Which staining technique is used to visualize bacteria cell walls?

Which staining technique is used to visualize bacteria cell walls?

• A. Gram stain
• B. Tissue pathology
• C. Punch biopsy
• D. Edema

Answer: (A)

Visualizing bacteria cell walls is accomplished with the Gram stain. This technique uses differential staining to separate bacteria by cell wall structure: Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet-iodine complex during the alcohol decolorization step, so they appear purple. Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane; the alcohol dissolves the outer membrane and the crystal violet-iodine complex is washed away, allowing a pink/red counterstain to show, so they appear red or pink. This contrast makes Gram staining the standard method for seeing cell walls and for classifying bacteria as Gram-positive or Gram-negative, which also informs approach to treatment since cell wall properties influence antibiotic susceptibility. Other options aren’t staining techniques for bacteria walls: tissue pathology is a broader field, punch biopsy is a procedure to obtain tissue, and edema is a swelling condition.

Visualizing bacteria cell walls is accomplished with the Gram stain. This technique uses differential staining to separate bacteria by cell wall structure: Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet-iodine complex during the alcohol decolorization step, so they appear purple. Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane; the alcohol dissolves the outer membrane and the crystal violet-iodine complex is washed away, allowing a pink/red counterstain to show, so they appear red or pink. This contrast makes Gram staining the standard method for seeing cell walls and for classifying bacteria as Gram-positive or Gram-negative, which also informs approach to treatment since cell wall properties influence antibiotic susceptibility. Other options aren’t staining techniques for bacteria walls: tissue pathology is a broader field, punch biopsy is a procedure to obtain tissue, and edema is a swelling condition.