Download Bacteria and Viruses

Viruses and Bacteria
What is a Virus?
• A virus is a noncellular
particle made up of genetic
material and protein that can
invade living cells
• Structure
– Core of nucleic acid
surrounded by a protein coat
called a capsid
– Capsid can be DNA or RNA,
but not both
– Core can be several to several
hundred genes
SO HOW BIG ARE
VIRUSES???
• Viruses are
REALLY small.
• They are much
smaller than
bacteria.
• They can only be
seen with an
electron
microscope.
Bacteriophage
• Bacteriophages are viruses
that infect bacteria
• Bacteriophage
– Head – capsid and DNA
– Tail – with fibers to attach to
bacteria
VIRUS SHAPES
• Round
• Rod-shaped
• Many sided
(icosohedral)
ROUND VIRUSES
• Herpes
virus
–There
are two
types:
• Genital
• oral
ROD-SHAPED
• Tobacc
o
mosaic
virus
Why viruses infect us?
All viruses are parasites.
Parasites depend entirely
upon other living organisms
for their existence, harming
these organisms in the
process.
• Viruses take advantage of
the nutrients and cellular
machinery of their hosts.
Viruses Living ??
• Viruses have many of the
characteristics of living
things.
– After infecting living cells,
viruses can reproduce,
regulate gene expression,
and even evolve.
Virus Specificity
• Specificity – usually infect
specific organisms
– Cannot infect animals if it infects
plants
– Some can infect wider variety
– Rabies – all mammals, some
birds
VIRUSES ARE
SPECIFIC IN THE
CELLS THEY INFECT
Tobacco mosaic virus: only
tobacco plants…not wheat or
corn
Rabies: only nervous system cells of
mammals
Common cold: infects cells on
airway passage to lungs
Lytic Infection
Lytic infection:
• virus nucleic acid
enters a bacterial cell
• makes copies of itself
• causes the cell to
burst or lyse.
Lytic Cycle
Section
19-3
Bacteriopha
ge protein
coat
Bacteriophage DNA
Bacterial
chromoso
me
Bacteriophage attaches
to bacterium’s cell wall
Bacteriophage enzyme lyses the
bacterium’s cell wall, releasing
new bacteriophage particles that
can attack other cells.
Lytic
Cycle
Bacteriophage
injects DNA into
bacterium
Bacteriophage
proteins and
nucleic acids
assemble into
complete
bacteriophage
particles
Bacteriophage
Bacteriophage takes
over bacterium’s
metabolism, causing
synthesis of new
bacteriophage proteins
and nucleic acids
Bacteriophage
DNA
Bacteriophage
protein
Lysogenic Cycle
• viral nucleic acid is inserted
into host cell’s DNA
• copied along with host DNA
without damaging host.
• Viral DNA multiplies as host
cells multiply so each
• generation of daughter cells
is infected.
Lysogenic Cycle
Retroviruses
• RNA viruses
• When they infect a cell, they
produce DNA copies of their RNA
genes.
• Retroviruses have their genetic
information copied backwards.
RNA  DNA
• One Ex of a retrovirus is HIV.
Others cause cancer in animals
and humans.
• The theory is that viruses were not
the first living things. They are
dependent on living things to
survive.
The two bacterial
kingdoms
EUBACTERIA &
ARCHAEBACTERIA
Bacteria on a pin head
PROKARYOTIC
CELLS
Classification of Prokaryotes
lacking a nucleus
• All prokaryotes were in
kingdom Monera.
