Bacteriopolis | Exploratorium

The colored areas are different types of bacteria. The colors come from different pigment molecules that the bacteria use to capture energy from light.

All these bacteria were in the pond mud we used to make this exhibit. But bacteria in a pond don't look like this. We've added nutrients such as carbon and sulfur to encourage the growth of a colorful diversity of organisms.

A bacterial culture like this is called a "Winogradsky column," named after Ukrainian biologist Sergei Winogradsky. You can make one using pond mud, newspaper, eggs, and water.