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Chapter 2: Microbial Cell Structure and Function

Alexandra Bozan Microbiology Inglés 86 fichas

Chapter 2: Microbial Cell Structure and Function

Fichas del conjunto (86)

  1. 1Properties of all cells- metabolism
    - growth
    - evolution
  2. 2properties of some cells- differentiation
    - communication
    - motility
    - genetic exchange
  3. 3morphologycell shape
  4. 4MORPHOLOGY coccus (plural, cocci)- A cell that is spherical or ovoid
    - staph: clusters
    - strips: strepto    MORPHOLOGY coccus (plural, cocci)
  5. 5MORPHOLOGY rod, bacilluscylindrically shaped cellMORPHOLOGY rod, bacillus
  6. 6MORPHOLOGY spirillacurved (vibrio) or loose spiral shapes (spirilum)MORPHOLOGY spirilla
  7. 7MORPHOLOGY spirochetestightly coiledMORPHOLOGY spirochetes
  8. 8MORPHOLOGY budding and appendagedextensions of their cells as long tubes or stalksMORPHOLOGY budding and appendaged
  9. 9MORPHOLOGY filamentous bacteriaform long, thin cells or chains of cellsMORPHOLOGY filamentous bacteria
  10. 10Size range for prokaryotes:- 0.2 µm to > 700 µm in diameter
  11. 11hypothesized that the upper size limit for prokaryotic cells results from ...- decreasing ability of larger cells to transport nutrients
    - surface-to-volume ratio is very small
    - metabolic rate varies inversely w/square of cell size
    - nutrient uptake limits metabolism to where cell can't compete w/smaller cells
  12. 12The S/V ratio of a cell controls many of its properties, including its ...- growth rate and evolution
  13. 13higher S/V ratio of small cells supports ...- faster rate of nutrient and waste exchange
  14. 14because prokaryotic cells are quite small and genetically haploid (typically have one copy of each gene, allowing mutations to be expressed immediately), prokaryotic cells can ...- grow faster and evolve more rapidly than larger cells
  15. 15when the genomes of ultramicrobacteria are unraveled, they are typically found to be _____ ______ and to be _____ many genes whose products or functions must be ... sometimes both cannot ...- highly streamlined
    - missing
    - supplied to them by other microbial cells or by the host organisms
    - survive w/out each other
    - mycobacterium (TB), mycoplasma
  16. 16cytoplasmmixture of macromolecules and small molecules inside the cell
  17. 17cytoplasmic membrane- surrounds cytoplasm & separates it from environment
    - selective permeability: “gatekeeper” for entrance & exit of dissolved substances
    - has proteins facilitate
    - physically weak
  18. 18BACTERIAL & EUKARYA CYTOPLASMIC MEMBRANE- phospholipid bilayer w/embedded proteins
    - some are strengthened by hopanoids (sterol-like molecules) that strengthen the membranes of eukaryotic cells
  19. 19BACTERIAL CYTOPLASMIC MEMBRANE Phospholipids- has hydrophobic / hydrophilic parts
    - hydrophilic (glycerophosphates): glycerol molecule w/phosphate and a functional group bonded to phosphate
    - hydrophobic: fatty acids
    - ester link between hydrophilic/phobic
  20. 20lipid bilayer / unit membrane- hydrophilic region faces environment
    - hydrophobic region faces cytoplasm & interacts with cytoplasmic milieu
  21. 21amphipathichas both a hydrophilic region and a hydrophobic region
  22. 22integral proteins- spans membrane
    - amphipathic
    - majority are transmembrane proteins
    - some extend partway into the hydrophobic interior
    - i.e. lipoproteins
  23. 23Peripheral proteins- Not embedded in the lipid bilayer
    - loosely bound to surface of membrane, often exposed to integral proteins
    - typically interact w/integral proteins in energy metabolism and transport
  24. 24BACTERIAL CYTOPLASMIC MEMBRANEBACTERIAL CYTOPLASMIC MEMBRANEBACTERIAL CYTOPLASMIC MEMBRANE
  25. 25ARCHAEAL CYTOPLASMIC MEMBRANE- has hydrophobic / hydrophilic parts
    - hydrophilic (glycerophosphates): glycerol molecule w/phosphate and a functional group bonded to phosphate
    - hydrophobic: isoprene (phytanil, biphytanil, crenarchaeol)
    - ether link between hydrophilic/phobic
    - no hopanoids
  26. 26—
  27. 27—
  28. 28—
  29. 29list 3 major cytoplasmic membrane function- permeability barrier: prevents passive leakage of solutes in or out of cell
    - anchors several proteins
    - energy conservation and consumption
  30. 30CYTOPLASMIC MEMBRANE permeability barrier - transport proteins part 1 of 2- carries most substances in/out of cell
    - accumulate solutes against [ ] gradient
    - requires energy
    - displays high sensitivity & high specificity
  31. 31CYTOPLASMIC MEMBRANE permeability barrier - transport proteins part 2 of 2some transport proteins of a single kind while others carry related class of molecules (different sugars or amino acids)
  32. 32CYTOPLASMIC MEMBRANE energy & conservation- cytoplasmic membrane energized when protons (H+) are separated from hydroxyl ions (OH−) across membrane
    - charge separation creates an energized state (proton motive force), similar to potential energy present in a charged battery
