Transcript 18.1 Studying Viruses and Prokaryotes

18.1 Studying Viruses and Prokaryotes
KEY CONCEPT
Infections can be caused in several ways.
18.1 Studying Viruses and Prokaryotes
Viruses, viroids, and prions can all cause infection.
• Any disease-causing agent is called a pathogen.
1 nanometer (nm) = one
billionth of a meter
100 nm
eukaryotics cells
10,000-100,000 nm
viruses
50-200 nm
prokaryotics cells
200-10,000 nm
viroids
5-150 nm
prion
2-10 nm
18.1 Studying Viruses and Prokaryotes
• A virus is made of DNA or RNA and a protein coat.
– non-living pathogen
– can infect many
organisms
• A viroid is made only
of single-stranded
RNA.
– causes disease in
plants
– passed through
seeds or pollen
18.1 Studying Viruses and Prokaryotes
• A prion is made only of proteins.
– causes misfolding of other proteins
– results in diseases of the brain
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
and Prokaryotes
Characteristics of Viruses
• NO - nucleus, cytoplasm, organelles, or cell membrane
• NOT capable of carrying out cellular functions
• NOT alive!
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
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Viruses
Obligate Intracellular parasites - depend on host cells for
replication
• Spread by wind, water, food, blood or other bodily
secretions
• Named for the disease they cause or the tissue they
infect
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Structure Viruses
and Reproduction
18.1Viral
Studying
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Viral Structure
Nucleic acid
• Either DNA or RNA, but not both
• Helical, closed loop, or a long strand
• Protein coat surrounds nucleic acid (capsid)
• Some have a membrane like structure outside capsid
called an envelope
• Ex: influenza, herpes, chickenpox, HIV
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
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Viruses differ in shape and in ways of entering host
cells.
enveloped
(influenza)
capsid
nucleic acid
lipid
envelope
polyhedral
(foot-and-mouth
disease)
helical
(rabies)
Surface proteins
capsid
nucleic acid
surface
proteins
lipid envelope
surface
proteins
capsid
nucleic acid
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
and Prokaryotes
• Bacteriophages – virus that infects bacteria.
capsid
DNA
tail sheath
tail fiber
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Structure Viruses
and Reproduction
18.1Viral
Studying
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colored SEM; magnifications:
large photo 25,000; inset 38,000x
18.1 Studying Viruses and Prokaryotes
Flu Attack
• http://www.youtube.com/watch?v=Rpj0emEGShQ
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
and Prokaryotes
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
and Prokaryotes
Attachment to a host cell
• Virus - recognize and attach to a receptor site on the
plasma membrane of host
• Protein on capsid locks with receptor site
• Each virus has a specifically shaped attachment protein
(jigsaw puzzle)
– Can only attach to a few hosts
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
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Viruses cause two types of infections.
1. Lytic
2. Lysogenic
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
and Prokaryotes
Lytic cycle
• Virus invades a host cell
•  produces new viruses (transcription, translation and
assembly)
•  immediately destroys host releasing newly formed
viruses - virulent virus
• Lysis - cell disintegration
18.1 Studying Viruses and Prokaryotes
host bacterium
Lytic Cycle
The bacterophage attaches
and injects it DNA into a host
bacterium.
The host bacterium breaks apart, or
lyses. Bacteriophages are able
to infect new host cells.
The viral DNA forms
a circle.
The viral DNA directs the host
cell to produce new viral parts.
The parts assemble into new
bacteriophages.
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
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Lysogenic Cycle
• Infect a cell without causing its immediate destruction - temperate
virus
• Viral DNA is integrated into hosts DNA – prophage
• Can stay in host cell for an extended period of time
• Every time host cell reproduces = prophage is replicated
• Every cell is also infected
• Trigger will activate lytic cycle later
• Ex: Herpes, chicken pox
18.1
StudyingCycle
Viruses and Prokaryotes
Lysogenic
The prophage may leave the
host’s DNA and enter the
lytic cycle.
The viral DNA is called a prophage
when it combines with
the host cell’s DNA.
Many cell divisions produce a
colony of bacteria infected
with prophage.
