Winogradsky column

The Winogradsky Column is a simple device for culturing a large diversity of microorganisms. Invented by Sergei Winogradsky, the device is a column of pond mud and water mixed with a carbon source such as newspaper (containing cellulose) or egg-shells (containing calcium carbonate) and a sulfur source such as gypsum (calcium sulfate) or egg-yolk. Incubating the column in sunlight for months results in an aerobic/anaerobic gradient as well as a sulfide gradient. These two gradients promote the growth of different micro-organisms such as clostridium, desulfovibrio, chlorobium, chromatium, rhodomicrobium, beggiatoa, as well as many other species of bacteria, cyanobacteria, and algae.

The column provides numerous gradients, depending on additive nutrients, from which the variety of aforementioned organisms can grow. The aerobic water phase and anaerobic mud or soil phase are one such distinction. Due to low oxygen solubility in water the water quickly becomes anoxic towards the interphase of the mud and water. Anaerobic phototrophs are still present to a large extent in the mud phase, there is still capacity for biofilm creation and colony expansion, as noted by the images. Algae and other aerobic phototrophs are present along the surface and water of the upper half of the columns. Green growth is often attributed to these organisms.

Construction

The column is a rough mixture of ingredients and exact measurements are not critical. A tall glass or plastic tube (30cm long, >5cm wide) is filled by a third with pond mud, omitting any sticks, debris or air bubbles. Supplementation of ~0.25% w/w calcium carbonate and ~0.50% w/w calcium sulfate or sodium sulfate is required. Mixed in with some shredded newspaper or hay (for cellulose), ground egg-shell and egg yolk respectively are rich in these minerals. An additional anaerobic layer, this time of un-supplemented mud, brings the container to two thirds full. This is followed by water from the pond to saturate the mud and occupy half the remaining volume. The column is sealed tightly to prevent evaporation of water and incubated for several months in strong natural light.

External links

* [http://serc.carleton.edu/resources/2577.html Animated tutorial by Science Education Resource Center] — Carleton College
* [http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/winograd.htm Winogradsky column: perpetual life in a tube] — Edinburgh University