What role does lipopolysaccharide (LPS) play in Gram-negative bacteria?

Lipopolysaccharide (LPS) is a significant component of the outer membrane of Gram-negative bacteria, and it primarily functions as an endotoxin. When Gram-negative bacteria invade a host, LPS can be released into the bloodstream or other tissues. This triggers a robust immune response because LPS is recognized by the immune system as a signal of infection. The immune response can include the release of pro-inflammatory cytokines, activation of complement pathways, and recruitment of immune cells to the site of infection. This can lead to both protective effects, such as clearing the infection, and potentially harmful effects, such as septic shock, if the response is excessive.

While LPS does play a role in structural integrity and can contribute to resistance to phagocytosis and antibiotic treatment, its most distinguished characteristic in the context of pathogenic Gram-negative bacteria is its ability to act as an endotoxin that stimulates immune responses. This is critical for understanding how Gram-negative infections can impact human health and the body's reaction to such infections.