Transcript Virus and bacteria ppt

Viruses,
Bacteria &
Diseases
Viruses
Viruses are NOT cells. A virus is an infectious
agent made up of:
•a core of nucleic acid (RNA or DNA)
•a protein coat (capsid)
•Genetic material carries information for
multiplication
•Hijacks biochemical machinery of host
cell to carry these processes out
•So…viruses are NOT LIVING
Characteristics
of life
CELL
VIRUS
Made of cells
YES
NO
Obtain & use
energy
YES
NO
Grow & develop
YES
Reproduce
YES
Respond &
adapt
Contain RNA or
DNA
Only inside a
living cell
Only inside a
living cell
YES
YES
YES
YES
Re-Cap
Viruses are NOT ALIVE. Viruses
do not:
•Grow
•Have homeostasis
•Metabolize
Viruses do:
•Infect cells and use the cell to make more viruses
•Cause disease in many organisms
Structure
of a virus
ENVELOPE
• Envelope (part of
the protein coat)
• Capsid (part of
the protein coat)
• Nucleic acid
(either DNA or
NUCLEIC
RNA)
ACID
CAPSID
Retrovirus
ENVELOPE
• A virus that
contains RNA
instead of DNA
• Human
RNA
Immunodeficiency
Virus (HIV) is a
retrovirus
• HIV causes AIDS
CAPSID
Bacteriophage
• A virus that
only infects
bacteria
CAPSID
HEAD
DNA
CAPSID
TAIL
FIBER
Ticking time
bombs . . .
Viruses do not reproduce by
themselves. They invade a
living cell and let the cell do
the work for them.
Lytic Cycle
The viral infection that
rapidly kills the host cell is
the lytic cycle.
Cycle Illustration
1
2
4
3
5
Lysogenic Cycle
The viral infection that enters
a cell, remains harmless for a
period of time (sometimes
years), and then becomes
harmful later is called the
lysogenic cycle.
Lysogenic
Cycle
In the lysogenic
cycle, the virus
reproduces by
first injecting its
genetic material,
indicated by the
red line, into the
host cell's genetic
instructions.
Role of viruses
• All viruses act like parasites, harming
the host cell.
• Viruses cause disease in every kind of
organism—animals, plants, fungi,
protists, and bacteria.
Some viral diseases
•
•
•
•
•
HIV
Measles
Smallpox
Influenza
Chicken pox
•
•
•
•
•
Common cold
Herpes
Warts
Mononucleosis
Mumps
HIV
• A retrovirus
• Infects human helper T-cells, which are
associated with the immune system.
• Modes of transmission:
–
–
–
–
–
Sexual contact with an infected person
Sharing needles with an infected person
Blood transfusions (rare)
Breast feeding
Etc.
HPV
•
•
•
•
Human Papilloma Virus
Causes warts
Most common STD in the United States
80% of women by the age of 50 will
have acquired some strain of genital
HPV.
• HPV vaccine
Influenza (flu)
• Symptoms: body aches, fever, coughing,
runny nose, fatigue, usually lasting about
a week.
• Mode of transmission
– Airborne (air droplets)
People still die from influenza.
Viral diseases
usually cannot be cured,
but many can be prevented
by
•Good hygiene
•Immunization
Bacteria
Bacteria are
Prokaryotes.
Prokaryotic Cells:
• Have no nucleus
• Do not have membrane
bound organelles
• Are very small
• Often have a flagellum
for movement
Shapes of bacteria
Bacteria are classified according to their
shape:
• Round is called cocci
• Rod shaped is called bacilla
• Spiral shaped is called spirilla
Where do they live?
• Bacteria are found in
all environments
Role of bacteria
• Some bacteria are helpful
–
–
–
–
E. coli
Yeast
V.streptococci
Lactobacillus
• Some bacteria are harmful
–
–
–
–
E. coli
S. pyogenes
S. aureus
Y. pestis
Streptococcus
• Causes strep throat, pneumonia, and
other infections.
• Named based on the shape and
orientation of the bacteria.
Staphylococcus
• Cause of staph infections that occur on
the skin or in wounds. (ex. MRSA)
• But, Certain types of staph reside
normally on the skin.
Diphtheria
• Swelling of the upper respiratory tract
• DPT Vaccine
• Can also infect skin cells.
• How do bacteria cause
disease?
–The release toxins that
interfere with normal
activity.
Prevention/Cure
• Vaccines to prevent.
• Antibiotics to cure (pennicillin,
amoxycillin, etc).