Exam 1 Flashcards
what is microbiology?
study of entities too small to be seen with the unaided human eye
what are some infectious diseases caused by microbes?
influenza and pneumonia septicemia (bloodstream infection) respiratory infectin HIV/AIDS diarrheal diseases tuberculosis
Van Leeuwenhoek
Dutch
1676
first to see bacteria
“animalcules” reported to Royal Society in London—thought too small to harm humans
simple microscope – from well-ground lenses
spontaneous generation still the prevalent thinking (challenged for 200 years, disproven in late 1800s)
classified eukaryotes and prokaryotes**
Carolus Linnaeus
Swedish
created the taxonomic system for naming plants and animals and grouping similar organisms together
binomial nomenclature: Genus Species
Binomial nomenclaure
Genus species Rules: 1. italicized 2. Capitalize Genus 3. Lower case species 4. if handwritten- underline both (bc cant italicize)
Eukaryotes
(cellular) fungi protozoa algae animals plants
Prokayotes
(cellular)
bacteria
archaea
Acelluar
Viruses
spontaneous generation
also called abiogenesis
proposes that living organisms can arise from nonliving matter
proposed by aristotle (384-322 BC)
widely accepted for almost 2000 years
Redi
challenged spontaneous generation
flask unsealed = flies
flask corked = no flies
flask covered with cheese cloth= no flies
Needham
challenged spontaneous generation
boiled broth in sealed flask = bacterial growth
Spellanzani
challenged spontaneous generation
boiled broth in sealed flask = no growth
Pasteur
mid 1800s
Father of Microbiology
disproved spontaneous generation–discovered fermentation!
found Acetobacter bacilli (staff/rod-chaped cells) in “sick wine”—normally only find yeast cells
heated (Pasteurized) the wine to kill bacteria, reinoculated with Saccharomyces (still used in winemaking)
Tried unsuccessfully to prove the germ theory of (infectious) disease, using flasks of broth (very labor- and time-consuming).
Advised animals that die of Anthrax be buried deep or cremated. [Bacillus anthracis: soil bacterium, infects cuts in mouth of animal, makes spores, produce deadly toxins in the blood]
later, pasteur developed successful vaccines agains fowl, cholera, anthrax, and rabies
saccharomyces cerevisiae
sugar fungus that makes beer
works in fermentation
-a microbiological even that has had a greater impact on culture and society than of any disease or epidemic
germ theory of disease
= discovery of bacteria spoiling wine + hypothesis that microbes are responsible for disease
Koch
mid1800s
German M.D., contemporary of Pasteur
Father of Diagnostic Microbiology
investigations in etiology
- study of causation of disease
race with pasteur to discover the cause of anthrax
- Bacillus anthracis
- the first time that bacterium was proven to cause a disease
discovered cause of tuberculosis
- mycobacterium tuberculosis
method of isolation
- used gelatin/potato. now days use agar
use petri dishes
Koch’s Postulates
Steps that must be taken to prove the cause of any infectious disease
- suspected causative agent must be found in every case of the disease and be absent from healthy hosts
- agent must be isolated and grown outside the host
- when agent is introduced into a healthy, susceptible host, the host must get the disease
- same agent must be found in the diseased experimental host
Semmelweis
handwashing
1847
women who gave birth in hospital were more likely to die from infection (child bed fever/puerperal fever—due to infeciton with Streptococcus pyogenes)–caused puerperal fever
said needed required handwashing in clorinated lime water = decreased mortality (18.3-1.3%)
Lister
Antiseptic technique
1860s
antiseptics in surgery (not the first)—used carbolic acid=phenol
decreased deaths by 2/3 in his patients
known as antisepsis- method was accepted into common practice
Nightingale
Cleanliness techniques in nursing
Snow
infection control/field of eidemiology
1854
linked cholera (Vibrio cholerae) with certain water sources in London (Broad Street pump)
classic cholera symptom: rice water stools with death by dehydration
his study founded other branches of microbiology:
- infection control
- epidemiology: study of occurrence, distribution, and spread of disease in humans
Jenner
smallpox vaccine/ field of immunology
showed that vaccination with pus collected from cowpox lesions prevented smallpox
field of immunology: study of body’s specific defenses against pathogens
Ehrlich
“magic bullets”/ field of chemotherapy
searched for a “magic bullet” that could kill microorganisms but remain nontoxic to humans
discovered chemicals effective against the agents that cause sleeping sickness and syphillis
chemotherapy: branch of medical microbiology, chemicals are studies for potential to destroy pathogenic organisms.
