Bacteria come in three different shapes: (1) coccus
or sphere shaped; (2) bacillus or rod shaped; (3) spirillum or spiral,
corkscrew shape. Bacteria have a tough outer coating which gives
them a cell-like shape.
Viruses are non-living and cannot reproduce without using the
mechanisms of a host cell. Once a virus enters a host it can cause great
damage. Viruses come in different shapes. Viruses are smaller
than bacteria, have no nucleus, no cytoplasm, and no surrounding cell membrane.
There are, however, some viruses, that produce a "fake" cell membrane that
is used in tricking the immune system. Actually, a virus can almost
be considered a chemical crystal.
Bacteria and viruses that cause disease are called pathogens.
Pathogens can enter a body through the air, water, or through contact with
an infected body. Diseases caused by bacteria can usually be cured
with medication. Viral diseases on the other hand cannot be cured
because there is no medication that will stop viruses. The immune
system of the human body has to fight the viruses, sometimes the body wins
but many times it loses. Vaccines can help prevent the virus in the
first place. Viruses are very difficult to study.
- Go over the characteristics of bacteria and
viruses using the student's lab sheet.
- Instruct the students to cut out the viruses and bacteria
and try and sort them into their respective groups. Tell students
to write their answer on the back site of each picture with the reason
for the student putting it in its group. This is not an easy lab,
because the weird shapes that both bacteria and viruses take.
- The bacteria and viruses on the chart are:
a virus that invades the cells of bacteria
- Influenza virus, causes influenza
- generalized mycoplasma (bacteria)
mosaic virus, results in disease of tobacco plants
- smaller tobacco
- micrococcus radiodurans (bacteria)
- spirillum bacteria
- crystal of adenovirus particles within the nucleus
of a human cell
- polio virus
- bacillus bacteria
- tumor virus
- pseudomonad bacteria
- prochloron bacteria
- spirillum bacteria
- cell invaded by bacillus bacteria