The Winogradsky Column

A Winogradsky column is a self-organizing, artificial microbial ecosystem for studying microbial diversity and metabolism.

It is constructed by filling a glass cylinder halfway with organic-rich sediment.

Shredded paper is added as a carbon source, gypsum as a sulfate source, and calcium carbonate as a buffer.

The column is filled with water and exposed to light.

Over time, distinct microbial layers develop in the column, creating oxygen and sulfur gradients.

At the top, cyanobacteria perform oxygenic photosynthesis, producing oxygen, and keeping the upper zone aerobic.

Below this, chemolithotrophic sulfur bacteria use this oxygen to oxidize hydrogen sulfide.

In the lower anoxic zones, purple and green sulfur bacteria perform anoxygenic photosynthesis, using hydrogen sulfide to fix carbon dioxide.

In the deeper anoxic layers, anaerobic bacteria such as sulfate reducers and fermenters reduce sulfate to hydrogen sulfide, which diffuses upwards and is used by sulfur-oxidizing bacteria, creating a vertical sulfur cycle.