PART ONE: BASIC
CHARACTERISTICS OF VIRUSES,
BACTERIA, FUNGI, AND
PARASITES: AGENTS OF DISEASE
MICROBIOLOGY- the study of microorganisms .
• A microorganism or microbe is a microscopic
organism that comprises either a single cell
(unicellular) or cell clusters.
• The study of microorganisms is called
microbiology, a subject that began with Anton
van Leeuwenhoek's discovery of microorganisms
in 1675, using a microscope of his own design.
• Microorganisms are very diverse; they include
bacteria, fungi, archaea, and protists;
microscopic plants (green algae); and animals
such as plankton and the planarian.
Some microbiologists
also include viruses, but
others consider these as
nonliving. Why?
All living things (organisms)
have 5 characteristics
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•
•
•
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Composed of cells
Perform chemical processes such as growth and digestion
They reproduce
Make their own nutrients or ingest them from their habitat
Respond to stimuli such as light or touch
VIRUSES only do ONE of these!
They reproduce. That’s it.
•
• So what exactly are viruses?
Really they are just genetic
material
bacteriophage
(plant virus that attacks bacteria)
They ride around in these alien-looking microscopic things that are less than a
nanometer.
IMPORTANT! They can only replicate within a host cell. They destroy the host cell they
are in.
Bacteriophage in action
• http://www.youtube.com/watch?NR=1&feature=fvwp&v=xXb
yJNRwjlg
• IMPORTANT! They can only replicate within a host cell. They
HARM the host cell they invade.
The virus uses the spikes to recognize
and attach to the cells they infect.
• Works like a “lock and
key”. The key fits the lock so
the host cells internalize
viruses because the host cell
"thinks" the virus is
something it "wants", such as
food, a hormone, etc.
Because it only works like a
lock and key, viruses have
specificity of infection.
Certain viruses can only attack
certain host cells.
Examples of Viruses
• ff
Foot and Mouth Virus
Influenza Virus