1 - Microbial World and Prokaryotic Cell Anatomy

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  • Methanogens – produce methane as a waste product from respiration, Halophilis (salt loving) Dead Sea, Thermophilis – sulfurous water: Yellowstone These are not know to cause disease in humans.
  • Ecology – used in water pollution and toxic chemical disposal, bioremediation – toxins can be removed from ground Exxon Valdez . Also have bacterial enzymes in drain cleaners to remove clogs without adding harmful chemicals to the environment. Biotech – gene therapy and agriculture
  • Cause disease and often resistant to antibiotics
  • Evolution – Vibrio Cholerae (Haiti), Ecological – Venezuela deforestation and construction led to hemorrhagic virus. Antimicrobial – vancomycin resistant Staph into MRSA
  • 1 - Microbial World and Prokaryotic Cell Anatomy

    1. 1. Lecture 1: Microbial World and Procaryotic Cell Anatomy
    2. 2. Microbes/Microorganisms? • Too small to see with the “naked” eye • Beneficial – Ecological: Recycle nutrients • Bioremediation – Industrial: Food, chemicals, drugs • Fermented Foods • Antibiotics • Ethanol and other chemicals • Enzymes – Cellulase, Peroxidase • Destructive/Pathogenic – FEW
    3. 3. Nomenclature • Scientific Nomenclature – System devised by Linnaeus • Genus and species – Both italicized or underlined – Genus name Upper-case; species lower-case – Name describes the organism • Ex. Staphylococcus aureus – Staphylococcus: cluster of spheres – aureus: golden aura of colonies – Name honors the scientist • Ex. Escherichia coli – Escherich: honors the discoverer, Theodor Escherich – coli- describes the habitat – the colon or the small intestine
    4. 4. Three Domains of Life – Archaea • prokaryotes • Primarily extremophiles • Not disease-causing – Bacteria • prokaryotes – Eukarya • Nucleated organisms • Uni- or multi-cellular • Fungi • Protista • Plants • Animals
    5. 5. Classification of Microbes • Archaea • Bacteria • Fungi • Algae • Protozoa • Multicellular Animal Parasites • Viruses
    6. 6. Classification of Microbes Bacteria Sporangia Prey Pseudopods CD4+ T cell HIVs
    7. 7. Archaea • Prokaryotes • No peptidoglycan in cell wall • Habitat – Extreme environments • Methanogens (methane) • Halophiles (salt) • Thermophiles (heat) • Not known to cause disease in humans
    8. 8. Bacteria • Prokaryotes • Cell structure – Bacillus, Coccus, Spiral • Cell wall – Peptidoglycan • Cell Division – Binary Fission • Metabolism: Energy source – Inorganic/ organic chemicals – Photosynthesis
    9. 9. Fungi • Eukaryotes • Chitin cell walls • Energy Source: – Organic matter • Multicellular – Molds and mushrooms • Unicellular – Yeasts
    10. 10. Protozoa • Eukaryotes • Unicellular • Motile – Pseudopodia – Cilia – Flagella • Shape – Variety of shapes • Habitat – free entities or parasites • Energy source – organic compounds
    11. 11. Algae • Eukaryotes • Cellulose cell walls • Energy source – Photosynthesis • Produce molecular oxygen and organic compounds
    12. 12. Viruses • Neither eukaryote or prokaryote • Acellular • Obligate Intracellular Parasites – Only replicate when present in living host cell • Genetic Material – Either DNA or RNA • Structure – Nucleocapsid • Nucleic acid core • Protein coat surrounds core – Lipid Envelope • Not always present
    13. 13. Multicellular Animal Parasites • Eukaryotes • Multicellular • Parasitic flatworms and roundworms.
