What is an antigen in bacteriology?

An antigen is defined in bacteriology as a substance that can induce an immune response. This is typically a molecule or part of a molecule that is recognized by the immune system as foreign. Antigens can be proteins, polysaccharides, or other types of biomolecules found on the surface of pathogens, including bacteria. When an antigen is introduced into the body, it triggers the immune system to generate antibodies specific to that antigen, leading to the activation of immune cells that work to eliminate the invading microorganisms.

Understanding the role of antigens is crucial in the context of infections, vaccines, and immune responses. For instance, when a vaccine containing an attenuated or inactivated form of a bacterium is administered, it prompts the body to recognize the bacterial antigens and develop immunity without causing disease. This highlights the importance of antigens in the field of bacteriology and immunology, as they are central to the recognition and response to pathogens by the immune system.