Hello and welcome to Introduction to Microbiology.
My learning goals for you include, you will
be able to define a microbe, you'll understand
the differences among archaeal, bacterial
and eukaryotic microbes, you will appreciate
that microbes are everywhere and outnumber
all other living things, you'll know why microbes
are essential for life and you'll appreciate
how microbes shape the earth. Let's begin
with the definition of a microbe. The word
microbe has 'micro' in it, and that comes from
'microscope' and that's because what these are
small organisms visible only under the microscope.
The study of microbes is called microbiology.
There are a number of different kinds of microbes
that we're going to be talking about, and
the first group is called the bacteria. Here
is an electron micrograph, a high magnification
image of a common bacteria that's in your
intestine, E. coli, you can see that they're
rod shaped, they are individual cells and they
have a number of properties that we're going
to be discussing, this is magnified about
Bacteria have a number of properties that
distinguish them from the cells that are in
you and I. For example, they don't have nuclei
as do ourselves and they don't have membrane-bound
organelles like mitochondria or chloroplasts
which are found in plants. There are a lot
of different shapes of bacteria, they include
rods, spheres and spirals and a few others.
There are many, many bacteria on earth; our
estimate is about 5×10 to the 30th, that's
a huge number, actually bigger than we can
really comprehend. You may be used to about
a billion which is a giga of something, well
10 to the 30th is a lot more than that.
The bacteria can be found in every environment
on earth, wherever you look, whether it be
in soil, in the oceans, in rocks even, you
can find bacteria.
Another group of microbes that I'd like to
tell you about are the archaea. When the archaea
were first discovered, they looked like bacteria,
they can occur as spheres or rods, and so
scientists thought these must be bacteria, so they
were classified along with them. These archaea
lack nuclei and they also lack membrane-bound
organelles like mitochondria and chloroplast
and so it was thought these must be bacteria,
but it turned out that we were wrong.
The archaea are evolutionarily closer to eukaryotes,
the cells within us, in you and I, these are
eukaryotic cells, archaea resemble them more
than they resemble bacteria. Archaea are often
found in extreme environments and we like
to call them extremophiles, because they love
those extreme environments and here's one
of them, this is a hot spring in Yellowstone
National Park in the US where the waters are
over 90°C, some of the archaea love to grow
in these environments, it is truly amazing.
One of the archaea that grows in such extreme
environment is called pyrococcus furiosus,
and I love this particular archaea. You can
see it's an oval shaped cell with lots of
what we call flagella at one end, and this
is how these cells move around. But they are
not always present in just extreme environments,
some of the archaea live more normally, like
we do, you can find them in soils, you can
find them in oceans, you can find them in
other wet areas like marshlands and they are
also in us, in you and I, we contain archaea.
You can find them in your colon, your large
intestine, they are in your mouth and they
are also found on your skin.