    14. 14. Conditions Results Nutrient broth placed in flask, heated, NOT sealed Microbial growth Nutrient broth placed in flask, heated, then sealed No microbial growth Louis Pasteur • 1861: Louis Pasteur demonstrated that microorganisms are present in the air
    15. 15. Important Events in Microbiology • Germ Theory of Disease – Germs present in the air cause disease, spoil food • Louis Pasteur’s work – Cleaning with disinfectants decreases infection • Joseph Lister’s work • Vaccination – Jenner – Pasteur (small pox) • Discovery of Antibiotics and Synthetic Drugs – Fleming – Penicillin – Sulfa drugs
    16. 16. The Birth of Modern Chemotherapy • Chemotherapy – Treatment with chemicals • Treatment of infections – Antibiotics • Naturally synthesized • bacteria and fungi – Synthetic Drugs • Artificially synthesized • First Drugs: Sulfa drugs
    17. 17. A Fortunate Accident—Antibiotics • 1928: Alexander Fleming discovered the first antibiotic • Fleming observed that Penicillium fungus made an antibiotic, penicillin, that killed S. aureus • 1940s: Penicillin was tested clinically and mass produced
    18. 18. Normal bacterial colony Area of inhibition of bacterial growth Penicillium colony Figure 1.5 The discovery of penicillin.
    19. 19. Microbes in Human Welfare • Microbial ecology: – Bacteria recycle inorganic material • carbon, sulfur, phosphorus • Used by plants and animals – Turns N to Nitrates and Nitrites so plants can use it • Bioremediation: – Bacteria degrade organic matter • Sewage treatment • Detoxify pollutants – Oil and mercury spills • Biotechnology
    20. 20. Biotechnology • Recombinant DNA technology – Taking parts of DNA and recombining it back into the DNA (E. coli produces purple because it was engineered then recombined into the DNA to make it happen) – Engineer viruses, bacteria and fungi • Produce proteins – Vaccines, enzymes, hormones – Gene therapy • Replace missing or defective genes in human cells – Hemophilia – Blindness – Agriculture • Genetically modified bacteria – Protect crops from insects and freezing
    21. 21. Normal Microbiota/ Normal Flora • Nomenclature – Old: Normal Flora • Because bacteria initially classified as plants – New: Normal microbiota • Microbes present on or in the human body – prevent growth of pathogens – produce growth factors, such as folic acid and vitamin K
    22. 22. Biofilms  Complex aggregation of microbes  Microbes attach to solid surfaces and grow into masses  grow on rocks, pipes, teeth, and medical implants  Difficult to treat with antibiotics
    23. 23. Infectious Diseases  When a pathogen overcomes the host’s resistance, disease results  Emerging infectious diseases (EIDs): New diseases and diseases increasing in incidence 1. Evolutionary 2. Increased human exposure in undergoing ecological changes 3. Antimicrobial resistance
    24. 24. MRSA • Methicillin-resistant Staphylococcus aureus • 1950s: Penicillin resistance developed • 1980s: Methicillin resistance • 1990s: MRSA resistance to vancomycin reported – VISA: Vancomycin-intermediate-resistant S. aureus – VRSA: Vancomycin-resistant S. aureus
    25. 25. Figure 25.12 Escherichia coli O157:H7 • Toxin-producing strain of E. coli • First seen in 1982 • Leading cause of diarrhea worldwide
    26. 26. Figure 23.21 Ebola Hemorrhagic Fever • Ebola virus • Causes fever, hemorrhaging, and blood clotting • First identified near Ebola River, Congo • Outbreaks every few years
    27. 27. Prokaryotic Anatomy
    28. 28.  Average size: 0.2–1.0 µm in diameter 2–8 µm in length (10^-6 meters)  Most bacteria are monomorphic (single shape)  What can alter shape?  Cell wall (membrane or wall) Prokaryotic Cells: Shapes
    29. 29. Figure 4.2b-c Bacilli. Streptobacilli Diplobacilli
    30. 30. Figure 4.1ad Arrangements of cocci. Plane of division Diplococci Streptococci Staphylococci
    31. 31. Arrangements • Pairs: diplococci, diplobacilli • Clusters: staphylococci or staphylobacilli • More than one plane of division • Chains: streptococci, streptobacilli • One plane of division • Grows in strands
    32. 32. Vibrio Spirochete Spirillum Figure 4.4 Spiral bacteria.
    33. 33. Star-shaped bacteria Figure 4.5a Star-shaped and rectangular prokaryotes.
    34. 34. Rectangular bacteria Figure 4.5b Star-shaped and rectangular prokaryotes.
