POST LAB: LABORATORY 10: Observing bacterial cultures - Questions 1&2 as well as
ID: 257518 • Letter: P
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POST LAB: LABORATORY 10: Observing bacterial cultures - Questions 1&2 as well as questions 3-6: 3) In heat-fixing, what would happen if too much heat was applied? 4) Explain the mechanism of gram staining? 5) What term best describes heterotrophic bacteria that feed on living tissue? 6) The disk diffusion technique is not a perfect indication of how an antimicrobial(s) wil perform in living organism. Explain why and what other factors should be considered.
POST-LAB: LABORATORY 10 QUESTIONS 1. Can dyes other than methylene blue be used for direct staining? Explain. 2. What do you think is the purpose of fixing the smear? 3. In heat-fixing, what would happen if too much heat was applied? Laboratory 10 Observing Bacterial Cultures: Post-Lab 183Explanation / Answer
3) In heat-fixing, what would happen if too much heat was applied?
Answer : it will distort cell structure and hence you cannot view cells clearly under microscope.
4) Explain the mechanism of gram staining?
Answer : crystal violet (CV) stain breaks into CV ion and chlorine ion. CV ion goes inside cell wall and interact with -vely charged molecules. After addition of iodine, it forms a large complex with crystal violet stain.
Gram +ve bacteria shows violet stain because of presence of a thick peptidoglycan layer in their cell walls. While Gram -ve bacteria shows pink stain because of presence of a thin peptidoglycan layer in their cell walls which cause washing off voilet stain by ethanol.
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