Winogradsky Columns

STUDENT HANDOUT:

• The Winogradsky Column Student Handout

INTRODUCTION:

Soil is considered to be an ecosystem.  Some organisms like earthworms and other invertebrates can easily be seen in soil.  Other organisms, like bacteria and other microorganisms are not easily seen.  There exists a class of bacteria that use light as an energy source.  These bacteria are known as phototrophs.  These phototrophs contain pigments that allow them to absorb light energy.  

The different types of phototrophic bacteria present are shown in Figure 1. 

Figure 1.  Phototrophs found in Winogradsky columns based on oxygen requirements 

We could use a microscope to see what bacteria are present in soil.  However, in this activity, we will use another technique.  To see what phototrophic bacteria are present in soil, you will be preparing a Winogradsky column.  

Environmental samples of soil and water are packed into a column and incubated for several weeks under light.  Over time, an oxygen gradient is generated due to the metabolisms of bacteria.  The column promotes growth of organisms at various depths corresponding to the oxygen requirements of the bacteria present in the soil.  Bacteria at the top of the column will be aerobes.  Obligate aerobes are organisms that can grow only in the presence of oxygen.  Bacteria at the bottom of the column will be anaerobes.  Obligate anaerobes are organisms that can grow only in the absence of oxygen.  Facultative anaerobes are organisms that prefer oxygen, but can grow in the absence of oxygen.  

OBJECTIVES:

1.  Learn how to culture phototrophic bacteria from soil using a Winogradsky Column. 

PRECAUTIONS:

1. Once you have made the column, you should not open the column.  The column will be enriching for specific soil-borne bacteria.  Even non-pathogenic bacteria can cause infections if not properly handled.  

MATERIALS (Per person):

1. Empty CLEAR tennis ball container (with cap).

2. Mud or soil.

3. Shredded newspaper (this will be our cellulose source).

4. Corn starch

5. Epsom salts

6. Stream or pond or distilled water (do not use tap water!)

7. Window that receives a lot of sunlight (or a lamp)

PROCEDURE:

You can watch a video on how to make a Winogradsky Column. 

2.  Mix some shredded newspaper with some soil and add it to the container.  

3.  Fill the container until the bottom ⅓ of the column is filled (up to the first dot).

4.  Mix some corn starch (carbon-source) OR epsom salt (magnesium sulfate, a sulfur-source) with some soil and add it to the container.  Fill the container until ⅔ of the column is filled (up to the second dot).

5.  Gently tap the container on the counter to make sure the soil is packed and there are no air pockets. 

6.  Pour some water (either stream, pond or distilled water) into the column.  Continue pouring until the water reaches the top of the column.

7.  Cap your container and seal it using tape.  

8.  Make some initial observations of your column.  Record your observations in Table 1 of the Laboratory Report Form.   

9.  Place your column on a windowsill (or in front of a lamp).  Over the next few weeks, various colors will appear in the soil.  These colors represent the different phototrophic organisms present in the soil.

10.  Make sure your column does not dry out.  Add water if necessary.

OBSERVATIONS/CONCLUSIONS:

1. Each week, record your observations in Table 1 of the Laboratory Report Form.  Be sure to draw (or take a picture) of your column and write a description of your observations.

2. Over time, what happened to the column?

QUESTIONS:

1. Where in the column did you see colors?  For each color seen, answer the following questions:  

(a)  What bacteria did you observe in your column?  

(b)  What is their probable oxygen requirement?  (Aerobic, Anaerobic?).

To help you with this question, look back at Figure 1.

2. Why do you think there are different colors of pigments?

KEY TERMS:

• aerobes

• anaerobes

• bacteria 

• ecosystem

• facultative anaerobes

• microorganisms

• obligate aerobes

• obligate anaerobes

• phototrophs

• pigments

• Winogradsky column

SUGGESTED READINGS:

Martin Dworkin , David Gutnick, Sergei Winogradsky: a founder of modern microbiology and the first microbial ecologist, FEMS Microbiology Reviews, Volume 36, Issue 2, March 2012, Pages 364–379.