Transcript Prokaryotes

Prokaryotes
16.1-16.10
Phylogenic Tree of the Three Domains
Prokaryote: Bacteria & Archaea
Prokaryotes: Archaea
• = Ancient
• Exist in harsh habitats; early Earth
• “Extremophiles”
– Thermophiles: hot springs/
volcanic vent
– Halophiles: salty bodies of water
– Methanogens” anaerobic mud;
give off methane; “swamp gas”
Similar to Bacteria: small size; lack most organelles; no
true nucleus
Similar to Eukaryotes: similar DNA sequences for ribosomes
& enzymes; “junk” or intron DNA sequences (don’t code for
protein); don’t respond to antibiotics (cell wall is different from
proks)
Prokaryotes: Early Bacteria Forms
• Stromatolites= cyanobacteria that grow in mats on rocklike mounds in shallow reefs; dominate oceans(3 bya)
• Cyanobacteria - Early aerobic bacteria; oxygenate Earth;
cause mass extinction; game changer (oxygen atmosphere:
~2.5 bya)
http://www.bbc.co.uk/science/earth/earth_timeline/first_life
The Oxygen Revolution
• ~2.4 bya
• Evolution of photosynthetic cyanobacteria( ~3 bya) -->
free oxygen in oceans, lakes & the atmosphere
• O2 toxic to most existing organisms --> Mass Extinction
• Stimulates evolution of aerobic organisms (requiring
oxygen)
• Some forms of anaerobic bacteria (no or low O2) still
survive (muddy lake bottoms/swamps)
Bacteria: Pathogens
• Pathogens: disease causing bacteria
How?
1. Secrete protein exotoxins (poisons)
Clostridium toxin --> muscle spasms/lockjaw(tetanus)
S. Aureus --> multiple toxins (necrotizing tissue; vomiting,
diarrhea, fever)
E. Coli --> food poisons
2. Endotoxins = fragments of outer membrane act toxins; fever,
aches, drop in blood pressure
Meningitis - swelling of brain membranes
Salmonella - food poisoning; typhoid
List of bacterial infections;
http://classes.midlandstech.edu/carterp/Courses/bio225/InfectiousDiseases_all_print.htm
Bacteria: Pathogens (Bioweapons)
• Anthrax: live in soil (farms); skin infection not
harmful; inhaled = deadly
• Y. pestis (Plague): bubonic (black death);
pneumonic (disintegrates lungs)
• Clostridium botulinum: 7 toxins;
– Food poisoning
– Deadliest: blocks nerve transmission; stops muscle
contractions (breathing)
– Diluted in botox - relax facial muscles
MRSA =
Methicillin-resistant
Staph. Aureus
Hard to treat staph infection;
Resistant to most antibiotics
Commonly starts as a skin
infection (lesion/wound)
Harmful in elderly; nursing
home & hospitals (weakened
immune systems)
Superbugs: http://www.sosq.vcu.edu/videos.aspx
NY Hostpitals & Superbugs: cbs news http://www.cbsnews.com/videos/cre-superbug-cases-found-in-at-least-43-states/
Antibiotics in animal feed: http://www.cbsnews.com/videos/fda-to-roll-back-use-of-antibiotics-in-beef-pork-and-poultry/
Bacterial Meningitis
http://www.huffingtonpost.com/2013/12/05/meningitis-princeton-uc-santa-barbara-infectionbacterial_n_4392509.html?utm_hp_ref=college&ir=College
http://www.nbcnews.com/health/princeton-agrees-meningitis-vaccine-fight-outbreak-2D11616706
Beneficial Uses of Bacteria
• Medicine/Pharmaceutic:
– Produce desired gene
products (insulin)
• Food: Cheese & Yogurt
• Aid Digestion (probiotics)
• Make vitamin K in
intestines
• Break down cellulose in
termite guts
Beneficial Uses of Bacteria
• Chemical recycling:
– Decomposers: replenish soil nutrients and release CO2 back to the
atmosphere
– N.-fixing bacteria: convert nitrogen gas in the atmosphere to an organic
form usable by plants; grow on roots of beans, nuts, clover
• Bioremediation:
– Sewage treatment: decompose organic matter in sewage sludge
– Oil spill clean-up: genetically modified digest oil
– Clean old mining sites: detoxify by extracting lead & mercury,arsenic
Bacteria: Shape
• Cocci – spherical
• Bacilli – rod-shaped
• Spirilla – spiral shaped
Structure & Function of Bacteria:
Cell Wall
• Gram + (stain):
purple; thick layer
of peptidoglycan
retains dye
• Gram( –) pink
stain; thin layer of
peptidglycan with
outer membrane
Structure & Function of Bacteria: Motility
• Flagellum
• Pilli
• Slime secretion
Bacterial Repro.: Binary Fission
= DNA copied; moved to opposite ends of cell as the cell
divides; occurs almost continuously; ASEXUAL
•Rapid; 20 min.
