The words “fun” and “bacteria” aren’t commonly associated together, especially by those of us who prefer not to think exactly how cheese is made, let alone what goes on in our septic tanks and wastewater treatment plants. Nonetheless, bacteria are everywhere, and humanity should be very glad about that. Here are some fun facts about bacteria and some of the good they are bringing about in our lives.
♦ Our old, one-celled benefactor
Bacteria are one-celled critters that lack a cell nucleus or any complex material inside their cell membrane. Scientists call these “prokaryotes” to distinguish them from the “eukaryotes,” or plants, animals, and fungi that do have a cell nucleus and complex structures within each cell membrane.
This lack of a nucleus and internal complexity would seem to put bacteria at a disadvantage, but they have been around far longer than us. The oldest known fossils on this roughly 4.6-billion-year-old planet are bacteria, specifically, fossilized mats of cyanobacteria called “stromatolites” or “oncoids” (depending on their shape) that go back some 3.5 billion years, as compared to 1.8 billion years for plants and fungi and 600 million years for animals.
In fact, we have cyanobacteria to thank for the presence of oxygen in Earth’s atmosphere, the development of plants, petroleum deposits, and today, nitrogen fertilization for rice and bean crops. Yes, cyanobacteria are still around today. You may know them by the popular name for one species: “blue green algae.”
♦ Going to extremes
Surviving over most of geologic time is the ultimate accomplishment to us, but some bacteria are extreme performers in other ways as well.
The hot springs of Yellowstone National Park are famous for their brilliant colors. These colors come from the mats of trillions of hyperthermophilic (really hot water loving!) bacteria known as Thermus aquaticus. This little bug was first found in Yellowstone’s Lower Geyser Basin but has since been found all over the world. It thrives at around 160° F (70° C) but can stand a range from 120°to 175° F (50° to 80° C).
Scientists have been able to harvest T. aquaticus, without harming the delicate ecosystem it lives in, and to use its enzyme Taq DNA polymerase to replicate DNA as part of the polymerase chain reaction (PCR). This has led to, among other things, advanced medical and forensics tests that are in common use today.
Cyanobacteria use light to live, by way of photosynthesis. T. aquaticus is a chemotroph: it “eats” chemicals to live. Another extreme and related chemotroph is the “rock-eater,” or lithoautotroph.
At first no one could believe that the bacteria coming up in drilled oil from great depths were anything but contaminants, but research has proven that there are indeed bacteria living in either granitic or basaltic rock as far as almost 2 miles (3 km) below the planet’s surface. They “eat” chemicals of mineral origin to survive, and are the organisms responsible for acid mine drainage that pollutes streams and groundwater near mines.
That isn’t the only connection between mines and bacteria.
♦ Biominers and microbial fuel cells
Lithoautotrophs pollute mine water by converting energy-rich pyrite into sulfuric acid, but there are other, more “normal” bacteria, found on Earth’s surface, that metabolize sulfur, and in the process, concentrate minerals like copper and gold, thus making it possible to mine low-grade ores. This effect has been known since the days of ancient Rome, but it was only about 50 years ago that the bacterium behind this process, Thiobacillus ferrooxidans, was recognized.
Other bacteria, like some Geobacter species, are electrifying; that is, they can exchange electrons with an electrode. This has made possible microbial fuel cells in which bacteria consume waste water and produce electricity. In 2007, such a fuel cell could produce 2 kilowatts. However, over the intervening time, limitations on this particular technology have been found, and today a more effective use for microbial fuel cells may be the manufacture of butanol—liquid fuel that can be burned in auto engines without modification—from renewable but intermittent sources like wind and solar power.
Few of us lay people realize that some of the antibiotics in use today are natural molecules first made by bacteria as a defense against other bacteria. Bacteria make one group in particular, the macrolides, in such a way that it is very easy for scientists to synthesize thousands of slightly differing materials that can be tested for antibiotic activity; so far this has given us such drugs for humans as erythromycin, clarithromycin, and azithromycin.
Bacteria also provide the polymers with which we make biodegradable plastic, oddly enough. In fact, more than 600 types of bacteria are capable of this, and researchers are working on additional uses for these polymers, including artificial tendons and substances that will carry drugs to wherever they may be needed in the body and then disintegrate.
Most people think of the “three D’s” in connection with bacteria: dirt, disease, and death. Our relationship with these one-celled organisms is much more complex, and over time, we have actually benefited greatly from them. Bacteria are the oldest known form of life on Earth and are responsible for the air we breathe, the petroleum-based fuels we use for power, and fertilizer for our basic foods. They have helped us mine ore for thousands of years. Today, using advanced techniques, we have developed antibiotics and complex medical diagnostic and forensics tests from bacteria. Soon, they may even help us make auto fuel from sun and wind power.
Truly bacteria, while undeniably the source of much human distress and hardship down through the ages, have also brought us much good.
The Virtual Museum of Bacteria at http://bacteriamuseum.org/cms/
“Taq polymerase.” Wikipedia (n.d.) at http://en.wikipedia.org/wiki/Taq_polymerase
“Microbial ‘fuel cell’ squeezes energy from brewery wastewater.” New York Times” Business (May 2, 2007) at http://www.nytimes.com/2007/05/02/business/worldbusiness/02iht-beer.1.5529489.html?_r=1
"Geobacter: Microbial Superhero." Suzanne Winter (March 28, 2011) at http://schaechter.asmblog.org/schaechter/2011/03/geobacter-microbial-superhero.html
“A shift in the current: New applications and concepts for microbe-electrode electron exchange.” Derek R. Lovley and Kelly P. Nevin. http://dx.doi.org/10.1016/j.copbio.2011.01.009 (Adobe Acrobet Reader required)
“Deep dwellers.” Richard Monastersky (March 29, 1997) at http://www.sciencenews.org/sn_arc97/3_29_97/bob1.htm
“New Way To Make Antibiotics: Discovery Will Help In Fight Against 'Superbugs.'” Science Daily (September 18, 2006) at http://www.sciencedaily.com/releases/2006/09/060915203637.htm