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Viruses
• Viruses are nucleic acids
(DNA/RNA) wrapped in
protein
• Typically the protein coat, or
capsid, of an individual virus
particle, or virion, is composed
of multiple copies of one or
several types of protein
subunits, or capsomeres. Some
viruses contain enzymes, and
some have an outer
membranous envelope. Many
viruses have striking
geometrically regular shapes
Virus Shapes
3 main shapes:
• Icosohedron/polyhedron: 20 triangular
sections (HIV)
• Spiral: RNA surrounded by capsomere
proteins
• Bacteriophage: spaceship
• Others (ebola)
Types of Viruses
• Viruses depend on the
host cells that they
infect to reproduce.
When found outside of
host cells, viruses exist
as a protein coat or
capsid, sometimes
enclosed within a
membrane. The capsid
encloses either DNA
or RNA which codes
for the virus elements.
Sizes of Viruses
Nucleic Acid
Plus/Minus strand designation mRNA = +polarity
mRNA
+DNA
-DNA
+RNA
-RNA
5’ GAC UCG AGC 3’
5’ GAC TCG AGC 3’
5’ CTG AGC TCG 3’
5’ GAC UCG AGC 3’ (operates like mRNA)
5’ CUG AGC UCG 3’ (euk. cells don’t have enz)
ssDNA(+)-DNA+mRNA
Retrovirus= RNAdsDNA using reverse transcriptase
Reverse transcription of retroviruses
Reverse Transcriptase 2
Classification of Viruses (reference)
Exceptions
• Viroids circular ssRNA
material, infectious to plants,
escaped introns???
• Prions proteinaceous
infectious particles, no n.a.
Against dogma of molecular
biology
Scrapie (sheep), kuru (Papau New
Guinea), bovine spongiform
encephalitis (Mad Cow Disease), and
Creutzfeldt-Jakob disease.
Harmful Viruses
• Viruses are notorious for
the plethora of diseases
they cause, including
influenza, rabies, AIDS,
polio, herpes, ebola,
measles, mumps, chicken
pox, warts, small pox -->
Lewandowsky-Lutz/ 2
Epidermodysplasia verruciformis,
herpes
Warts
Helpful Viruses
• Viruses carry out natural "genetic
engineering": by incorporating
genetic material into its host
• This is known as transduction, and
in some cases it may serve as a
means of evolutionary change
• Certain varieties of flowers have
been developed using viruses to
alter the genetic code.
• Dr Patrick Lee uses reovirus to kill
brain cancer cells transplanted into
laboratory mice, while sparing
normal, healthy cells. Clinical trials
involving reovirus in people are
now underway.
• Virus Rap
Helpful Viruses
• A good virus
• Most of us go out of our way to avoid viruses. But
Dr Patrick Lee - formerly of the University of
Calgary and now at Dalhousie University - spends a
lot of time in the company of a very common virus
known as a reovirus. Normally this bug causes
nothing more serious than a mild infection. But Dr
Lee’s team discovered that the reovirus has the
ability to kill brain cancer cells transplanted into
laboratory mice, while sparing normal, healthy
cells. Clinical trials involving reovirus in people are
now underway.
How do they get in?
• Lambda phage Replication
• Replication of a Positive (+) Sense Strand of
Lytic RNA Phage
• T4 Replication
• Entry into Animal Cell
• Release of Enveloped Viruses
• Replication of Retrovirus
• Influenza
Essential knowledge 3.C.3: Viral replication results in
genetic variation, and viral infection can introduce
genetic variation into the hosts.
b. The reproductive cycles of viruses facilitate transfer of
genetic information.
1. Viruses transmit DNA or RNA when they infect a host cell.
• Transduction in bacteria (Specialized Transduction)
• Transposons present in incoming DNA
2. Some viruses are able to integrate into the host DNA and establish
a latent (lysogenic) infection. These latent viral genomes can result
in new properties for the host such as increased pathogenicity in
bacteria.
LO 3.29 The student is able to construct an explanation of
how viruses introduce genetic variation in host organisms.
Lysogenic Cycle
• When it comes into contact
with a host cell, a virus can
insert its genetic material into
its host, literally taking over the
host's functions. An infected
cell produces more viral protein
and genetic material instead of
its usual products. Some viruses
may remain dormant inside host
cells for long periods, causing
no obvious change in their host
cells (a stage known as the
lysogenic phase).
Lytic Cycle
• when a dormant virus is
stimulated, it enters the lytic
phase: new viruses are formed,
self-assemble, and burst out of the
host cell, killing the cell and going
on to infect other cells
• Attachmententryreplication
assemblylysis & release
• 1, 2, 3
Essential knowledge 3.C.3: Viral replication results in
genetic variation, and viral infection can introduce
genetic variation into the hosts.
a. Viral replication differs from other reproductive strategies and generates genetic
variation via various mechanisms.
