Without microorganisms humans would not be able to survive. Especially our gut flora is an extremely densely populated ecosystem that houses billions of bacteria which help us to digest or detoxify food, supply us with vitamins, or modulate our immune system. Similarly, plants have also a so-called microbiome. In contrast to animals and humans, microorganisms associated with plants are primarily soil microbiota. Scientists consider the soil microbiome as a kind or external plant immune system. However, due to the enormous complexity of these microbiomes it is very difficult for scientists to group bacteria as beneficial or deleterious, and some bacterial taxa are even able to morph from Dr. Jekyll into Mr. Hyde upon environmental stresses.