What are pathogens primarily known for?

Pathogens are primarily known for their ability to cause diseases, particularly by being introduced into water systems through fecal contamination. This mode of transmission is significant in public health, as many waterborne diseases stem from pathogens found in human and animal waste. When these pathogens enter the water supply, they can lead to outbreaks of illnesses such as cholera, dysentery, and hepatitis A, posing serious health risks to populations consuming contaminated water.

In contrast, the other options highlight either benign or beneficial aspects of microorganisms or focus on specific transmission methods that are not representative of the broader impact of pathogens. While airborne transmission does occur, it is just one of many ways diseases can spread and does not capture the primary characteristic of pathogens. Additionally, being harmless microorganisms or contributing positively to soil fertility aligns more with non-pathogenic types of microbes rather than the harmful effects associated with pathogens. Thus, the focus on fecal contamination leading to disease transmission accurately encapsulates the primary concern regarding pathogens in environmental and public health contexts.