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INVADERS
Chapter 24: Viruses
Objectives:
• Summarize the discovery of viruses
• Describe why viruses are not considered
living organisms
• Describe the basic structure of viruses
• Compare the lytic and lysogenic cycles of
virus replication
• Summarize the origin of viruses
Virus
nonliving particle that can infect
both prokaryotic and eukaryotic
cells
Virus Structure-vary in shape and size
All viruses contain two main parts:
1)
Nucleic Acid (Genome) – Either DNA or RNA
2)
Capsid – protein coat or lipid protein coat (many different shapes)
–
–
–
Helical – Tobacco Mosaic Virus (TMV), Rabies, measles
Icosohedreon – Adenovirus, Herpes Simplex, Chicken Pox, Polio
Spherical – Influenza Virus
Envelope – bilipid membrane that surrounds the capsid (only
some viruses)
3)
–
–
Formed from nuclear membrane or cell membrane as it leave the
host cell
Proteins in the envelope helps new viruses recognize host cell.
Examples: Influenza, chicken pox (varicola), HIV
Function of Viruses
1) Cause Disease by infecting the host cell
2) Used in Genetic Research and
biotechnology
Characteristics of Viruses
Virus are nonliving!
– Are not made of cells
– Do not have organelles or cytoplasm
– Can’t carry out metabolic processes such as
metabolism and homeostasis
– Do not grow through Cell Division
– Can’t reproduce outside their host cell
(Need host cells structures to reproduce)
Wendell Stanley was the first scientist to crystallize a virus. This is
evidence that viruses are not made of cells and are not alive.
Classification of Viruses
A. Genetic Material:
1) RNA or DNA
2) Single Stranded or Double Stranded
3) Linear or Circular Genetic Information
B. Capsid:
1)Shape
2)Presence or absence of an envelope
Example: SARS – RNA, Single Stranded, Linear,
lollipop-shaped capsid and enveloped (chart pg485)
Classification cont.
- Different viruses infect bacteria, plant and animal hosts
- due to receptor site forming to specific proteins on cell
wall or membrane
Bacteriophages – viruses that infect bacteria
How do Viruses Spread
•
•
•
•
Air
Water
Food
Bodily Fluids
Obligate intracellular parasites
(Viruses)
Viruses replicate only by using the host cells
enzymes and organelles to make more
viruses. Protein synthesis is controlled by the viral
genome and the host cell becomes a virus making
factory.
Protein Synthesis review
1) Transcription:
DNA -> mRNA
2) Translation: mRNA -> proteins
Replication in DNA viruses
Two methods:
1) vDNA->mRNA –> make new viruses (in
cytoplasm)
2) DNA – Provirus – (Gets incorporated into
Host Cell’s DNA) – Makes new viruses
Replication in DNA Viruses
Method 1
1. Virus enters the host cells cytoplasm and takes
control of the host cells protein synthesis
pathway
2. Enzymes transcribe mRNA from the viral DNA
3. Host ribosomes translate Viral mRNA into viral
proteins and enzymes replicate the viral DNA
4. New viral particles are assembled (Capsids and
nucleic acids)
Replication in DNA Viruses
Method 2
1) Viral DNA is injected into the host cell
2) Viral DNA moves into the nucleus and
becomes incorporated into the host cells
DNA as a provirus
3) Virus takes over the cell and makes
newe viruses as a provirus
Replication in RNA viruses
RNA Viruses
RNA
1) The vRNA serves right away as mRNA and
then is translated into proteins (New Viruses)
2) Viral RNA is transcribed into mRNA and then
is translated into proteins and new viruses
Retro RNA Viruses
Contain Reverse Transcriptase which uses RNA
as a template to create DNA, which is then
inserted into the host cells DNA
Lytic Cycle vs. Lysogenic Cycle
Reproduction of viruses
Lytic Cycle: Reproduction of Virulent Virus
•
Destroy the cell they infect
Stages:
1) Adsorption
2) Penetration
3) Replication
4) Maturation (Assembly)
5) Release
Lysogenic Cycle: Reproduction of Temperate Virus
•
Lays dormant in the host cell before it destroys it
•
When triggered will go into the lytic cycle
Lytic Cycle –
followed when virus is virulent (active)
1. ADSORPTION- virus particle attaches
to a host cell.
2. ENTRY
The particle injects its genetic
instructions (DNA or RNA) into the host
Injected genetic material ‘hi-jacks’ the
cell’s machinery and recruits the host’s
enzymes.
