ProkaryotesProkaryotes16.1-16.10

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 rock-like 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 bacteriaHow?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; typhoidList 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.aspxNY 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-infection-bacterial_n_4392509.html?utm_hp_ref=college&ir=Collegehttp://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

• 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.

Viruses & Bacteriophage: The Boundary of Life

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) Polio (RNA)

Common cold(RNA) Hepatitis (DNA)

Measles (RNA) Herpes (DNA)

Mumps (RNA) Smallpox (DNA)

AIDS (RNA) Rabies (RNA)

Viral InfectionViral 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 CycleLytic 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.

ProvirusesProvirusesDNA 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 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

ViroidsViroids• 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 AIDSFrom 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 EpidemicAIDS: 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