Transcript Prokaryotes and Viruses - shsbiology / FrontPage

Prokaryotes and Viruses
Biology I
16.1 Prokaryotic life began on a young Earth
Stromatolites=
Ancient fossils found
in dome-shaped rocks
Used as evidence
bacteria were present
3.5 billion years ago.
How did life begin?
Origin of small molecules
1953 Stanley Miller, simulated
conditions on early Earth
Formation of Organic
Polymers
How did polymers form?
Heat and clay help bind organic
monomers together
Lightening was energy source
Formation Cont.
What was the original process of inheritance?
RNA, short strands could replicate without the use of
enzymes
Formation of Pre-Cells
Early organic materials and RNA became encased in
membranes
Supports 4 stage process:
First, small organic molecules, such as amino acids and
nucleotides
Second, these small molecules joined together into
larger ones such as proteins and nucleic acids.
Third, molecules that could copy themselves provided a
basis for the inheritance of molecular information.
In the last stage, these various organic molecules
became packaged within membranes and separated
from their surroundings. In other words, they formed
pre-cells.
Where did life begin?
Shallow waters and
moist sediments such as
clay
Deep-sea thermal vents
16.2 Diverse prokaryotes populate the biosphere
Diversity of Prokaryotic Life
-found EVERYWHERE
Archaea
“ancient” bacteria
Extremophiles:
Consists of three types
Thermophiles – heat lovers
Halophiles – salt lovers
Methogens – live anaerobic environment, produce
methane gas
DNA evidence indicates closer relationship to
eukaryotes than bacteria
Differences between Archaea and Bacteria
Differences in RNA and DNA information
Enzymes that catalyze RNA are different
Bacteria lack introns
Antibiotics effective only to Bacteria
Archea cell walls lack petidoglycan
Structure and Function of Bacteria
Bacteria is identified and distinguished based
partly on three characteristics.
Cell Shape



–cocci (round)
bacilli(rod)
spiral(spirochetes)
Structure and Function of Bacteria
Cell Wall Structure
Two types of cell walls
Determined by a Gram
stain


Gram positive
bacterium (purple)
Gram negative
bacterium (pink)
Structure and Function of Bacteria
Motility
Flagella
Pili
Slimy threads
Asexual Reproduction
Binary fission
Rapid reproduction
Cloning of the parent
Can have mutations, antibiotic resistance
Sexual Reproduction
Transformation – bacterium takes up free DNA
from the environment
Conjugation – two bacterial cells temporarily join
and directly transfer genetic material between them
Transduction – virus phage inserts genetic
material
Endospore Formation – dormant bacteria with
highly resistant outer wall
Genetic Variation
Modes of Nutrition
Cyanobacteria and Oxygen
Believe to be the first
photoautotrophs.
Helped bring oxygen in
the atmosphere
Revolutionized the
evolution of aerobic
organisms and cellular
respiration.
16.3 Prokaryotes perform essential
functions in the biosphere
Chemical recycling– help in
breaking down or
decomposing, organic waste
products and dead
organisms
e.g. carbon locked in organic
compounds returned to
atmosphere as CO2
Used in nitrogen gas
conversion through legumes
Nitrogen Cycle
Human uses of bacteria
Use of organisms to
remove pollutants
from water, air and
soil – bioremediation
Used in sewage
treatment, oil clean
up, mining clean up,
genetic exploration
PCB clean up
16.4 Some Prokaryotes cause disease
Pathogen – bacteria or other microorganism that
cause a disease.
Bacteria can invade the cell and destroy it
Develop toxins
Secrete toxins from the bacterial cell Exotoxins


can destroy the cell or interfere with cell function
Cause digestive problems or paralysis
Toxin is a component of the bacterial cell wall
Endotoxins

Causes the body to respond (immune system) with fever,
aches, weakness, or can lead to shock.
Diseases and Methods of Transmission
Inhalation
Anthrax
Tuberculosis
Sexual
Syphilis
Gonorrhea
Bites
Lyme disease
Improperly stored or prepared foods
Botulism
salmonella
Bacterial Diseases
Tuberculosis
Invades tissues and
destroys cell
Engulfs white blood cells
Bacterial Diseases caused by
poisons
Closstridium botulinum –
botulism
1 gram of pure toxin
could kill 1 million people
Staphylococcus aureus –
Staph infection
Secretes a poison by the
bacterial cells
Proteins secreted cause
the illness
Diseases caused by bacteria
Salmonella –
Is a component of the cell
wall that causes the
illness
Can also cause typhoid
fever
Defense against bacteria
Hygiene –wash your hands, stay clean
Clean drinking water
Don’t get run down, weakens the immune
system
Antibiotics, resistance to antibiotics
16.5 Viruses infect cells by inserting genes
Virus is not a cell, cannot
reproduce on its own.
Structure of a virus
Protein coat
Genetic material, either RNA
or DNA
Virus reproduction
Two reproductive cycles
Lytic cycle
1. Host cell produce virus parts
2. Virus parts assemble
3. Host cell bursts, releasing hundreds of complete,
functioning viruses
Lysogenic cycle
1. Viral DNA combines with host DNA
2. Host cell replicates as normal
3. Then converts to lytic cycle
Viral reproduction
Viruses and Disease
Viruses have an outer envelop that help the virus
enter and leave a cell
Contain RNA as genetic material
Common cold, flu, measles, mumps, polio, AIDS
Contain DNA as genetic material
Hepatitis, herpes infections
Antibiotic do not work against viruses
HIV– A retrovirus
Retrovirus –
uses RNA as
genetic material
versus DNA
Defense against Viruses
Vaccines –dead or disabled pieces of virus that
fool immune system, form future resistance
First vaccine –Edward Jenner, small pox vaccine
Some may not work as the virus mutate too
quickly for a vaccine to work (HIV)