Download Bacteria and Viruses

Viruses
A
virus is not a cell. It lives only
within a living cell and has no
attributes of a living organism.
 It is an obligate intracellular parasite.
Viruses
Review!
What
does
obligate
 A virus
is not
a cell. Itmean?
lives only
Capable
functioning
within
a livingof
cell
and has no or
attributes
of a living
surviving
only organism.
in a particular
 It is
an obligate intracellular parasite.
condition
What is a parasite?
Organism that lives and
derives nourishment at the
detriment of the host
What is an obligate parasite?
Viruses
 It
is made up of DNA or RNA inside
a protein coat called a capsid.
RNA
Virus
 Some
take lipids from the cell it infects
and make a covering over the capsid
that has glycoprotein receptors.
 Receptors are used to attach to the
host’s membrane.
RNA
Virus Structure
Viruses
A
virus is not a cell
 It is made up of genetic material inside
a protein coat
 Viruses
do not
carry on
most
metabolic
activities
Viruses
 Viruses
that attack
only bacteria are
known as
bacteriophages.
Virus Reproduction – Lytic Cycle
Multiplication of
Bacteriophages (Lytic Cycle)

Attachment

Penetration

Biosynthesis


Maturation
Release
Phage attaches by tail fibers to
host cell
Phage lysozyme opens cell wall,
tail sheath contracts to force tail
core and DNA into cell
Production of phage DNA
and proteins
Assembly of phage particles
Phage lysozyme breaks cell wall
Virus Reproduction – Lysogenic Cycle
Lytic or Lysogenic Cycle?
The animation on
the next slide
demonstrates which
cycle?
Lytic vs Lysogenic
 Lytic
cycle
– Phage causes lysis and death of
host cell
 Lysogenic
cycle
– Prophage DNA incorporated in
host DNA
Virus Classification
Smallpox

Although smallpox was
declared extinct in the
wild in 1979 (last natural
infection recorded in
1977) there is increasing
concern about its potential
use as a biological
weapon. Although only
two locations officially
hold variola (one at the
CDC in the USA and one in
Russia) it is feared that
secret stockpiles exist.
Smallpox
 CLASSIFICATION
OF THE SMALLPOX
VIRUS
 GENOME: Linear Double Stranded
DNA
 Family: Poxviridae
 Subfamily: Chordopoxvirinae
 Genus: Orthopoxvirus
 Species: Variola
Prions and Viroids
Bits and Pieces that cause
disease
Viroids
Small,
circular
RNA molecules
without a protein
coat
Infect plants
Potato famine in
Ireland
Resemble introns
cut out of
eukaryotic
copyright cmassengale
18
Prions
Prions
are “infectious
proteins”
 They are normal body
proteins that get
converted into an alternate
configuration by contact
with other prion proteins
 They have no DNA or
RNA
The main protein involved
in human and mammalian
prion diseases is called
“PrP”
copyright cmassengale
19
Prion Diseases
Prions
form insoluble
deposits in the brain
Causes neurons to
rapidly degenerate.
Mad cow disease
(bovine spongiform
encephalitis: BSE) is an
example
People in New Guinea
used to suffer from
kuru, which they got
from eating the brains
of their enemies
copyright cmassengale
20
Virus Reproduction
Negative Virus Influences
 They
cause infections in both
plants and animals
 Some viruses cause tumors and warts
 They also destroy cells and are
responsible for human diseases such as
– polio
– measles
– mumps
– influenza
– hepatitis
– colds
– AIDS
Human Papilloma Virus - Warts
Rabies Virus
Influenza Virus - Flu
Human Immunodeficiency Virus
AIDS
Positive Virus Influences
 Certain
viruses are
used in the control
of insect pests
 Others are used in
genetic research
 Scientists have been
able to use viruses to
biologically control
caterpillars of the
European pine sawfly and
the gypsy moth