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The Bacteria and Archaea


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The Bacteria and Archaea

  1. 1. Foundations in Microbiology Chapter 4 PowerPoint to accompany Fifth Edition Talaro Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  2. 2. Prokaryotic Profiles: the Bacteria and the Archaea Chapter 4                                
  3. 3. Fig. 4.1
  4. 4. flagella <ul><li>3 parts </li></ul><ul><ul><li>filament – long, thin, helical structure composed of proteins </li></ul></ul><ul><ul><li>hook- curved sheath </li></ul></ul><ul><ul><li>basal body – stack of rings firmly anchored in cell wall </li></ul></ul><ul><li>rotates 360 o </li></ul><ul><li>1-2 or many distributed over entire cell </li></ul><ul><li>functions in motility </li></ul>
  5. 5. Fig 4.2b
  6. 6. Flagellar arrangements <ul><li>monotrichous – single flagellum at one end </li></ul><ul><li>lophotrichous – small bunches arising from one end of cell </li></ul><ul><li>amphitrichous – flagella at both ends of cell </li></ul><ul><li>peritrichous – flagella dispersed over surface of cell, slowest </li></ul>
  7. 8. Fig 4.5
  8. 9. Chemotaxis Fig 4.6
  9. 10. axial filaments <ul><li>periplasmic, internal flagella, enclosed between cell wall and cell membrane of spirochetes </li></ul><ul><li>motility </li></ul>
  10. 11. Fig 4.7a b
  11. 12. fimbrae <ul><li>fine hairlike bristles from the cell surface </li></ul><ul><li>function in adhesion to other cells and surfaces </li></ul>
  12. 13. pili <ul><li>rigid tubular structure made of pilin protein </li></ul><ul><li>found only in Gram negative cells </li></ul><ul><li>Functions </li></ul><ul><ul><li>joins bacterial cells for DNA transfer (conjugation) </li></ul></ul><ul><ul><li>adhesion </li></ul></ul>
  13. 14. Conjugation
  14. 15. glycocalyx <ul><li>Coating of molecules external to the cell wall, made of sugars and/or proteins </li></ul><ul><li>2 types </li></ul><ul><ul><ul><li>capsule - highly organized, tightly attached </li></ul></ul></ul><ul><ul><ul><li>slime layer - loosely organized and attached </li></ul></ul></ul><ul><li>functions </li></ul><ul><ul><li>attachment </li></ul></ul><ul><ul><li>inhibits killing by white blood cells </li></ul></ul><ul><ul><li>receptor </li></ul></ul>
  15. 16. Fig 4.10
  16. 17. 2 Types of Glycocalyx
  17. 18. Biofilms
  18. 19. Peptidoglycan <ul><li>unique macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments </li></ul><ul><li>provides strong, flexible support to keep bacteria from bursting or collapsing because of changes in osmotic pressure </li></ul>
  19. 20. Peptidoglycan
  20. 21. 4 groups based on cell wall composition <ul><li>Gram positive cells </li></ul><ul><li>Gram negative cells </li></ul><ul><li>Bacteria without cell walls </li></ul><ul><li>Bacteria with chemically unique cell walls </li></ul>
  21. 22. Gram positive Gram negative Fig 4.16
  22. 24. Gram positive cell wall <ul><li>Consists of </li></ul><ul><ul><li>a thick, homogenous sheath of peptidoglycan 20-80 nm thick </li></ul></ul><ul><ul><li>tightly bound acidic polysaccharides, including teichoic acid and lipoteichoic acid </li></ul></ul><ul><ul><li>cell membrane </li></ul></ul><ul><li>Retain crystal violet and stain purple </li></ul>
  23. 25. Gram positive wall
  24. 26. Gram negative cell wall <ul><li>Consists of </li></ul><ul><ul><li>an outer membrane containing lipopolysaccharide (LPS) </li></ul></ul><ul><ul><li>thin shell of peptidoglycan </li></ul></ul><ul><ul><li>periplasmic space </li></ul></ul><ul><ul><li>inner membrane </li></ul></ul><ul><li>Lose crystal violet and stain red from safranin counterstain </li></ul>
  25. 27. Gram negative cell wall
  26. 28. Cytoplasm <ul><li>dense gelatinous solution of sugars, amino acids, & salts </li></ul><ul><li>70-80% water </li></ul><ul><li>serves as solvent for materials used in all cell functions </li></ul>
  27. 29. Chromosome <ul><li>single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell </li></ul><ul><li>DNA is tightly coiled around a protein, aggregated in a dense area called the nucleoid </li></ul>
  28. 30. plasmids <ul><li>small circular, double-stranded DNA </li></ul><ul><li>free or integrated into the chromosome </li></ul><ul><li>duplicated and passed on to offspring </li></ul><ul><li>not essential to bacterial growth & metabolism </li></ul><ul><li>may encode antibiotic resistance, tolerance to toxic metals, enzymes & toxins </li></ul><ul><li>used in genetic engineering- readily manipulated & transferred from cell to cell </li></ul>
  29. 31. ribosomes <ul><li>made of 60% ribosomal RNA & 40% protein </li></ul><ul><li>consist of 2 subunits: large & small </li></ul><ul><li>procaryotic differ from eucaryotic ribosomes in size & number of proteins </li></ul><ul><li>site of protein synthesis </li></ul><ul><li>All cells have ribosomes. </li></ul>
  30. 32. ribosomes
