Which of the following is an example of a pathogen?

A pathogen is specifically defined as an organism that is capable of causing disease in its host. This includes various types of microorganisms such as bacteria, viruses, fungi, and protozoa that disrupt normal biological processes and can lead to illness. In this context, the reference to a microorganism causing disease is the clearest representation of what constitutes a pathogen.

The other options describe elements that do not fit the definition. For instance, bacteria that support the local ecosystem play a vital role in environmental health, contributing to nutrient cycling and habitat support without necessarily causing disease. Similarly, minerals that are beneficial to human health are essential nutrients that support bodily functions and promote health, rather than being disease-causing. A component of purified water pertains to substances that are essential for life but do not exhibit pathogenic properties, assuming the water is free from harmful organisms. Hence, the understanding of pathogens is crucial for identifying potential health risks, underscoring the accuracy of identifying a microorganism causing disease as an example of a pathogen.