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Disease
Many different organisms cause
disease. This presentation will
show you some organisms that
cause disease and the diseases
they cause.
Bacteria
Bacteria are believed to be the oldest, of
all life forms found on earth today.
Bacteria are prokaryotes.
Bacteria do not have a nucleus.
There are two kingdoms of bacteria:
– Archaebacteria
– Eubacteria
Bacteria come in 3
different shapes:
Coccus: sphere-shaped cells
Bacillus: rod-shaped
Spirillum: shaped like coiled
rods or corkscrews
Bacilli bacteria
Cocci bacteria
Spirilla bacteria
Structure of a
Bacteria Cell
Most bacteria have a rigid cell wall.
Many bacteria are surrounded in a capsule.
– The capsule protects the bacteria
DNA is not found in a nucleus.
Many bacteria have one or more flagella.
(For movement)
Bacteria are covered with pilli.
– This allows bacteria to attach to another
surface.
Structure of bacteria
Identifying bacteria
A very important test used to identify bacteria
is the gram stain.
This technique was developed by the Danish
microbiologist Hans Christian Gram.
Gram Staining
In this process bacteria are put onto a slide
and stained with purple dye.
– Bacteria that retain the purple dye are gram
positive.
– Bacteria that do not keep the purple dye are
gram negative.
• The difference in staining is due to the
composition of their cell walls.
Gram Staining
• Gram negative bacteria have a protective
layer covering their cell wall.
• This covering makes them more resistant
to drugs and other chemicals that destroy
bacteria cells.
• Antibiotics are more effective against
gram-positive bacteria.
Gram staining example
Gram negative
gram positive
Steps of Gram-staining
Comparison of gram
negative & gram positive
bacteria
Nutrition in bacteria
Most bacteria are heterotrophic. They use
organic compounds made by other
organisms.
Many are decomposers. They obtain their
nutrition from dead organisms.
Some bacteria are parasites. They live in
or on another organism. (Disease causing
bacteria)
Nutrition in bacteria
 Some bacteria live in a state of mutualism. Both
host and bacteria benefit from this type of
association.
– Example: intestinal bacteria in humans and nitrogen fixing
bacteria in the roots of some plants.
 Some bacteria are photosynthetic.
 Some bacteria obtain energy from the oxidation of
inorganic substances instead of from the sunlight.
– Nitrifying bacteria: can oxidize ammonia to nitrates.
Nitrogen fixation
These are root
nodules on the
roots of a bean
plant. The
nodules contain
the nitrogen
fixing bacteria
Rhizobium.
Bacteria
reproduction
Most Bacteria have a very simple way of
reproducing.
They simply split in two in the process
called binary fission.
They double their DNA and divide.
Binary
Fission
Disease Causing
Bacteria
There are many different
types of disease causing
bacteria. The following
slides are just a few of the
many examples.
Anthrax
Bacillus anthracis is the causative agent of anthrax. It is a
Gram-positive, aerobic, spore-forming large bacillus.
Spores are formed in culture, in the soil, and in the tissues
and exudates of dead animals, but not in the blood or
tissues of living animals. Spores remain viable in soil for
decades.
Bacillus
anthracis
Anthrax
Cutaneous
anthrax
The Anthrax Scare
The letter
that
contained
anthrax
spores
The Bubonic Plague
Plague is caused by Yersinia pestis and is
the disease known in the middle ages as the
black death. This is because it frequently
leads to gangrene and blackening of various
parts of the body. Capillary fragility results in
hemorrhages in the skin which also result in
black patches.
The Bubonic Plague
The three documented pandemics of plague
(Black Death) have been responsible for the
death of hundreds of millions of people.
Today, sporadic infections still occur. In the U.S.,
animal plague occurs in a number of western
states, usually in small rodents and in
carnivores which feed on these rodents.
The Bubonic Plague
PANDEMIC- AFFECTING A LARGE
AREA, WIDESPREAD
The Bubonic Plague
Buboes (Swollen
lymph node)
The Flea that
carries the plague
Gangrene
caused by
the plague
The Bubonic Plague
Drawing of the
outfit that people
would wear to
prevent from
smelling or coming
in contact with the
dead .