Lab Questions

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64.Interpret the following results:

A. The color of the medium remains purple or light blue-gray; there is also no change in the texture of the medium. * No change

B. Change in the color of litmus from purple to pink or pink-red throughout the tube. Upon further incubation a white ring of litmus forms at the bottom of the tube at the pink-red color is now present only at the top of the tube. Still further incubation leads to the formation of a rennet curd at the bottom of the tube. * Production of Acid:

C. The color of the litmus has changed from purple to white and there is a purple band at the top of the medium. * Reduction:

D. The turbidity of the milk is seen to decrease and its consistency becomes watery; a purple band forms at the top of the medium while the rest of the medium turns a brownish color. * Peptonization:

E.The medium changes in color from purple to blue or dark blue. * Alkalinization

F. The milk has changed from a liquid to a more solid consistency; clear, amber fluid is present in the upper portion of the tube above the solid material; a white ring of litmus has formed at the bottom of the tube, and litmus has formed a pink band at the surface of the clear liquid as well. * -Coagulation

65.Describe the physical change that occurs during lactose fermentation. Name one microbe capable of producing this reaction. * Lactose Fermentation involves the initial breakdown of lactose to glucose and the subsequent fermentation of glucose to produce an acid end product.

66. Describe the physical change that occurs during an alkaline reaction. Name one microbe that would produce this response. * This change to the media will impart a blue color throughout the media or cause a blue band to form at atop of the media. This PH change is a result of proteolytic and degradative enzymes producing ammonia or amines form the breakdown of proteins. * Proteus Vulgaris

67.Describe the physical change that occurs during clot formation. Name one microbe that would produce this response. * This change to the casein leads to the formation of a curb or clot. A casein clot can be distinguished from a an acid clot as an acid clot will dissolve in an alkaline environment. If the bacterium being tested possesses the enzyme rennin casein will be converted to paracasein and a translucent watery liquid called whey will appear at the top of the tube. * Lactobacillus Acidophilus

68.Describe the physical reaction that occurs during litmus reduction. Name one microbe that would produce this response. * This change of litmus is seen as a whitening of the media due to the action of reductase enzyme that remove oxygen from the media. * Enterococcus Faecalis

69.Describe the physical change that occurs during peptonization or digestion. Name one microbe capable of producing this response. * This change is evident when proteolytic bacteria digest milk proteins leading to the formation of a translucent often brown liquid and the dissolution of any clots. * Bacillus Cereus

70.Why does the lab manual suggest using the microbes it does for the litmus milk reaction? * I don’t have a lab manual?

SIM Medium:

71.What is the indicator for hydrogen sulfide production in SIM medium? * The production of ferrous sulfate

72.List all determinations that can be made with SIM medium? * Reduction of sulfur
* Production of indole from the breakdown
* Mobility

73What indicates a positive reaction for hydrogen sulfide production? What indicates a negative reaction? * Positive Reaction: Black Precipitate
* Negative Reaction: No Black Precipitate

74.What indicates a positive reaction for indole production? What indicates a negative reaction? * Positive Reaction: A ring on top
* Negative Reaction: No red ring on top

75.What indicates a positive reaction...
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