Understanding the role of germs (Part 1)

 


Many kinds of illnesses are caused
by microbes—tiny life-forms that are
too small to be seen with the naked eye.
There are many kinds of microbes,
including bacteria, protozoa, and
fungi. Bacteria are simple one-celled
creatures. Two kinds of bacteria
are Salmonella, a common cause of food poisoning, and
Streptococcus, the cause of

Viruses: Living, Nonliving, or in Between?

Is a dog or a cat a living thing? Sure. A tree? Absolutely.
A rock? Of course not.
But a virus? That’s a much trickier question.
Viruses—which cause illnesses and conditions such as the
common cold, influenza, herpes, and rabies—are unlike living
things in several important ways. First of all, they do not even
have a single cell—the basic building block of life. Instead,
they are mostly a strand of genetic material curled up inside
a tiny bag made of protein. Second, viruses cannot grow or
reproduce on their own.
Viruses also can’t take in energy: Unlike animals, they don’t
eat, and unlike plants, they don’t use sunlight to make their
own food. They can’t move on their own, so they have to be
carried along in air, water, food, or body fluids, or passed
around from one surface to another.
However, viruses do share some characteristics with living
things. They contain DNA (or a similar chemical called RNA),
the genetic code for life. They can reproduce with the help of
a living cell. (They do this by injecting their DNA into the cell
and “hijacking” the cell’s own reproductive system, forcing it
to make new viruses.) And over time, they can evolve—for
example, by developing a resistance to a drug. Some viruses
that cause human diseases are rhinoviruses, which cause
colds; herpesviruses, which can cause cold sores and blisters;
and the human immunodeficiency virus (HIV), which causes AIDS.
Some scientists classify viruses as living
things. Others classify them as non-living.
Still others believe that they belong to
their own unique category. But even
if they’re not alive themselves, viruses
definitely play a big role in life on Earth.
Smallpox virus

“strep” throat. Protozoa are also one-celled creatures, but unlike
bacteria, protozoa have a nucleus inside them. In this way, they are
more like animals or people than they are like bacteria. Protozoa
are known to cause only a few human diseases, of which two of
the most common are malaria and dysentery. Fungi can grow
on or in the body and live by breaking down dead cells or body
fluids. Examples of common fungal infections include athlete’s
foot and yeast infections. Fungal infections can also occur inside
the lungs. People with weakened immune systems, including elderly
people and patients with AIDS, are especially vulnerable to some
kinds of fungal infections. Some scientists say that microbes
include viruses, which cause many human diseases, from the
common cold to AIDS. Viruses are extremely simple life-forms—so
simple that many scientists argue that they are not life-forms at all.
Others put them in a class by themselves, somewhere between
living and nonliving things. For the purposes of this book, it is
easier to lump viruses in with microbes.

The world is full of microbes, and so is your body. A great many of
them are harmless to people. Some are even helpful.

To be continue....+