Creutzfeldt-Jakob disease (vCJD)
an emerging disease (a disease arising in the past two decades, either bc its new to a population, or bc its newly recognized
slowly erodes nervous tissure and leaves the brain full of sponge-like holes
no treatment
processes of life
growth: increase in size
reproduction: change in number
responsiveness: react to stimuli in the environment– (-taxis) chemotaxis and phototaxis
metabolism
Prokaryotes
archaea and bacteria never have a nucleus lack internal membrane bound organelles circular DNA simple structure smaller then 1um in diameter
eukaryotes
algae, fungi, protozoa, animals and plants have nucleus linear DNA complex structure larger - 10-100um in diameter
external structures of bacterial cells (prokaryote)
glycocalyces
flagella
fimbriae
pilli
glycocalyces
gelatinous, sticky substance that surrounds outside of cell
composed of polysaccharides, polypeptides, or both
two types: capsule or slime layer
capsule glycocalyx
firmly attached to cell surface
may prevent bacteria from being recognized by host
slime layer glycocalyx
loosely attached to cell surface
sticky layer allows prokaryotes to attach to surfaces
flagella
responsible for movement
long structures that extend beyond cell surface
composed of: filament, hook, basal body
not present on all bacteria
flagella function
rotation propels bacterium
rotation is reversible (clockwise or counterclockwise)
bacteria move in response to taxis (stimuli)-chemotaxis/phototaxis
flagella runs (move in unison and propel forward) or tumbles (move in circles)
fimbriae
rod-like proteinaceous extension
sticky, bristlelike projections
used to adhere to one another, to hosts, and to sub. in environment
shorter than flagella
serve an important fxn in biofilms (ex. plaque on teeth)
pili
rod-like proteinaceous extension
tubules on pilin
also known as conjugation pili
(conjugation= “coming together”)
longer than fimbriae but shorter than flagella
only have one or two per cell
mediate the transfer of DNA from one cell to another (conjugation)**
Bacterial cell walls
provide structure and shape and protect cell from osmotic forces
give bacterial cells characteristic shapes
composed of peptidoglycan
two main types: gram + and gram -
(gram is a type of stain)
gram + cell walls
stronger than gram -
thick layer of peptidoglycan
contain teichoic acids- help provide rigidity
appear PURPLE after gram stain
gram - cell walls
thin layer of peptidoglycan
bilayer membrane outside peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS)
appear RED after gram stain
lipid A
endotoxin that causes damage
may be impediment to the treatment of disease
dead cells release lipid A
- may trigger fever, vasodilation, inflammation, shock and bld clotting
which cellular structure is important in classifying bacterial species as gram + or -?
