Choose one topic featuring a particular microbe, microbial habitat, or microbial process in relation to the environment. Write a short essay on the topic, with your own illustrations wherever appropriate. Use the index in your text as a starting point. Also browse chapters 40-44 in your text for ideas.

Do not choose a topic involving microbial diseases for this topic -- that will be the focus of extra credit paper #3.

Survival of microbes in rocks

The recent discovery of possible microbial remains in Martian rocks (found as meteors on Earth) has galvanized interest in the study of terrestrial microbes in rocks. Viable bacteria have been found in rocks from deserts, and in subterranean rocks taken from core samples 1 mile or deeper. How do they survive? How did they get there? An interesting topic. Start with the article: "Looking for Life in All the Wrong Places" by Will Hively. (DISCOVER MAGAZINE - MAY 1997). Note: this article is available on-line.

Microbial Life in Hydrothermal vent communities .

The discovery of abundant communities of organisms growing around deep-sea hydrothermal vents is a remarkable one. The source of energy for this community is not light but reduced molecules such as hydrogen sulfide. Chemolithotrophic bacteria "eat" the sulfide and, are in turn eaten by other organisms of the community. See box 40.4 (p. 847) and box 6.1 (p. 128) in your text for an introduction to this topic.

Microbial Leaching of Ores

Concentrating certain minerals (e.g. Copper) from low-grade ores can be too expensive to be practical by conventional smelting technology. An alternative, if the minerals contain sulfide, is to use bacteria to "mine" the ore. See pp. 955-956 in your text for an introduction to this topic.

Methanogenesis and Global Warming.

Methane is a significant greenhouse gas, and contributes to global warming. Methanogenic bacteria are a major source of this gas, with cows providing the single largest source. Investigate the numbers and the trends of this phenomenon, and find out for yourself the magnitude of the situation. Include some description of the biological process by which methane is formed. See p. 433 and box 42.3 (p.904) in your text for an introduction to this topic.

Dynamics of the Nitrogen Cycle .

Nitrogen is one of the macroelements required by all life-forms. Its chemistry is complicated by having many different forms that can be interconverted by different aerobic and anaerobic processes, both biotic and abiotic. Investigate the numbers involved -- come up with some graphical or tabular way of illustrating accurately how these various fluxes occur, and why. See pp. 836-839 in your text for an introduction to this topic.

Biodegradation of Xenobiotics .

Xenobiotics are chemicals synthesized by human design that did not evolve naturally. Such chemicals may accumulate as pollutants in the environment, because microbes have not had time to evolve chemical pathways for degradation. But some such chemicals can be degraded, and there is strong interest in the mechanisms involved. See box 44.2 (p.955) in your text for an introduction to this topic.