Which of the following organisms is gramnegative Staphylococ

Which of the following organisms is gram-negative? Staphylococcus aureus Escherichia coli Bacillus cereus None of the above Why is it recommended that Gram staining be performed on young bacterial cultures (not older than 24 hours)? Over time, gram-negative cells gain the ability to retain the crystal violet stain after decolorization. Over time, gram-negative cells lose their ability to retain the crystal violet stain after decolorization. Over time, gram-positive cells lose their ability to retain the crystal violet stain after decolorization. Increased incubation times lead to increased risk of contamination.

Solution

PART A

Escherichia coli

E.coli is gram negative as this will not retain the crystal violet stain, but will retain the safranin used during the Gram staining method. Here in Gram-negative bacteria, the cell wall is made up of single layer of peptidoglycan and can found outer membrane surrounding it.

PART B

Why is it recommended that gram staining be performed on young bacterial cultures.

Answer is C) Over time, gram-positive cells lose their ability to retain the crystal violet stain after decolorization

If the cultures becomes old, gram positive bacterial will tend to stain gram negative as their cell walls becomes weak and could not be able to retain crystal violet stain.