Chapter 16Prokaryotes and Viruses

16.1 Prokaryotic Life

• Earth’s timescale in a year/ 365 days

• formed at midnight Jan 1• time now at 11:59:59 on Dec 31

– Early February ~ 400 million years after forming• Earth’s crust began to cool and solidify

– Mid February ~ 3.9 billion years ago• simple forms of life

– Late March ~ 3.5 billion years ago• fossil evidence of life; found in stromatolites

Tree of Life video

Early Earth

• atmosphere contained carbon monoxide, carbon dioxide, nitrogen, water vapor, no oxygen

• more intense volcanoes, UV light, lightning

Stromatolites

• stromatolites: composed of thin layers of sediment pressed tightly together– similar to layered

mats found by colonies of photosynthetic prokaryotes

– photosynthesis is complex, so these were probably not first

Stanley Miller (1958)• simulated conditions on early Earth• experiment produced variety of small organic

molecules essential to life, including amino acids– organic polymers, polypeptides, could have formed under

conditions found on early Earth

Original Process of Heredity

• Hypothesis: genes were short strands of RNA that could replicate without enzymes– experiments show that

short RNA can replicate in a solution of nucleotides without enzymes

Formation of Pre-Cells

• Early organic molecules became organized into increased levels of order by becoming encased in a membrane

• Experiments show: polypeptides come together and form microscopic , fluid-filled spheres

4-Stage Sequence to Cells

1. Small organic molecules formed simpler molecules present in the environment

2. The molecules joined together into larger ones, like proteins

3. Molecules that could copy themselves provided a basis for inheritance

4. Various organic molecules became packaged within membranes and separated from surroundings

Where Did Life Begin?

• Most likely: Deep sea vents; provided energy– land surface too hot

http://www.sciencechannel.com/tv-shows/greatest-discoveries/videos/100-greatest-discoveries-hydrothermal-vents/

16.2 Prokaryotes populate the biosphere

• Prokaryotic organisms outnumber all eukaryotes combined

• Cause diseases and infection: TB, strep throat, STD, food poisoning

• Helpful: E. coli releases vitamins, bacteria in mouth prevents fungi

• Convert nitrogen in air to soil for plants

Archaea

• Live in some of the most extreme environments; resemble early Earth

• Archaea and Bacteria diverged early in their evolution

• As closely related to bacteria as they are eukaryotes

https://www.youtube.com/watch?v=0W-uItr5M4g

Extremophiles

• “extremophiles” = lovers of the extreme

• Thermophiles = heat– Makes sulfur that

hardens into fossils

• Halophiles = salt• Oxygen free swamps

where they produce methane

https://www.youtube.com/watch?v=VU-A6Sx7k-U

Bacteria

• Differ from archaea in features of structure and chemical makeup; DNA/RNA

• RNA polymerase small and simple in bacteria; archaea are complex and similar to eukaryotes

• Some antibiotics that kill bacteria, do not kill archaea

• Cell wall contains peptidoglycan (sugars and polypep.); not in archaea or eukaryotes

Bacteria Classification

• Cell Shape

• Cell Wall structure

• Motility

• Nutrition

1. Cell Shape

• 3 basic shapes: spherical, rod-shaped, spiral-shaped

• Cocci: spherical bacteria; form chains (Streptococcus) or clusters

• Bacilli: rod-shaped (E. coli)

• Spirilli: spiral-shaped (syphilis and Lyme disease)

2. Cell Wall Structure

• Two types of cell walls next to plasma membrane

1. Mostly of peptidoglycan;

2. Has less peptidoglycan and an outer membrane

Gram Staining

• Distinguishes between the two types; some antibiotics only work against one type (Gram-positive)

• Stain bacteria with violet dye, then pink

• Gram-positive - retain purple dye

• Gram-negative - takes on pink dye

3. Motility

• Half of all prokaryotes are motile• Move toward or away from chemical and physical

signals; toward food, light, oxygen; away from toxins• Some form chains of cells that secrete slimy threads;

move along by extending threads

Bacterial flagellum (different than eukaryotes) - scattered on surface or concentrated at an end

Pili - shorter and thinner ; help bacteria stick to each other or surfaces

4. Modes of Nutrition• Photoautotroph: energy from light to make compounds from carbon

dioxide• *Chemoautotrophs: use carbon dioxide as carbon source, but get energy

from inorganic substances (ex ammonia) • *Photoheterotrophs: use light to make ATP but get carbon from organic

compounds• Chemoheterotrophs: consume organic molecules for energy and carbon * = found only in prokaryotes

Reproduction• Binary fission: DNA copies move to opposite

ends of cell as it splits; much simpler than mitosis

• Rapid Reproduction– Many are capable of copying

themselves every 20 minutes– 12 hours, single cell =

68 billion cells– Run out of food and space

Genetic Variation

• Transformation: take up pieces of DNA from the environment• Conjugation: two bacterial cells join and transfer DNA between