3. REPLICATION
Enzymes make parts for the new virus
particles
4. ASSEMBLY -new particles assemble the
parts into new viruses
5. RELEASE -Cell explodes (lyses)
releasing new viruses which search for
a new host cell
Lysogenic Cycle - followed when virus is in latent or
temperate state
The steps of the lysogenic cycle:
1) Viral nucleic acid enters cell
2) Viral nucleic acid attaches to host cell nucleic acid,
creating a prophage
3) Host cell enzyme copies viral nucleic acid
4) Cell divides, and virus nucleic acid is in daughter
cells
5) At any moment when the virus is "triggered", the
viral nucleic acid detaches from the host cell's DNA
and enters stage 2 of the lytic cycle.
Common symptoms that appear to "trigger" the viral
DNA are hormones, high stress levels (adrenaline),
and free energy within the infected cell.
Viral Diseases
• Vector – intermediate host that transfers a
pathogen or parasite to another organism
– Ex: humans, mosquitos, ticks, fleas.
• Human viral diseases - chickenpox, shingles,
viral hepatitis, AIDS, etc…
• Protease inhibitors – drugs that block virus
reproduction
• Oncogenes – viral genes that cause cancer by
messing with cell division checkpoints
• Proto-oncogene – controls cell growth
Prevention and Treatment
Vaccine – weakened sample of virus or virus parts
which triggers your body’s immune system
Attenuated virus – weakened virus that cannot cause
disease
Inactivated virus – unable to replicate in host
Natural immunity - antibodies are specialized proteins
formed in B cells of immune system
- antibodies block attachment sites of viruses
http://www.pbs.org/wgbh/nova/bioterror/vaccines.html
Disease causing particles even smaller than viruses
Viroids
– short single strand of RNA without a capsid
- interfere with cell processes and cause new viroids
to be made
- are found only in plants
Prions
- glycoprotein particle
- able to reproduce in mammalian cells
- Prion diseases: mad cow disease; Creutzfeldt-Jakob
disease & kuru (degenerative nerve diseases of the brain)
Genetic engineering
Genetic engineers use viruses to carry desirable genes from one
cell to another
Improved agriculture – herbicide tolerant soybeans; rot
resistant tomatoes; fast growing fish; meatier chickens
Correcting genetic disorders - experimental; only done in
animal with success; not allowed in humans
Pest control – insert genes of plants that create chemical to
resist insects into crop plants such as corn
Manufacturing of medicine - human insulin &clotting factors 8
&9
http://www.pbs.org/wgbh/harvest/engineer/transgen.html
Chapter 23: Bacteria
Archaea and Bacteria
Bacteria Objectives
• Describe the common methods used to
identify bacteria
• Identify 3 Archael groups, 5 bacterial
groups
Characteristics of Domain
Archaea
•
•
•
•
Prokaryotic cells
Unicellular
Cell Walls do not contain peptidoglycan
Cell Membranes contain other types of
hydrocarbons in addition to fatty acids
• rRNA shows they are more like Eukaryotes
• Contain Introns in their DNA
• Heterotrophs and Autotrophic Chemotrophs
III. Kingdom Archaebacteria – the most primitive organisms
(archae = ancient)
live in harsh conditions including
- acidic hot springs
- very salty water
- environments with no oxygen
- near undersea volcanic vents
- different from other bacteria
- cell wall composition (pseudomurien)
- Cell membrane
- rRNA
Phyla 1: Methanogens:
- obligate anaerobes (oxygen kills them)
- metabolizes hydrogen gas and CO2 to methane gas
- live in the bottom of swamps, sewage, and inside the
digestive tracks of many animals
Helps
- grazing animals process cellulose
- termites process wood
- in industry to treat sewage, purify water.
Phyla 2: Thermoacidiphiles
- can live in extremely hot and
acidic water or deep in the
ocean near hydrothermal vents
in the ocean floor
- Ex: hot springs of
Yellowstone Natl Park, ice
of Iceland
- chemotrophs = process sulfur
compounds to produce energy
Phyla 3: Halophiles:
- live in extremely
salty (saline)
environments,
ex: Dead Sea
- use the salt to
generate ATP.
IV. Kingdom Eubacteria
(Eu = true) “Germs”
• Found almost every where on Earth
• Characteristics:
– peptidoglycan in cell wall
– may have outer covering of glycocalyx
(sticky sugars) that keeps cells from
