Bacterial Classification and Structure

  1. what are the methods to classify and distinguish bacteria?
    • macroscopic: colony appearance
    • microscopic: gram stain, immunostaining (ELIZA)
    • serologic: reactions with antibodies
    • Molecular: nucleic acid or protein detection/sequence, cell surface structures
    • metabolic: growth on/use of certain nutrients, by products, aerobic/anaerobic
  2. describe macroscopic traits
    • colony morphology, solor, shape, size, patterns
    • hemolysis on blood agar
    • growth and color on selective and differential media
  3. describe this types of hemolysi
    • Alpha-hemolysis
    • partial lysis leaving greenish/brownish halo around colonies
  4. describe this type of hemolysis
    Beta+haemolysis Beta+haemolysis
    • strong B-hemolysis
    • total clear zone around the colonies
  5. describe this type of hemolysis?
    • weak beta hemolysis
    • lighter cloudy zone around the colonies
  6. describe this type of hemolysis
    white%20staphylococcus%20aureus white%20staphylococcus%20aureus
    • non hemolytic
    • no clear zone or color on blood agar
  7. describe types of gram stain for microscopic traits
    • gram pos: stain purple, crystal violet stain gets trapped in thick peptidoglygan wall surrounding inner membrane
    • gram neg: stain red, crystal violet cannot penetrate outer membrane and safranin red stain adheres to thin peptidoglycan cell wall between two cell membranes
  8. what are some problems that arise when using gram stain on old/weakened bacteria
    may not stain properly
  9. gram +/- ?
    300px-Gram_Stain_Anthrax 300px-Gram_Stain_Anthrax
    Gram (+)
  10. gram +/-?
    Pseudomonas_aeruginosa_Gram Pseudomonas_aeruginosa_Gram
    gram (-)
  11. describe the crystal violet dye, decolorizer, and safranin red steps in gram stain
    • crystal violet dye: ppt'd by iodine and trapped by the thick outer cell wall of G(+) bacteria
    • decolorizer (ethanol/acetone): disperses the outer membrane of G(-) bacteria and strips the crystal violet. Creates holes on outer membrane
    • safranin red: a counterstain that binds to now exposed thin cell wall of G(-) bacteria
  12. what can you observe from gram stain morphology
    • cell shape: may differ depending on cell's development, environment, nutrient availability, stress
    • arrangement of cells
  13. what are some of the stains used to reveal bacteria? (4)
    • gram stain
    • silver stain
    • giemsa stain
    • immunostaining: fluorescent
  14. what is darkfield microscopy
    a technique used to see very small bacterial not visible by typical staining methods
  15. how is serology used to ID bacteria
    • "antigenic classification"
    • using antibodies to detect the specific antigens on bacteria
    • ex) ELIZA, fluorescence, clumping/agglutination
  16. what is serology useful for
    • organisms that do not grow well in culture
    • organisms that are too dangerous to grow in the lab
    • organisms that need to be ID's quickly
  17. how is molecular identification used for bacterial classification
    • "culture independent characterization"
    • ID using highly conserved DNA which is amplified by PCR (polymerase chain reaction)
  18. what is molecular ID useful for
    • differentiate different strains of the same bacterial species, such as pathogenic vs commensal strains
    • presence/absence of genes
    • comparing DNA,RNA sequences to large databases and can identify species or strains without any previous information about the organism
  19. what is the most common gene sequence used to determine bacteria and is found in all bacteria
    • 16S rRNA
    • the most highly conserved bacteria ribosomal RNA
  20. how is metabolic activity used to classify bacterial DNA
    • certain bacteria metabolizes specific carbohydrates and different compounds using carbon, nitrogen, and water as an energy source.
    • ex) catalase +/-
  21. how is bacteria classified by oxygen requirements
    • obligate anaerobes: can only grow without oxygen. Ex) clostridium perfringens
    • obligate aerobes: can only grow in oxygen. Ex) mycobacterium tuberculosis
    • facultative anerobes/aerobes: can grow with/without oxygen. Are able to adapt and change their metabolism based on the oxygen environment but may grow better in one condition than the other
  22. what are the enzymes released by aerobic (obligate and facultative) bacteria and what is its function
    • superoxide dismutase
    • catalse
    • f(x): detoxifies hydrogen peroxide and superoxide radicals (toxic by products)
  23. does fermentation or cellular respiration produce more energy
    cellular respiration
  24. what are the fermentation products
    produces organic acids that reduces the pH level
  25. what is the indicator that is used to ID pH and does each color change indicate?
    • bromocresol purple
    • acid: yellow <6.3
    • basic: purple
  26. what are the three tests used to determine enzymes or metabolic processes
    • gelatinase: hydrolyze (+), remain solid (-)
    • urease: red (+), yellow (-)
    • indole test: for tryptophanase pathway. Red (+), gold (-)
Card Set
Bacterial Classification and Structure
how bacterial is described and classified