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Nitrous oxide (N2O) is an important greenhouse gas in the troposphere controlling ozone concentration in the stratosphere through nitric oxide production. In order to quantify bacteria capable of N2O reduction, we developed a SYBR green quantitative real-time PCR assay targeting the nosZ gene encoding the catalytic subunit of the nitrous oxide reductase. Two independent sets of nosZ primers flanking the nosZ fragment previously used in diversity studies were designed and tested (K. Kloos, A. Mergel, C. Rösch, and H. Bothe, Aust. J. Plant Physiol. 28:991–998, 2001). The utility of these real-time PCR assays was demonstrated by quantifying the nosZ gene present in six different soils. Detection limits were between 101 and 10a target molecules per reaction for all assays. Sequence analysis of 128 cloned quantitative PCR products confirmed the specificity of the designed primers. The abundance of nosZ genes ranged from 105 to 107 target copies g-1 of dry soil, whereas genes for 16S rRNA were found at 108 to 109 target copies g-1 of dry soil. The abundance of narG and nirK genes was within the upper and lower limits of the 16S rRNA and nosZ gene copy numbers. The two sets of nosZ primers gave similar gene copy numbers for all tested soils. The maximum abundance of nosZ and nirK relative to 16S rRNA was 5 to 6%, confirming the low proportion of denitrifiers to total bacteria in soils. [ABSTRACT FROM AUTHOR]

The new ecological approach to viticulture emphasises ecologically sound grape production and recognizes the importance of grapevine ( Vitis vinifera ) interactions with soil microbial communities. Due to different viticulture measures, distinctly different microbial communities can form, which affects the potentially beneficial interactions with the grapevines. Therefore, the objective of the present study was to identify differences in the community structures of fungal and bacterial soil communities on a landscape scale, and to relate these to the type and duration of soil management, and to within vineyard habitats. Soil fungal and bacterial communities were screened in vineyards with different soil management (ecological, conventional) and ages (3, 10, 35 years). In each vineyard, 35 rhizosphere soil samples were acquired from beneath the grapevines and between the rows, using a grid covering of 240 m 2 per vineyard. Automated ribosomal intergenic spacer analysis of the microbial soil samples was carried out, with the microbial lifeforms compared among the vineyards (bacteria vs. fungi). There was high variability in the local microbial diversity for all of the sampled plots, with significant differences among the vineyards under ecological and conventional soil management. In comparison to fungi, soil management and age of vineyard had significantly greater impact on bacteria. Microbial communities showed no general overlap in diversity spots or simultaneous changes in community composition along the sampling grids. These results suggest that the microbial communities reflect the influences of highly localised biogeographic factors and vineyard management, with the most profound effects observed after deep tillage. Furthermore, fungal and bacterial communities forming in the vineyard soils appear to be influenced by different sets of environmental factors. [ABSTRACT FROM AUTHOR]