drying out
Characteristics used for classifying:
1) Composition of the cell wall –
identified with Gram staining technique
Gram positive – stains purple – thick
outer layer of peptidoglycan
Gram negative – stains pink/red – lipid
layer covering thin layer of peptidoglycan
2. Method of getting energy
autotroph – chemotroph or
phototroph
heterotroph - free living or parasite
saprophytes – break down other
organisms into nutrients
3) Type of metabolism
obligate aerobe – must have oxygen; dies without it
obligate anaerobe – dies if exposed to oxygen; processes
ATP by fermentation
facultative anaerobe – uses oxygen when it can but
doesn’t need it
4) Shape of bacterial cells
round
coccus (cocci)
rod shaped
bacillus (bacilli)
spiral shaped
spirillus
Domain Bacteria
• Shapes (cont’d)
– Spiral-shaped
• Called spirilla
Domain Bacteria
• Occur in many shapes including
– Rod-shaped
• Called bacilli
Domain Bacteria
• Shapes (cont’d)
– Sphere-shaped
• Called cocci
– In chains, called streptococci
– In grapelike clusters called
staphylococci
5) How cells grow (prefixes are added to
coccus)
a) staphylo – cells grow in clumps
b) strepto - cells grow in chains
c) diplo - cells grow in pairs
6) Motility – movement
a) flagellated – move with flagellum or
flagella
b) slime layer allows gliding
c) spirochete - cork-screw rotation
Reproduction – 2 types
Asexual - most common
Binary fission – chromosome replicates cytoplasm,
membrane and wall divide into two new cells
Sexual – exchanges genetic info giving variation
a)
conjugation – two bacterial cells get side by
side and hair-like “pili” connect to provide tube
to pass info
b)
transformation – living bacterial cell absorbs
dead related bacterial DNA and incorporates it
into genome
c)
transduction – a virus transfers DNA from one
bacterium to another
Endospores
- special dehydrated cells formed by some bacteria
to survive bad living conditions
- ex: high temperatures, harsh chemicals,
radiation, lack of moisture
- dormant as endospore
- when conditions improve cell is revived
- ex. Anthrax
Structure of a Bacterial Cell
Phyla groups:
Gram positive
- thick outer layer of peptidoglycan (stains purple)
- may be beneficial or cause disease
- may be used to make yogurt, pickles, and buttermilk
- or to make medicines using biotechnology
Ex. Strep throat ; staph infections; tuberculosis
Phyla groups:
Gram negative taxa
A)
Proteobacteria
• may have symbiotic lifestyle
• ex. Nitrogen fixing bacteria
inside legumes (peas, beans,
alfalfa, and clover)
• In human and animal
intestines, help break down
foods (enteric bacteria)
• Some in soil or fresh water
and process iron and other
minerals as an energy
source (chemotrophs)
B) Gram-positive bacteria
- most are gram-positive
- ex: botulism, Lactobacilli (yogurt),
C) Cyanobacteria
• Gram-negative
• contain chlorophyll (but not
chloroplasts), perform a
plant-like photosynthesis
releasing oxygen as a byproduct
• Ex. Filamentous bacteria
(grow in stagnant water)
D) Spirochetes
- gram negative
- spiral shaped
E) Chlamydia (no peptidoglycan)
- gram negative
- round shape
- are parasites to animal cells
Bacteria and Disease
Toxins – poisons produced by some bacteria
1) endotoxin - created inside the bacterial cell and
released as the cell dies; usually Gram negative
bacteria
2) exotoxin – secreted by living bacterial cell into
surrounding environment (host); usually Gram-positive
bacteria
3) enzymes – some bacteria secrete enzymes that
break down the surrounding tissue and damage it
Pathogens – bacteria that cause disease
Antibiotics – chemicals that kill bacteria by interfering with
cellular functions such as protein or cell wall synthesis
Gram positive bacteria that cause disease need different
antibiotics than Gram negative bacteria
Broad spectrum antibiotics affect a wide variety of bacteria
within the taxa
Antibiotic Resistance in Bacteria
• most of the population dies, some survive
• Survivors reproduce and are no longer affected by
antibiotic
• Occurs when antibiotics are overused or used improperly
Vocabulary list for honors
Taxonomy
binomial nomenclature
phylogeny
Dichotomous key
phylogenetic chart
binary fission
Virus
capsid
antibiotics
Envelope
lytic cycle
endospore
Lysogenic cycle
