10 marks; due: Sept. 17-21 (beginning of lab) 1. Explain why staining is so valu
ID: 145756 • Letter: 1
Question
10 marks; due: Sept. 17-21 (beginning of lab) 1. Explain why staining is so valuable when observing bacterial cells. (2 marks) Complete the following table with the expected colour for each type of cell after each stage of the Gram stain. (4 marks) 2. Step Gram-positive cell Gram-negative cell Crystal violet Gram's iodine 95 % ethanol Safranin 3. Contrast the structure of Gram-positive and Gram-negative cell walls by providing TWO (2) differences. (2 marks) The endospore stain must be incubated over steam for 30 min in order for the stain to be pushed into the endospore. Describe what you should be doing during that 30 min for this staining procedure. (2 marks) 4.
Explanation / Answer
Answer 1 Staining is valuable because
Answer 2 Gram stain table
Step
Gram positive cell
Gram negative cell
Crystal violet
Violet
Violet
Gram’s iodine
Violet
Violet
95 % ethanol
Violet
Colorless
Safranin
Violet
Pink
Answer 3 Differences in cell wall of gram positive and gram negative bacteria
Answer 4 During the time (30 minutes) of steaming, I will ensure that the primary stain saturated paper which is kept on bacterial smear should cover the smear and remain saturated during whole of the incubation time. This would be confirmed by checking if steaming is there from slide. If steaming would not be there, more of primary stain would be added on to the paper.
Step
Gram positive cell
Gram negative cell
Crystal violet
Violet
Violet
Gram’s iodine
Violet
Violet
95 % ethanol
Violet
Colorless
Safranin
Violet
Pink
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