Lab test # 2

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Lab test # 2
2013-09-15 17:04:07
Lab test

Lab test # 2
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  1. define differential medium
    growth medium that allows two or more organisms to be distinguished from one another by some parameter, such as growth vs. no-growth, distinguishing colors, distinguishing morphologies, etc
  2. the fermentable carbohydrate in lysine iron agar is dextrose glucose
    is dextrose glucose
  3. the primary substrate for deamination and decarboxylation reations in this expirement is
  4. the ph indicator in this medium is
  5. broncesa
    is purple at ph 6.8 or higher and yellow at ph 5.2 and bellow
  6. thiosulfate when reduced becomes
    reducible sulfer
  7. ferric iron ion in this expirment reacts with hydrogen sulfide to form
    black drecipitate oxygen
  8. this medium provides an oxygen zone for growth on the slant and
    no oxygen zone (anaerobic)  for growth in the butt
  9. new portion 
    bile esculin agar is both a selective and differential medium
    selective growth medium that favors growth of one group of micro organisms inhibits or prevents growth to others 

    differential growth media contains an indicator usually color to detect the presence or absence of a specific metabolic activity
  10. what is a presumptive identification of a micro- organism
    tentative identification of an isolate based on one or more key test results
  11. esculin is an example of a type of molecule known as a glycoside its 2 components are the sugar _____ and a compound called ____
    • 1. glucose 
    • 2. escultin
  12. the bile in bile esculin agar inhibits the growth of most ____ organisms
  13. what is the bile in bile esculin agar
  14. when esculin molecules are split by bacteria _____ reacts with ferric citrate and forms a ____ color phenolic iron complex
    • 1.esculitin 
    • 2. black
  15. describe a positive result in this experiment including time frame
    48 hours enterococcus faccalis is positive and tunrs esculin into esculetin the escultin reacts with iron and produces a black color giving it a positive 
  16. describe  a negative results in this expirment indcluding time frame 
    citrobacter freundii is negative because it cant hydrolze esculin 
  17. explain how bile esculin agar acts as a differential medium 
    because it contains ferric ammonium citrate to practice the black color and the bile inhibits the growth of the negative c freundii 
  18. explain how the ferric citrate in bile esculin agar allows you to observe a positive result. 
    the bile inhibits its growth for other 
  19. explain how an exoenzyme works and an endoenzyme works in relationship to the cell 
    exoenzyme is a enzyme produced by cell that catalyze reactions outside of the cells endoenzyme is a enzyme that catlyze reaction inside the cell 
  20. a lactose fermenter is an organism that splits the ___ lactose into ___ and____ then ferments the ________.
  21. phenol red broth contains a fermentable _____ included in the base medium are ____ and the ph indicator _____
  22. phenol red broth is ____below pH 6.8 and ____above 7.4 
  23. as prepared the phenol red is at pH ____and appears red. 
  24. _________of peptone amino acids produces ____which raises the pH and turns the broth_____
  25. an inverted durham tube small test tube is placed inside the the test tube to: 
  26. if the medium is inoculated, incubated and then observed to produce a pink results this indicates an alkaline condition caused by deamination. So reading carbohydrate fermentation test can be unreliable if reversion has occurred why?
  27. understand /define completely reversion and apply to #7 and above 
  28. how many carbohydrates are added to each phenol broth and why 
  29. list the gram reaction and morphology of the enteric bacteria 
  30. Macconkey Agar is used to isolate and differentiate members of family enterobacteriacea based on their ability to ferment 
  31. know the terms selective medium and differential medium 
  32. what is the pH indicator used in MacConkey agar 
  33. the inclusion of bile salts and crystal violet makes Macconkey agar a _____ medium. 
  34. the pH indicator, neutral red is__ at a pH less than 6.8: and is ____at ph above 6.8 
  35. when bacteria are growing on MacConkey agar what will cause the Ph indicator to turn red 
  36. What do colonies of lactose nonfermenters look like on MacConkey agar what do fermenters (coliform) colonies look like 
  37. Which of bacteria used is/are coliforms 
  38. what will gram positive bacteria look like when plated on MacConkey agar 
  39. Any organism that grows well on macConkey agar regardless of appearance of growth is gram ______.