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0:00
Hello, I'm Dr. Martin Goldberg.
I'm a senior lecturer in
Clinical Microbiology at
Birmingham City University.
This lecture is part of a
series that we're making
on An Introduction to
Microbiology for level 4 students
but would also be eligible for
anybody working in
the health service
or anywhere in
academia or industry.
Today's lecture is intended
as an introduction to
bacterial genetics,
which is an area I've spent
many years working in.
0:35
The areas I'll be
talking about include:
looking at the structure
and function of DNA,
very simple overview of
how DNA is replicated,
looking at some of the features
of the bacterial chromosome,
bacterial gene
expression, the nature
of bacterial plasmids and
their medical importance,
the transfer of DNA
between bacteria,
bacteriophages or viruses
which affect bacteria
looking at their life cycles
and how they can impact
on the biology of bacteria.
1:10
Here are a couple
of useful textbooks
that I refer students to.
They cover a lot of the areas
that I'll be talking about.
1:20
Starting right at the beginning,
we have to go back to 1926,
and Fred Griffith did a
really important experiment
in terms of providing
evidence of the role of DNA
as a molecule which
stores all the
information required for
cells to grow, survive
and propagate themselves.
He was working with
an organism called
Streptococcus pneumoniae,
which is a pathogen that
resides in the upper
respiratory tract and
it's capable of causing a
nasty form of pneumonia,
but it can also
cause meningitis,
particularly in newborn infants.
There are essentially
two types of
Streptococcus
pneumoniae, if you're
looking at the growth
on agar plates.
There are the so-called
smooth strains
and these have a capsule,
which is a gel-like
substance coating the cells.
So these bacteria
appear quite shiny,
smooth and glistening on
the surface of the plate.
Then there are the
so-called rough strains,
which lack that capsule.
They're relatively
small colonies.
They're quite dry-looking.
An important difference in
their phenotypes is that
the smooth strains of
Streptococcus pneumoniae
are the virulent strains.
These are the strains
which cause disease,
whereas the rough strains,
the small, dry-looking
strains, do not cause disease.
If you were to inject
the smooth strain
into a mouse, it would kill it,
whereas these mice would
survive the rough strains.
The capsule, that surface layer,
is made of a polysaccharide,
and one of its roles is
to prevent the macrophages that
normally circulate in
the bloodstream from
phagocytosing the bacteria
and killing them.
Then in 1944, Oswald
Avery showed that DNA,
and not protein or lipids,
was responsible for
the observations
which Fred Griffith made,
and I'm going to describe
it in the next slide.
