The Microbial World
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1-4 Microbes have profound effects on the environment
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[Prev] | [Next]- Microbes make up the major portion of the biomass present on the Earth. Therefore, the nutrients they eat and the products they form greatly influence the environment.
- Cyanobacteria and algae in the oceans are responsible for most photosynthesis and are a major sink for carbon dioxide, a greenhouse gas.
- Microbes release nutrients from dead organisms, making them available to the rest of the ecosystem.
- Some microbes play a role in the production of energy, while other microbes interfere with energy production.
Whether measured by the number of organisms or by total mass, the vast majority of life on this planet is microscopic. These teaming multitudes profoundly influence the make-up and character of the environment in which we live. Presently, we know very little about the microbes that live in the world around us because less than 2 % of them can be grown in the laboratory. Understanding which microbes are in each ecological niche and what they are doing there is critical for our understanding of the world. Figure 1-2 shows some examples of environments where microbes are present
Microbes are the major actors in the synthesis and degradation of all sorts of important molecules in environments. Cyanobacteria and algae in the oceans are responsible for the majority of photosynthesis on Earth. They are the ultimate source of food for most ocean creatures (including whales) and replenish the world's oxygen supply. Cyanobacteria also use carbon dioxide to synthesize all of their biological molecules and thus remove it from the atmosphere. Since carbon dioxide is a major greenhouse gas, its removal by cyanobacteria affects the global carbon dioxide balance and may be an important mitigating factor in global warming.
Figure 1-2 A sampling of the different types of environments where microbes flourish
Microbes are capable of growing in a wide variety of environments. Bacteria will grow in frigid glaciers to boiling volcanic springs, dry sands to the open ocean. Figure courtesy of Kelsea Jewell
In all habitats, microorganisms make nutrients available for the future growth of other living things by degrading dead organisms. Microbes are also essential in treating the large volume of sewage and wastewater produced by metropolitan areas, recycling it into clean water that can be safely discharged into the environment. Less helpfully (from the view of most humans), termites contain microorganisms in their guts that assist in the digestion of wood, allowing the termites to extract nutrients from what would otherwise be indigestible. Understanding of these systems helps us to manage them responsibly and as we learn more we will become ever more effective stewards.
Energy is essential for our industrial society and microbes are important players in its production. A significant portion of natural gas comes from the past action of methanogens (methane-producing bacteria). Numerous bacteria are also capable of rapidly degrading oil in the presence of air and special precautions have to be taken during the drilling, transport and storage of oil to minimize their impact. In the future, microbes may find utility in the direct production of energy. For example, many landfills and sewage treatment plants capture the methane produced by methanogens to power turbines that produce electricity. Excess grain, crop waste and animal waste can be used as nutrients for microbes that ferment this biomass into methanol or ethanol. These biofuels are presently added to gasoline and thus decreasing pollution. They may one day power fuel cells in our cars, causing little pollution and having water as their only emission.
Finally, we are increasingly taking advantage of the versatile appetite of bacteria to clean up environments that we have contaminated with crude oil, polychlorinated biphenyls (PCBs) and many other industrial wastes. This process is termed bioremediation and is a cheap and increasingly effective way of cleaning up pollution. Figure 1-18 shows before and after photographs of the clean up of the Exxon Valdez oil spill in Prince William Sound.
Figure 1-18 The Exxon Valdez oil spill
Microorganisms played an important role in removing many of the pollutants released during the Exxon Valdez oil spill in Prince William Sound. Interestingly, microbes were not added to the site, but the clean-up relied on bacteria from that environment. A nutrient solution was sprayed onto the oil to encourage the growth of oil-degrading microbes. Though this was one of the more successful methods used to clean up the oil, but no treatment removed all of the pollutants. (Source: http://www.battelle.org/environment/exxon-valdez.stm.)
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