Page 6 - The Science of Infectious Diseases

sea level in the snow on Mount Everest and 36,089 feet
(11,000 m) below the surface of the ocean in sediments at
the bottom of the Mariana Trench. An individual bacterial cell
cannot be seen with the naked eye, but large populations of
bacteria, known as colonies, can be visible. For example, the
rings of bright colors that can be seen in the hot springs of
Yellowstone National Park are created by colonies of bacteria
living in the hot water.
There are about thirty thousand species of bacteria, but less
than one hundred are known to cause disease in human beings.
Once inside a person, harmful bacteria reproduce, and as their
numbers grow, they can crowd out the bacteria that keep the
body healthy. When a person’s healthy bacteria are unable to per-
form their usual functions, the person becomes sick. In addition,
some harmful bacteria emit toxins that can damage or kill healthy
cells, causing disease. Some of these toxins are incredibly lethal.
According to the scientifi c journal Nature, a bacterium known as

Bacteria like these, known as
Clostridium botulinum, produce
a toxin so potent that just 400
grams would be enough to kill
everyone on the planet.