Questions: You are performing a Gram stain on gram-negative bacteria and you stop after the decolorizer step. What is the appearance of the bacteria at this point?

The answer is: colorless.

Explanation for each option:

• Purple: Gram-negative bacteria do not retain the crystal violet stain after the decolorizer step. Therefore, they would not appear purple.
• Red: Gram-negative bacteria would appear red only after the application of the counterstain (safranin or fuchsine), which has not been applied yet at this stage.
• Colorless: After the decolorizer step, gram-negative bacteria lose the crystal violet-iodine complex and appear colorless because the counterstain has not yet been applied.
• Brown: There is no step in the Gram staining process that would cause the bacteria to appear brown.

Summary: At the point after the decolorizer step in a Gram stain procedure, gram-negative bacteria would appear colorless.