Bacteria are monerans, the simplest single-celled
organisms. They are the smallest of all cells, visible only through powerful
microscopes. Bacteria are also the most abundant forms of life. They live in
the air, on land, in water, and even inside the bodies of animals and plants.
Some bacteria cause diseases, but others are useful. Bacteria recycle nutrients
in the soil and aid the human digestive system.
Without bacteria, other life on Earth could not survive. Bacteria in
the soil release nitrates, a usable form of the element nitrogen. All plants
need nitrates to make vital chemicals called amino acids. Pea and bean plants,
such as soybeans, use bacteria called Rhizobium which
convert nitrogen straight into amino acids. The bacteria live on the
plants’ roots in swellings called root nodules.
BIOGRAPHY: LOUIS PASTEUR French, 1822-1895
Pasteur was a chemist who showed that food decays because of
microorganisms, such as bacteria. He found that heat treatment killed these
microbes. This process, pasteurization, is still used to preserve foods.
Pasteur also showed how bacteria can cause disease and developed the use of
vaccines to control them.
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