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BACTERIA. Structure of a Bacterium. Cell membrane. Ribosome. Cell wall. Peptidoglycan. Flagellum. DNA. Pili. Structure of a Bacterium. Capsule : some have a sticky gelatinous capsule around the cell wall (these bacteria are more likely to cause disease)

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  2. Structure of a Bacterium Cell membrane Ribosome Cell wall Peptidoglycan Flagellum DNA Pili

  3. Structure of a Bacterium • Capsule: some have a sticky gelatinous capsule around the cell wall (these bacteria are more likely to cause disease) • Cell wall: gives the cell shape; composed of a peptidoglycan (sugar-protein complex) • Plasma membrane: surrounds the cell and regulates what enters and leaves

  4. Structure of a Bacterium • Pilus: hairlike structures emerging from the cell surface; helps bacteria stick to a surface or exchange DNA between bacterial cells • Flagellum: long, whiplike structure that enables movement

  5. Structure of a Bacterium • Chromosome: single DNA molecule arranged as a circular chromosome; not enclosed in a nucleus • Plasmid: small circular chromosome piece containing a few genes

  6. Classifying Bacteria • Bacteria are classified according to: • Shape • Arrangement • Gram stain

  7. Classifying Bacteria • Shape • Spherical - Cocci • Rod - Bacilli • Corkscrew - Spirillae

  8. Classifying Bacteria • Arrangement • Singular • Pairs – Diplo • Chains – Strepto • Clusters – Stapylo

  9. Classifying Bacteria • Gram stain • Staining method involving two dyes • The dye absorbed by the bacteria depends on properties of the cell wall • Bacteria are either Gram positive or Gram negative • Positive stain bluish-purple • Negative stain reddish-pink

  10. outer membrane of lipopolysaccharides Gram-negative bacteria Gram-positive bacteria peptide side chains outer membrane cell wall peptidoglycan cell wall peptidoglycan plasma membrane plasma membrane protein Prokaryote Cell Wall Structure Gram-Positive bacteria That’simportant foryour doctorto know! peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides

  11. Metabolism • Obligate aerobes – must have oxygen to survive • Obligate anaerobes – cannot live if oxygen is present • Facultative anaerobes- can live either with or without oxygen

  12. Eukaryote Prokaryote Archaebacteria&Bacteria Classification • 3 Domain system • reflects a greater understanding of evolution & molecular evidence • Bacteria: Eubacteria • Archae: Archaebacteria • Eukaryotes: • Protists • Plants • Fungi • Animals

  13. Classification of Bacteria • All bacteria are prokaryotes • Very simple organisms • All are unicellular • In general, they are smaller than eukaryotes • Circular DNA which is not enclosed in a nucleus • Lack membrane-bound organelles

  14. Classification of Bacteria • Archaebacteria • Eubacteria • Heterotrophic eubacteria • Autotrophic eubacteria • Chemosynthetic eubacteria

  15. Archaebacteria • a.k.a. Extremophiles • Live in oxygen-free environments • Obtain energy from sun or inorganic molecules

  16. Archaebacteria: Thiobacilli • Heat- and acid-loving bacteria • Live in sulfur springs

  17. Archaebacteria: Thiobacilli • Consume sulfur • Combine it with oxygen to produce energy • Produce sulfur dioxide as by-product

  18. Archaebacteria: Thiobacilli • Sulfur dioxide can combine with water to form sulfuric acid

  19. Archaebacteria: Halobacteria • Salt-loving bacteria • Live in saturated salt water like the Great Salt Lake

  20. Archaebacteria: Halobacteria • Produce purple pigments • Use purple pigment to carry out photosynthesis the way plants use chlorophyll

  21. Archaebacteria: Alkalophytes • Live in aquatic environments with high pH • Forms the food basis upon which thousands of large organisms are dependent Lake Nakuru

  22. Archaebacteria: Methane Bacteria • Cannot live in the presence of oxygen • Live in stomachs of cows and sewage treatment ponds

  23. Archaebacteria: Methane Bacteria • Obtain energy from CO2 and hydrogen gas

  24. Archaebacteria: Deep Subsurface Bacteria • Live in rocks beneath Earth’s surface (as deep as 3,000 feet)

  25. Archaebacteria: Deep Subsurface Bacteria • Obtain energy from H+ produced from reaction between minerals in rock and groundwater seeping in