•Parents &
Offspring
genetically
identical
Plasmids:
•
Loops of DNA found in some bacteria; can
integrate into chromosome & be translated into
proteins
• Can be shared b/w bacteria
• “R” plasmids – carry genes for antibiotic
resistance
Genetic Variation: Sharing Genes
1. Conjugation:
2 bacteria join thru.
temporary bridge and
exchange plasmids.
• Can be b/w diff. species
Genetic Variation: Sharing Genes
2. Transformation:
incorporates DNA
fragments (fr. dead
bacteria) in surroundings
into genome.
3. Transduction:
Bacteriophage (virus
that infects bacteria)
inject fragment of DNA
from previous host
along w/ viral DNA
Original Source of Variation: Mutation
= any alteration of
nucleotide sequence
• Usually results in
malfunction/cell
death
• Occasionally –
translates into new
beneficial trait!
(antibiotic resistance)
Endospores
• Allow bacteria to survive harsh conditions; go into a dormant
endospore form
• DNA copied: one copy surrounded by a thick protective coat:
outer cell disintegrates
• When conditions are favorable, endospores absorb water &
grow again. Ex: anthrax
Modes of Nutrition
Viruses & Bacteriophage:
The Boundary of Life
• All living things share 8 characteristics. Viruses do not meet
all of these characteristics.
• Attack eukaryotic cells; Bacteriophages attack prokaryotic
cells.
• Capable of reproducing at a very rapid rate, but only in
host cell.
• Responsible for many diseases
• Found everywhere.
Viral Structure
Protein coat (capsid)
surrounds viral DNA
or RNA
Viral Structure: Variations
Viruses & Disease
• Method of causing disease is very different from that of
bacteria (…different treatment & prevention methods
too)
• Antibiotics will not work on viruses because they target
specific enzymes not found in viruses or host cells
• Some examples of viral diseases include:
Influenza (RNA)
Common cold(RNA)
Measles (RNA)
Mumps (RNA)
AIDS
(RNA)
Polio (RNA)
Hepatitis (DNA)
Herpes (DNA)
Smallpox (DNA)
Rabies (RNA)
Viral Infection
• Invade cells; use the host cell's
machinery to synthesize own
macromolecules.
• Reproduce in 2 ways:
– 1. Lytic cycle: destroying
the host cell during
reproduction.
– 2. Lysogenic Cycle – a
parasitic type of partnership
with the cell
Lytic Cycle & Lysogenic Cycle
Viruses are host specific – a protein on the surface of the
virus has a shape that matches a molecule in the plasma
membrane of its host, allowing the virus to lock onto the
host cell.
Proviruses
DNA virus that has been inserted into a host cell chromosome.
Retroviruses & HIV
• Retroviruses reverse the
normal DNA to RNA to
protein flow
– RNA viruses: RNA 
DNA  protein
• Reverse transcriptase
catalyzes synthesis of DNA
fr. RNA template
• DNA intermingles w/ host
DNA as a provirus making it
difficult to detect
Prions
• Proteins that cause several diseases
of the brain: Mad cow disease, Kuro,
Creutzfeldt-Jacob disease (CJD) &
Scrapie (in sheep)
• Only infectious agent that do not
contain genetic material
• Normal form play important roles in
helping brain function (nerve cells
communication)
• Abnormal prions destroy the brain
• Three ways to acquire abnormal
prions:
– Infection with abnormal prions
– Inherited genes that give rise to abnormal
prions
– Spontaneous genetic mutations that give
rise to abnormal prions
Viroids
• Small strands of RNA rather than strands of protein.
• Smaller than the strands of genetic info in viruses and contain no
protein coat.
• Replicated using host cell machinery, like viruses
• Cause plant diseases: potato spindle tuber, avocado sunblotch,
chrysanthemum stunt, and chrysanthemum chlorotic mottle
Immune Response
VACCINES: Defense Against
Viral Diseases
Vaccines =
immunizations
Made from weakened
(attenuated)
bacteria/viruses or parts
(anitgens/ fragments) of
bacteria/viruses
Antigens of pathogen
elicit immune response
without you “getting” sick.
HIV doesn’t target just any cell, it goes right for the cells that want to kill
it. “Helper" T cells are HIV's primary target. These cells help direct the
immune system's response to various pathogens.
HIV is an RNA retro-virus that targets helper T cells.
Helper T cells deplete & immune response is compromised.
The virus can infect 10 billion cells a day, yet only about 1.8
billion can be replaced daily.
From HIV to AIDS
• During first few years (7-10) after HIV infection, person is
usually asymptomatic.
• During the symptomatic phase, the body has insufficient
numbers of T-Cells (from normal 800-1200 /mm3 to 200/ mm3 )
to mount an immune response against infections.
– Chronic diarrhea, minor mouth infections, night sweats, headache
& fatigue are common
• At the point when the body is unable to fight off infections,
a person is said to have the disease AIDS. (Generally when
count drops below 200 /mm3 )
• It is not the virus or the disease that ultimately kills a
person; it is the inability to fight off something as minor as
the common cold.
AIDS: The Global Epidemic
• Around 2.6 million people became infected with HIV in 2009.
• Sub-Saharan Africa has been the hardest hit by the epidemic. In 2009
over two-thirds of AIDS deaths were in this region