vaccine
conjugation
Natural immunity
morphology
pathogen
Viroids
prions
tranformation
Methanogens
thermoacidiphiles
transduction
Halophiles
obligate aerobes
saprophyte
Obligate anaerobes
facultative anaerobes
endotoxin
Chemotrophs
phototrophs
exotoxin
Protists
V.
Kingdom Protista
Basic Characteristics: eukaryotes; most are
unicellular; most are heterotrophs
Habitats: aquatic habitats or moist soil
Characteristics used for classification
•how they obtain energy – heterotrophic;
autotrophic; saprophytic
•number of cells – unicellular or multicellular
•Motility – ability to move and movement
structures
Reproduction
Asexual (most common): Binary fission(unicellular)
Multiple fission (divide into more than 2 cells)
Sexual:
Conjugation (genetic information is swapped
and stored in a 2nd nucleus)
Protozoans – “animal-like” protists
Characteristics: unicellular; heterotrophs
Phlya Groups:
Sarcodinians – feed and move with pseudopods
(streaming cytoplasm) freshwater- amoebas; marine
– forminiferans and radiolarians
Ciliaphorans – feed and move using cilia (small
whisker –like structures)
Ex.
Paramecium, stentor
Zooflagellates (Sarcomastigophora)- move with one
or more flagella
May be free-living or parasitic and cause disease
Ex. Trichonympha, trypanosoma, giardia
Sporazoans (Apicomplexa) – no motility structures
All animal parasites; spore-formers; have complex
life cycles with two or more host organisms
Ex. Plasmodium
Algae – “plant-like” protists
Characteristics: unicellular or multicellular
All are phototrophs with chloroplasts and pigments
Unicellular phyla are grouped together under the
heading phytoplankton
Phlya Groups:
Dinoflagellates (Dinoflagellata)
Unicellular with two unequal sized flagella; marine;some
species exhibit bioluminescence (light producing) others
produce toxins (Gonyaulax) that cause “red tide”
Euglenophytes (Euglenophyta) have two flagella no
cell wall;cell membrane has flexible pellicle; all
freshwater habitat;
Ex. Euglena
Diatoms (Bacillariophyta) have 2 sided cell walls
made of silica (glass) that fit into each other like a
petri dish; may have circular, triangular (mostly
marine)or rectangular (mostly freshwater) body
shapes
Gold Algae (Chrysophyta) contain gold
pigments(carotenoids) as well as chlorophyll; most
unicellular but some species form colonies
Green algae (Chlorophyta)
contain chlorophyll a & b; have cell walls composed of
cellulose;unicellular, colonial, and multicellular species;
freshwater and marine habitats as well as moist land
Ex. Ulva (sea lettuce), volvox, spirogyra
Red algae ( Rhodophyta)
contain red pigment as well as chlorophyll; most
species tropical marine; all multicellular; may live in deep
water habitats because red pigment helps absorb red
lower energy light
ex. seaweeds
Brown algae (Phaeophyta)
All cold water marine; all multicellular; include
sargassum and kelp
Slime Molds – “Fungi-like” protists
Characteristics: all saprophytes; live in moist soil
or moist organic matter
plasmodial slime molds - 2 stage life cycle
feeding stage – (plasmodium) very large digesting mass
of cytoplasm that creeps along the decaying material
reproducing stage (fruiting body) stalked structures that
hold haploid spores which fuse when living conditions are good
or stay dormant if living conditions are bad
Cellular slime molds – 2 stages
feeding – single haploid cells that creep along like an
ameoba;
pseudoplasmodium – matting of individual cells in a colony
to share nutrients during bad living conditions; they
eventually form fruiting bodies that produce more
haploid spores which become individual organisms
Water molds
Grow in filaments called hyphae which break down organic
matter
Some are parasitic to animals like fish or plants like blight on
potatoes
Genetic engineering
Genetic engineers use viruses to carry desirable
genes from one cell to another
Examples: improved agriculture; correcting
genetic disorders; pest control; manufacturing of
medicine
http://www.pbs.org/inthebalance/terrorism/virus-orbacteria.html
Fungi Kingdom
·
Eukaryotes
·
Heterotrophic:
- most saprophytes
- some parasites
·
Most multicellular;
one is unicellular
·
Most sessile
Structure:
•
Cell walls made of chitin (tough, flexible
carbohydrate)

