I lovw bacteria, they are marvellous little things that can be eithee good or bad.
I bought in some chromogenic agar which we used to use whilst working in Microbiology. The substrates and enzymes in the agar and bacteria create chromogens which make the bacteria coloured on the agar.
The bacteria can be then identified depending on the colours produced.
Ecoli produces pink colonies
Enterococcus produces light blue colonies.
Using different types of bacteria we could make pictures on the agar.
Which is one reason why I love bacteria!!!!