Extreme Environments
Raina M. Maier
1. Define the term ecosystem services.
Natural ecosystems provide resources that benefit society including healthy soils for growing
crops, biogeochemical cycling activities, climate regulation, water purification. Taken together
these resources are termed ecosystem services.
2. Give two example of extreme environments not discussed in this Chapter.
High salinity environments such as the Great Salt Lake in Utah or the Cabo Rojo Salterns in
Puerto Rico
High radiation environments such as the upper atmosphere or radioactive wastes.
3. Which of the extreme environments discussed in this Chapter likely has the slowest
growth rates.
This is debatable because both the low temperature environment in the McMurdo Dry Valleys
and the low moisture environment in the Atacama Desert likely exhibit very slow growth rates.
4. Of the five extreme environments discussed in this Chapter, which two are based on
chemoautotrophy.
The Deep Sea Hydrothermal vents and Acid Mine Drainage environments.
5. If you were a microorganism, what type of extreme environment would you choose
to live in?
This is a great discussion question, there is no correct answer.
6. Discuss adaptations for enzymes at low and high temperature.
The key to enzyme function, whether in cold or hot environments, is the maintenance of an
appropriate balance between molecular stability and structural flexibility at a given temperature.
At low temperature, microorganisms make enzymes with structural modifications that make
them highly flexible particularly around the active site of the enzyme (the site where the enzyme
interacts with its substrate) at low temperatures to allow efficient enzyme activity.
At high temperature, some microorganisms produce chaperonins, which are specialized
thermostable proteins that help refold and restore other proteins to their functional form
following thermal denaturation. In addition there are microbe-specific adaptations to increase
protein stability at high temperature including an increased number of disulfide bridges,
increased interactions among aromatic peptides, and increased hydrogen bonding among
peptides
7. Compare and contrast a thermocline (Chapter 6) and a chemocline.
The thermocline is the region in an aquatic environment that is characterized by a rapid change
in temperature. This induces a density stratification (which is the thermocline) because
water is most dense at 4°C. The chemocline is defined as the interface between two
different chemistries in a body of water. For example this could be the interface between
oxygenated and anoxic water. In general, both nutrients and bacteria tend to accumulate
at a chemocline or a thermocline.