– Involves plasmids

• Transduction: viruses infect bacteria

Endospore Formation• Endospores: specialized

“resting” cell that forms in harsh conditions (ex. Anthrax)

• Inner cell, endospore, can survive without food, water, heat, cold, etc for long periods of time

• When exposed to good conditions, they can absorb water and become active

Cyanobacteria

• Cyanobacteria: photoautotrophic bacteria that generates oxygen as waste product

• Oxygen was toxic to organisms of early Earth because it reacted with bonds

• Some organisms were able to use the oxygen produced by the cyanobacteria in helping to extract energy from food

• *cellular respiration

16.3 Prokaryotes perform essential functions in the biosphere

• Chemical Recycling– nitrogen-fixing bacteria convert

nitrogen in the air to nitrogen in soil for plants to use; nitrogen cycle

– Return carbon dioxide into the air and decompose waste; carbon cycle

Human Uses

• bioremediation: use of organisms to remove pollutants from water, air, and soil– Sewage treatment; prokaryotes

decompose organic matter in sludge which can then be used as landfill or fertilizer

Cleaning Oil Spills and Mining Sites

• Pseudomonas - clean oil spills• Mining sites have toxic chemicals

– Thiobacillus thrive in acidic waters of mines to extract lead and mercury from the runoff

– The metabolic process also adds sulfuric acid to the water; acid rain

• Also use bacteria to make vitamins and antibiotics

Do Now

• Take out your poster and hang it on the wall somewhere in the room.

• What is a pathogen?

• HW: Ch 16 Quest on Friday• You are responsible for EVERYTHING in the

PP notes, even if we didn’t go over it in class

Posters

• Find 3 posters that are interesting or gross

• Write down:– The name of the disease– Symptoms – How you get it– Anything interesting

16.4 Some prokaryotes cause disease

• pathogens: bacteria and other microorganisms that cause disease

• The body’s defenses prevent the growth but can become sick when the balance shifts

• Can be transmitted by touch, inhalation, sexual contact, a bite, eating contaminated food

How bacteria effect body cells

• Invade tissues and destroy cells– TB - destroys white blood cells

• Produce poisonous proteins– Clostridium botulinum produces toxic protein that

causes botulism– Staphylococcus aureus is ok on surface, but

causes illness if it enters body by a cut or food

• Poison in bacterial cell wall– Salmonella; food poisoning and typhoid fever

Defense against bacterial diseases

• Skin and mucous lining of mouth, nose and digestive system provide barrier to bacteria

• White blood cells attack invaders

• Antibiotics prevent or damage bacterial cell wall

Let’s get Mono!

• You are going to transmit Mono to other people in the class by “swapping fluids”

• You will each get a cup filled with either water or a base (which reacts to turn pink)

• Rules:– Mix your fluid with 3 people– Keep track of the order that you swapped– Walk around the room. Do not stay in the

same circle of mixers.

Do Now

• How are viruses different than bacteria?

• HW: 16.5 CC and 17.1 CC

16.5 Viruses infect cells

• A virus is not a cell because it lives off of other organisms’ cells only

• Composed of a short piece of DNA or RNA and a protein coat

• Called a “phage”

Reproduction• Bacteriophage= virus that infects bacteria• Lytic cycle: phage attaches to the host cell and injects its DNA

– cell makes copies of viral DNA and proteins– Make copies of original virus and releases from host cell

• Lysogenic cycle: virus injects genes into host– Viral DNA adds itself

to host’s DNA; each time host cell replicates the viral DNA is copied

– Some can remain dormant

Viruses and Disease

• Many animal viruses have outer envelopes made of a phospholipid membrane with spikes of protein

• Flu virus uses RNA not DNA; also colds measles, and HIV

HIV

• HIV has membranous envelope that helps recognize host cells and merge with membrane

• Retrovirus: reverse usual DNA-RNA transcription flow– Carry reverse transcriptase that help

reverse transcription; RNA to DNA

HIV infected cell

• After HIV enters, the protein coat is removed.

• The RNA makes a viral DNA strand and enters the nucleus; can remain inactive for years

• Cell can make new virus particles that bud off

• AIDS occurs when virus reproduces and destroys host cells

Defense against viral diseases

• vaccine: deactivated small pieces of pathogens that stimulate the immune system to defend itself against the actual pathogen

• Edward Jenner (late 1700’s) - first vaccine– Injected a child with cowpox; later

immune to smallpox

• No vaccines against HIV or colds because it mutates too fast

• Some new research on HIV

Concept Check 16.5

1. Describe the lytic and lysogenic life cycles of viruses.2. How is a viral infection different from a bacterial infection?3. During what point of the HIV life cycle does an infected person develop AIDS?4. Describe techniques used to fight viruses in humans.