.