Phylogenetic, taxonomic and functional diversity of fungal denitrifiers and associated N2O production efficacy

Fungi generally dominate microbial biomass in various soils and play critical roles in ecosystem functioning including nutrient cycling, disease ecology and food production. Therefore, fungal denitrification, phenotypically typified by nitrous oxide (N2O) production, presents another avenue other than N mineralization and heterotrophic nitrification for progress to better understand the multiple roles of fungi in sustaining the biosphere. The discovery of N2O production and consequently denitrification in Fusarium oxysporum Schltdl. in early 1970's has led to identification of many taxonomically diverse species of N2O-producing fungi. This review evaluates the current status of knowledge on species composition of fungal denitrifiers and their N2O-producing activity. Here we describe challenges with assessment of fungal N2O-producing activity across genera and suggest prospects for future studies. We also discuss species diversity in order to gain knowledge of important taxonomic and phylogenetic groups mediating N2O production and provide insight on ecological cues associated with fungal N2O production. Currently, the extent to which species phylogeny and the functional trait, i.e. N2O-producing activity, are linked remains to be determined; even so, it is evident that some related taxa exhibit similar N2O production efficacy than distant relatives.