Closing the Global Energy and Nutrient Cycles through Application of Biogas Residue to Agricultural Land – Potential Benefits and Drawback

We re-evaluated PCR primers targeting nirS, nirK and nosZ genes for denaturing gradient gel electrophoresis as a tool to survey denitrifying community composition in environmental samples. New primers for both nirS and nosZ were combined with existing primers, while for nirK the previously published F1aCu:R3Cu set was chosen for denaturing electrophoresis. All three sets yielded amplicons smaller than 500 bp and amplified the correct fragment in all environmental samples. The denaturing gradient gel electrophoresis worked satisfactorily for nirK and nosZ, but not for nirS. This was probably due to the multiple melting domains in this particular nirS fragment. From the excised and sequenced bands, only sequences related to the target genes were detected and tree analysis showed that the selected primers acted as broad range primers for each of the three genes. By use of the new nirS primers it was demonstrated that agricultural soil harbours a substantial diversity of nirS denitrifiers.

Human intestinal bacteria have many roles in human health, most of which are beneficial or neutral for the host. In this review, we explore a more sinister side of intestinal bacteria; their role as traffickers in antibiotic resistance genes. Evidence is accumulating to support the hypothesis that intestinal bacteria not only exchange resistance genes among themselves but might also interact with bacteria that are passing through the colon, causing these bacteria to acquire and transmit antibiotic resistance genes.

Broad spectrum biological control of diseases caused by soilborne plant pathogens such as Pythium, Phytophthora, and Rhizoctonia solani requires the introduction into or presence of edaphic sources of organic nutrients in soil for sustenance of biocontrol agents. The decomposition level of organic matter critically affects the composition of bacterial taxa as well as the populations and activities of biocontrol agents. Competition, antibiosis, parasitism, and systemic induced resistance are all affected. Highly stabilized sources of Sphagnum peat consistently fail to support sustained biological control, even when inoculated with biocontrol agents. Composts, on the other hand, can serve as an ideal food base for biocontrol agents and offer an opportunity to introduce and establish specific biocontrol agents into soils, which in turn leads to sustained biological control based on the activities of microbial communities.