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Disease Notes Bacteria and Viruses

Disease Agents (Pathogens)

S  There are many organisms in the world that can cause diseases

1.  Bacteria 2.  Viruses

3.  Protists

4.  Fungi

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Bacteria

S  Prokaryote

S  Unicellular (Only ONE Cell)

S  Bacteria have: S  Cell Wall

S  DNA

S  Capsule

S  Endospore (protective outer covering)

S  No Nucleus

S  Free Floating DNA

Bacteria Shapes

S  Three Shapes 1.  Bacillus (Rods)

2.  Spirrilum (Spirals)

3.  Coccus (Spheres)

S  Arrangements S  Diplo- (2)

S  Staphlo- (Clusters)

S  Strepto- (Straight line)

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Treating Disease Agents

S  Bacteria can be treated by antibiotics. They will kill the bacteria. Viruses cannot be treated at all. They have to run their course.

S  Protists (like amoebic dysentery) and fungi (like athlete’s foot) can be treated by a variety of medicines.

Bacterial Resistance

S  If you try to treat a sickness that is not caused by a bacteria with an antibiotic, or if you do not take your antibiotics correctly (not taking ALL of them) this may cause bacterial resistance (MRSA)

S  We call these SUPERBUGS

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Viruses

S  Viruses are non-living organisms/things. They are considered to be non-living because they can not reproduce on their own successfully.

S  They have to have a “Host Cell” which is YOU (or whatever organism it is infecting) This one of the characteristics of life.

S  They also do not contain cells.

Viral Structure

S  Viruses come in many different shapes – practically any shape you can think of.

S  BUT! All Viruses have certain things in common 1.  Nucleic Acid (DNA or RNA)

2.  Capsid (Used for protection)

3.  Very, very, very small – much smaller than bacteria

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Vaccines

S  Viruses can be prevented – not treated by vaccines

S  Once you have a viral disease, it has to run its course

S  You can prevent some viral diseases by vaccines

S  In a vaccine, a weak strain of the virus is injected into the organism and the organism produces antibodies to fight off the virus next time the body is exposed to it!

Viral Reproduction

S  Viruses can reproduce in two ways – depending on the type of virus 1.  Lytic Cycle (Flu)

2.  Lysogenic Cycle (HIV)

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Lytic Cycle

S  Virus attaches to host cell

S  Virus enters nucleus of host cell

S  Virus replicates MANY times

S  Viruses break out of host cell to infect other cells.

S  VIRUS ATTACK!

Lysogenic (Latent) Cycle

S  Virus attaches to host cell

S  Virus enters nucleus of host cell and its DNA becomes part of the host cells DNA

S  Virus can become inactive for long periods of time

S  As the host cell duplicates through mitosis, the viral DNA is also replicated

S  Eventually, the virus breaks out of the cells