|
Procedure
- Check the assigned soil sample for clumps that will prevent packing. Break up the soil if necessary. It can be stirred up to gain a uniform consistency.
- The amount of mud you add will depend on the size of the container. As well, it’s important to keep the type of mud consistent with the water (fresh with fresh, marine with marine, etc.)
- Mix the sulfur source and carbon dioxide source (optional) in with the mud. They should be 1 to 2% of the final mass.
- Then mix in an equal volume of cellulose. The cellulose should be near the bottom but it can be in the middle if a variation is desired. However, it can’t be near the top since the bacteria involved are
anaerobic.
- Add the mud and pack this material into layers of 2-3 cm. Use the dowel or something equivalent to tamp down the mud to force out trapped air. Your last layer (water) should be about 5 cm from the
top.
- Cover the top with plastic film and secure with a rubber band. Place the column next to a low heat/high intensity light source probably less than 60 watts. It is important that it doesn’t over
heat.
- Examine the columns weekly for at least a month, recording changes in color and depth as they occur.
- Sampling can occur at weekly intervals to check succession or can be done at the end of the month to see the final flora of bacteria that develops.
Variations
If a freshwater model as described above is used, this is the standard Winogradsky Column. However, with just a few changes, some different columns can be created
to compare for growth rates, etc.
- sodium sulfide can be added in place of a sulfate. This may inhibit growth of the sulfur reducing bacteria bringing about different species of bacteria.
- Changing the pH may effect which species grow. Many of the standard sulfur reducers are comfortable in a pH of 6-8 (Brock 2000) Creating a more acidic or alkalinic environment may change the species
diversity as well.
- Enriching for Extremophiles. There are three basic types that may be created:
- Thermophiles – these species are very tolerant of high heat and if you put the column in front of a light source that creates more heat, thermophiles may be developed.
- Acidophiles – will develop when the pH is significantly acidic.
- Halophiles – If you opt to create a marine environment, Halophilic bacteria will predominate. The same can occur if your soil is inoculated with a 10% NaCl solution. Pickles or Saurkraut in the
substrate would work as well (Levandowsky, oral communication)
|
