History of Microbiology



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History of Microbiology.

    • History of Microbiology.
    • Classification of bacteria.
    • Structure of bacterial cell














  • Morphologic

  • Physiologic

  • Prophylactic



























Bergey’s Manual of Systematic Bacteriology

  • Bergey’s Manual of Systematic Bacteriology

    • Classifies bacteria via evolutionary or genetic relationships.
  • Bergey’s Manual of Determinative Bacteriology

    • Classifies bacteria by cell wall composition, morphology, biochemical tests, differential staining, etc.














Microscopic morphology

  • Microscopic morphology

  • Macroscopic morphology – colony appearance

  • Physiological / biochemical characteristics

  • Chemical analysis

  • Serological analysis

  • Genetic and molecular analysis

    • G + C base composition
    • DNA analysis using genetic probes
    • Nucleic acid sequencing and rRNA analysis


Bergey’s Manual of Determinative Bacteriology – five volume resource covering all known procaryotes

  • Bergey’s Manual of Determinative Bacteriology – five volume resource covering all known procaryotes

    • classification based on genetic information –phylogenetic
    • two domains: Archaea and Bacteria
    • five major subgroups with 25 different phyla


Domain

  • Domain

  • Kingdom

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • species



Vol 1A: Domain Archaea

  • Vol 1A: Domain Archaea

    • primitive, adapted to extreme habitats and modes of nutrition
  • Vol 1B: Domain Bacteria

  • Vol 2-5:

    • Phylum Proteobacteria – Gram-negative cell walls
    • Phylum Firmicutes – mainly Gram-positive with low G + C content
    • Phylum Actinobacteria – Gram-positive with high G + C content


Phylogeny of domain Bacteria

  • Phylogeny of domain Bacteria

    • The 2nd edition of Bergey’s Manual of Systematic Bacteriology divides domain Bacteria into 23 phyla.


Phylogeny of domain Bacteria (cont.)

  • Phylogeny of domain Bacteria (cont.)

      • Phylum Proteobacteria
        • The largest group of gram-negative bacteria
        • Extremely complex group, with over 400 genera and 1300 named species
        • All major nutritional types are represented: phototrophy, heterotrophy, and several types of chemolithotrophy
        • Sometimes called the “purple bacteria,” although very few are purple; the term refers to a hypothetical purple photosynthetic bacterium from which the group is believed to have evolved


Phylogeny of domain Bacteria (cont.)

  • Phylogeny of domain Bacteria (cont.)

      • Phylum Proteobacteria (cont.)
        • Divided into 5 classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria


Phylogeny of domain Bacteria (cont.)

  • Phylogeny of domain Bacteria (cont.)

      • Phylum Proteobacteria (cont.)
        • Significant groups and genera include:
          • The family Enterobacteriaceae, the “gram-negative enteric bacteria,” which includes genera Escherichia, Proteus, Enterobacter, Klebsiella, Salmonella, Shigella, Serratia, and others
          • The family Pseudomonadaceae, which includes genus Pseudomonas and related genera
          • Other medically important Proteobacteria include genera Haemophilus, Vibrio, Camphylobacter, Helicobacter, Rickessia, Brucella


Phylogeny of domain Bacteria (cont.)

  • Phylogeny of domain Bacteria (cont.)

      • Phylum Firmicutes
        • “Low G + C gram-positive” bacteria
        • Divided into 3 classes
          • Class I – Clostridia; includes genera Clostridium and Desulfotomaculatum, and others
          • Class II – Mollicutes; bacteria in this class cannot make peptidoglycan and lack cell walls; includes genera Mycoplasma, Ureaplasma, and others
          • Class III – Bacilli; includes genera Bacillus, Lactobacillus, Streptococcus, Lactococcus, Geobacillus, Enterococcus, Listeria, Staphylococcus, and others


Phylogeny of domain Bacteria (cont.)

  • Phylogeny of domain Bacteria (cont.)

      • Phylum Actinobacteria
        • “High G + C gram-positive” bacteria
        • Includes genera Actinomyces, Streptomyces, Corynebacterium, Micrococcus, Mycobacterium, Propionibacterium
      • Phylum Chlamidiae


Phylogeny of domain Bacteria (cont.)

