Introduction
The Winogradsky column is used as a "microcosim" of a natural setting in a lake or stream where microorganisms live and flourish. It is an effective tool because almost all the variables that effect the water and soil in a stream, which can’t be controlled in nature, can be controlled in the lab with the development of a Winogradsky Column. Variables such as light, temperature, nutrients, etc., all effect the water and soil and can be controlled by the scientist, thus reducing experimental error during expirements. The Winogradsky column is used to view the microbial ecology of the soil and water of a lake or stream. The column is useful in being able to cultivate microorganisms effectively for further study of the ecology. Scientists can view the succession and enrichment of various microorganisms throughout the various microhabitats within the column itself (water and mud, aerobic to anaerobic environments). Thus giving great insight to the ecology of microorganisms in lakes and streams or in almost any environment.
Our Winogradsky columns were pre-prepared first semester so the initial steps were fairly easy. We decided to switch the columns so that the column that did not receive constant light would now receive constant light, and the column that received constant light would now be deprived of constant light. Before we made the switch we made some initial observations of both columns. The column that had received light had an orange colored growth and somewhat cloudy water. The soil was black but contained random spots of yellow, red, orange, and brown growth. The column that had not received light had somewhat clear water with a slight green hue and some green growth on the sides of the column. The soil was black with a limited amount of green growth in it. We switched the columns and placed one column by a 75 watt light bulb that remained on 24 hours a day. The second column was placed on the lab bench and received no light, with exception of the laboratory ceiling lights during the day. After a few days there was some growth in the lit column. The cloudy water had turned a greener color and there was some green growth on the sides. There was also some more green growth in the soil. There was also some change documented in the unlit column as well. The water appeared clearer and some of the random spots of various colors in the soil were diminished or disappeared all together. We then added some nutrients to both columns. We accurately weighed out and added 4 grams of calcium carbonate, 4 grams of calcium sulfate, and 1 gram of sodium sulfide.
We returned after a week to make additional observations. We saw that the lit column had under gone dramatic changes. The water was very cloudy and had an orange tint to it. There was a film of growth at the water surface. There was also ample growth on the sides of the column. The soil was changing color as well with large spots of orange, red, yellow, and brown colored growth concentrated where the light was shining. The surface of the soil had a layer of colorful growth on top of it. The column also had a pungent odor like rotting eggs. The non-lit column had also gone through some changes. The water was very clear and the colored areas in the soil had disappeared except for a few green spots.
From these results over the first week and a half period, we could see and hypothesize that the microorganisms in the lit column were able to survive first semester being in the absence of constant light. Now that they had received both light and nutrients they bloomed in the column. We can see that this lack of light had an adverse affect on the microorganisms in the column regardless of the nutrients they received. We can also make some initial observations of the kinds of microorganisms growing in the column. The film on top of the water in the lit column was probably made up of strictly aerobic microbes. They were only able to grow on the surface of the water where they were directly exposed to air. The microbes that made up the bloom in the water were probably aerobic near the top and facultatively anaerobic throughout. It is doubtful that the aerobic microbes were able to survive towards the bottom of the column because there is less oxygen there, and this minimal amount of oxygen would have probably been used up early on in the development of the column. Due to the fact that the column is composed of stagnant water, there is not much mixing going on in the column's water portion. The microorganisms on the top layer of soil were most likely facultatively anaerobic. The microbes in the soil were composed of facultative anaerobes and obligate anaerobes.
We continued to make observations on the column up to spring break. The week before spring break we noticed that the unlit column had slightly cloudy water. Our hypotheses were that either there was a spontaneous mutation of bacteria, enabling it to grow well in low light environments, or the loss of the microbes that dominated the column while it was lit, enabled a weaker microbe, which didn’t need light to grow, to take advantage of the nutrients and bloom. The lit column didn’t change much, except that the colorful bloom in the soil where the light was shining grew larger.
Hard times fell on the lit column over spring break when the light burned out. When we returned we found not only that the light was out, but that bloom of microorganisms in the water was all but gone and the bloom in the soil was greatly reduced. We replaced the bulb and hoped for the best. The unlit column didn’t change much and the somewhat cloudy bloom within remained.
There was a small bloom in the lit column after a week but it wasn’t as Impressive as it had been prior to spring break. The reason for this may be that the lack of light for 1 to 10 days (nobody knows), had a drastic effect and the nutrients needed to sustain such a rich bloom. These nutrients were probably exhausted during this period. The bloom in the soil fared better, looking as though it might return to normal. Undaunted, we took our slides from the columns and began obtaining our isolates. We plated the entire slide on an agar plate and let it grow. After a few days we got a wide variety of microbes on each agar plate. Each member of our laboratory group then attempted to isolate our own microorganisms. After a few series of streak plates, we were each able to obtain or own isolate and we began running tests to identify them.
During this time we continued to observe the columns. The bloom in the water of the lit column continued to grow slowly. In addition, a lot of the growths on the side of the column had returned. The bloom in the soil was back to normal and growing well. Yet the side where the light did not shine remained unchanged with no growth. The non-lit column remained unchanged and didn’t change much for the remainder of the experiment.
We were able to identify our isolates fairly accurately and we made our final observations on the column on May 7th and presented our results to the class on May 14th. The bloom in the lit column finally returned to full strength and the bloom in the soil was now wrapped almost 3/4 around the column. The unlit column was stabilized and unchanged.
Our final observations of the lit column included the documentation of a large bloom of microbes in the water that gave it a cloudy orange tint. There was a thin layer of aerobic microbes on the surface of the water. There was a thick, colorful layer of bacteria on top of the mud. In the mud itself there was a large, thick bloom of microbes that went around almost the entire column. The unlit column had a slightly cloudy bloom of microbes in the water and limited growth in the mud. There were a few small patches of growth visible. The minimal growth in the unlit column does not mean there are no microbes. As we saw from the switch of the column that did not receive light to receiving light, there are numerous microbes which we hypothesized as still flourishing or remaining stagnant, forming dormant spores.
Both columns obviously went through a great deal of changes over the semester. The most dramatic physical changes documented within the lit column, both intentional and accidental. The lit column turned into a very diverse and active ecosystem during the semester, while the unlit column became less active, yet still remaining diverse. We took two of our isolates from the unlit column and one from the lit column. Although there are only three isolates, they are a diverse group.
1 - Aureobacterium
2 - Mycobacterium