Bacteria, Viruses, Prions, and Protists. Bacteria Unicellular or Multicellular? Prokaryotic or Eukaryotic? Cells Walls?

Bacteria, Viruses, Prions, and Protists

Bacteria

• Unicellular or Multicellular?

• Prokaryotic or Eukaryotic?

• Cells Walls?

Bacteria

• Unicellular

• Prokaryotes

• Cells walls containing peptidoglycan

Bacteria

• Extremely Abundant– Cover nearly every square centimeter of Earth

What are the differences between eubacteria and

archaebacteria?

Eubacteria versus Archaebacteria

• Cell walls of Eubacteria have peptidoglycans while those of Archaebacteria do not.

• DNA sequences of archaebacteria is more similar to that of eukaryotes than to the DNA of eubacteria

• Archaebacteria often live in very extreme environments (hot springs, digestive tracts, Great Salt Lake, etc.)

Bacterial Shapes

• Bacilli: rod shaped

• Cocci: spherical

• Spirilla: spiral, corkscrew

Cell Walls

• Gram positive: stain violet due to thick peptidoglycan walls

• Gram negative: stain pink/red, have much thinner walls inside lipid layer

Metabolism

Heterotrophs:

• Chemoheterotrophs: must take in organic molecules and a supply of carbon

• Photoheterotrophs: are photosynthetic but also need to take in organic molecules for carbon source

Metabolism

• Photoautotrophs: use light energy to make carbon compounds

• Chemoautotrophs: use energy from chemical reactions to make carbon compounds

• Where might each type of bacteria be found?

Binary Fission

• When a bacteria grows so that it has doubled in size, it replicates its DNA and divides in half

• Is this sexual or asexual?

• Identical or different daughter cells?

Conjugation

• Some bacteria are able to exchange genetic information

• A hollow bridge forms between two bacteria and genes move from one cell to the other

• Increases genetic diversity of a population

Conjugation

Spore Formation

• Spores are formed when the bacteria produces a thick internal wall that encloses the DNA and part of the cytoplasm

• Why do you think this would be beneficial for bacteria?

Spore Formation

• Occurs when conditions are unfavorable for growth

• Can remain dormant for years until conditions improve

Spore Formation

What are some benefits of bacteria?

Benefits of Bacteria• Some are producers that undergo

photosynthesis

• Some are decomposers that break down dead matter to recycle the nutrients

• Some convert nitrogen gas to a form that can be used by plants (nitrogen fixation)

What are some dangers of bacteria?

Dangers of Bacteria

• Break down cells and tissues for food Example: Tuberculosis (destroys lung

tissue)

• Release toxins (poisons) that travel through the body

Example: Streptococcus releases toxins into the blood stream causes strep throat and scarlet fever

Vaccines

• A vaccine is a preparation of weakened or killed pathogens that are injected into the body

• This stimulates the body to produce immunity to the disease

Vaccines

• Why do you think we don’t vaccinate everyone for all disease we have created vaccines for?

Antibiotics

• Antibiotics block the growth and reproduction of bacteria

• Used to treat bacterial infections

Solve the Problem

• What would you do to find out what causes the tobacco leaves to be diseased?

Viruses

• A virus is a core of DNA or RNA surrounded by a protein coat (capsid)

Viruses• They can only reproduce by infecting living

cells

• They enter a cell and use its cell machinery to produce more viruses

Retroviruses

• Contain RNA as genetic information instead of DNA

Would you consider viruses living?

Are Viruses Living?

• Cannot reproduce alone, must have a host cell

• Do not undergo growth or development

• Do not obtain or use energy

• Evolve

Prions

• Diseases such as Scrapie (in sheep) and Mad Cow Disease are not caused by bacteria or viruses. What could cause them?

Prions

• Contain only protein

• Cause disease by forming protein clumps which then induce normal proteins to become Prions

• The build up eventually damages nerve tissue

Protists

• Domain?

• Kingdom?

• Prokaryotic or Eukaryotic?

Protists

• Domain: Eukarya

• Kingdom: Protists

• Eukaryotic

Protists

• Protists are defined by what they are not.

Protists are eukaryotes that are not animals, plants, or fungi.

They were the first eukaryotic organisms on earth.

Types of Protists

• Animal-Like Protists: heterotrophs

• Plant-Like Protists: produce food through photosynthesis

• Fungus-Like Protists: obtain food by external digestion

Animal-Like Protists

• Heterotrophs

cilliate

Sarcodine (amoeba)

sporozoan

zooflagellate

Animal-Like Protists

• Malaria

• African Sleeping Sickness

Plant-Like Protists

• Carry out photosynthesis

Fungus-Like Protists

• Grow in damp, nutrient rich environments

• Absorb food through cell membranes

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