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Ammonia oxidation is the first step in nitrification, a key process in the global nitrogen cycle that results in the formation of nitrate through microbial activity. The increase in nitrate availability in soils is important for plant nutrition, but it also has considerable impact on groundwater pollution owing to leaching. Here we show that archaeal(More)
Genes of archaea encoding homologues of ammonia monooxygenases have been found on a widespread basis and in large amounts in almost all terrestrial and marine environments, indicating that ammonia oxidizing archaea (AOA) might play a major role in nitrification on Earth. However, only one pure isolate of this group from a marine environment has so far been(More)
The relative importance of size and composition of microbial communities in ecosystem functioning is poorly understood. Here, we investigated how community composition and size of selected functional guilds in the nitrogen cycle correlated with agroecosystem functioning, which was defined as microbial process rates, total crop yield and nitrogen content in(More)
Data on the diversity and distribution of enzyme activities in native ectomycorrhizal (ECM) communities are inadequate. A microplate multiple enzymatic test was developed which makes it possible to measure eight enzyme activities on 14 individual, excised ECM root tips. Hydrolytic and oxidative enzymes are involved in the decomposition of lignocellulose,(More)
The aim of this study was to investigate potential effects on the composition of the bacterial and fungal diversity in rhizosphere and soil of a transgenic potato line (SIBU S1) which was modified in its starch composition by RNA anisensing, compared to the non-transgenic parental cultivar (SIBU) at the flowering stage in 2000. Furthermore a second(More)
A microplate fluorimetric assay was developed for measuring potential activities of extracellular enzymes of individual ectomycorrhizal (EM) roots using methylumbelliferone (MU)-labelled fluorescent substrate analogues and microsieves to minimise damage due to manipulation of excised mycorrhizal roots. Control experiments revealed that enzyme activities(More)
Soil pH is a major determinant of microbial ecosystem processes and potentially a major driver of evolution, adaptation, and diversity of ammonia oxidizers, which control soil nitrification. Archaea are major components of soil microbial communities and contribute significantly to ammonia oxidation in some soils. To determine whether pH drives evolutionary(More)
Real-time quantitative PCR assays were developed for the absolute quantification of different groups of bacteria in pure cultures and in environmental samples. 16S rRNA genes were used as markers for eubacteria, and genes for extracellular peptidases were used as markers for potentially proteolytic bacteria. For the designed 16S rDNA TaqMan assay,(More)
The residual N contribution from faba bean (Vicia faba L.), pea (Pisum sativum L.) and white lupin (Lupinus albus L.) to microbial biomass and subsequent wheat (Triticum aestivum L.) and oilseed rape (Brassica napus L.) was studied in a greenhouse experiment. The grain legumes were 15N labelled in situ with a stem feeding method before incorporated into the(More)
This review summarizes aspects of the current knowledge about the ecology of ammonia-oxidizing and denitrifying bacteria. The development of molecular techniques has contributed enormously to the rapid recent progress in the field. Different techniques for doing so are discussed. The characterization of ammonia-oxidizing and -denitrifying bacteria by(More)