1. Viruses have highly efficient replicative capabilities that allow for rapid evolution
and acquisition of new phenotypes. Viral Recombination , 1918 Spanish Flu, 2, 3
2. Viruses replicate via a component assembly model allowing one virus to produce
many progeny simultaneously via the lytic cycle.
3. Virus replication allows for mutations to occur through usual host pathways.
4. RNA viruses lack replication error-checking mechanisms, and thus have higher rates
of mutation.
5. Related viruses can combine/recombine information if they infect the same host cell.
(Antigenic Shift)
6. HIV is a well-studied system where the rapid evolution of a virus within the host
contributes to the pathogenicity of viral infection.
Life Cycle of HIV
HIV Replication
HIV Life Cycle 2
Future of HIV
LO 3.30 The student is able to use representations and appropriate models to
describe how viral replication introduces genetic variation in the viral
population.
Vaccines
• Constructing a Vaccine
•
•
•
•
Engineering the Avian Flu
1918 Flu
Malarial Vaccine
Virus Rap
Lysogenic Cycle vs Lytic Cycle
• Attachmententryreplicationassemblylysis & release
Eubacteria “true bacteria”
• Typical “monerans” found
where humans live
• Evolution of the 3 Domains
Archaea “archaic/old”
extremophiles
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Methanogens
Thermophiles
Acidophiles
Halophiles
Alkaliphiles
Psychrophiles
Xerophiles
Barophiles
• Archae vs Bacteria
Bacteria Characteristics
• Bacteria are
distinguished from
other living things
because of their
cell structure:
• All bacterial cells
have a cell wall
surrounding a cell
membrane, inside
of which lies the
unbound nuclear
matter and other
material.
• Bacteria have
extra genomic
DNA that is
round and called
a “plasmid”
• Plasmid
Cloning
Bacteria: Classified by Shape
• There are three types of bacterial cells, based on
shape: spherical (coccus), rodlike (bacillus), and
spiral (spirillum).
• Some bacteria have flagella for locomotion and
some have pili to transfer DNA (conjugation)
and to stick to substrates of host cells
Bacterial Chemotaxis
Harmful Bacteria
• A number of bacteria
cause disease, these
are called pathogenic
bacteria.
• They can cause
diseases of plants,
animals, fungi,
protists and other
bacteria
• E. coli infection
• Salmonella infection
• Some bacterial
diseases include: strep
throat, scarlet fever,
toxic shock syndrome,
pneumonia, ear
infections, gonorrhea,
syphilis, Tuberculosis
• Bacteria can also be
used by some
countries to harm
other countries in an
act called bioterrorism
Eczema w/ 2o infection
Helpful Bacteria
• actinomycetes,
produce antibiotics
such as streptomycin
and nocardicin
Symbiotic bacteria assist in digestion
• live symbiotically in
the guts of animals
• put the tang in
yogurt and the sour
in sourdough bread,
cheese = spoiled
milk
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Bacteria are useful in making
antibiotics and in biotechnology.
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• Nitrogen Fixation roots of
certain plants, converting nitrogen
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Producers in Geothermal Vents
Reproduction
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Bacteria reproduce asexually by binary fission
Bacterial Conjugation (lateral/horizontal gene exchange)
Bacterial Transformation (lateral/horizontal gene exchange)
Bacteria life cycle
BB Checkpoint
BB#1SB1a. Explain the role of cell organelles for
both prokaryotic and eukaryotic cells, including the cell
membrane, in maintaining homeostasis and cell
reproduction.
BB#8  SB2e. Compare the advantages of sexual
reproduction and asexual reproduction in different
situations
BB#10  SB3b. Compare how structures and function
vary between the six groups (archaebacteria, eubacteria,
protists, fungi, plants, and animals).
Kingdom Protista
• All protists are eukaryotes.
This means that their cells
contain a nucleus, a
membrane-bounded
structure that encloses the
cell's genetic material.
• Some protists are
autotrophs like plants,
others are consumers like
animals. Unlike plants and
animals, however, protists
do not have cells organized
into specialized tissues.
Protista Classified by Nutrition
• The first detailed descriptions of
protists were made in 1676 by the
inventor of the microscope, Dutch
naturalist Leewenhoek.
• The classification is currently based
on the structure and organization of
the cell, the presence of organelles,
and the pattern of reproduction or life
cycles. The five-kingdom system
divides the Protista into 27 phyla.
However, classifications based on
DNA sequences suggest that many
protist phyla may be sufficiently large
and diverse to be classified as
kingdoms.
•
Gallimaufry, cornucopia, hodge-podge,
potpourri
• Auto trophic Protists are called
“Algae”. Scientists believe they
gave rise to the kingdome Plantae
• Ingestive Heterotrophic protists
are called “Proto zoa”.
Scientists believe they gave rise
to the kingdom Animalia
• Absorptive heterotrophic protists
are called “Slimemolds”.