the cell wall
bacterial cytoplasmic membranes
phospholipid bilayer structure- composed of lipids and associated proteins
fluid mosaic model
1. energy storage- harvest light in photosynthetic bacteria
2. selectively permeable- h2o and lipid soluble mol, or ex. small mol can pass in and out
3. maintain concentration and electrical gradient
passive process in crossing the cytoplasmic membrane of bacterial cells
diffusion
facilitated diffusion
osmosis
active process in crossing the cytoplasmic membrane of bacterial cells
active transport
group translocation: substance chemically modified during transport
diffusion
passive process through phospholipid bilayer
molecules move down electrochemical gradient
ex. oxygen, c02, lipid soluble chemicals
facilitated diffusion
passive process through a nonspecific channel protein or through a permease specific for one chemical (binding of substrate causes shape change in the channel protein)
molecules move down electrochemical gradient through channels or carrier proteins
ex. fructose, glucose, urea, some vitamins
osmosis
passive process of the diffusion of water through a specific channel protein or through the phospholipid bilayer
water molecules move down [ ] gradient across a selectively permeable membrane
active transport
uniport: one mol in
antiport: one mon in and one mol out
coupled transport- uniport and symport: one out in one channel and two in in another channel
ATP- dependent
carrier proteins brain substances into cell (against electrochemical gradient)
ex. Na, K, Ca, Cl
group translocaiton
substance is chemically altered during transport
found only in some bacteria
ex. glucose, mannose, fructose
cytoplasm of bacteria
cytosol: liquid portion of cytoplasm
inclusions
endospores
inclusions
may include reserve deposits of chemicals
stored when nutrients are in abundance, used when nutrients are scarce
endospores
unique structures produced by some bacteria that are defensive strategy against unfavorable conditions
cytoplasm of prokaryotes: nonmembranous organelles
- cytoskeleton: role in forming cells basic shape
2. ribosomes
ribosomes of prokaryotes
site of protein synthesis
size expressed in svedbergs (S)
70S are size
composed of 2 subunits (30S and 50S)
external structures of archaea
glycocalyces
flagella (differences from bacterial flagella)
fimbriae
hami
archaea hami (external structure)
attach archaea to surfaces
have a grappling-hook shaped structure to end
archaea cell walls
most archaea have them
do not have peptidoglycan
contain a variety of specialized polysaccharides and proteins
archaea cytoplasmic membranes
all archaea have them
maintain electrical and chemical gradients
control import and export of substances from the cell
cytoplasm of archaea
have 70S ribosomes
- ribosomal proteins are similar to eukaryotes
similar genetic code as eukaryotes
fibrous cytoskeleton
circular DNA
has different metabolic enzymes than bacteria to make RNA
glycocalyces of eukaryotic cells
never a prokaryotic capsule help anchor animal cells to each other strengthen cell surface provide protection against dehydration fxn in cell-to-cell recognition and communication
eukaryotic cell walls
animals and most protozoan lack them
fungi, algae, plants and some protozoa have them
composed of various polysaccharides
eukaryotic cytoplasmic membranes
all eukaryotes have them
fluid mosaic of phospholipids and proteins
contain steroid lipids to help maintain fluidity
contain regions of lipids and proteins called membrane rafts
have passive and active processes
membrane rafts
in eukaryoic cytoplasmic membrane
to compartmentalize cellular processes
composed of lipids and proteins
passive processes of eukaryotic cytoplasmic membranes
diffusion
facilitated diffusion
osmosis
active processes of eukaryotic cytoplasmic membranes
active transport endocytosis exocytosis phagocytosis pinocytosis
endocytosis
physical manipulation of cytoplasmic membrane around cytoskeleton
form pseudopodia
exocytosis
substances exported from cell
vesicles containing substances are fused w/ cytoplasmic membrane, dumping their contents outside of cell
phagocytosis
solids imported into cell
substances are surrounded by pseudopodia and brought into cell
pinocytosis
liquid imported into cell
substances are surrounded by pseudopodia and brought into cell
eukaryotic flagella
within cytoplasmic membrane
filaments anchored to cell by basal body (not hook)
may be single or multiple, generally found at one pole of the cell
fxn by undulate rhythmically (not rotation)
cytoplasm of eukaryotic: cilia
shorter and more numerous than flagella
coordinated beating propels cells through environment
