What is the primary role of the outer membrane in Gram-negative bacteria?

What is the primary role of the outer membrane in Gram-negative bacteria?

• A. To allow nutrients to enter the cell freely
• B. To regulate the temperature of the bacterial cell
• C. To act as a barrier against harmful substances, including antibiotics
• D. To facilitate the exchange of genetic material between bacteria

Answer: (C)

The primary role of the outer membrane in Gram-negative bacteria is to act as a barrier against harmful substances, including antibiotics. This outer membrane is a crucial component of the cell envelope that provides an additional protective layer beyond the inner membrane. It contains lipopolysaccharides, which contribute to its structural integrity and protective functions. The outer membrane selectively permits the passage of certain molecules while effectively blocking others, thereby playing a significant role in the bacterium's defense mechanisms. This characteristic makes Gram-negative bacteria inherently more resistant to many antibiotics and chemical agents, which might be able to penetrate the membranes of Gram-positive bacteria more easily. The other options address functions that are not accurate representations of the outer membrane's primary role. For instance, while some nutrients can enter through porins in the outer membrane, this does not reflect the primary function. Regulation of temperature is not a role of the outer membrane; bacteria rely on other mechanisms for thermoregulation. Lastly, while some genetic exchange can occur in Gram-negative bacteria through conjugation, this process is facilitated by specific structures like pili rather than the outer membrane itself.

The primary role of the outer membrane in Gram-negative bacteria is to act as a barrier against harmful substances, including antibiotics. This outer membrane is a crucial component of the cell envelope that provides an additional protective layer beyond the inner membrane. It contains lipopolysaccharides, which contribute to its structural integrity and protective functions.

The outer membrane selectively permits the passage of certain molecules while effectively blocking others, thereby playing a significant role in the bacterium's defense mechanisms. This characteristic makes Gram-negative bacteria inherently more resistant to many antibiotics and chemical agents, which might be able to penetrate the membranes of Gram-positive bacteria more easily.

The other options address functions that are not accurate representations of the outer membrane's primary role. For instance, while some nutrients can enter through porins in the outer membrane, this does not reflect the primary function. Regulation of temperature is not a role of the outer membrane; bacteria rely on other mechanisms for thermoregulation. Lastly, while some genetic exchange can occur in Gram-negative bacteria through conjugation, this process is facilitated by specific structures like pili rather than the outer membrane itself.