  33. 33cell wall- a layer outside the cytoplasmic membrane that prevents cell lysis due to osmotic pressure (2 atm)
    - two major types identified via gram stain: gram-positive and gram-negative
  34. 34BACTERIA CELL WALL Peptidoglycan- key molecule found in cell wall
    - confers structural strength on the cell
    - in all bacteria
    - not present in Archaea or Eukarya
  35. 35BACTERIA CELL WALL peptidoglycan structure part 1 of 2- alternating repeats of 2 modified glucose residues N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
    - and amino acids (l-alanine, d-alanine, d-glutamic acid) and either l-lysine or diaminopimelic acid (DAP)
  36. 36BACTERIA CELL WALL peptidoglycan structure part 2 of 2- constituents form glycan tetrapeptide
    - long chains of this form peptidoglycan (universal across bacteria)
    - when adjacent forms sheet around cell
    - strands are connected by peptide cross-links, which are different in gram (-) and gram (+)
  37. 37BACTERIA CELL WALL lysozyme- destroys peptidoglycan by cleaving glycosidic bond between NAG & NAM
    - weakens peptidoglycan, causing cell lysis
  38. 38BACTERIA CELL WALL Gram Positive Cell Wall- one layer: 90% peptidoglycan
    - many form several layers of peptidoglycan stacked one upon another
    - many produce teichoic acids embedded in cell wall linked to peptidoglycan or lipids
  39. 39BACTERIA CELL WALL very few bacteria and archaea ______ cell walls altogether; when they do they contain unusually ...- lack
    - tough cytoplasmic membranes
  40. 40BACTERIA CELL WALL Gram Positive Cell Wall visualBACTERIA CELL WALL Gram Positive Cell Wall visual
  41. 41BACTERIA CELL WALL Gram Negative Cell Wall- 2 layers: peptidoglycan & LPS
    - small amount of peptidoglycan
    - mostly made of lipid & polysaccharide linked to form the outer membrane/ lipopolysaccharide LPS
  42. 42BACTERIA CELL WALL Gram Negative Cell Wall - LPS- confers only modest structural strength
    - effective barrier against many substances such as lipophilic antibiotics
    - replaces much of the phospholipid in the outer half of the outer membrane
    - anchored to the peptidoglycan layer by the Braun lipoprotein
  43. 43BACTERIA CELL WALL Gram Negative Cell Wall - LPS Structure- 3 layers: O-specific polysaccharide, Core polysaccharide, and Lipid A
    - lipid A can be toxic to animals and comprises the endotoxin complex
  44. 44BACTERIA CELL WALL Gram Negative Cell Wall - Braun lipoproteinmolecule that spans the gap (periplasm) between the LPS layer and the peptidoglycan layer
  45. 45—
  46. 46BACTERIA CELL WALL periplasm- space located between the outer surface of the cytoplasmic membrane and the inner surface of the outer membrane
    - spans about 15 nm
  47. 47BACTERIA CELL WALL porinfunction as channels for the entrance and exit of solutes
  48. 48BACTERIA CELL WALL outer membrane is _____ to proteins and large molecules. A major function of it is to prevent ...- impermeable
    - cellular proteins whose activities must occur outside the cytoplasm from diffusing away from the cell
  49. 49ARCHAEAL CELL WALL- variety of cell wall structures: Pseudomurein and Other Polysaccharide and S Layer
    - no peptidoglycan
    - typically no outer membrane
  50. 50ARCHAEAL CELL WALL Pseudomurein and Other Polysaccharide- polysaccharide similar to peptidoglycan
    - backbone made of alternating repeats of N-acetylglucosamine and N-acetyltalosaminuronic acid
    - immune from destruction by lysozyme & penicillin
    - in certain methanogenic Archaea
  51. 51ARCHAEAL CELL WALL Cell walls of some other Archaea lack ______ and instead contain other polysaccharides- pseudomurein
  52. 52ARCHAEAL CELL WALL S-Wall part 1 of 1- most common type of cell wall
    - paracrystalline surface layer
    - interlocking molecules of protein or glycoprotein
    - can form various symmetries
    - sufficiently strong to withstand osmotic pressures w/out any other components
  53. 53ARCHAEAL CELL WALL S-Wall part 2 of 2- present in addition to other cell wall components, usually polysaccharides
    - when it's accompanied by other wall components, the S-layer is always the outermost wall layer; that is
  54. 54capsule- tight matrix that excludes small particles and is tightly attached
    - visible by light microscopy when treated w/India ink (stains background & not capsule) or electron microscope
  55. 55slime layer- layer more easily deformed & loosely attached
    - will not exclude particles and is more difficult to see microscopically
  56. 56capsule and slime layer functions- Surface polysaccharides assist in attachment to surfaces & in development & maintenance of biofilms
    - virulence factors: contribute to pathogenicity, protect against phagocytosis
    - prevents dehydration by binding water
  57. 57biofilma thick layer of cells on solid surface
  58. 58pelliclesthin sheets of cells on liquid surface
  59. 59twitching motility- gliding motility, movement along a solid surface
    - extension of pili followed by retraction drags cell along a solid surface
    - assists in locating specific sites for attachment
  60. 60Fimbriae- thin (2–10 nm in diameter)
