What group of microorganisms can be either beneficial or pathogenic to plants and animals?

Bacteria are a diverse group of microorganisms that can play a variety of roles in the environments they inhabit. They can be beneficial, such as those involved in nitrogen fixation, which enhances soil fertility, or in the gut microbiome, where they aid in digestion and overall health of animals, including humans. Conversely, certain bacteria can also be pathogenic, causing diseases in plants and animals. This dual capacity to exist as beneficial or harmful agents underlines the significant impact bacteria have on both ecosystems and agricultural practices.

While protists, fungi, and viruses also interact with plants and animals in various ways, their specific roles often lean more toward either beneficial or pathogenic without the same level of widespread dual functionality seen in bacteria. For instance, some protists can cause diseases in plants (like phytophthora) but are not typically classified as beneficial microbes, while fungi can also be both beneficial (like mycorrhizae) and pathogenic. Viruses, on the other hand, are generally pathogenic as they infect and harm host organisms rather than providing beneficial interactions.