Abundance of microbial genes associated with nitrogen cycling as indices of biogeochemical process rates across a vegetation gradient in Alaska.

Nitrification and denitrification processes are crucial to plant nutrient availability, eutrophication and greenhouse gas production both locally and globally. Unravelling the major environmental predictors for nitrification and denitrification is thus pivotal in order to understand and model environmental nitrogen (N) cycling. Here, we sampled five plant community types characteristic of interior Alaska, including black spruce, bog birch, tussock grass and two fens.

Combined effects of pyrene and UV-light on algae and bacteria in an arctic sediment.

The phototoxicity potential of pyrene on natural algae and bacteria in an arctic sediment was evaluated and compared to that of pyrene treatment alone based on some functional and structural endpoints. Microcosms with arctic sediment from a shallow-water marine bay were incubated with pyrene under three different light regimes, natural sunlight with UV-light (Light(UV)), natural sunlight without UV-light (Light) and dark.Presence of pyrene directly affected the algal community measured as decreased (14)C-incorporation and decreased ammonium, nitrate and silicate uptake.

Improvements for comparative analysis of changes in diversity of microbial communities using internal standards in PCR-DGGE.

The use of internal standards both during DNA extraction and PCR-DGGE procedure gives the opportunity to analyse the relative abundance of individual species back to the original sample, thereby facilitating relative comparative analysis of diversity. Internal standards were used throughout the DNA extraction and PCR-DGGE to compensate for experimental variability. Such variability causes decreased reproducibility among replicate samples as well as compromise comparisons between samples, since experimental errors cannot be differentiated from actual changes in the community abundance and structure.

Effects of zinc pyrithione and copper pyrithione on microbial community function and structure in sediments.

The effects of the new antifouling biocides, zinc pyrithione (ZPT) and copper pyrithione (CPT), on microbial communities in estuarine sediments were studied in microcosms. As functional endpoints, fluxes of nutrients (NO3-, NH4+, HPO4(2-), Si(OH)4) and protein synthesis ([14C]leucine incorporation) were used, whereas molecular fingerprinting methods (polymerase chain reaction/denaturing gradient gel electrophoresis) were used to describe the bacterial community structure. The lowest-observed-effect concentration (LOEC) for ZPT was 0.