  • Phylogeny of domain Bacteria (cont.)

      • Phylum Spirochaetes
        • The spirochaetes
        • Characterized by flexible, helical cells with a modified outer membrane (the outer sheath) and modified flagella (axial filaments) located within the outer sheath
        • Important pathogenic genera include Treponema, Borrelia, and Leptospira
      • Phylum Bacteroidetes
        • Includes genera Bacteroides, Flavobacterium, Flexibacter, and Cytophyga; Flexibacter and Cytophyga are motile by means of “gliding motility”




Binomial naming system

  • Binomial naming system

    • Two word naming system
  • First word is genus name

    • Always capitalized
      • Escherichia
  • Second word is species name

    • Not capitalized
      • coli
  • When writing full name genus usually abbreviated

    • E. coli
  • Full name always italicized



























































Storage granules

  • Storage granules

    • Metachromatic granules
    • Polysaccharide granules
    • Lipid inclusions
    • Sulfur granules
    • Carboxyzomes
    • Magnetosomes
  • Gas vesicles













Unique chemical structure

  • Unique chemical structure

    • Distinguishes Gram positive from Gram-negative
    • bacteria and archaea bacterial species
  • Rigidity of cell wall is due to peptidoglycan (PTG)

    • Compound found only in bacteria
    • Archaea –psudomurein or other sugars, proteins, glycoproteins
  • Many antimicrobial interfere with synthesis of PTG

      • Penicillin; Lysozyme


Basic structure of peptidoglycan

  • Basic structure of peptidoglycan

    • Alternating series of two subunits
      • N-acetylglucosamin (NAG)
      • N-acetylmuramic acid (NAM)
    • Joined subunits form glycan chain
      • Glycan chains held together by string of four amino acids
        • Tetrapeptide chain:
    • L-ala-D-glu-DAP-D-ala
    • L-ala-D-glu-Lys-D-ala
  • Interpeptide bridge







Capsule

  • Capsule

    • Protects bacteria from phagocytic cells
  • Slime layer

    • Enable attachment and aggregation of bacterial cells












3 parts

  • 3 parts

    • filament – long, thin, helical structure composed of proteins
    • hook- curved sheath
    • basal body – stack of rings firmly anchored in cell wall
  • rotates 360o

  • 1-2 or many distributed over entire cell

  • functions in motility



1. Monotrichous – single flagellum at one end (cholera vibrio, blue pus bacillus),

  • 1. Monotrichous – single flagellum at one end (cholera vibrio, blue pus bacillus),

  • 2. Lophotrichous – small bunches arising from one end of cell (blue-green milk bacillus, Alcaligenes faecalis)

  • 3. Amphitrichous – flagella at both ends of cell (Spirillum volutans),

  • 4. Peritrichous – flagella dispersed over surface of cell, slowest E. coli, salmonellae of enteric fever and paratyphoids A and B





Short, hair-like structures on the surfaces of procaryotic cells

  • Short, hair-like structures on the surfaces of procaryotic cells

  • Proteinaceuse filaments (~20 nm in diameter)

  • Very common in Gram-negative bacteria

  • Functions:

    • Adherence to surface/ substrates: teeth, tissues
    • Involved in transfer of genetic information btw cells
    • Have nothing to do with bacterial movement (Except the twitching movement of Pseudomonas)


Bacterial spores are often called “endospore” (since they are formed within the vegetative cell)

  • Bacterial spores are often called “endospore” (since they are formed within the vegetative cell)

  • Produced in response to nutrient limitation or extreme environments

  • Highly resistant

  • Highly dehydrated (15% water)

  • Metabolically inactive

  • Stable for years

  • Not reproductive

  • Functions: to survive under an extreme growth conditions such as high temperature, drought, etc.

  • Bacillus, Clostridium, Sporolactobacillus, Thermoactinomyces, Sporosarcina, Desulfotomaculum species sporulate





Key compositions:

  • Key compositions:

    • Dipicolinic acid (DPA)
    • Calcium (Ca2+)
  • Structure

    • Core / Cytoplasm
    • Plasma membrane
    • Core wall/ spore wall
    • Cortex
    • Spore coat
    • Exosporium














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