What are exotoxins?

Exotoxins are indeed poisonous substances produced by bacteria, and this definition encapsulates their essence and significance in microbiology. These toxins are typically secreted by living bacteria into their environment, and they can cause damage to host tissues or interfere with normal physiological functions. Exotoxins are known for their potency and specificity; they can elicit strong immune responses and are often associated with significant diseases.

For instance, common examples of exotoxins include the diphtheria toxin produced by Corynebacterium diphtheriae and the cholera toxin produced by Vibrio cholerae. Both of these exotoxins can lead to severe health issues, demonstrating how they function as virulence factors that enhance the bacteria's ability to cause disease.

Understanding the nature of exotoxins is crucial in disease prevention and treatment strategies, as they can be targeted by vaccines or specific therapies. In contrast, the other options refer to different cellular components or functions. Internal enzymes of bacteria, for example, typically function in metabolic processes rather than causing direct harm to the host. Membrane-bound proteins play various roles in transport and signaling but are not classified as toxins. Components of bacterial cell walls, like peptidoglycan, provide