Download Viruses and Bacteria

Viruses and Bacteria
Why Do We Need To Know?
• Viruses and bacteria are
some of the most
simple and elegant
organisms on the planet
• However, just because
they are not complex
does not mean that
they are not important
• Viruses and bacteria
shape the world as we
know it
Why Do We Need To Know?
• There are at least ten
times more viruses than
there are all other species
on earth
• Viruses are some of the
most simple “living”
things on the earth
– They test our definitions of
what is alive and not alive
• They can actually be
reverse engineered to
carry out work that
impossible for humans
Why Do We Need To Know?
• Bacteria are
everywhere inside and
on living organisms
• There are over 100
Trillion bacteria that call
the human body home
• That means between 35 lbs of your body mass
is bacteria
Viruses
• Viruses are simple
organisms
• They are nothing more
than genes in a box
• The genes that they
carry can be in the form
of DNA or RNA
• They are protected by a
tough outer layer called
capsid
Viruses
• Viruses can have one of
two life cycles
• In the lytic cycle the virus
injects its genetic material
into a cell and the
resulting viruses will
break free of the host cell
• In the lysogenic cycle the
virus replicates without
destroying the host cell
Viruses
• In the lytic cycle, the
virus in essence hijacks
the cell and causes the
cell to create more
viruses
• When the cell has
created more viruses,
they will cause the cell
to lyse and the new
viruses are released
Viruses
• In the lysogenic cycle a
virus incorporates its
DNA to a host’s genome
• The cell then proceeds
like normal
• When there is an
environmental trigger,
the viral genome then
switches on and follows
a path similar to the
lytic cycle
Video
• https://www.youtube.c
om/watch?v=TVLo2CtB
3GA
Bacteria
• Bacteria are simple
prokaryotic organisms
• They have a single
circular loop of DNA
that is in the cytoplasm
• Bacteria normally use
the asexual binary
fission to reproduce
Bacteria
• However there are
three different ways
that bacteria can
exchange genetic
material with other cells
– Transformation
– Transduction
– Conjugation
Bacteria
• Transformation is a
process where bacterial
cells uptake DNA from the
surrounding environment
and incorporate it into
their genome
• This allows bacteria to
inherit new
characteristics from
organisms that are no
longer functional, alive or
whole
Bacteria
• Sometimes viruses guide
the genome of a bacteria
• During the lytic cycle a
section of the host cell’s
DNA might be put into a
virus
• This means that the next
cell it infects is receiving
new bacterial DNA
instead of a viral genome
• This process is called
transduction
Bacteria
• Bacteria can also
“mate”
• This mating is different
from prototypical
eukaryotic mating,
however genetic
information is
transferred from a host
cell to a recipient cell
• Bacterial mating is
called conjugation
Bacteria
• When conjugation
occurs the donor cell
copies a part of its DNA
and sends it or it sends
a plasmid
• A plasmid is a small
circular section of DNA
that is separate from
the rest of the bacterial
DNA