Question

4. Amelia performs a Gram stain of Staphylococcus aureus but forgets to add the iodine. How will her slide appear when she examines it under the microscope? Explain why. (15 points)

Answer 1

4.Iodine acts as mordent and it increases the avidity of stain with bacteria. Staphylococcus aureus is gram positive bacteria and it stains in violet colour in gram staining . If iodine is not added, initial crystal violet die will be washed off from s.aureus and it stains pink after second stain ( safffranin) is added. It will look pink instead of violet

6 . Nigrosine , india ind, eosin , picric acid are examples of acidic stains and it is used to stain capsule staining to determine whether the cell has capsule or not

7. Gram staining of streptocoocus pyogenes gives more information than simple staining

In simple stain with safffranin the bacteria stains pink and in gram staining it stains violet since it is gram positive bacteria. Hence we can get information about the plasma membrane components and characters in the gram staining and it is better than simple staining