Although the prophage is not
active, it replicates along with
the host cell’s DNA.
18.2
Structure Viruses
and Reproduction
18.1Viral
Studying
and Prokaryotes
Retroviruses
• RNA viruses
• Most complex replication cycle
• Ex: HIV
Once inside host retrovirus makes DNA
• Reverse transcriptase – produce DNA from viral RNA
• Then it is integrated and becomes a prophage
If reverse transcriptase is in a person then they have been infected with
a retrovirus
18.3
Diseases Viruses and Prokaryotes
18.1Viral
Studying
Viruses cause many infectious diseases
18.3
Diseases Viruses and Prokaryotes
18.1Viral
Studying
Common human viral diseases
• Rabies - transmitted by the bite of an infected animal
– virus is carried in saliva
– virus travels from wound to central nervous system
– fever, headache, throat spasms, paralysis, coma
18.3
Diseases Viruses and Prokaryotes
18.1Viral
Studying
Chicken pox
• Virus multiplies in lungs, uses blood vessels to reach
skin
• Fever, skin rash
• Transmission from direct contact with the skin rash and
through the air
• Recover - usually followed by a lifelong resistance to
re-infection
• Can persist in nerve cells as a prophage - cause
shingles later in adulthood
• Fever is higher
• Immune system weakens
• Pneumonia may occur
18.3
Diseases Viruses and Prokaryotes
18.1Viral
Studying
HIV
• Human immunodeficiency virus
• Infects white blood cells
• Prophage eventually enters lytic cycle leading to rapid decrease in
white blood cells
• AIDS - acquired immunodeficiency syndrome
• Person dies from other infections
18.3
Diseases Viruses and Prokaryotes
18.1Viral
Studying
Prevention and Treatment
Treatment
•
Antiviral Drugs- interfere with viral nucleic acid
synthesis
Prevention
•
Vaccination - stimulates body’s immune system to
provide protection against that pathogen
1. Inactivated - viruses do not replicate in a host system
2. Attenuated - viruses are genetically altered so that
they are incapable of causing disease under normal
circumstances
• (preferred - protection is greater and lasts longer)
18.3
Diseases Viruses and Prokaryotes
18.1Viral
Studying
18.4
and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
KEY CONCEPT
Bacteria and Archaeabacteria are both singlecelled prokaryotes.
18.4
and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Bacteria
Classification:
• Kingdom: Monera
• Eubacteria (germs)
&
Archaeabacteria
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and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Microscopic Prokaryotes
• Unicellular
• No nucleus
• No membrane-bound organelles
• Alive!
• Can do cell functions!
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and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Archaebacteria: The extremists
• Unusual lipids (fats) in their cell membranes
• Introns (junk) in their DNA
• Cell wall lacks Peptidoglycan (protein carbohydrate
compound found in cell walls of eubacteria)
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and Archaeabacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Extreme Environments: Examples
Methanogens - convert hydrogen and carbon dioxide into
methane gas
•
Live in anaerobic conditions ex: bottom of a swamp and
sewage, intestinal tract of humans and other animals
Extreme Halophiles - live in high salt concentrations
•
Use salt to generate ATP
18.4
and Archaeabacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Thermoacidophiles - live in extremely acidic environments
that have extremely high T
• T up to 110 degrees C (230 degrees F)
• Ph less than 2
• Hot springs, volcanic vents, hydrothermal vents
18.4
and Archaebacteria
18.1Bacteria
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Viruses and Prokaryotes
Eubacteria commonly named for shape
•
•
•
•
•
•
Rod-shaped - bacilli
Spiral - spirilla or spirochetes
Spherical – cocci
Streptococci – chains of cocci
Staphylococci – grapelike clusters of cocci
Vibrio - coma shaped
Lactobacilli:
rod-shaped
Enterococci: spherical
Spirochaeta: spiral
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and Archaebacteria
18.1Bacteria
Studying
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Eubacteria:
Streptococci
Staphylococci
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and Archaebacteria
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Studying
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Eubacteria structure
• Cell membrane - contains enzymes that catalyze the
reactions of cellular respiration
• DNA is a single, closed loop
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and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
• Capsule - outer covering made of polysaccharides
(sugars) protect it against drying out or harsh chemicals
• Pili - short hair-like protein structures found on the
surface of some species of bacteria
*help bacteria adhere to host cells
*used to transfer genetic material
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and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Movement Structures
• Flagella - turn and propel the bacterium (single or
multiple)
• Layer of slime - wavelike contractions of
outer membrane propel it
• Spiral - shaped bacteria move by corkscrew-like rotation
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and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
pili
plasma
membrance
chromosome
cell wall
plasmid
This diagram shows the typical structure
of a prokaryote. Archaea and bacteria
look very similar, although they have
important molecular differences.
