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EXTENSIONS
General Biology of the Column
After a month to six weeks, the column should stabilize into three distinct environments and develop
communities of bacteria specific to their environmental requirements and should resemble Figure 1.
Aerobic Zone (Oxygen Rich)
The top of the water column can contain large populations of diverse bacteria.
These are aerobic organisms that are found in organic-rich freshwater habitats such as shallow ponds, polluted streams, etc. These are generally flagellated
which allows the bacteria to migrate and establish themselves in new areas. In addition, there may be a diverse phototrophic fauna as well from the original
water and mud source. At the very top of the zone the mud is characterized by a light brown color. This is the most oxygen rich part of the mud and the most sulfur poor.
Photosynthetic cyanobacteriacan grow in the upper zones. This area is characterized by a Grass green color These are the only bacteria that have
photosynthesis like that of plants. In fact, there is very strong evidence that the chloroplasts of plants were originally ancestral cyanobacteria that established
themselves as symbionts inside the cells of a primitive eukaryote. Similarly, there is equally strong evidence that the mitochondria of present-day eukaryotes were derived from purple bacteria.
From the mud source below, H2S will diffuse upward into the aerobic zone and can be oxidized to sulfate by the sulfur-oxidizing bacteria such as Beggiatoa and
Thiobacillus. These bacteria gain energy from oxidation of H2S, to elemental sulfur and they synthesize their own organic matter from CO2. So they are termed chemoautotrophs.
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