Questions you need to be able to
• What are bacteria?
• How do bacteria affect the human
• How are bacteria prevented and
• How do bacteria reproduce?
• Bacteria are prokaryotic unicellular
• Different types of bacteria have different
shapes which are often used in their
• Possible shapes:
– Bacillus (rod like)
– Coccus (sphere like)
– Spirillum (spiral like)
• Example: streptococcus (strep throat)
• There are typically:
– 40 million bacterial cells in a gram of soil
– 1 million bacterial cell in a milliliter of fresh
– In all, there are approximately five nonnillion
(5x1030) bacteria in the world.
– There are approximately 10 times as many
bacterial cells as human cells in the human
body, with large numbers of bacteria on the
skin and in the digestive tract.
• Bacteria reproduce by a process called
binary fission in which they make an
identical copy of themselves.
• Under optimal conditions, bacteria can
grow and divide extremely rapidly.
– Bacterial populations can double as quickly as
every 9.8 minutes
• Bacteria can form endospores which are
highly resistant, dormant structures.
– In the dormant state these organisms may
remain viable for millions of years.
– Endospores are so resilient that they can
survive exposure to a vacuum or radiation in
• 99% of bacteria are helpful or do no harm
• About 1% of bacteria are pathogenic
(meaning they cause disease).
– Cholera, syphilis, anthrax, leprosy, and
bubonic plague are all caused by bacteria.
• Bacteria enter the body because the body
offers an environment that the bacteria
can flourish in.
• Pathogenic bacteria generally enter the
body and begin reproducing.
• The damage they cause can be due to
toxins released by the bacterial cells, or by
bacterial cells actually entering body cells.
Treating Bacterial Infections
• Antibiotics are used to treat bacterial infections.
• Antibiotics affect different bacteria in different
ways. They could:
– inhibit a bacterium's ability to turn glucose into energy
– Inhibit a bacterium’s ability to construct its cell wall.
• Avoiding exposure can prevent infections.
Questions you need to be able to
• What are viruses?
• How do viruses affect the human body?
• How do viruses reproduce?
• How are viruses prevented and
• Viruses are non-living pathogens that
consist of genetic materials (DNA or RNA)
surrounded by a protective coat of protein.
• Since viruses are non-living, they are
unable to reproduce on their own, and
instead need to invade a host cell and
force it to make new viruses.
• Viruses generally follow one of two
• The virus invades a cell and replaces the
cell’s genetic material with its own.
• The cell then begins producing virus
particles instead of what it was producing
• Eventually the cell bursts oopen (lyses)
and the new virus particles are released.
• The virus invades a cell and adds its own
genetic material to the cell so that when
the cell divides all of the new cells get the
viral geneitc material as well.
• The virus remains dormant but after some
time the virus will become active and enter
the lytic cycle.
Treatment of Viruses
• Antibiotics DO NOT work on viral
• Often vaccinations are created in which a
weakened or dead form of the virus is
introduced to the body.
• The body then fights the virus and
remembers how it won, so that if it ever
gets infected again the virus will be