Fungi and their Environmental Micropredators

Abstract

Predator–prey interactions are obvious drivers in the evolution among higher animals, but until today, there is little known about such relationships in the microverse. Like any other microbes, fungi can be prone to predation by bacteria, amoebae, or nematodes. While the boundaries between parasitism, biotrophy, and predation appear to be less sharp for bacteria, highly sophisticated mechanisms to feed on are obvious for unicellular amoebae and nematodes. Even phagocytic amoebae are not restricted to the ingestion and intracellular killing of single yeast cells or conidia but they can also attack and invade entire hyphae of filamentous fungi. Nematodes, in turn, can specifically open hyphae via injection-needle like stylets. In this chapter, we provide a selected overview of examples from recent years on how fungal preys exploit a variety of strategies to either escape or survive attacks by these specialized environmental predators. At least some of these factors have been shown to fulfil a dual function, serving in predator defence but also against innate immune cells when colonizing higher animals. Whether predatory defence has thus acted as a selection pressure towards virulence determinants in fungi is a matter of ongoing research.