The Fungal Contribution to the Nitrogen Cycle in Agricultural Soils
Markus Gorfer, Sylvia Klaubauf, Harald Berger and Joseph Strauss
from: Metagenomics of the Microbial Nitrogen Cycle: Theory, Methods and Applications (Edited by: Diana Marco). Caister Academic Press, U.K. (2014)
Nitrate assimilation and its regulation is well studied for several model fungi but little is known about the fungal contribution to microbial nitrogen cycles in agricultural soils, although fungal dominated systems are less prone to nitrogen losses via leaching and denitrification. Tools were recently developed to characterise gene pools and expression levels of fungal assimilatory nitrate reductases in environmental samples and carbon source availability was identified as one of the major parameter determining nitrate assimilation capacities. Even though the majority of the environmental sequences could be classified to family, genus or species level, a considerably high number could only be assigned to higher taxonomic levels. Ongoing addition of new fungal nitrate reductase genes from whole genome sequencing efforts and from PCR amplification from pure culture isolates already led to improved affiliation of environmental sequences. Precaution is however necessary in the interpretation of higher order affiliations: Horizontal gene transfer events seem to be rather common in the evolution of fungal nitrate assimilation. No fungal nitrate reductases are found in publicly accessible soil metagenomic and metatranscriptomic libraries. Future studies will focus on integration of data from metagenomics, metatranscriptomics, stable isotope probing, isotope pool dilution assays and modelling approaches. The goal of these studies is to obtain a comprehensive picture of the fungal contribution to the soil microbial nitrogen cycle read more ...