used to move substances past the surface of the cell
movement of cilia help cleanse human respiratory tract of dust and microorganisms
no prokaryotic cells have cilia
cytoplasm of eukaryotes
nonmembranous: flagella, cilia, ribosomes, cytoskeleton, centrioles, centrosomes
membranous: nucleus, endoplasmic reticulum, golgi body, mitochondria, chloroplasts
eukaryotic ribosomes
80S
composed of two subunits (60S and 40S)
eukaryotic cytoskeleton
extensive network of fibers and tubules
anchors organelles
produces basic shape of the cell
made up of tubulin microtubules, actin microfilaments, and intermediate filaments
eukaryotic centrioles and centrosomes
animal cells and some fungal cells contain two centrioles
plants, algae, most fungi, and prokaryotes lack centrioles
centrioles
play a role in mitosis, cytokinesis (cell division), and formation of flagella and cilia
centrosomes
region of cytoplasm where centrioles are found
eukaryotic nucleus
largest organelle in cell contains most of cells DNA nucleoplasm: semi-liquid portion one or more nucleoli present in nucleoplasm surounded by nuclear envelope
eukaryotic endoplasmic reticulum
netlike arrangement of flattened, hollow tubules continuous with nuclear envelope
fxns as transport system
smooth ER and rough ER
eukaryotic golgi body
not in all eukaryotic cells
- receives, processes, and packages large molecules of export from cell
- packages mol in secretory vesicles that fuse with cytoplasmic membrane
- composed of flattened hollow sacs surrounded by phospholipid bilayer
eukaryotic mitochondria
2 membranes composed of phospholipid bilayer
produce most of cells ATP
interior matrix contains 70S ribosomes and circular molecule of DNA
eukaryotic chloroplasts
light harvesting structures
have 2 phospholipid bilayer membranes and DNA
70S ribosomes
prokaryotes lack chloroplasts but have photosynthetic lamelle
photosynthetic lamelle
instead of chloroplast prokaryotes have these
resolution
shortest distance btwn two points on a specimen that can still be distinguished by the observer as separate entities
contrast
differences in intensity btwn two objects, or btwn an object and background
important in determining resolution
staining increases contrast
ex. x-rays
staining
increases contrast and resolution by coloring specimens with stains/dyes
smear of microorganisms made prior to staining bust be fixed with heat
simple stains
crystal violet- purple
safranin- magenta
methylene blue- blue
malachite green- green
differential stains
gram stain
acid fast stain
endospore stain
special stain
negative (capsule) stain
flagellar stain
mycobacteria
group of bacteria that do not have the typical peptidoglycan cell wall
their cell walls have a high waxy mycolic acid content- makes them resistant to decolorization by acids during staining procedures such as the gram stain
referred to as acid- fast bacteria
ziehl-neelson acid fast stain
- red primary stain
- decolorize (alcohol): acid fast cells retain red color bc acid cannot pennetrate waxy walls
- counterstain (methylene blue): stains only bleached, non-acid fast cells
RESULTS
red acid-fast cells = mycobacteria
blue non-acid fast cells = including human cells and tissue
schaeffer-fulton endospore stain
- malachite green primary stain: use heat to drive into the endospore
- decolorize (water)
- counterstain (safranin)
RESULTS
green stained = endospores
red colored = vegetative cells
negative (capsule) stain
primarily used to reveal the presence of negatively charged bacterial capsules
flagellar stain
applied in a series of steps
stains bind to flagella, increase their diameter, and change their color– all increase contrast and make them visible
Linnaeus
system classified organisms bases on characteristics in common
used binomial nomenclature in his system
proposed only two kindoms: animals and plants
whittaker
proposed taxonomic approach based on 5 kingdoms: animalia, plantae, fungi, protista, prokaryotae
Carl woese
compared nucleotide sequences of rRNA subunits
proposed 3 domains (as determined by ribosomal nucleotide sequences): eukarya, bacteria, and archaea
- eukarya has: fungi, protista, algae, plantae, animalia
cells in domains also differ w/ respect to many other characteristics
dicotomous keys
series of paired statements where only one of two “either/or” choices applies to an organism
key directs user to another pair of statements, or provides name of organism
necrotizing fasciitis
emerging disease
red, purple, and black inflammation- grows large
extremely painful
“flesh-eating” disease
caused by Group A streptococcus- gram + bacteria
which differential stain ends up with red and blue cells?
