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Bacteria Bacteria • Unicellular • Prokaryotes • Cells walls containing peptidoglycan Bacteria • Extremely Abundant – Cover nearly every square centimeter of Earth Bacterial Shapes • Bacilli: rod shaped – Bass-ill-eye • Cocci: spherical – Cox-eye • Spirilla: spiral, corkscrew – Spy-rill-uh What are the differences between eubacteria and archaebacteria? Eubacteria versus Archaebacteria • Cell walls of Eubacteria have lots peptidoglycans (mesh of sugar and amino acids) – Archaebacteria do not • Archaebacteria often live in very extreme environments (hot springs, digestive tracts, Great Salt Lake, etc.) Cell Walls Gram staining is a diagnostic tool used to classify bacteria • Gram positive: stain violet – due to thick peptidoglycan walls – Eubacteria or archaebacteria? • Gram negative: stain pink/red – No peptidoglycans in cell walls Metabolism • Bacteria can be heterotrophic or autotrophic – Remember: autotrophs are not ALL photosynthesizers! – Some are chemosynthesizers (convert carbon into organic compounds) How Bacteria Reproduce: Binary Fission • When a bacterium has doubled in size, it replicates its DNA and divides in half • Sexual or asexual? • Identical or different daughter cells? If bacteria are identical, how do they evolve? Where does genetic variety come from (besides natural mutation rate)? Genetic Variety in Bacteria • Conjugation: cell-to-cell contact • Transformation: bacterium takes up foreign DNA from surrounding environment • Transduction: DNA is transferred from one bacterial cell to another by a virus Conjugation • A hollow bridge (pilus) forms between two bacteria and genes move from one cell to the other • Increases genetic diversity of a population Conjugation Transformation • Bacteria take in foreign DNA from surroundings and incorporate it into their own DNA *Remember Griffith’s experiment Transduction • DNA is transferred from one bacterium to another by a virus • When new bacteriophages are made, they may contain a small amount of the host cell’s DNA 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 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 sporozoan zooflagellate Sarcodine (amoeba) 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 Review!