Scientists believe they gave rise
to the kingdom Fungi
• Protist Rap
Harmful Protists
• Produce a nerve poison in
shellfish that kills humans
and fish in red tide
• Cause diseases: Chaga’s disease,
Malaria, 2, Lyme disease,
diarrhea, toxoplasmosis,
dysentary, Trypanosomaisis, 2,
Leishmaniasis, 2, Toxoplasma,
Cryptospiridium, Leishmaniasis,
Brain Amoeba
• Cause mold and mildew
which can spoil food and
cause allergic reactions
• Cause algal blooms which
can result in eutrophication
Beneficial Protists
• Used as insect pathogens
• Used in ice cream, soups, nori
(seaweed in sushi), jello, agar, vitamin
supplements, or eaten as a sea
vegetable
• Ancient dinoflagellates formed oil
deposits
• Bioluminescent
• Diatoms mined for fine abrasives in
silver polish and toothpaste and as
packing in air and water filters
• Marine phytoplankton make up ~70%
of the oxygen on the planet
• Forensic uses: Diatom Detectives
• Algae for Biofuel
BB Checkpoint
BB#9SB3a. Explain the cycling of energy
through the processes of photosynthesis and
respiration.
BB#10  SB3b. Compare how structures and
function vary between the six groups
(archaebacteria, eubacteria, protists, fungi,
plants, and animals).
Fungi: Multicellular absorptive
heterotrophs
• Though they grow in soil
like plants, they are not
autotrophic.
• The have cell walls made
of the polysaccharide
chitin
• What are the cell walls of plants
made of? Bacteria?
Fungi Anatomy
Hyphae basic
structural unit of a
fungus made up of
branching filaments
Mycelium tangled
network of fibers
Fruiting body
reproductive structure. In
Phylum Basidiomycota it
is the mushroom itself
Fungi: Classified by Reproduction
Division Zygomycota form
zygospores i.e. Rhizopus (bread mold)
Division Ascomycota form
ascospores i.e. yeast, morels, ergot,
Dutch elm disease
Division Basidiomycota
Most commonly known, forms
basidiospores i.e. shelf fungi,
mushrooms
Division Deuteromycota/
Imperfecti sexual reproduction
unknown i.e. Penicillium, Aspergillus
Fungi Life Cycle
Harmful Fungi
• Many fungi are parasitic
and cause diseases like
ringworm, athletes foot,
• Can rot and contaminate
foods
• Can destroy almost every
type of product or food
aside from some plastics
• Black Mold in Buildings
• Building a House: Recipe
for Disaster
• Lungus Fungus
Beneficial Fungi
• People eat mushrooms, truffles and
other fungi, citric acid in Coke
• Fungi are decomposers like bacteria
and help to recycle organic matter to
inorganic = saprophytic
• Yeasts are used in making bread,
wine, beer, solvents, cheese.
• Drugs made from fungi cure diseases
and stop the rejection of transplanted
hearts and other organs.
• Fungi are also grown in large vats to
produce flavorings for cooking,
vitamins and enzymes for removing
stains.
• Beneficial Protists & Fungi
Fungi Engage in
Symbiosis
• Parasitic +/-: Mind control
• Mutualistic +/+: Lichens,
a pioneer organism, a fungus
and algae living together
• The mycorrhizal fungi live as
partners with plants, helping
them absorb nutrients
• Predatory +/-:
Arthrobotrys, a deuteromycete
BB Checkpoint
BB#9SB3a. Explain the cycling of energy
through the processes of photosynthesis and
respiration.
BB#10  SB3b. Compare how structures and
function vary between the six groups
(archaebacteria, eubacteria, protists, fungi,
plants, and animals).
Resources
Virus Links
•
Virus Pictures:
•
Virus Review:
•
Exploring Life:
•
Big Picture Book of Viruses:
•
AIDS Online:
•
Replication of Herpes Animation:
•
Influenza Entry Animation:
•
Antigenic Shift Animation
•
Immuno- biology Animations
•
Biological Diversity
Protists
• Protist Kingdom:
• Phylogenetic Tree:
• Protozoa Bio 4 Kids:
• Microbe Zoo, Dirtland:
Bacteria Links
• Bioterrorism:
• Bacterial Cell Walls:
• 10 Ways a World Will End: Monster Plague
• Discovery of the Germ Theory
• Antibiotics Tutorial
• Anti-antibiotics/Efflux Pump
• Immunology Primer
• When Worlds Collide, Macro vs. Micro
• Immuno- biology Animations
Fungi Links
• Fungi Chapter 30
• Tom Volk’s Fungi
Virus Links
Virus Pictures:
Virus Review:
Exploring Life:
Big Picture Book of Viruses:
AIDS Online:
Replication of Herpes Animation:
Influenza Entry Animation:
Antigenic Shift Animation
Immuno- biology Animations
Chapter 6 Viruses
Introduction to Plasmids & Viruses
Bozeman Viral Replication
Super Flu: Antigenic shift in influenza