    35. 35. Figure 4.6 The Structure of a Prokaryotic Cell. Capsule Cell wall Plasma membrane Fimbriae Cytoplasm Pilus 70S Ribosomes Plasma membrane Inclusions Nucleoid containing DNA Plasmid Flagella Capsule Cell wall . Not all bacteria have all the structures shown; only structures labeled in red are found in all bacteria. Although the nucleoid appears split in the photomicrograph, the thinness of the “slice” does not convey the object’s depth. © 2013 Pearson Education, Inc.
    36. 36. Bacterial Cell: Specific Roles • Capsule: bacterial virulence • Cell Wall or Flagella: bacterial identification • Cell Wall: target for antimicrobial agents • Plasmids: encode genes for production of toxins – Circular DNA that is independent to all the rest of the chromosomal DNA. They are not needed for the survival unless an it contains genetics that help it in it’s outside living conditions
    37. 37. Glycocalyx  Outside cell wall  Usually sticky, “sugar coating” (glue)  Capsule: neatly organized  Slime layer: unorganized and loose  (EPS) Extracellular polysaccharide (glycocalyx in general) allows cell to attach, chemical composition varies by species  Capsules (negative stain [will not stain]) prevent phagocytosis Example: Streptococcus pneumoniae
    38. 38. Figure 24.12 Streptococcus pneumoniae, the cause of pneumococcal pneumonia.
    39. 39. Flagella • Motility – Propel bacteria (word to move is taxis [move to light=phototaxis]) • Long filamentous appendages – Three basic parts • Filament (outermost region): globular protein • Hook: different protein • Basal body • Anchored to cell wall and membrane by the basal body • Distribution – No Flagella: ATRICHOUS – Evenly distributed: PERITRICHOUS – Polar: at one or both poles/ends
    40. 40. Figure 4.7 Arrangements of bacterial flagella. Peritrichous Monotrichous and polar Lophotrichous and polar Amphitrichous and polar
    41. 41. Basal body Peptidoglycan Hook Cell wall Gram- positive Filament Flagellum Plasma membrane Cytoplasm Parts and attachment of a flagellum of a gram-positive bacterium Figure 4.8b The structure of a prokaryotic flagellum.
    42. 42. Plasma membrane Cell wall Basal body Gram- negative Peptidoglycan Outer membrane Hook Filament Cytoplasm Flagellum Parts and attachment of a flagellum of a gram-negative bacterium Figure 4.8a The structure of a prokaryotic flagellum.
    43. 43. Motility • The ability of an organism to move by itself toward a favorable environment (taxis) • Chemotaxis signals: oxygen, ribose and galactose receptors • Flagella proteins are H antigens (e.g., E. coli O157:H7)
    44. 44. Axial Filaments • Also called endoflagella • In spirochetes • Anchored at one end of a cell • Rotation causes cell to move • Treponema pallidum: syphilis
    45. 45. Figure 4.10a Axial filaments. A photomicrograph of the spirochete Leptospira, showing an axial filament
    46. 46. • Thinner than flagellum • Attachment and DNA transfer • Fimbriae allow attachment: involved in forming biofilms • What happens if fimbriae are absent (genetic mutation)? – Becomes less virilant, disallows attachment Fimbriae and Pili
    47. 47. Figure 4.11 Fimbriae. Fimbriae
    48. 48. Fimbriae and Pili • Pili – Usually longer than fimbriae – Gliding motility – Twitching motility (like a worm)
    49. 49. The Cell Wall • Major function: prevents osmotic lysis • Maintains shape and point of anchorage for basal bodies • Made of peptidoglycan (in bacteria) • Gram positive and Gram negative
    50. 50. Peptidoglycan • Major component of cell wall in bacteria • Polymer of sugars and amino acids – Form a mesh-like layer – Each strand two sugars linked alternatively • N-acetylglucosamine • N-acetylmuramic acid – peptide chain of three to five amino acids. – peptide chain of one strand cross-linked to the peptide chain of another strand forming the 3D mesh-like layer.