  26. Classification of Bacteria • Archaebacteria • Eubacteria • Heterotrophic eubacteria • Autotrophic eubacteria • Chemosynthetic eubacteria

  27. Heterotrophic Eubacteria • Obtain food from other living organisms • parasites • Obtain food from dead organisms or organic waste • Recycle nutrients in decomposing organic material

  28. Classification of Bacteria • Archaebacteria • Eubacteria • Heterotrophic eubacteria • Autotrophic eubacteria • Chemosynthetic eubacteria

  29. Autotrophic Eubacteria • Obtain energy from light • Perform photosynthesis

  30. Autotrophic Eubacteria • Cyanobacteria • Most contain blue-green pigment (but some are red or yellow) • Form chains: not unicellular

  31. Classification of Bacteria • Archaebacteria • Eubacteria • Heterotrophic eubacteria • Autotrophic eubacteria • Chemosynthetic eubacteria

  32. Chemosynthetic Eubacteria • Obtain energy from breakdown of inorganic substances (S and N compounds) • Key for agriculture: • Convert atmospheric N to a form plants can use

  33. Reproduction in Bacteria • Can reproduce rapidly (every 20 minutes) • Luckily, most run out of nutrients and water before the colony gets very large • Most reproduce by binary fission • Bacterium copies its chromosome • Old chromosome and copy attach to the plasma membrane at opposite ends • Cell grows and becomes larger

  34. Reproduction in Bacteria • Most reproduce by binary fission • Growth causes two chromosomes to separate • Partition forms and separates the cell into two • Each new cell has one copy of the original chromosome • Creates two cells genetically identical to one another

  35. Genetic Exchange in Bacteria • Conjugation • Sexual form of bacterial reproduction • One bacterium passes all or part of its chromosome to another cell • Transfer occurs across pili • Creates two bacteria genetically different from one another • They then reproduce by binary fission

  36. Genetic Exchange in Bacteria • Transduction: Transfer of genes from one bacterium to another by a bacteriophage. • Ex. Toxin gene in Corynebacterium diphtheriae

  37. Genetic Exchange in Bacteria • Transformation: Taking in DNA from the outside environment. • Ex. Rough Streptococcus pneumoniae transformed into smooth S. pneumoniae. Bacterial species in biofilm communities.

  38. Survival • If conditions become less than ideal some bacteria can form endospores • Tough outer covering resistant to: • Drying out • Temperature extremes (boiling water) • Harsh chemicals

  39. Survival • Closturidium botulinum • Produces a deadly toxin • Endospores can withstand boiling temperatures • Canned foods must be pressure cooked to kill the endospores

  40. Six week old infant with botulism, which is evident as a marked loss of muscle tone, especially in the region of the head and neck.

  41. Survival • Closturidium tetani • Obligate anaerobe that produces a deadly neurotoxin • Endospores are found on nearly every surface on the planet • When endospores get into a moist, oxygen-free environment (such as inside a puncture wound) they germinate • Reason for getting a tetanus shot

  42. Tetanus

  43. Survival • Bacillus anthracis • Aka. Anthrax • Endospores live in soil • When inhaled they germinate

  44. Decomposers • Break down dead organisms and recycle the nutrients that make them • Without decomposition we would run out of the molecules necessary for life

  45. Nitrogen-fixation • Plants and animals need nitrogen to make protein • The atmosphere is mostly nitrogen but plants and animals can’t use it

  46. Nitrogen-fixation • Nitrogen-fixing bacteria convert nitrogen in the atmosphere into nitrogen plants can take up with their roots • Animals get their nitrogen by eating plants

  47. Biotechnology • Production of foods like butter, cheese, and yogurt • Cleaning up oil spills • Synthesizing drugs and chemicals

  48. Digestion • Much of what we eat would pass through our bodies without being digested if we didn’t have bacteria in our digestive tracts • They break down plant matter and synthesize vitamins for us

  49. Bacterial Diseases • Bacteria cause illness one of two ways: • Breaking down host cells or tissues for food • Normal metabolic processes generate toxins

  50. Bacterial Diseases • Most food-borne illnesses are caused by bacteria: • E. coli comes from infected, undercooked beef • Salmonella comes from infected, undercooked poultry (meat and eggs) • Botulinum causes botulism – a deadly form of food poisoning

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