Biodiversity of Nitrate-Reducing Microbes in Grassland Soils by Massive Cultivation and Genomics
The project BE-Cult will gain insights into the biodiversity and relative importance of soil DNRA bacteria compared to denitrifiers. We will assess the impact of land use intensity on these bacterial groups, and reveal novel genomic and physiological traits of NO3- reducers in managed grassland, which are globally important N2O emitting ecosystems.
Denitrification (DEN) and dissimilatory nitrate reduction to ammonium (DNRA) are important NO3– reduction processes through various reductive steps to N2 or ammonium (NH4+). They are the only microbial processes that are capable of both reducing NO3– and producing the potent greenhouse gas N2O. Both processes can take place under similar conditions of low oxygen concentrations and compete for the available nitrate and nitrite. DNRA is considered as a crucial process of the N cycle that conserves N in terrestrial ecosystems by the conversion of NO3– and NO2– to the less mobile NH4+, which keep N available for microorganisms and plants, whereas gaseous reduction products through DEN contribute substantially to N losses in soils. While there is a general agreement about the significance of DEN in soils, the importance and occurrence of DNRA is controversially debated.
The following specific objectives will be addressed by the two partner teams of LUH and ZALF:
- Isolation of NO3– reducing bacteria and systematic analysis of their physiology and taxonomic affiliations in relation to management intensities
- Draft genome sequencing and annotation of representative NO3– reducing strains to reveal presence and genotypes of functionally relevant genes
- Identification of pathways and taxonomic affiliations of NO3– reducing C1 compound utilizers
- Primer development for the detection of specific marker genes and investigation of their abundance an distribution
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