flagellum
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and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Endospores
• Dormant structure that is produced by some (grampositive) bacterial species that are exposed to harsh
environmental conditions
• Help bacteria resist high temperatures, harsh chemicals,
radiation, drying and other environmental extremes
• Conditions become favorable endospore will open,
allowing the living bacterium to emerge and multiply
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and Archaebacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
• Gram staining identifies bacteria.
– stains peptidoglycan
– gram-negative - stains pink - less peptidoglycan
– gram-positive - stains purple - more peptidoglycan
Gram-negative bacteria have a thin layer of
peptidoglycan and stain red.
Gram-positive bacteria have a thicker peptidoglycan
layer and stain purple.
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and Archaebacteria
18.1Bacteria
Studying
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Gram-positive bacteria
Examples:
• Streptococci - causes strep throat
• Grow in milk producing lactic acid  yogurt
• Lactobacilli - found on teeth cause tooth decay
• Actinomycetes - form branching filaments, found in soil, and
produce antibiotics
• Exotoxin - secreted into the environment and cause disease
(Tetanus)
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and Archaebacteria
18.1Bacteria
Studying
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Gram-Negative Bacteria
Examples:
• Escherichia coli - lives in human intestine where it produces
vitamin K and assists enzymes in the breakdown of foods
• Salmonella - responsible for food poisoning
• Chemoautotrophs
• Endotoxin - Not released until bacteria die
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and Archaebacteria
18.1Bacteria
Studying
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*Gram positive and gram negative have different
susceptibilities to:
• antibacterial drugs
• produce different toxic materials
• react differently to disinfectants
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and Archaebacteria
18.1Bacteria
Studying
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Heterotroph
• Saprophyte - feed on dead and decaying material
• parasitic
Autotroph
• Photoautotrophs - sunlight to make E (Cyanobacteria)
• Chemoautotrophs – chemicals to make E
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18.1Bacteria
Studying
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Eubactria can be grouped by their need for oxygen.
• Obligate anaerobes - are poisoned by oxygen
• Obligate aerobes - need oxygen
• Facultative aerobes - live with or without oxygen
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and Archaeabacteria
18.1Bacteria
Studying
Viruses and Prokaryotes
Examples:
• Obligate Anaerobes - Clostridium tetani – Tetanus
• Facultative anaerobes - E. coli
• Obligate Aerobes - Mycobacterium tuberculosis Tuberculosis
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Spirochetes
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•
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Gram-negative, spiral shaped, heterotrophic bacteria
Aerobic or anaerobic
Move by corkscrew rotation
Live freely, symbiotically, or parasitically
Treponema pallidum causes syphilis
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and Archaebacteria
18.1Bacteria
Studying
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Cyanobacteria (Blue-Green algae)
• Photosynthetic
• Encased in a jellylike substance and often cling together in
colonies
Eutrophication - population bloom - sudden increase in the
number of an organism due to large increase of nutrients
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and Archae
18.1Bacteria
Studying
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Asexual Reproduction
• Binary Fission
• rapid
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18.4
Beneficial
and
Roles
Archaebacteria
of Prokaryotes
18.1Bacteria
Studying
Viruses
and Prokaryotes
Genetic Recombination
• Transformation - bacterial cell takes in DNA from
external environment
• Conjugation - two living bacteria bind together and one
bacterium transfers genetic information to the other
• Pili binds to bacteria to form a conjugation bridge
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and Archaebacteria
18.1Bacteria
Studying
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conjugation bridge
TEM; magnification 6000x
18.5
Roles
of Prokaryotes
18.1Beneficial
Studying
Viruses
and Prokaryotes
KEY CONCEPT
Prokaryotes perform important functions for
organisms and ecosystems.
