Bacteria Viruses Prions and Protists Bacteria Unicellular or

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