  31. 33. Inclusions, granules <ul><li>intracellular storage bodies </li></ul><ul><li>vary in size, number & content </li></ul><ul><li>bacterial cell can use them when environmental sources are depleted </li></ul><ul><li>Examples: glycogen, poly-  -hydroxybutyrate, gas vesicles for floating, sulfur and polyphosphate granules </li></ul>
  32. 34. Inclusions
  33. 35. endospores <ul><li>Resting, dormant cells </li></ul><ul><li>produced by some G+ genera: Clostridium , Bacillus & Sporosarcina </li></ul><ul><li>Have a 2-phase life cycle – vegetative cell & an endospore </li></ul><ul><li>sporulation -formation of endospores </li></ul><ul><li>germination - return to vegetative growth </li></ul><ul><li>hardiest of all life forms </li></ul><ul><li>withstand extremes in heat, drying, freezing, radiation & chemicals not a means of reproduction </li></ul>
  34. 36. endospores <ul><li>resistance linked to high levels of calcium & dipicolinic acid </li></ul><ul><li>dehydrated, metabolically inactive </li></ul><ul><li>thick coat </li></ul><ul><li>longevity verges on immortality 25, 250 million years. </li></ul><ul><li>pressurized steam at 120 o C for 20-30 minutes will destroy. </li></ul>
  35. 37. endospores
  36. 38. 3 shapes of bacteria <ul><li>cocci - spherical </li></ul><ul><li>bacilli - rod </li></ul><ul><li>spiral - helical, comma, twisted rod, spirochete </li></ul>
  37. 40. Methods in bacterial identification <ul><li>Microscopic morphology </li></ul><ul><li>Macroscopic morphology – colony appearance </li></ul><ul><li>Physiological / biochemical characteristics </li></ul><ul><li>Chemical analysis </li></ul><ul><li>Serological analysis </li></ul><ul><li>Genetic & molecular analysis </li></ul><ul><ul><li>G + C base composition </li></ul></ul><ul><ul><li>DNA analysis using genetic probes </li></ul></ul><ul><ul><li>Nucleic acid sequencing & rRNA analysis </li></ul></ul>
  38. 41. Major Taxonomic Groups of Bacteria per Bergey’s manual <ul><li>Gracilicutes – gram-negative cell walls, thin-skinned </li></ul><ul><li>Firmicutes – gram-positive cell walls, thick skinned </li></ul><ul><li>Tenericutes – lack a cell wall & are soft </li></ul><ul><li>Mendosicutes – archaea, primitive procaryotes with unusual cell walls & nutritional habits </li></ul>
  39. 42. <ul><li>species –a collection of bacterial cells which share an overall similar pattern of traits in contrast to other bacteria whose pattern differs significantly </li></ul><ul><li>strain or variety – a culture derived from a single parent that differs in structure or metabolism from other cultures of that species (biovars, morphovars) </li></ul><ul><li>type – a subspecies that can show differences in antigenic makeup (serotype or serovar), susceptibility to bacterial viruses (phage type) and in pathogenicity (pathotype). </li></ul>
  40. 43. Procaryotes with unusual characteristics
  41. 44. Rickettsias <ul><li>very tiny, gram-negative bacteria </li></ul><ul><li>most are pathogens that alternate between mammals and fleas, lice or ticks </li></ul><ul><li>obligate intracellular pathogens </li></ul><ul><li>cannot survive or multiply outside of a host cell </li></ul><ul><li>cannot carry out metabolism on their own </li></ul><ul><li>Rickettsia rickettisii – Rocky Mountain spotted fever </li></ul><ul><li>Rickettsia prowazekii – epidemic typhus </li></ul><ul><li>Coxiella burnetti – Q fever </li></ul>
  42. 45. Chlamydias <ul><li>tiny </li></ul><ul><li>obligate intracellular parasites </li></ul><ul><li>not transmitted by arthropods </li></ul><ul><li>Chlamydia trachomatis – severe eye infection and one of the most common sexually transmitted diseases </li></ul><ul><li>Chlamydia psittaci – ornithosis, parrot fever </li></ul><ul><li>Chlamydia pneumoniae – lung infections </li></ul>
  43. 46. Mycoplasmas <ul><li>naturally lack a cell wall </li></ul><ul><li>stabilized by sterols, resistant to lysis </li></ul><ul><li>extremely small </li></ul><ul><li>range in shape from filamentous to coccus or doughnut shaped </li></ul><ul><li>Mycoplasma pneumoniae – atypical pneumonia in humans </li></ul>
  44. 47. Free-living nonpathogenic bacteria <ul><li>Photosynthetic bacteria </li></ul><ul><ul><li>Cyanobacteria </li></ul></ul><ul><ul><li>Green & purple sulfur bacteria </li></ul></ul><ul><li>Gliding, fruiting bacteria </li></ul><ul><li>Appendaged bacteria </li></ul><ul><ul><li>produce an extended process of the cell wall in form of a bud, stalk or long thread </li></ul></ul>
  45. 48. Archaea: the other procaryotes <ul><li>constitute third Domain Archaea </li></ul><ul><li>seem more closely related to Domain Eukarya than to bacteria </li></ul><ul><li>contain unique genetic sequences in their rRNA </li></ul><ul><li>have unique membrane lipids & cell wall construction </li></ul><ul><li>live in the most extreme habitats in nature, extremophiles </li></ul><ul><li>adapted to heat salt acid pH, pressure & atmosphere </li></ul><ul><li>includes: methane producers, hyperthermophiles, extreme halophiles, and sulfur reducers </li></ul>