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Bacteria

Bacteria. Learning Targets:. Describe the structure and function of a typical bacterial cell Classify bacteria based on shape and arrangement Describe how bacteria reproduce Summarize the history and adaptations of bacteria Evaluate the importance of bacteria

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Bacteria

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  1. Bacteria

  2. Learning Targets: • Describe the structure and function of a typical bacterial cell • Classify bacteria based on shape and arrangement • Describe how bacteria reproduce • Summarize the history and adaptations of bacteria • Evaluate the importance of bacteria • Identify diseases cause by bacteria

  3. What are bacteria? • Prokaryotes • unicellular • lack a nucleus and membrane-bound organelles • classified in 2 kingdoms • archaebacteria • eubacteria

  4. What are archaebacteria? • live in extreme habitats • Methanogens = oxygen-free environments • Halophiles = very salty environments • Thermoacidophiles = hot, acidic environments

  5. What are eubacteria? • Heterotrophs • Found everywhere • parasites obtain nutrients from living organisms • saprophytes feed on dead organisms/organic waste

  6. Autotrophic eubacteria • photosynthetic autotrophs • Obtain energy from light • Make own food Cyanobacteria

  7. Chemosynthetic autotrophs • break down & release the energy of inorganic compounds containing S & N to make organic molecules that are their food

  8. Anatomy of a bacterium? • Cell wall gives shape & prevents osmosis from bursting the cell • Capsule surrounds cell wall • Circular chromosome (single DNA molecule) not enclosed in a nucleus contains most of the genes • Few genes are located in a small circular plasmid • Plasma (cell) membrane regulates what enters & leaves the cell • Hair-like pilus helps a bacterium stick to a surface • helps exchange DNA • Whip-like flagellum enable them to move

  9. Flagellum • Clip 1 • Clip 2

  10. Bacterial culture techniques • Carefully & thoroughly swab selected surface • Transfer bacteria from broth culture to nutrient agar plate by touching swab to agar surface in a single spot • Isolate bacterial colonies by streaking the plate, being careful not to tear agar • Incubate plate

  11. Pure culture • population of bacterial cells growing in the absence of other types • streak plate technique is used to spread millions of cells so that some are deposited a distance from all others • these cells grow & reproduce, forming an isolated colony (represents a pure culture)

  12. How can bacteria be identified? • Gram staining checks for differences in the structure of their cell walls • gram-positive bacterial cells turn purple • gram-negative cells turn pink • doctors know which antibiotics to use based on the results

  13. Antibiotics • Bacteria live in hypotonic environments • higher concentration of water outside than inside cell • water is always trying to enter cell • A bacterial cell remains intact & doesn’t burst open as long as its cell wall is intact • scientists used this need to develop antibiotics Penicillin inhibits Stapylococcus

  14. Disc diffusion • antibiotic discs release antibiotic into surrounding medium • zone of growth inhibition • Area of no bacterial growth • around the disc will occur if the bacteria are susceptible to the antibiotic

  15. Antibiotic resistant bacteria

  16. Shapes of bacteria • another way to identify bacteria • sphere = coccus • rod = bacillus • spiral = spirillium

  17. Growth pattern of bacteria • also used to identify bacteria • pairs = diplo- • grape clusters = staphylo- • long chains = strepto-

  18. Draw the following… • Diplococcus meningitidis causes meningitis • Streptococcus pneumoniae causes pneumonia • Staphylococcus aureus causes toxic shock syndrome and boils

  19. 2 kinds of Reproduction

  20. How do bacteria asexually reproduce? • Binary fission • makes a copy of its chromosome • cell grows larger • chromosomes move to opposite ends of the cell • a wall begins to form in the middle • 2 new cells are genetically identical

  21. Binary fission video clip • Clip 1 • Clip 2

  22. How do bacteria sexually reproduce? • Conjugation • pilus = bridge-like structure that one bacterium uses to connect to another • 1st bacterium transfers all or part of its chromosome to the second through the pilus • 2nd bacterium has a mix of genetic material & reproduces by binary fission • produces bacteria with a whole new genetic combination

  23. Conjugation video clip

  24. Obligate aerobes require oxygen for respiration Mycobacterium tuberculosis causes tuberculosis Obligate anaerobes are killed by oxygen Treponema pallidum causes syphilis Clostridium botulinum causes botulism Diversity of metabolism Mycobacterium tuberculosis Clostridium botulinum

  25. Facultative anaerobes • Bacteria that prefer an aerobic condition • Can make ATP with no oxygen if put into that situation Ex’s • Staphylococcus (g+) • E. coli (g-) • Listeria (rare food borne illness-25% lethal) • Corynebacteria- skin flora

  26. Which tube flourishes in O2?

  27. Whats up?

  28. A survival mechanism • Endospore • tiny structure that contains bacterium’s DNA & small amount of cytoplasm • encased by tough outer covering that resists drying out, temperature extremes, & harsh chemicals • bacterium rests & doesn’t reproduce

  29. The importance of bacteria • Disease-causing bacteria are few in number compared with the number of harmless & beneficial bacteria on Earth • help to fertilize fields • help to recycle nutrients • help to produce foods & medicine

  30. Food Safety

  31. Nitrogen fixation • All organisms need nitrogen, yet few can directly use it from air • nitrogen fixation – process of converting nitrogen gas into ammonia • other bacteria convert ammonia into nitrate & nitrite which plants can use • Animation Rhizobium on plant nodules convert nitrogen gas into ammonia

  32. Recycling of nutrients • Life could not exist if decomposing bacteria didn’t break down organic materials in dead organisms and wastes • returns nutrients to the environment

  33. During respiration, different bacteria produce diverse products which have distinctive flavors & aromas vinegar yogurt & cheeses sauerkraut sour cream Some bacteria produce important antibiotics that destroy other types of bacteria streptomycin erythromycin bacitracin neomycin Food and medicines

  34. What diseases do bacteriacause?

  35. Bacteria and Disease • 50% of all diseases are thought to be caused from bacteria • In 1900, tuberculosis and pneumonia were the two most common diseases • Factors that increased life expectancy: Less poverty, better health systems, increased water and sewage systems, increased nutrition, better medical care

  36. Are there bacteria on cell phones?

  37. Controlling Bacteria • Cooking Foods • Referigeration/freezing • Drying foods • Pickling

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