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The Challenge: Make an Antibacterial Cream



How can we grow bacteria?

We need a suitable surface and container to grow bacteria. Petri dishes are used in biology laboratories but on the island, bottle top lids were a perfect substitute.

As well as a stable physical environment, bacteria need nutrients on which to feed. Traditionally, scientists have used types of jelly. The most common are agar and gelatin. Agar is made by boiling seaweed in fresh water, straining and reducing it to a thick syrup. When it cools it forms a jelly-like substance.

 

Is agar alone sufficient for growing bacteria?

Bacteria need vitamins, proteins and minerals not found in agar and so we add a nutrient broth, which is also referred to as 'media' by microbiologists, to the Petri dishes.

Growing bacteria