CO2 that is used by other bacteria and thus the cycle begins. Eventually colour layers of different bacteria will appear in the column. At the bottom of the column will be black anaerobic H2S dominated zone with sulfur reducing bacteria, the layer above will be green sulfur photosynthetic anaerobic bacteria, then the layer will be purple which is sulfur anaerobic bacteria, followed by another column of purple anaerobic non-sulfur bacteria and at the top will be a layer of Cyanobacteria which are sulfur oxidising bacteria. This top layer of aerobic bacteria produces O2 which feeds back into the column to facilitate further reactions. While the Winogradsky column is an excellent tool to see whole communities of bacteria, it does not allow one to see the densities or individual bacterial colonies. It also takes a long time to complete its cycle. However its importance in environmental microbiology should not be overlooked and it is still an excellent tool to determine the major bacterial communities in a sample. See also List of Ukrainian inventions References External links Animated tutorial by Science Education Resource Center — Carleton College Winogradsky column: perpetual life in a tube — University of Edinburgh Cell culture media Russian inventions Laboratory techniques Environmental microbiology