Editorial: The impact of fungi on other organisms
Fungi are pivotal components of biological communities and are major contributors to global biodiversity and key ecosystem processes. Fungi are perhaps best known for their role as decomposers and, although fungal hyphae often account for the greatest proportion of soil biomass, fungi directly shape the community dynamics of plants, animals and other organisms through a wide range of interactions. As parasites, fungi are common and important pathogens that not only cause serious crop loss and disease in animal and human populations but also shape the composition and structure of natural biological communities. The recent worldwide spread of the frog pathogen, Batrachochytrium dendrobatidis, which has caused a global decline in amphibian, and recent epidemics among bats of “white nose syndrome” in the USA demonstrate the importance of fungal pathogens. Fungi can parasitize invertebrates, such as insects and nematode pests, and be exploited as biological control agents. Some fungi are predators - the best-known examples being the nematode-trapping fungi. Mycorrhizae, which are symbiotic associations between fungi and the roots of vascular plants, are present in 92% of plant families and 80% of species studied thus far. The nature of many fungal interactions is unclear and some species, including endophytic and gut-inhabiting fungi are often present in a quasi-quiescent state.
Our understanding of fungal ecology and communities has been greatly increased by the direct extraction of DNA from environmental samples coupled with PCR amplification and community-profiling techniques. Many environmental DNA sequences have been detected in various niches, and a recent literature survey has shown that culture-independent methods typically detect about four-times more OTUs than culture-dependent methods. Studies of the fungi associated with natural Ophiocordyceps sinensis specimens (fungal-parasitized caterpillars) has revealed, however, that there was little overlap in the fungi detected by culture-independent (108 OTUs) and culture-dependent (98 OTUs) methods; only 13 OTUs were detected by both methods (PLoS One 5(12): e15570. doi:10.1371). A previously unrecognized and highly diverse form of fungus that does not produce the rigid chitin-rich cell wall typical of other fungi has recently been discovered in soil, fresh water and aquatic sediments by environmental DNA analyses and fluorescent detection with DNA probes (Jones et al., Nature 474 (2001) 200–203). This research demonstrates that much remains to be learned about fungi and that our ability to detect fungi and to understand how they affect other organisms will greatly increase as new tools are developed and applied.
This special issue includes several invited papers on recent advances in understanding the impact of fungi on other organisms. One paper deals with the life strategy and ecology of Ophiocordyceps sinensis, the extraordinary Chinese caterpillar fungus, which is nominated as the national fungus of China. Another paper focuses on the interactions between saprotrophic basidiomycete mycelia and mycophagous soil fauna. Two other papers review how plant and fungal cell structures are modified to interface between host root and ECM hyphae and that the arginine biosynthesis is critical for the early stages of plant infections by Colletotrichum higginsianum. One original research paper reports the interactions between ammonia and non-ammonia fungi based on the variation in inorganic nitrogen. Another paper summarizes various technological approaches applied to the studies on entophytic fungi, with particular emphasis on comparing traditional and molecular approaches. We believe these papers will be of major interest to and as an essential reference source for anyone working in this field.