Prokaryotic Metabolism

Free Response

Think about the conditions (temperature, light, pressure, and organic and inorganic materials) that you may find in a deep-sea hydrothermal vent. What type of prokaryotes, in terms of their metabolic needs (autotrophs, phototrophs, chemotrophs, etc.), would you expect to find there?


Responses will vary. In a deep-sea hydrothermal vent, there is no light, so prokaryotes would be chemotrophs instead of phototrophs. The source of carbon would be carbon dioxide dissolved in the ocean, so they would be autotrophs. There is not a lot of organic material in the ocean, so prokaryotes would probably use inorganic sources, thus they would be chemolitotrophs. The temperatures are very high in the hydrothermal vent, so the prokaryotes would be thermophilic.

Farmers continually rotate the crops grown in different fields to maintain nutrients in the soil. How would planting soybeans in a field the year after the field was used to grow carrots help maintain nitrogen in the soil?


Soybeans are members of the legume family, so their roots have nodules that are colonized by nitrogen-fixing bacteria (ex. Rhizobium). Planting a crop that promotes nitrogen fixation after growing a crop that depletes nitrogen from the soil ensures that the soil continues to contain sufficient nutrients to grow more crops in the future.

Imagine a region of soil became contaminated, killing bacteria that decompose dead plants and animals. How would this effect the carbon cycle in the area? Be specific in stating where carbon would accumulate in the cycle.


Losing the bacteria that serve as decomposers in the ecosystem would disrupt the carbon cycle, but not stop it completely since fungi can also serve as decomposers. Without bacterial decomposers functioning, organic waste would accumulate in the area, and less carbon dioxide would be released back into the atmosphere.