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Bacteria come in many shapes
and sizes, from minute spheres,
cylinders and spiral threads, to
flagellated rods and filamentous
chains. Although generally less
than 5 micrometers long (smaller
than human red blood cells),
bacteria are found practically
everywhere and live in some of
the most unusual and seemingly
inhospitable places on Earth.
As prokaryotes, bacterial cells have few
of the cell parts of typical cells.
Although there are many bacteria on Earth,
they were not discovered until the late 1600s.
A Dutch businessman and amateur
microscopist, Anton van Leeuwenhoek,
found them while looking at scrapings from
his teeth.
His microscope was not very powerful and he
could not see any details, but Leeuwenhoek is
considered to be the Father of Bacteriology.
This is Anton van
Leeuwenhoek. In
the 1600s, he
discovered
bacteria in teeth
scrapings.
This is
Leeuwenhoek’s
drawing of bacteria.
Until recently, biologists grouped all
bacteria together in a single kingdom on the
basis of their similar cellular structure.
However, although all bacteria look similar,
some differ chemically. After analyzing the
chemical differences, scientists have
reclassified bacteria into two
separate kingdoms Archaebacteria
and Eubacteria.
The word Archaebacteria
means “ancient” bacteria.
They already existed on Earth
for billions of years before
dinosaurs appeared.
Scientists think that
Archaebacteria closely
resemble Earth’s first life
forms. Many Archaebacteria
live in extreme
environments such as hot
springs and in sewage.
Eubacteria do not live in
as extreme environments
as Archaebacteria.
However, they live
everywhere else.
Millions live in and on
your body. They coat
your skin and swarm in
your nose. Don’t be
alarmed! They are either
useful or harmless to you.
Some Eubacteria are
autotrophs that float near the
surfaces of Earth’s waters.
These bacteria use the sun’s
energy to produce food and
oxygen. Scientists think that
billions of years ago
autotrophic Eubacteria
were responsible for
producing the oxygen that
created Earth’s atmosphere.
This is a cladogram showing the
evolution of bacteria.
Bacteria are found nearly
everywhere on Earth - in soil,
rocks, Arctic ice, volcanoes, and
in all living things. When you
hear the word bacteria, you may
think about getting sick. After
all, strep throat, ear infections,
and many other diseases are
caused by bacteria. It is true that
some bacteria cause diseases
and other harmful effects.
Of all the
microorganisms,
bacteria are the
greatest threat to
food safety. Food
handling practices are
risky when they allow
harmful bacteria to
contaminate and grow
in food.
Asexual reproduction- involves
only one parent cell and produces
offspring identical to the parent
Sexual reproduction- involves two
parents who combine their genetic
material to produce a unique
offspring