    51. 51. L-Ala, d-Glu-NH2 etc. are amino acids This is the cell wall, the more ladders, the thicker the wall is
    52. 52. • Thick peptidoglycan • Teichoic acids – makes the wall like crosshairs + where – is peptidoglycan and | is teichoic acids Gram-Positive Cell Wall  Thin peptidoglycan  Outer membrane Gram-Negative Cell Wall
    53. 53. Plasma membrane Cell wall Lipoteichoic acid Peptidoglycan Wall teichoic acid Protein Gram-negative cell wall Lipopolysaccharide Outer membrane Peptidoglycan Plasma membrane Cell wall Lipid A Porin protein Phospholipid Lipoprotein Periplasm Protein Lipid A Core polysaccharide O polysaccharide Parts of the LPS Core polysaccharide O polysaccharide Gram-positive cell wall Figure 4.13b-c Bacterial cell walls.
    54. 54. • Many layers (thick) of peptidoglycan • Teichoic acids – Alcohol and phosphate; negative charge • May regulate movement of cations: cell growth, preventing extensive wall break down and possible cell lysis • Polysaccharides provide antigenic variation = identification Gram-Positive Cell Walls
    55. 55. • Thin layer of peptidoglycan and an outer membrane • Lipopolysaccharides (LPS) (outer) • LPS: evade phagocytosis and actions of immunity, provide barrier to certain antibiotics and enzymes • Porins: proteins that form channels, selective permeability Gram-Negative Cell Wall
    56. 56. Gram-Negative Outer Membrane LPS Composition:  Lipid A – functions as an endotoxin , responsible for symptoms associated with gram - infections  Core Polysaccharide – attached to Lipid A, provides stability  O Polysaccharide – functions as an antigen, useful in identification
    57. 57. The Gram Stain Mechanism • Crystal violet-iodine crystals form in cell • Gram-positive: Purple – Alcohol dehydrates peptidoglycan – CV-I crystals do not leave • Gram-negative: Red – Alcohol dissolves outer membrane and leaves holes in peptidoglycan – CV-I washes out
    58. 58. • 2-ring basal body – In the membrane • Thick Peptidoglycan • Purple Gram Stain • Disrupted by lysozyme (breaks the bonds between NAM’s and NAG’s • Penicillin sensitive • Exotoxins Gram-Positive Cell Wall  4-ring basal body  1 outer  1 wall  2 inner  Thin Peptidoglycan  Red Gram Stain  Outer Membrane  Tetracycline sensitive  Exo and Endotoxins Gram-Negative Cell Wall
    59. 59. Damage to the Cell Wall • Exposure to digestive enzyme lysozyme, destroys peptidoglycan (gram positive) • Penicillin inhibits peptide bridges in peptidoglycan (prevents formation of functioning cell wall)
    60. 60. The Plasma Membrane • Contains enzymes for metabolic reactions • Most lack sterols, Mycoplasma is exception • Disruption: membrane’s phospholipids = antibiotics: polymyxins
    61. 61. Cytoplasm • Contains nucleoid, ribosomes and inclusions • 80% water and contains primarily proteins (enzymes), carbs, lipids, inorganic ions and many lower molecular weight compounds
    62. 62. The Nucleoid • Bacterial chromosome: cell’s genetic information • Not surround by a nuclear envelope • Plasmids: not connected to main bacterial chromosome but have very important functions Antibiotic resistance Tolerance to toxic metals Production of toxins Can be transferred from one bacterium to another
    63. 63. The Prokaryotic Ribosome  Protein synthesis  Consist of two subunits: protein and type of RNA (rRNA)  Prokaryotic: 70S ribosomes  50S(subunit = protein plus two molecules of rRNA) + 30S subunits (subunit = protein plus one molecule rRNA)  Antibiotics: inhibit protein synthesis. Examples: gentamicin and streptomycin attach to 30S subunit and interfere with protein synthesis  Erythromycin and chloramphenicol interfere with 50S Why can these antibiotic drugs work without affecting host cells? Host cells are made up of 80S ribosomes
    64. 64. Inclusions • Located within cytoplasm • Reserve deposits: environment is deficient • Some are common to a wide variety of bacteria • May serve as a basis for identification • Example: C. diphtheriae
    65. 65. Endospores • Resting cells: when essential nutrients are depleted • Resistant to desiccation, heat, chemicals • Bacillus, Clostridium; Gram positive • Sporulation: endospore formation • Germination: return to vegetative state – Germination <-> Sporulation

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