In This Issue:
Bacteria may be microscopic in size, but they make up for it in sheer number. You have millions of bacteria living on your skin alone, and lots more inside of you! Does that thought give you the creeps? We usually think of bacteria as the harmful germs that make us sick, and while that is often true, there are lots of other things bacteria do that we couldn't live without. Read on for some fascinating facts about bacteria: where they live, how they can harm us, and how they can help us.
Where They Live
Where they live is one of the most surprising things about bacteria. The truth is, they live everywhere, even places on earth where we once thought nothing could survive!
In the heat. The hot springs of Yellowstone National Park contain highly toxic, sometimes boiling water. In this environment, where most living things couldn't survive, bacteria called thermophiles (heat-lovers) thrive. These bacteria are fueled by hydrogen and sulfur in the water, and they produce many of the brilliant colors in Yellowstone's hot springs.
Other thermophiles live near hydrothermal vents on the ocean floor. These vents are usually more than 7,000 ft (1.3 miles) below the surface, and at this depth the water pressure is extreme—it would crush us in no time at all! In addition, the temperature fluctuates drastically between hot vent water pouring out from cracks in the ocean floor and cold sea water. There is no natural light that deep in the sea, and the water spouting from the vents is full of harsh chemicals and minerals. And yet bacteria live there, and even help other creatures (like tubeworms) live by converting the toxic chemicals from the vents into food for them.
In the cold. Most bacteria don't grow as well in colder temperatures, which is why putting your food in the refrigerator helps keep it from spoiling. There are bacteria called psychrophiles (cold-lovers), though, that can live and reproduce in cold temperatures — even below the freezing point. Researchers in Antarctica have discovered bacteria in ice samples taken from about 11,700 feet deep in the ice above Lake Vostok.
In radioactive environments. One type of bacteria, called Dienococcus radiodurans, can survive lethal amounts of radiation, up to 1000 times more than would kill a human!
Inside you. Bacteria live on your skin, on your teeth, on your tongue, in your intestines, in your eyes, and more. You are host to millions of them! Some of them can harm you, but many of them help you. How? Keep reading to find out! But first: what exactly are bacteria?
What They Are
Bacteria are one-celled or unicellular microorganisms. They are different from plant and animal cells because they don't have a distinct, membrane-enclosed nucleus containing genetic material. Instead, their DNA floats in a tangle in the interior of the cell. Individual bacteria can only be seen with a microscope, but they reproduce so rapidly that they often form colonies that we can see. Bacteria reproduce when one cell splits into two cells in a process called binary fission. Fission occurs rapidly in as little as 20 minutes. Under perfect conditions a single bacterium could grow into over one billion bacteria in only 10 hours! (It's a good thing natural conditions are rarely perfect, or the earth would be buried in bacteria!)
How They Can Harm Us
Disease-causing bacteria are called pathogenic. These come in many forms and can cause illnesses from an ear infection to strep throat to cholera. They can get into our bodies via our mouth and nose, or through cuts and scrapes. Some are airborne, others are found in food, resulting in food poisoning. Bacteria are also the cause of plaque buildup on our teeth, which can lead to cavities and gum disease.
Before the discovery of antibiotics, many severe bacterial diseases had no cure and usually resulted in death. Antibiotics work by destroying bacteria or inhibiting their reproduction while leaving the body's own cells unharmed. After a time, some bacteria develop resistance to an antibiotic, and it will no longer be effective against them. Because of this, scientists are always researching new antibiotics. (Many diseases, such as chicken pox, hepatitis, or polio, are caused by viruses rather than bacteria. Antibiotics have no effect against these diseases.)
Bacterial infections are common, but many of them can be avoided by good cooking, cleaning, and hand-washing practices.
How They Can Help Us
Where would we be without bacteria? Well, we might not be getting bacterial diseases, but we would still be a lot worse off! Bacteria perform all sorts of very important functions, both in our bodies and in the world around us. Here are just a few.
Digestion. Our large intestines are full of beneficial bacteria that break down food that our bodies can't digest on their own. Once the bacteria break it down, our intestines are able to absorb it, giving us more nutrients from our food.
Vitamins. Bacteria in our intestines actually produce and secrete vitamins that are important for our health! For example, E. coli bacteria in our intestines are a major source of vitamin K. (Most E. coli is good for us, but there is a harmful type that causes food poisoning.)
Food. Bacteria are used to turn milk into yogurt, cheese, and other dairy products.
Oxygen. Cyanobacteria (which used to be called blue-green algae) live in water and perform photosynthesis, which results in the production of much of the oxygen we need to breathe.
Cleanup. Oil spills, sewage, industrial waste — bacteria can help us clean all of these up! They "eat" the oil or toxins and convert them into less harmful substances.
Bacteria are amazing creatures, aren't they? They can be so dangerous and yet so important at the same time. Since they are everywhere, you can easily experiment with them yourself, even without a microscope. Try it out with the science project below.
Stop the Bacteria: Soap Survey Project
Every time you touch something you are probably picking up new bacteria and leaving some behind. This is how many infectious diseases spread — we share our bacteria with everyone around us! Even bacteria that lives safely on our skin can make us sick if it gets inside our bodies through our mouths or cuts and scrapes. This is one reason why it is so important that we wash our hands frequently and well.
What kind of soap works best for cutting down on the bacteria on our hands? You can test this by growing some bacteria cultures using agar and petri dishes.
While most environmental bacteria are not harmful to healthy individuals, once concentrated in colonies, they can be hazardous. To minimize risk, wear disposable gloves while handling bacteria, and thoroughly wash your hands before and after. Never eat or drink during bacteria studies, nor inhale or ingest growing cultures. Work in a draft-free room and reduce airflow as much as possible. Keep petri dishes with cultured mediums closed—preferably taped shut—unless sampling or disinfecting. Even then, remove the petri dish only enough to insert your implement or cover medium with bleach or 70% isopropyl alcohol. When finished experimenting, seal dishes in a plastic bag and dispose. Cover accidental breaks or spills with bleach or alcohol for 10 minutes, then carefully sweep up, seal in a plastic bag, and discard.
What To Do
After 3-7 days, take your petri dishes out and observe the bacteria growth (without removing the lids). There might be some mold growth, too, since you may have swabbed microscopic mold and fungi spores along with the bacteria. Compare the amount of bacteria in the control dish to the amount in the test dish. Next, compare the amount of bacteria growth around each paper square. Which one has bacteria growing closest to it? Which one has the least amount of bacteria growing near it? If you did more than one test dish, are the results similar in all the test dishes? If not, what variables do you think might have caused the results to be different?
Which soap inhibited bacteria growth the most? Which one would you recommend using when you wash your hands? What other substances could you test for antibacterial effects? Try some of these ideas:
Don't stop there—there are lots of other projects you can do with bacteria
As you experiment, you'll notice that the bacteria growth in your petri dishes will often be different colors or textures. These are colonies of different types of bacteria. If you have a microscope, look at a sample of each colony and observe the differences. Bacteria come in three different shapes; see if you can distinguish these shapes under the microscope.
Ready for some candy that will help prevent cavities? A UCLA microbiologist has invented lollipops that kill bacteria that cause tooth decay!
Bacteria come in all sorts of fascinating shapes and sizes. Check out some great images in the MicrobeWorld photo gallery.
Want to know about the biggest, smallest, and deadliest bacteria? Visit MicrobeWorld's Microbial Book of World Records.