Explain the Gram staining process for Gram-negative bacteria and identify a factor that inhibits bacterial growth in food preservation.

Here are the answers to your questions.

Question 1:
Assertion (A): Gram-negative bacteria appear pink after staining.
Reason (R): They have a thin peptidoglycan layer and lose crystal violet during decolorization.

• Assertion (A) is true. Gram-negative bacteria do appear pink or red after Gram staining because they take up the counterstain (safranin).
• Reason (R) is true. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane. During the decolorization step of Gram staining, the alcohol washes away the crystal violet-iodine complex from these cells due to their cell wall structure.
• The reason (R) directly explains why Gram-negative bacteria do not retain the primary stain and thus appear pink after counterstaining.

Therefore, both A and R are true, and R explains A.

The correct option is:

• Both A and R are true, and R explains A

Question 2:
Which factor would MOST likely inhibit bacterial growth in food preservation?

• High moisture content: Promotes bacterial growth.
• Neutral pH: Many bacteria thrive at a neutral pH.
• High salt concentration: Creates a hypertonic environment, drawing water out of bacterial cells through osmosis, which inhibits their growth and can kill them. This is a common method for food preservation (e.g., salting meat, pickling).
• Warm temperature: Promotes bacterial growth.

Therefore, high salt concentration is the factor that would most likely inhibit bacterial growth in food preservation.

The correct option is:

• High salt concentration