18.5
Roles
of Prokaryotes
18.1Beneficial
Studying
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and Prokaryotes
Prokaryotes provide nutrients to humans and other
animals.
• Prokaryotes live in digestive systems of animals.
– make vitamins
– break down food
– fill niches
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Roles
of Prokaryotes
18.1Beneficial
Studying
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and Prokaryotes
• Bacteria help ferment many foods.
– yogurt, cheese
– pickles, sauerkraut
– soy sauce, vinegar
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Roles
of Prokaryotes
18.1Beneficial
Studying
Viruses
and Prokaryotes
Prokaryotes play important roles in ecosystems.
• photosynthesize
• recycle carbon, nitrogen,
hydrogen, sulfur
• fix nitrogen
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Roles
of Prokaryotes
18.1Beneficial
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Viruses
and Prokaryotes
• Bioremediation uses prokaryotes to break down
pollutants.
– oil spills
– biodegradable materials
18.6
Diseases
and Antibiotics
18.1Bacterial
Studying
Viruses
and Prokaryotes
KEY CONCEPT
Understanding bacteria is necessary to prevent
and treat disease.
18.6
Diseases
and Antibiotics
18.1Bacterial
Studying
Viruses
and Prokaryotes
Some bacteria cause disease.
18.6
Diseases
and Antibiotics
18.1Bacterial
Studying
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and Prokaryotes
Bacteria cause disease
•
•
•
•
Plants and animals
Carried in air, food, and water
Sometimes invade through skin wounds
Growth of bacteria can interfere with normal function of
body tissue
• Or it can release a toxin that directly attacks host
18.6
Diseases
Antibiotics
18.5 Bacterial
Beneficial
Roles
of and
Prokaryotes
18.1
Studying
Viruses
and Prokaryotes
Bacterial Diseases
• Transmitted by ticks
• Borrelia burgdorferi - causes Lyme disease
– Bull’s eye rash around bite mark
– Sever headaches, backaches, chills, and
fatigue- can lead to death
• Rickettsia rickettsii - causes Rocky Mountain
spotted fever
– 3-12 days after infection- high fever and
severe headache
– 3-5 days after that- rash on extremities,
diarrhea, cramps- can lead to death
18.6
Diseases
and Antibiotics
18.1Bacterial
Studying
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and Prokaryotes
• Normally harmless bacteria can become destructive.
– may colonize new tissues
18.6
Diseases
and Antibiotics
18.1Bacterial
Studying
Viruses
and Prokaryotes
• Normally harmless bacteria can become destructive.
– immune system may be lowered
18.6
Diseases
Antibiotics
18.5 Bacterial
Beneficial
Roles
of and
Prokaryotes
18.1
Studying
Viruses
and Prokaryotes
Antibiotics - interfere with bacteria cellular functions
Antibiotics do not work on viruses
• Penicillin - interferes with cell wall synthesis
• Tetracycline - interferes with protein synthesis
• Sulfa Drugs - are made in laboratories
18.6
Diseases
and Antibiotics
18.1Bacterial
Studying
Viruses
and Prokaryotes
Bacteria can evolve resistance to antibiotics.
• Bacteria are gaining resistance to antibiotics.
A bacterium carries genes
– overuse
for antibiotic resistance on
a plasmid.
– underuse
– misuse
A copy of the plasmid is
• Antibiotics must be transferred through
conjugation.
used properly.
Resistance is quickly
spread through many
bacteria.
18.6
Diseases
Antibiotics
18.5 Bacterial
Beneficial
Roles
of and
Prokaryotes
18.1
Studying
Viruses
and Prokaryotes
Antibiotic Resistance
• Population of bacteria exposed to antibiotic Most
susceptible bacteria die first a few mutant bacteria are
resistant and may continue to grow and multiply
results in a resistant population