Today we’ve created a special Christmas themed jigsaw. Please click the image to begin. A description of how they were made can be read below.


The petri dish was created by using a number of different selective and differential media were used to produce these plate cultures.

A selective medium contains chemicals which inhibit the growth of certain specific types of bacteria. A differential medium will allow the growth of several species of microorganism but contains compounds which give a different appearance to specific organisms.

The dark red plates are Eosin-methylene blue agar, which are selective against gram positive bacteria and differential for gram negative bacteria.

E.coli ferments lactose which produces acids which precipitate the methylene blue in the medium, giving a metallic green colouring. Salmonella doesn’t ferment lactose so cultures appear white.

A wire loop was used to draw fine lines on the plates using bacteria from plate cultures. For larger areas a sterile cotton wool swab was used like a paintbrush, dipped into broth cultures. It’s a bit like using invisible ink as you can’t see what the end product will look like until the bacteria have grown, usually after 16-24 hours.
This year, as well as the usual Christmas trees and snowflakes, we were inspired by the Andy Warhol exhibition currently running at the Whitworth gallery to try something a bit more colourful.
They were all made originally by the Stopford media team who work hard throughout the year to supply our practical classes.

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