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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 made of nucleic
acid surrounded by a protein or
lipoprotein coating
- not made of cells, do not have
cytoplasm, ribosomes, or
mitochondria
-Can replicate only by using host
cell “machinery”
Structure:
Capsid - protein coat surrounding nucleic acid (DNA or RNA)
Envelope
– protective coating some viruses have.
- made of lipids, proteins or carbohydrates.
- usually has projections (attachment sites) which attach
to the cell they will infect
Classification criteria:
Identification of nucleic acid: RNA or DNA
 4 basic shapes –
polyhedral - multifaceted geometric appearance
mosaic (helical) – tightly coiled like a spring
filovirus – no distinct shape; some thread-like
binal – has two distinct regions; capsid and tail
Host cells infected:
Bacteria viruses (bacteriophages); Plant viruses; Animal
viruses
This is due to receptor site forming to specific proteins on
cell wall or membrane
Way they behave in the cell:
DNA viruses make new RNA and make viral proteins
RNA viruses invade and then make proteins
Retroviruses contain enzyme (reverse transcriptase)to
make DNA from RNA
Lytic Cycle –
followed when virus is virulent (active)
1. virus particle attaches to a host
cell (ADSORPTION).
2. The particle injects its genetic
instructions (DNA or RNA) into the
host (ENTRY).
3. injected genetic material ‘hi-jacks’
the cell’s machinery and recruits
the host’s enzymes.
4. enzymes make parts for the new
virus particles (REPLICATION).
5. new particles assemble the parts
into new viruses (ASSEMBLY).
6. Cell explodes (lyses) releasing new
viruses which search for a new host
cell (RELEASE).
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: 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
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.
Phyla 4: Psychrophiles
- live in
temperatures
below 15C
- Found mostly
in the Arctic
and Antarctic
oceans sea
ice.
Kingdom Eubacteria
(Eu = true) “Germs”
• Found almost every where on Earth
• Characteristics:
– peptidoglycan in cell wall
– may have an outer covering of sticky
sugars called glycocalyx that prevents
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
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
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
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
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
Kingdom Protista
Basic
Characteristics:
- eukaryotes
- most are
unicellular
- most are
heterotrophs
- Habitats:
aquatic habitats
or moist soil
Characteristics used for classification
• energy – heterotrophic; autotrophic;
saprophytic
• cell number – 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
Phlyum 1:Dinoflagellates
•
•
•
•
Unicellular
Marine
some bioluminescent (light producing)
some produce toxins (Gonyaulax) - “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
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
- 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
2 Club fungi (Basidiomycota)

Reproduce sexually by producing spores in basidium
Located in gills under the cap

Examples: mushrooms, bracket fungi, shelf fungi,
Puffballs
3.
Sac Fungi ( Ascomycota)

reproduce sexually by means of ascus,
bulb like projections that form from the hyphae

examples: yeasts, truffles, morels, powdery mildews
4.

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