A 19-year-old man presents to a clinic with a purulent urethral discharge and dysuria. A Gram stain of the discharge shows intracellular Gram-negative diplococci. The causative organism, Neisseria gonorrhoeae, has an outer membrane that contains channels allowing for the passage of hydrophilic molecules.
Which of the following structures forms these channels in the outer membrane?
- Lipid A
- Peptidoglycan
- Porins (correct answer)
- Teichoic acids
Explanation: Gram-negative bacteria, such as Neisseria gonorrhoeae, have an outer membrane that acts as a permeability barrier. To allow the passage of small hydrophilic molecules like nutrients and some antibiotics, this membrane is embedded with channel-forming proteins called porins. These proteins form water-filled channels that permit passive diffusion. Teichoic acids are found in Gram-positive bacteria, not Gram-negative.