Which microorganisms are known to be both beneficial and harmful to human health?

Pathogens are microorganisms that can cause disease; however, the term encompasses a wide range of harmful agents. Interestingly, some pathogens can also play a beneficial role in certain contexts or stages of life. For example, some pathogens can stimulate the immune system, leading to enhanced immune responses that ultimately protect against more harmful infections. Additionally, certain infections can trigger beneficial physiological responses, promoting health in specific scenarios.

Understanding that pathogens can have both detrimental and beneficial effects highlights the complexity of interactions between microorganisms and the human body. This duality is why pathogens are often studied not only in terms of their negative impacts but also in terms of potential applications in treatments and vaccines.

The other options each have distinct roles. Viruses are commonly viewed as harmful because they predominantly cause disease, and while some viruses can have beneficial aspects (like bacteriophages in treating bacterial infections), this is less commonly recognized. Fungi can be both pathogenic and beneficial (e.g., penicillin comes from a fungus), but they are not referred to as pathogens in the same way. Eyebacteria may refer to bacteria present in ocular environments but do not fit into the category of having widespread dual roles in human health as pathogens do.