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Viruses and Bacteria
Chapters 16 and 17
Infectious Disease
• Caused by the
invasion of a host by
agents whose
activities harm the
host’s tissues
• Can be transmitted
to others
• Pathogen –
microorganisms that
cause disease
Pathogens cause disease by:
• Enter host body
(mouth, open
wounds ,eyes)
• Adhere to specific
host cells
• Invade/colonize host
tissues
• Inflict damage to
tissues
5 agents of infectious disease
•
•
•
•
•
Viruses
Fungi
Bacteria
Protists
worms
2 Categories of infectious disease
• Emerging infectious disease
• Re-emerging infectious disease
Emerging infectious disease
• Have not occurred in humans before
• Have occurred in humans before, but
affected only small numbers of people
in isolated place (AIDS, Ebola)
• Due to environmental changes
Re-emerging infectious disease
• Once were a major health problem,
then declined dramatically …
• Again becoming health problems
(malaria, tuberculosis)
• Due to drug resistance, lack of
vaccination
Emerging
Re-emerging
Endemic
Flu Pandemics: 1918 Spanish Flu
• Killed up to 50 million
people worldwide
• Killed more Americans
than all the wars this
century combined
The Bird Flu (H5N1): Could this virus cause
the next pandemic?
•Highly pathogenic
•Since 2003 this the “bird flu” virus has caused
172 deaths worldwide.
•Humans that contracted the virus were in close
contact with infected birds.
Viruses
• Characteristics of Viruses
•
- is it alive?
•
- not cells
•
- parasites
•
- replicate themselves
•
- found everywhere
•
- DNA or RNA inside
•
- protein coat- capsid
•
- specific- species and cells
Classification of Viruses : A. Shape
• ROD Shaped
• Ex. Tobacco Mosaic
Virus
2. Spherical (bullet shaped)
• Ex. Rabies
Spherical:
• Influenza
3. Polyhedral
• Ex. Adeno virus
• Causes respiratory
illnesses, pink eye,
digestive illnesses
4. Bacteriophage
• A virus with a tail
• Affect bacteria
- B. Classified by their Vector
• - organism that carries virus
C. Classified by the disease it causes
• Ex. Rhinovirus –
group of viruses that
cause the common
cold.
Ex. Smallpox
• No longer a threat
due to vaccination
by Edward Jenner
Ex. Chicken pox
Ex. Warts - human papilloma virus
(HPV
Ex. Cold sores: herpes simplex virus,
Ex. Polio
Viruses and Disease
• - Table 21-1
• Immunity – white blood cells and your bodies
antibodies. There is no cure for a virus
• Vaccines – inject inactive virus to produce
antibodies.
White blood cells in action - Phagocyctes
- Interferon
• - inhibits virus replication
• - body produces when attacked
Viral Replication
• 100 new viruses
every minute
• Two cycles of
replication:
– 1. Lytic Cyclehost cell is
killed.
Stages of Lytic Cycle
• 1. Attachment –
• 2. Entry – Virus injects
its DNA or RNA into the
cell
• 3. Formation – viral
DNA or RNA replicates
• 4.Lysis and release –
cell bursts and releases
newly formed viral cells.
Stages of Lysogenic cycle
• Attachment –
• Prophage
formation - the viral
DNA or RNA
becomes part of the
cells DNA.
• Cell division –
make copies of the
recombined DNA
Bacteria
Archaebacteria
Eubacteria
Characteristics
• - unicellular- colonies or filaments
salmonella
E.coli
- prokaryotes
- Plasmid
• - circle of DNA
• - rigid cell wall and capsule
• - Pili- attachment hairs
• - Flagella- long hairs for locomotion
• - 3.5 billion years old
Life of a Bacterium
• - found everywhere
- reproduce rapidly
- live in extreme conditions
• - mutate quickly
• - reproduce by Binary Fission- cell
divides in half
- some don't need oxygen (Botulism)
• - Pathogenic
• - harmful to man
• Water treatment
vs
Friendly
- useful to man
Four groups of
Bacteria –
consumer types
chemosynthetic
photosynthetic
Heterotrophic bacteria
• - common bacteria
• - Bacillus- rod-shaped bacteria- tuberculosis
- Coccus
• - round bacteria- strep throat
- Spirillum
• - spiral bacteria- syphilis
- Metabolize host
- Toxins
• - poisonous secretions into host
•
- Ex. tetanus, anthrax, pneumonia
Chemoautotrophic bacteria
• - nitrifying bacteria
•
- convert nitrogen to plants in soil
Photosynthetic bacteria
• - blue-green color
• - contain chlorophyll
• - autotrophs- makes own food and 02
Gleocapsa
• Colony type
• Gel sheath
Oscillatoria
• Filament
• Moves in a wave like
manner
Lyngbya
• Filament
• Notice in a gel
sheath
Notoc
•
- blooms cause CO2 loss in water
- antibiotics
• - penicillin, ampicillin, omoxycillin, tetra
cycline
- immune system
• - white blood cells