Gram, Spore, & AF Staining


Q: Ex 15-17 A: Ex 15-17
what color would you expect S. aureus to be if the iodine step were omitted in the Grame-staining procedure? It would still be purple, maybe just a lighter color of purple because iodine serves to intensify the first color not make it stick
what structures of the bacterial vell appears to play the most important role in determining whether an organism is G+? The peptidodoglycan layer of the cell wall
Why would methylene blue not work just as well as safranin for ocunterstaining in the G-staining procedure? Methylen blue would not provide as strong of a contrast to the crystal violet as the safranin does.
Why are endospores so difficult to stain? The exosporium layer surrounding the endospore makes it difficult to stain.
How do the following two genera of spore-formers differ physiologically? Bacillus vs. Clostridium Bacillus is an aerobic form of spore-former while Clostridium is an anaerobic form of spore-former
How do you differentiate S. aureus and M.B. catarrhalis from each other on the basis of morphological characteristics? (blank)
Are the acid-fast mycobacteria G+ or G-? (blank)
For what two diseases is AF staining of paramount importance? a. Mycobacterium leprae (Leprosy) b. Mycobacterium tuberculosis (tuberculosis)
What two genuses of bacteria have a waxy material in their cell walls? a. Mycobacterium b. Nocardia
what is the waxy material in the cell walls of Mycobacterium and Nocardia? mycolic acid
Are the AF mycobacteria G+ or G- (blank)
Why is it desirable to combine S. aureus with AF organisms such as M. smegmatis when applying an AF staining technique? (blank)
What is a primary stain? (blank)
What is a secondary stain? (blank)
What color is a G+ organism? purple
what color is a G- organism? pink
what is a mordant? a chemical that complexes with the primary stain to enhance the primary stain
What is peptidoglycan? a thick cell wall that is a protein complex and carbohydrate; G+ organisms have a thick wall of it
What is S. aureus? colonizes mainly the nasal passages, but it may be found regularly in most other anatomical locales; causes pneumonia, mastitis, phlebitis, meningitis, and urinary tract infections; yields principally lactic acid; catalase-positive and oxidase-negative
What does S. aureus look like? fairly large yellow colony on rich medium



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