Micro Lab Practical

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  1. Antimicrobials
    cmpds that kill or inhibit microorgs
  2. Antibiotics
    antimicrobials produced by microorgs that kill or inhibit the growth of other microbes
  3. Narrow spectrum antibiotic
    specific for one bacterial strain
  4. broad-spectrum antibiotic
    effective against a wide range of bacteria (G-neg and G-pos)
  5. Disinfectant
    germicides (lethal to pathogens) for floors, workbenches, etc
  6. Antiseptics
    inhibit microbial growth or kill microorgs; can be used on living tissue
  7. Phenol Coefficient
    number on label, indicates killing power of disinfectant
  8. Bacteriostatic
    only inhibits growth; does not kill bacterial cells
  9. Phenol Red Broth
    Tests for carbohydrate fermentation (ie glucose, dextrose, lactose, sucrose

    pos result = acid produced; red changes to Yellow color, possibly gas produced
  10. Methyl Red Test
    tests ability of bact to metab glucose to produce acids

    • Pos test = Red color
    • Neg test = orange/yellow

    E. coli is pos
  11. Voges-Proskauer test
    Test if 2,3-butanediol is produced

    add Barritt's reagent

    Pos test = reddish color

    E. coli is pos
  12. Citrate Test
    Test if bact can use citrate to form oxaloacetate & pyruvate

    pos test = color change from green to BLUE means bact using citrate

    E. aerogenes is pos
  13. Oxidase Test
    tests for cytochrome oxidase

    pos test = color change from yellow to purple in presence of cyt ox

    P. aeruginosa is pos
  14. Catalase Test
    tests for catalase enzyme

    hydrogen peroxide (as by-product of respiration) broken down by catalase; releases water & oxygen

    Pos test = O2 bubbles

    P. aeruginosa is pos
  15. Starch Hydrolysis
    tests for production of amylase

    starch agar is differential medium - tests ability of orgnsm to produce amylase, which hydrolyzes starch

    add iodine to plate; iodine turns dark in presence of starch

    pos test = clearing around bacterial growth means org hydrolyzed starch
  16. Urea Hydrolysis
    Tests for Urease production

    urease brks down urea to ammonia and CO2, causes change in pH

    Pos test = color change from yellow to HOT PINK
  17. Nitrate Reduction
    Testing for Nitrate Reductase production (reduces nitrate to nitrite)

    add chem to react w/nitrate and pH indicator

    Pos test = red; nitrate is being reduced to nitrite

    • if not red, add zinc
    • Red = nitrate reduction
    • no color change = no nitrate reduction

    E. coli is pos
  18. Selective Media
    allows growth of certain types of orgs while inhibiting the growth of others
  19. Differential Media
    Allows to distinguish between or among diff microorgs based on diff in colony appearance
  20. Mannitol Salt Agar (MSA)
    Selective and Differential media

    Salt selects for G-pos bac and differentiates based on bact ability to ferment mannitol

    pos test = Phenol Red turns to yellow when acid is produced (meaning mannitol is fermented)

    if colony grows, is g-pos; if turns yellow, ferment mannitol
  21. Levine Eosin Methylene Blue Agar (EMB)
    select for G-neg and differentiate based on ability to ferment lactose

    pos test = lactose fermenters produce blue-black colonies; strong lac fermenters produce green metallic colonies

    non-lac fermenters produce colorless or amber colonies

    if nothing grows, is G-pos = neg test

    • E. aerogenes was pink
    • E. coli was green
    • P. aeruginosa was colorless
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Micro Lab Practical
2012-04-30 00:49:29
Micro Lab Practical

Micro Lab Practical
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