Winogradsky column

A Winogradsky column is a tube-like device used for growing diverse communities of microorganisms for scientific study. The experiment was named after its inventor, Russian microbiologist Sergei Winogradsky, who is considered one of the founding fathers of microbiology. The column uses different materials, such as mud, newspaper, and egg yolks, arranged in layers to create various environments within the tube. These environments range from those with low to high oxygen content to those with low to high sulfur content. Each environment provides different nutrients that support the growth of a different type of microorganism. A Winogradsky column is a self-contained ecosystem, with the waste products of certain bacteria becoming the nutrients for bacteria in another section of the device.

Background

Sergei Winogradsky was born in Kiev, Russia, in 1856. After briefly studying law and classical piano, he enrolled in the University of St. Petersburg, where he earned a master’s degree in science. While there, he studied the growth properties of yeast—a single-celled microscopic fungus—and observed how certain bacteria chemically reacted with sulfur to produce energy. From his work, Winogradsky developed the theory of chemolithotrophy, which is the oxidation of nonliving matter by living organisms to generate energy. Oxidation refers to the loss of electrons from an atom through a chemical reaction.

In 1888, Winogradsky accepted a position at the Swiss Polytechnic Institute, a university in Zurich, Switzerland, renowned for its chemical laboratories. His work focused on nitrifying bacteria, microorganisms that oxidize energy from nitrogen compounds. Other scientists had discovered that certain bacteria were able to convert nitrogen gas from the atmosphere into ammonia. Winogradsky noticed that some bacteria converted ammonia into substances known as nitrites. A nitrite consists of one nitrogen atom and two oxygen atoms; its chemical formula is NO₂. Other bacteria then converted nitrites into nitrates, a substance with one nitrogen and three oxygen atoms (NO₂). Nitrates are used by plants as a nutrient and are commonly used in fertilizer. Some of the nitrates are converted by other bacteria into nitrogen gas and released back into the atmosphere. This process is known as the nitrogen cycle; Winogradsky’s pioneering work helped identify the role bacteria played in the nitrogen cycle.

His research also recognized that some microorganisms can convert carbon molecules, such as carbon dioxide or methane, into organic matter for energy without the presence of sunlight. Plants had long been known to use sunlight to create energy through a process known as photosynthesis. Winogradsky discovered that some bacteria can naturally synthesize organic matter through chemical reactions alone. He called this process chemosynthesis.

Overview

As part of testing his research, Winogradsky developed the column experiment that would bear his name in the 1880s. The Winogradsky column created an environment capable of growing large populations of microorganisms from soil or mud. Usually, microorganism populations do not grow large enough in nature for scientific study. The column provided microorganisms already present in the soil with optimal conditions for growth.

A Winogradsky column can be made from any tall, clear container, such as a glass tube or bottle, or a clean plastic bottle. An amount of mud or dirt from a natural water source—a pond or stream, for example—should be collected and all rocks and twigs removed. Exact measurement of ingredients is not necessary, but in general, the bottom third of the column should be filled with mud mixed with egg yolk and shredded newspaper. The mud mixture needs to be packed down in the bottom of the column to remove any air pockets. The next third of the column should be filled with regular mud that has not been mixed with anything. One optional method allows for sand to be added between the layers to better illustrate the boundary between the mud layers. About half the remaining space in the column should be topped off with water from the same source as the mud. The column should then be sealed or securely covered with plastic wrap or aluminum foil and placed in a well-lit area.

The first microorganisms to grow in the columns will usually be anaerobic bacteria—bacteria that do not need oxygen to survive. They will feed on the cellulose in the newspaper, which is made of wood pulp. Cellulose is a substance found in the cell walls of plants and trees. These bacteria produce carbon dioxide, which will trigger the growth of other bacteria. After a few weeks, the Winogradsky column will begin to be streaked with colored layers.

The lower portions of the column contain less oxygen and support the growth of anaerobic bacteria. The amount of oxygen increases near the top of the column, supporting aerobic bacteria that need oxygen. At the same time, the sulfur content of the column is lower near the top and increases near the bottom. The egg yolk acts as a source for the sulfur. Bacteria that consume sulfur will grow in the bottom of the column—an environment low in oxygen but rich in sulfur. These organisms produce the substance hydrogen sulfide, which acts as a nutrient source for green and purple sulfur bacteria higher up.

The middle of the column may develop streaks of purple, red, orange, or brown, signs of bacteria that need carbon, not sulfur, to survive. Red streaks may indicate the presence of bacteria that oxidize iron and form rust. Because the top of the column receives more oxygen and light, algae and cyanobacteria tend to grow in that region. Cyanobacteria are a family of bacteria that rely on photosynthesis to produce energy. The microorganisms in the lower sections of the column rely on chemosynthesis.

The colors and boundaries of the column may vary depending on the bacteria present in the mud and the substances mixed with it. Some experiments mix liquid fertilizer with the mud to grow phosphorous-eating bacteria within the column. Other optional variations may call for adding antacid tablets to create carbon dioxide or nonfat milk to add protein and calcium.

Bibliography

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Chimileski, Scott. “How to Build a Giant Winogradsky Column.” American Society for Microbiology, 2014, schaechter.asmblog.org/schaechter/2018/08/how-to-build-a-giant-winogradsky-column.html. Accessed 30 Oct. 2018.

“The Columns.” University of Delaware, 2018, sites.udel.edu/winogradsky/the-columns/. Accessed 30 Oct. 2018.

Dworkin, Martin, and David Gutnick. “Sergei Winogradsky: A Founder of Modern Microbiology and the First Microbial Ecologist.” FEMS Microbiology Reviews, 1 Mar. 2012, academic.oup.com/femsre/article/36/2/364/565076. Accessed 30 Oct. 2018.

Fink, Mara R., Tyler Z. Sodia, and Kevin J. Cash. "Mini Winnies: Scaled Down and Transparent Winogradsky Columns for Microscopy in Microbiology Education." American Society for Microbiology, 30 May 2024, journals.asm.org/doi/10.1128/jmbe.00212-23. Accessed 15 Nov. 2024.

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Parks, Samantha T. “Microbial Life in a Winogradsky Column: From Lab Course to Diverse Research Experience.” Journal of Microbiology & Biology Education, vol. 16, no. 1, May 2015, pp. 82–84.

“Soil Science: Make a Winogradsky Column.” Scientific American, 19 Sept. 2013, www.scientificamerican.com/article/bring-science-home-soil-column/. Accessed 30 Oct. 2018.