acid fast
microbial colony
aggregation of cells arising from a single parent cell
microbial biofilm
collection of microbes in a complex community
microbial growth requirements
- oxygen: amt varies widely
- temperature: most important factor-large range
- pH: thrive in pH of 6-9 (animal pathogens best in pH 7)
- moisture
- osmotic pressure: created by osmosis
- light: most pathogens are killed by direct sun
- food
psychrophilic
prefer cold temps
take part in spoilage of food in refrigerator
mesophilic
prefer moderate temps
most pathogenic organisms
hyper thermophilic
prefer high temps
autotrophic
organisms thrive in areas where organic matter is scarce
they are self-nourishing
ex. algae and some bacteria
herterotrophic
organisms use organic matter for energy and synthesis of cell materials
can be:
1. strict (obligate) saprophytes- obtain nutritional need from non-living sources
2. strict (obligate) parasites- only grow on other living organisms
3. facultative organisms- live and adapt in food conditions that may vary
culturing microorganisms: inoculum
sample
- environmental specimen
- clinical specimen
- stored specimen
culturing microorganisms: medium
collection of nutrients
- broth (liquid)
- solid
culturing microorganisms: culture
microorganisms that form from an inoculum
act of cultivating microorganisms
culturing microorganisms: colonies
cultures that are visible on the surface of a solid media
culture media
some microbes are not particular and can be grown in a variety of media, others require specific nutrients 6 types: 1. defined media 2. complex media 3. selective media 4. differential media 5. anaerobic media 6. transport media
culturing microorganisms: defined media (synthetic media)
exact chemical composition is known
culturing microorganisms: complex media
exact chemical composition is unknown
contain a variety of nutrients
can support a wider variety of microorganisms
ex. nutrient broth, trypticase soy agar, Macconkey agar
culturing microorganisms: selective media
contain substances that favor or inhibit the growth of particular organisms
dyes and salts added; specific nutrients left out
ex. sabouraud dextrose agar, mcConkey agar
culturing microorganisms: differential media
presence of visible changes in medium or differences in the appearance of colonies help differentiate organisms
ex. blood agar, macconkey agar
culturing microorganisms: preserving cultures
refrigeration: stores for short periods of time
deep-freezing: stores for years
lyophilization (freeze dry): stores for decades
geneticcs
study of inheritance and inheritable traits as expressed in an organisms genetic material
genome
entire genetic complement of an organism
includes its genes and nucleotide sequences
structure of prokaryotic genomes: prokaryotic chromosomes
haploid: one copy of chromosome
circular molecule of DNA in nucleoid
structure of prokaryotic genomes: plasmids
small molecules of extra-chromosomal DNA that replicate independently
NOT essential for normal metabolism, growth, or reproduction
can confer survival advantages
structure of prokaryotic genomes: types of plasmids
fertility factors (F plasmid)
resistance factors (R plasmid)
bateriocin factors
virulence plasmids
structure of prokaryotic genomes: nuclear chromosomes
diploid: two chromosome copies
linear DNA sequestered w/in nucleus
gene function
relationship btwn genotype and phenotype
genotype: internally coded, inheritable info
phenotype: outward, physical appearance
central dogma of genetics
DNA transcribed to RNA, RNA translated to protein (polypeptides)
transcription
info in DNA copied as RNA
translation
polypedtides synthesized from RNA
A genotype can be expressed as a phenotype in what way?
by translation and transcription
what type of plasmid was the member of antibiotic resistance offering Albert?
R plasmid (resistance plasmid)
point mutations
most common
one base pair is affected
insertions and deletions (frameshift), substitutions
silent mutations
substitutions doesnt change amino acid sequence
due to redundancy of genetic code
missense mutations
codon changes into codon for a different amino acid- makes sense but not the right sense
nonsense mutations
codon changes into stop codon
results in nonfunctional protein
genetic recombinaiton
exchange of nucleotide sequences btwn 2 DNA molecules
recombinants
cells w/ DNA molecules that contain new arrangements of nucleotide sequences
vertical gene transfer
organisms replicate their genomes and provide copies to descendants
normal process in both prokaryotes and eukaryotes
horizontal gene transfer: prokaryotes
acquire genes from other microbes of the same generations
donor cell contributes part of genome to recipient cell–may be different species
three types:
- transformation
- transduction
- bacterial conjugation
horizontal gene transfer: transformation
recipient cell takes up DNA from environment
cells that take up DNA are called competent
occurs only a few types of bacteria
“gifted” bacteria can pick up info from the dead
horizontal gene transfer: transduction
transfer of DNA from one cell to another via a replicating virus
generalized and specialized
horizontal gene transfer: generalized transduction
transducing phage carries random DNA segment form donor to recipient
horizontal gene transfer: specialized transduciton
only certain donor DNA sequences are transferred
horizontal gene transfer: bacterial conjucation
not the same as reproduction
transfer of DNA from one cell to another, mediated by conjugation pili
donor cell requires F plasmid (F+)–“male”
recipient cell lacks F plasmid (F-)–“female”
Vibrio vulnificus
emerging disease
person fells chilled, feverish, extremely weak and tired.
