No matter where you go on this
planet, you?ll find bacteria.In the billions
of years bacteria have lived on Earth, these tiny survivors
have evolved and adapted to every environment. You?ll
find bacteria in icy regions, deserts, and rain forests?even
places without air. Some live in the extreme environments
of active volcanoes and hydrothermal vents on the ocean
floor. Bacteria also live in the human body. In fact,
the average healthy person is home to a stunning 100
trillion bacteria.
While some bacteria can move on
their own, others must be carried from one place to
another.Some bacteria rely on ocean tides, rushing
rivers, and other moving bodies of water. The bacterium
that causes tuberculosis and others travel on currents
of air when an infected person coughs, sneezes, or laughs.
Bacteria even hitch rides on animals and use magnetism
to point themselves in the right direction.
The first antibiotic grew out
of a lab mistake.In 1928 British chemist Alexander
Fleming found bacteria growing in petri dishes that
he forgotten about. Because the dishes were covered
with mold and probably contaminated by other microbes,
he decided to throw them away?until he saw something
peculiar. No bacteria grew wherever mold existed. Fleming
soon concluded that the penicillin mold in the dishes
had killed the bacteria. Today we use penicillin as
a medicine because it kills many kinds of pathogenic
bacteria.
To replenish the soil, farmers
introduce bacteria by growing peanuts.Legumes,
a group of plants that includes peanuts, peas, and beans,
have nodules, or bumps, in their roots. Caused by the
Rhizobium bacteria, the nodules absorb nitrogen from
the soil. They convert it to nitrate and create an essential
nutrient that plants can use. This process works so
well that farmers often plant legumes in fields every
few years to renew nitrogen-depleted soil where other
crops have been grown.
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