    - filamentous structures made of protein
    - extend from cell surface
    - enable cells to stick to surfaces
    - form pellicles or biofilms
  61. 61Pili- similar to fimbriae; longer, has 1 or few
    - All gram (-), many gram (+) have them
    - facilitating genetic exchange (conjugation)
    - stick to specific host tissues for invasion
    - twitching motility
  62. 62hamus- resemble type IV pili except for barbed terminus (tiny grappling hook)
    - affix cells to a surface to form a networked biofilm
    - attaches cells to surfaces & each other
  63. 63cell inclusions- function as energy/carbon reserves or have special functions
    - enclosed by a thin membrane that partitions off inclusion in cytoplasm
    - results in ↓ osmotic stress if same amt of substance in dissolved in cytoplasm
  64. 64different types of cell inclusions- Carbon Storage Polymers
    - Polyphosphate, Sulfur, and Carbonate Minerals
    - Magnetic Storage inclusions: Magnetosomes
  65. 65Carbon Storage Polymers- glycogen: glucose polymer
    - PHA
    - synthesized when there's excess C & broken ↓ as C or energy sources when conditions warrant
  66. 66gas vesicles- confer buoyancy allowing cells to position themselves in regions of water columns that best suit their metabolisms
    - not found in microbial eukaryotes
    - conical-shaped made of protein
    - composition/pressure of gas inside a gas vesicle is same as its environment
  67. 67endospores 1 of 3- formed during endosporulation
    - highly differentiated cells
    - resistant to heat, harsh chemicals & radiation
    - survival structures: allows organism to endure unfavorable growth conditions: temp, drying, nutrient depletion
  68. 68endospores 2 of 3- dormant stage of a bacterial life cycle: vegetative → endospore → vegetative
    - easily dispersed by wind, water, or through the animal gut, and hence
    - formed when growth ceases due to exhaustion of an essential nutrient
  69. 69endospores 3 of 3- only in some gram-positive bacteria
    - can remain dormant for years
    - sequential activation of endospore genes & inactivation of vegetative cell functions
    - quickly convert back to vegetative cell in 3 steps: activation, germination & outgrowth
  70. 70endospores activationendospores heated for several minutes at an elevated temperature
  71. 71endospores germination- signaled by loss of refractility, resistance to heat and chemicals of endospore
    - germinates when supplied with certain nutrients
  72. 72endospores outgrowth- visible swelling due to water uptake and synthesis of RNA, proteins, and DNA
    - vegetative cell emerges from endospore and begins to grow
    - remains in vegetative growth until environmental signals trigger sporulation
  73. 73Endospore Structure 1 of 3- visible by light microscopy as strongly refractile structures
    - impermeable to most dyes
    - special stains/procedures used: malachite green is used and is infused into the spore with steam
  74. 74Endospore Structure 2 of 3- outermost layer, exosporium, a thin protein covering
    - inward are several spore coats
    - Below spore coat is the cortex
    - inside cortex is the core: has core wall, cytoplasmic membrane, cytoplasm, nucleoid, ribosomes, cellular essentials
  75. 75Endospore Structure 3 of 3- differs structurally from vegetative cell primarily in kinds of structures found outside the core wall
    - has dipicolinic acid & SASPs not found in vegetative cells
    - Some survive 150°C temp → 121°C is standard for microbiological sterilization
  76. 76flagellum- long, thin appendages in bacteria that assist w/motility
    - don't rotate at constant speed but increase or decrease speed
    - not straight but helical
  77. 77tuftgroup of flagella
    lophotrichous: attached to one end
    amphitrichous: attached to both ends
  78. 78polar flagellation- flagella attached at one or both ends
    - can be lophotrichous or amphitrichous
    - move rapidly
  79. 79peritrichous flagellation- flagella are inserted around cell surface
    - typically move slowly in a straight line
  80. 80archaellum- long, thin appendages in archaea that assist w/motility
    - half the diameter of flagella
  81. 81gliding motility- Some bacteria are motile but lack flagella & move by gliding
    - slower/smoother & typically occurs along the long axis of the cell
    - typically filamentous or rod-shaped in
    morphology
  82. 82virus is a _____ not a microorganism- microbe
  83. 83LUCAlast universal common ancestor
  84. 84Eukaryia cell walls are made ofchitin or cellulose
  85. 85difference between prokaryotic and eukaryotic flagella attachment- Eukaryotic flagella: microtubule-based structures, anchored at the cell membrane
    - prokaryotic: spans LPS, peptidoglycan, cell membrane to cytosol
  86. 86examples of endosporesClostridium, Bacillus, anthrax

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(Exam I) Microbiology Fichas sobre Chapter 2: Microbial Cell Structure and Function, creado por Alexandra Bozan el 18/01/2020.
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