infected area can get tight, swollen, dark red, painful and covered in blisters
many ppl lose a limb or die
reproduction of prokaryotic cells
all reproduce asexually three main methods: 1. binary fission (most common) 2. snapping division 3. budding
special reproduction
epulopiscium and its relatives reproduce by live offspring emerging from the body of the dead mother cell (viviparity)
mycoplasma “fried egg”
bacteria with no cell wall
when grown on media will form a fried-egg appearance
colonize osmotically protected habitats such as animal and human bodies (mycoplasma- pneumonia, ureaplasma-urinary infection)
will stain red in gram-stain
pertusis
emerging diseases develop cold like symptoms constant coughing- can break ribs vomiting, fainting usually considered a childhood disease infected ppl can spread bordatella in respiratory droplets
Archaea: methanogens
largest group of archaea
convert co2 and h2 to methane gas
one of primary sources of environmental methane
“greenhouse gas”
Archaea: extremophiles
require extreme conditions to survive temp, pH, or salinity 4 types: thermophiles psychrophiles halophiles acidophiles
Archaea: extremophiles: thermophiles
require high temperatures to survive
hyperthermophiles- require temps higher than 176F
Archaea: extremophiles: psychrophiles (cryophiles)
require low temps to survive
Archaea: extremophiles: halophiles
inhabit extremely saline habitats
depend on greater than 9% NaCl (humans are only .9%)
may contain orange or red pigments
may protect from UV and visible light
Archaea: extremophiles: adiophiles
thrive under acidic environment pH less than 2
major groups of eukaryotes
protozoa fungi algae parasitic helminths arthropod vectors
reproduction of eukaryotes
multiple types of asexual reproduction:
- binary fission
- budding
- fragmentation
- spore formation (not same as sporeulation)
- schizogony
also reproduce sexually by forming gametes and zygotes
algae, fungi, and some protozoa reproduce both sexually and asexually
eukaryotes: protozoa
defined by eukaryotic, unicellular, and lack a cell wall
require moist environments: most live in ponds/streams/lakes/oceans- or in moist soil, decaying organic matter
very few are pathogenic**
eukaryotes: protozoa: morphology and reproduciton
all produce trophozoites (motile feeding stage)
some produce cysts (similar to endospore, resting stage)
some have contractile vacuoles (protect from osmotic lysis)
most reproduce asexually only
few have sexual reproduc.
the motile feeding stage of a protozoan is called what?
