Image from: https://ravensrambling.myportfolio.com/
Microbes are almost everywhere on earth: they are on your skin, in your gut and in your local pond as well! The mud and water in a pond are home to diverse microbial communities and their composition depends on the nutrients in the environment. Since most microbes are specialised for what they eat and where they grow, you can build your own microbial zoo at home – and you can influence which microbes will grow!
You can create a custom environment for your microbes by building a Winogradsky column, named after Russian microbiologist Sergei Winogradsky. The basic ingredients you need are mud and water from your local pond, egg yolk as a sulphur source, shredded paper as a carbon source and a clear bottle. Depending on the source of your mud and water, a colourful array of microbes should grow in different layers of the column. You can vary the experiment by changing the source of the mud (how about a river or the ocean?), change the nutrients (throw in a rusty nail?) or change the environment of the column (why not change the temperature or leave it in a dark place?). The columns start to change after 4 to 8 weeks, make sure to take pictures every week and maybe share them online.
For more information and pictures of gorgeous Winogradsky columns, check out this blog post.