Multicellular fungi are made up of hyphae
(small tubules filled with cytoplasm and nuclei)

Hyphae form an interconnected mass called the
mycelium and cytoplasm of all cells flow between the
hyphae

Hyphae may have walls called septa which still have
holes for the cytoplasm to flow through
Hyphae produce enzymes that are secreted into the
environment and then nutrients are reabsorbed through
hyphae
Asexual Reproduction:
3 ways depending on structure
•
Multi-cellular –regeneration; (single celledmitosis & cell division)

Budding - new organism forms from small piece of
mycelium

Asexual spore formation from fruiting bodies
Spores spread by wind,
water, animals (*most common)

Sexual reproduction – positive and
negative hyphae fuse together to form
spores
Sexual reproduction is possible in the
common molds, club fungi, and sac fungi
only
Classification:
Classified by structures used for reproduction
Group names are divisions not phyla (used to be
classified as plants):
Common molds
Club fungi
(Zygomycota)
(Basidiomycota)
Sac Fungi ( Ascomycota)
Imperfect fungi (deuteronomycota)
1. Common molds
(Zygomycota)

No septa in hyphae

Asexual reproduction - most common
Sexual reproduction spores formed in sporangium

Examples:
bread mold, fruit molds
Club fungi (Basidiomycota)

Reproduce sexually by producing spores in basidium
Located in gills under the cap

Examples:
Puffballs
mushrooms, bracket fungi, shelf fungi,
2.
Sac Fungi ( Ascomycota)

reproduce sexually by means of ascus
bulb like projections that form from the hyphae

examples:
yeasts, truffles, morels,
powdery mildews
Imperfect fungi (deuteronomycota)

no sexual reproduction; asexual only

examples: the fungus that cause ringworm, athete’s
foot, nail infections
Impact:

environment - help to eat up or break down dead
organisms

symbiosis
a) lichen live with cyanobacteria; fungus offers
protection, cyanobacteria offer food
b)plant growth – fungus grows on root tips of some
plants; plants get benefit of all ready broken down
nutrients as well as extra support; fungus get nutrition
from plant
human
help as food sources, medicines (penicillin), food
processing, genetic engineering of proteins
disease
destroy plants and trees
property damage to wood structures
human infection