Peek into a clean room with no one in it.
There are no pets in the room. There are no plants in the room. It looks like
there is nothing alive in the room. The room, however, is swarming with life.
Billions of tiny life forms called bacteria cover the tables and chairs and the
floor. You can’t see them, but they stick to the windows, they cling to the
ceiling, and they float through the air.
Suppose you looked at part of a chair in the room
through a microscope. Microscopes magnify bacteria. You would see pale forms
moving and bumping into each other like ghosts. These tiny life forms are
bacteria. They live everywhere in the world. Billions of them even live inside
of you!
WHAT DO BACTERIA LOOK LIKE?
Bacteria come in three basic shapes. Some are round
or shaped like a jellybean. Some are spiral-shaped like a corkscrew. Some are
long, like rods.
Each sphere or spiral or rod is called a cell.
Animals have millions of cells, but bacteria have only one cell. This single
bacterial cell is called a bacterium. An outer wall surrounds the cell and
protects it. A substance called DNA floats around inside the cell.
Some bacteria have hairlike parts called flagella.
The flagella help the bacteria move around in search of food. Flagella also
move bacteria away from things that could harm them.
WHAT DO BACTERIA DO?
Some bacteria help you. Bacteria in the body help
fight off disease and help you digest your food. Some bacteria that live in
soil help plants by producing substances plants need. They break down dead
plants and animals and animal waste. They make a gas called carbon dioxide from
decaying material. Other bacteria help plants take a gas called nitrogen out of
the air. Plants need carbon dioxide and nitrogen in order to grow.
Some bacteria can harm you. There are bacteria that
cause food poisoning, pneumonia, tuberculosis, and other sicknesses. Some
bacteria cause tooth decay. Bacteria can also infect farm animals and wild
animals.
Disease-causing bacteria are different from helpful bacteria.
You can swallow disease-causing bacteria in unclean food or water. Bacteria
that cause infections can get into cuts and sores. Bacteria can get on your
hands and go from your hands into your nose, eyes, or mouth. That is why it is
so important to wash your hands often.
HOW DO BACTERIA GROW AND SPREAD?
Most bacteria simply split in two. Bacteria
reproduce very rapidly. One bacterial cell can become two in just a few
minutes. Two bacteria become four bacteria and then four become eight bacteria.
Bacteria keep multiplying this way until there are billions of them.
Different kinds of bacteria must compete for food.
This competition keeps bacteria from overrunning Earth.
WHO DISCOVERED BACTERIA?
No one knew about bacteria until the
microscope was invented. Bacteria are so small that they must be magnified at
least 500 times their actual size for us to see them.
A Dutch microscope-maker named Antoni van Leeuwenhoek in
the 1670s was the first person to see bacteria under a microscope. He saw tiny
life forms swimming around in drops of rainwater and in scrapings from his
teeth. He called the bacteria “animalcules,” meaning tiny animals.
French scientist Louis Pasteur in the 1800s proved that
some bacteria are germs that cause disease. He found that heat kills bacteria.
Heating surgical instruments to kill bacteria is called sterilization. Heating
milk and other foods to kill bacteria is called pasteurization, a word named
for Pasteur.
A German scientist named Robert Koch also made
important discoveries about bacteria. He founded a field of science called
bacteriology, the study of bacteria.
WHY DO WE STUDY BACTERIA?
Scientists study bacteria to find out how these tiny
life forms behave. Scientists also want to know what diseases bacteria cause.
They look for ways to kill disease-causing bacteria.
In the mid-1800s, scientists learned that killing
bacteria can stop the spread of some diseases. Doctors learned that sterile
surgical instruments and operating rooms help prevent infection after
operations. Scientists learned that having clean drinking water and food
prevents the spread of deadly diseases such as cholera and typhoid.
Scientists also learned how to make vaccines that
protect against some diseases caused by bacteria. They made vaccines from dead
or weakened bacteria or from poisons bacteria produce. For example, a shot of
tetanus vaccine protects you from the bacteria that cause tetanus. Tetanus
bacteria live in the soil. They can get into even small cuts on your body.
Tetanus causes muscles to tighten. It can be deadly.
In the mid-1900s, scientists discovered
antibiotics, drugs that kill bacteria. Before antibiotics, many people died
from pneumonia and other infections caused by bacteria. Some bacteria have
become resistant to antibiotics. The antibiotics no longer kill them. Scientists
are working to make new kinds of antibiotics that will kill resistant bacteria.
