1. Ch 16: Prokaryotes & Viruses
Vocabulary
Stromatolite
Arachaea
Bacteria
Coccus
Bacillus
Spirochete
Binary fission
Endospore
Cyanobacteria
Bioremediation
Pathogen
Lytic cycle
Lysogenic cycle
Retrovirus
Vaccine

2. 16.1: Early Earth Earth is about 4.6 billion years old
Fossils resembling photosynthetic prokaryotes have been found in dome shaped rocks called stromatolites, date back to 3.5 billion year ago.

3. 16.1: Origin of Organic Molecules
In 1953, Miller & Urey designed an experiment to simulate conditions on early Earth
Under many different conditions produced all 20 amino acids, several sugars, lipids, the nitrogenous bases found in DNA & RNA and ATP
Solutions of amino acids dropped onto the surface of hot sand, clay or rocks has resulted in the formation of polypeptides

4. 16.1: The RNA World
A characteristic of life is the process of inheritance
Need molecules that can copy themselves.
Today: DNA  RNA  Protein
How did this information flow originate?
A popular hypothesis is that genes were originally short strands of RNA capable of replicating without enzymes
Scientists have observed RNA molecules copying themselves in solutions containing nucleotides without enzymes or cells present
During the “RNA world”, RNA might have stored genetic information in addition to directing protein synthesis

5. 16.1: Formation of Pre-Cells
Experiments have shown that polypeptides can form microscopic fluid-filled spheres.
If certain kinds of lipids are in the solution selectively permeable membranes will form.
These “molecular packages” are referred to as pre-cells

6. Hypothetical 4-Stage Sequence for Origin of Life
Small organic molecules formed fr. simpler inorganic molecules
Small molecules joined into complex ones
Molecules that could copy themselves provided a basis for inheritance of molecular information
These molecules became packaged within membranes and separated from their surroundings

7. 16.1: 1st Life is Prokaryotic
ARCHAEA
“archaea” = ancient
Exist in harsh habitats resembling conditions of early Earth
“Extremophiles”
Thermophiles (heat)
Halophiles (salt)
Anaerobic (no oxygen)
Believed to be as closely related to eukaryotes as they are to bacteria
BACTERIA
Contain diff. info. in nucleic acids
RNA polymerases differ
Lack introns (junk DNA)
Susceptible to antibiotics that do not affect archaea
Contain peptidoglycan in their cell walls

8. Phylogenic Tree of the Three Domains

9. 16.2: Bacteria Structure & Function
Cocci – spherical (Pnemonia)
Bacilli – rod-shaped (E.coli)
Spirilla – spiral shaped (siphilis)

10. 16.2: Structure & Function of Bacteria: Cell Wall
Gram + (purple stain): thick layer of peptidoglycan (absorbs more stain)
Gram – (pink stain): thinner layer of peptidglycan with outer membrane

11. 16. 2: Structure & Function of Bacteria: Motility
Flagellum (whip)
Pilli (hair)
Slime secretion (ooze)

12. Bacterial Reproduction: Binary Fission (ASEXUAL)
DNA is copied & moved to opposite ends of the cell as the cell divides; occurs almost continuously.
Rapid rate (every 20 min)
Results in a colony of cells that are clones (unless mutations occur)

13. Genetic Variation in Bacteria: Conjucation
2 bacterial temporarily join
exchange plasmid DNA; does not need to occur between cells of the same species/strain
not same as sex. Repro. (just involves exchange small amounts of DNA)

14. Genetic Variation in Bacteria: Transformation
Fragments of foreign DNA “picked up” and incorporated into bacteria chromosome (usu. Fr. Dead bacteria cells)

15. Endospores
Allow bacteria to survive periods of very harsh conditions by going into a dormant endospore form
After copying DNA, one copy is surrounded by a thick protective coat and the outer cell disintegrates
Can survive for years; when conditions are favorable, the endospores will absorb water and grow again.

16. Modes of Nutrition

17. 16.2: Evolution of Cyanobacteria
250 ma
Change Earth’s environment; CO2 atmosphere  O2 atmosphere; cool planet down.

18. 16.2: The Oxygen Revolution
The evolution of photosynthetic cyanobacteria resulted in the presence of free oxygen in oceans, lakes & the atmosphere
O2 = toxic to many existing organisms (attacks bonds of organic molecules); Causes a mass extinction
Some were not exposed to oxygen and remained anaerobic; their descendants still exist in similar environments today (anaerobic bacteria)
Some were able to use the oxygen to get energy fr. Food  diversify to become aerobic organisms in existence today

19. 16.3: Beneficial Uses of Bacteria
Chemical recycling:
Decomposers: replenish soil nutrients and release CO2 back to the atmosphere
Nitrogen fixing bacteria: convert nitrogen gas in the atmosphere to an organic form usable by other organisms for nucleotide and amino acid formation
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
Medicine/Pharmaceuticals:
Produce desired gene products: insulin, HGH
Probiotics: restore beneficical intestinal bacteria
Food:
Cheese
Yogurt

20. 16.4: Bacteria & Disease
Pathogens = Bacteria that cause disease. Prevention: Water filtration & hand washing Treatment: Antibiotics (prevent cell wall formation) Common bacterial infections: strep throat, pneumonia, staph (wound) infections, upper respiratory infections

21. 16.5: Viruses Not technically a living organism.
Much smaller than bacteria.
Cannot reproduce on its own; must infect and use living cells to repro.
Consist of DNA/RNA + protein coat

22. 16.5: Viral Structure

23. 16.5: Viral Reproductive Cycles
Lysogenic cycle
(No bursting open; viral DNA incorp. & copied)
Lytic cycle
(cell bursts open w/ viruses)

24. Viruses & Disease Different fr. bacteria
Antibiotics will not work on viruses b/c antibiotics target bacteria cell walls.
Some examples of viral diseases include:
Influenza (RNA) Polio (RNA)
Common cold (RNA) Hepatitis (DNA)
Measles (RNA) Herpes (DNA)
Mumps (RNA) Smallpox (DNA)
AIDS (RNA) Rabies (RNA)

25. Retroviruses & HIV
Retroviruses reverse the normal DNA to RNA to protein flow
In RNA viruses, the RNA nucleotide will be translated
Reverse transcriptase catalyzes the synthesis of DNA from an RNA template, the DNA intermingles with host DNA as a provirus making it difficult to detect

26. Defense Against Viral Diseases: Immunization (not antibiotics)
Vaccines are made from pieces of virus (antigens = surface markers)
Immune cells launch an “attack” and trigger formation of antibodies (memory cells) that will recognize that virus when it invades. When real virus enters body, body attacks virus b4 it can multiply.
Don’t get flu fr. Vaccine b/c it is not an intact working virus.