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Viruses - Coggle Diagram
Viruses
What a Virus Is
not a cell
needs host machinery
no metabolism alone
obligate intracellular parasite
core parts
nucleic acid genome
single or double stranded
capsid
protein coat
protects genome
Discovery of viruses
tobacco mosaic disease
filterable agent
smaller than bacteria
still infectious
scientific inquiry
experiments
filtration tests
infection results
Virus structure
shapes
helical
rod like capsid
icosahedral
many sided capsid
complex
phage head and tail
envelope
membrane from host
viral spikes
attachment to host cells
How viruses replicate
Replication only in host cells
host range
specific hosts
pecific cell types
receptor matching
general steps
attachment
receptor binding
entry
genome replication
uses host enzymes or viral enzymes
synthesis of viral proteins
assembly
capsids form
genomes packaged
release
lysis
cell bursts
budding
envelope taken
Phage cycles
lytic cycle
phage takes over
makes new phage
host cell lyses
lysogenic cycle
prophage integration
copied with host DNA
later induction to lytic
Animal virus cycles
entry methods
endocytosis
vesicle entry
membrane fusion
envelope merges
RNA viruses
RNA as template
RNA dependent RNA polymerase
high mutation rate
retroviruses
reverse transcriptase
RNA to DNA
provirus in host genome
Evolution of viruses
fast evolution
mutation and selection
host defenses pressure
new strains
Prokaryotic lineages
overview of diversity
huge genetic variety
many are uncultured
discovered by DNA sequencing
bacteria
many pathogens and decomposers
Gram stain groups
proteobacteria, cyanobacteria, etc
archaea
genetically distinct from bacteria
many extremophiles
thermophiles, halophiles
also common in oceans and soil
Plant viral diseases
transmission
insects as vectors
aphids
sap feeding
mechanical damage
wounds
farm tools
effects
stunted growth
reduced yield
leaf symptoms
mosaic patterns
discoloration
Prions
infectious proteins
no nucleic acid
misfold normal proteins
chain reaction
diseases
mad cow disease
brain damage
fatal
Creutzfeldt Jakob disease
human prion disease
neurodegeneration
Structure, function, genetic diversity
Adaptations and success
cell wall
protection and shape
Gram positive vs Gram negative
capsule
sticky layer
protects from drying
helps avoid immune attack
pili
attachment
biofilms
sex pilus
DNA transfer
motility
flagella
rotate like propeller
chemotaxis movement
gliding
surface movement
no flagella
internal organization and DNA
nucleoid
circular chromosome
not membrane bound
plasmids
extra DNA rings
carry useful genes
ribosomes
protein synthesis
smaller than eukaryotic
reproduction
binary fission
one cell splits into two
very fast generation time
endospores
survival form
extreme conditions
Genetic diversity
rapid reproduction and mutation
short generation time
lots of offspring
quick evolution
mutation
copying errors
new alleles
genetic recombination
transformation
uptake of DNA from environment
new traits
transduction
bacteriophages transfer DNA
viral vectors
conjugation
direct cell to cell transfer
plasmid moves through pilus
horizontal gene transfer
genes move across lineages
boosts diversity
Viruses and prions as pathogens
Formidable pathogens
animal diseases
flu
respiratory infection
transmission by droplets
HIV AIDS
immune system damage
targets T cells
herpes viruses
latency
reactivation
emerging viral diseases
zoonotic spillover
animal to human
new outbreaks
spread factors
travel
dense populations
habitat change
more contact with animals
Metabolism and diversity
Nutritional and metabolic adaptations
nutrition types
phototrophs
energy from light
photosynthesis
chemotrophs
energy from chemicals
oxidation reactions
carbon from CO2
carbon fixation
heterotrophs
carbon from organic compounds
decomposers
nitrogen metabolism
nitrogen fixation
N2 to NH3
makes nitrogen usable
nitrification
ammonia to nitrite and nitrate
soil cycling
denitrification
nitrate to N2
returns nitrogen to atmosphere
metabolic cooperation
biofilms
community living
protection and shared resources
symbiosis
cross feeding
one species uses another’s waste