• Now – 2 kingdoms
– Eubacteria
– Archaebacteria
Eubacteria
• “True” bacteria
• largest Kindgom of
prokaryotes
• generally surrounded by cell
wall composed of complex
carbohydrates
• have a cell membrane (some
have 2 cell membranes)
• Some have flagella for
movement
• Found everywhere
• Some produce disease
• Some photosynthetic
• some very useful – cheese is
just one example
Archaebacteria
• Archaebacteria includes
organisms that live in very
harsh environments
• Methanogens – live in oxygen
free environments – mud,
digestive tracts of animals
• Extremely salty environments
• Hot springs
Identifying Bacteria
• Cell Shape
– Rod – bacilli
– Sphere – cocci
– Spiral – spirilla
Bacterial Shapes
Round
Ro
d
Spiral
Arrangement
• 2 cocci – diplococci
• long chains – streptococci
• clumps, clusters –
staphylococci
Cell Wall
• Chemical nature – Gram staining
• Hans Christian Gram
• 2 dyes – crystal violet (purple) and
safranine (red)
– bacteria either take one or the other
– If only one thick layer of carbohydrate
and protein molecules outside the cell
membrane – picked up crystal violet –
appeared purple – GRAM POSITIVE
– If cell had 2nd, outer layer of lipid and
carbohydrate – picked up safranine –
appeared red GRAM NEGATIVE
Bacterial movement
• propelled by flagella
• lash, snake, or spiral forward
• no movement
Bacterial Respiration
• Obligate aerobes – require
oxygen
• Obligate anaerobes – must live
in absence of oxygen
– example is Clostridium
botulinum
• Facultative anaerobes – can
live with or without oxygen
Reproduction
• Some can reproduce every 20 minutes
• Held in check by food and production of
wastes
Types:
• Binary Fission
• Replication of DNA and division in half
• Asexual
• Conjugation
• Sexual – involves the exchange of
genetic material
• Long bridge of protein forms between the
cells
• Donor genetic information transferred to
recipient through bridge
• Recipient cell has different genes at the
end than it did to begin with
Importance of Bacteria
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Used in production of products we use every day
Yogurt
Cheese
Buttermilk
Sour cream
Pickles
Sauerkraut
Vinegar
Wine
Industry
digest petroleum
remove wastes and poisons from water
synthesizing drugs – through genetic engineering
Symbiotic Relationships
(mutuallism)
• E. coli in humans – help us
digest food – make vitamins
we can’t, we give them a
home, food, and transportation
• Bacteria in the intestines of
cattle allow them to break
down cellulose (in grass and
hay)
Bacteria in the
Environment
• Bacteria are like the stage
hands that allow the show to
go on without being seen (or
always given the credit)
• Bacteria recycle and
decompose dead material
• Saprophytes – organisms that
use the complex molecules of
a once living organism as their
food source
Sewage decomposition
• Sewage treatment – bacteria is
added directly to the raw
sewage
• How does a septic tank work?
Nitrogen Fixation
• All organisms are TOTALLY
dependent on monerans for
Nitrogen
• All Plants need nitrogen to make
amino acids (-NH2)
• Because animals eat plants, they
get their proteins from plants
• What percentage of the air is
Nitrogen?
• Plants, and most other organisms
cannot use this directly
• Need Nitrogen to be “FIXED”
chemically as ammonia
Nitrogen Fixation
• Scientists can make synthetic nitrogen
containing fertilizers by mixing Nitrogen
and Hydrogen gases, heating to 500
degrees C and compressing it to 300 X
normal atmospheric pressure –
dangerous, expensive, time consuming
• Many cyanobacteria can take nitrogen
from the air and convert it to a useable
form – this is called Nitrogen Fixation
• Bacteria are the only organisms that can
do this.
• Some plants have a symbiotic
relationship with nitrogen fixing bacteria
• soybean – Rhizobium grows in nodules
around roots
Diseases caused by Viruses and
Monerans
• only a small number of viruses
and bacteria can cause
disease
• Pathogens – organisms that
cause disease
• All viruses infect living cells
• Disease occurs when infection
causes damage to the cells
Viruses and Disease
• Examples are:
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Small Pox
Polio
Measles
AIDS
Mumps
Influenza
Yellow Fever
Rabies
Common Cold
Ebola etc…
Vaccine
• The body’s own defenses must
be used
• Vaccine – dead or weakened
viruses that stimulate the
bodies defense system
• Symptoms can be treated
sometimes, but once someone
is infected by a virus, there is
not much science can do
Bacteria and Disease
• Bacterial diseases include:
– Diptheria
– TB
– Typhoid
– Tetnus
– Hansen disease
– syphilis
– cholera
– bubonic plague
– Flesh Eating Bacteria
2 ways bacteria cause
disease
1. Damage cells and tissues of
infected organisms directly by
breaking down cells
2. Releasing toxins (poisons)
• Many bacteria can live without a
host organism (on a petri dish)
• Rickettsiae cannot live outside a
host cell. They have leaky cell
walls
• Rickettsiae cause Rocky Mountain
Spotted Fever, typhus, and
Legionnaire’s disease
• Measures to fight bacterial
infection include:
– Antibiotics – drugs and natural
compounds that attack and
destroy bacteria in the body
– NOT Effective against viruses