trophozoite
eukaryotes: protozoa: dinoflagellates
large proportion of freshwater and marine plankton
bioluminescent
many reproduce neurotoxins that can affect humans who ingest fish or shellfish that have been infected
eukaryotes: fungi
chemoheterotrophic
have cell walls typically composed of chitin
no photosynthesis
30% cause diseases of plants, animals, and humans (mycoses)
eukaryotes: fungi: morphology: thallus
nonreproductive body
composed of long, branched, tubular filaments called hyphae
eukaryotes: fungi: morphology: dimorphic
fungi that reproduce 2 types of thalli
generally yeast form of dimorphics cause diseases
eukaryotes: fungi: morphology: mycelium
tangled mass of hyphae
typically subterranean
eukaryotes: fungi: reproduction
all have some means of asexual reproduction
most reproduce sexually
budding and asexual spore formation
- produce psudohypha
eukaryotes: fungi: psudohypha
series of buds that remain attached to one another and to parent cell
Aspergillosis
emerging diseases
rare but increasingly more frequent
difficulty breathing, fever, chest pain, coughing up blood, extreme tiredness, weakness, delirium, possible paralysis
what term refers to a mass of intertwined fungal hyphae
mycelium
parasitic helminths
worms that have microscopic infective and diagnostic stages- usually eggs or larvae
arthropod vectors
animals that carry pathogens
mechanical vector
only carry the pathogen
biological vector
serve as host for pathogen
disease vectors
two classes:
arachnids- ticks and mites
insects- fleas, lice, flies, mosquitoes, true bugs
disease vectors: arachnids
adults have four pairs of legs
ticks and mites
ticks are most important
arthropod vectors: insects
adults have three pairs of legs and three body regions
mosquitoes are most imortant
characteristics of viruses
miniscule, acellular, infectious agent having either DNA or RNA
cause most diseases that plague industrialized world
cause many infections of humans, animas, plants, and bacteria
characteristics of viruses: extracellular state: viron
protein coat (capsid) surrounding a nucleic acid core
together these units are referred to as nucleocapsid
outer coat provides protection for viral nucleic acid and means of attachment to host cells
characteristics of viruses: extracellular state: envelope
outer structure that encloses the nucleocapsids of some viruses
characteristics of viruses: intracellular state
once the virus is inside the host the capsid is removed
virus exists simply as nucleic acid
host of viruses
most viruses infect only particular hosts cells
may be so specific that only infect particular kind of cell in particular host
some are general- infect many kinds of cells in many hosts
viral shapes
complex: capsids of many shapes
polyhedral: geodesic dome
helical: spiral
viral envelope
acquired from host cell during viral replication or release
some have viral glycoproteins that project, called spikes
provides protection, plays role in host recognition, helps viruses enter host cells
has envelope = enveloped viron
no envelope = noneveloped/naked viron
classification of viruses
by type of nucleic acid, presence of an envelope, shape, and size
recognized by family and genus names
typically written with virus on end w/ italics
viral replicaiton
dependent on hosts organelles and enzymes to produce new virons
lytic replication- results in death and lysis of host cell
viral replication: stages of lytic replication
- attachement of virion to host cell
- entry of virion or its genome into host cell
- synthesis of new nucleic acids and viral proteins by the host cell’s enzymes and ribosomes
- assembly of the new virions w/in the host cell
- release of the new virions from the host cell
viral replicaiton: lysogeny
modified replication cycle
infected host cells grow and reproduce normally for generations before they lyse
temperate phages
- prophages: inactive phages
viral replicaiton: lysogenic conversion
when phages carry genes that alter phenotype of a bacterium
can turn bacterium from harmless to pathogen
replication of animal viruses
same basic replication pathway as bacteriophage EXCEPT:
- presence of envelope around some viruses
- eukaryotic nature of animal cells
- lack of cell wall
attachment of animal viruses
chemical attraction
animal viruses do not have tails or tail fibers
- have glycoprotein spikes or other attachment molecules that mediate attachment
latency of animal viruses
or proviruses
when animal viruses remain dormant in host cell
incorporation of provirus into host DNA is permanent
oncovirus
result in cancer
genes for cell division turned on or genes for inhibiting division turned off
neoplasia
uncontrolled cell division in multicellular animal
tumor (neoplasm)
mass of neoplastic cells
malignant tumor
cancer
metastasis
viroids
extremely small
circular pieces of RNA that lack capsids
infectious and pathogenic in plants
viroidlike agents
infectious
pathogenic RNA particles that lack capsids
do not infect plants
- affect some fungi
prions
proteinacious infectious agents
lack nucleic acid
only destroyed by incineration or autoclaving in sodium hydroxide
cellular PrP protein
made by all mammals
normal structure w/ alpha helices
prion PrP
disease causing form w/ beta sheets
prion PrP converts cellular prp into prion PrP
by inducing conformational change
prion diseases
expression is most predominant in the nervous system
large vacuoles form in brain- spongy
spongiform encephalopathies: BSE, vCJD, Kuru
composed of different protein may lie behind other neuronal degenerative diseases like: alzheimers, parkinsons, ALS
