In the region of King William Island, Nunavut, in the Canadian high Arctic, populations of salmonids including Arctic char (Salvelinus alpinus), cisco (Coregonus autumnalis and C. sardinella) as well as lake whitefish (C. clupeaformis) are diadromous, overwintering in freshwater and transitioning to saline waters following ice melt. Since these fish were sampled at the same time and from the same traditional fishing sites, com...

Summary Intestinal microbial communities from 362 anadromous Arctic char ( Salvelinus alpinus ) from the high Arctic Kitikmeot region, Nunavut, Canada, were characterized using high‐throughput 16S rRNA gene sequencing. The resulting bacterial communities were compared across four seasonal habitats that correspond to different stages of annual migration. Arctic char intestinal communities differed by sampling site, salinity and...

Summary Denitrification transforms nitrogen applied as fertilizer and emits N 2 O, which is a potent greenhouse gas. Very little is known about the identities of abundant and active denitrifiers in agricultural soils. We coupled DNA stable‐isotope probing (DNA‐SIP) with flow‐through reactors (FTRs) to detect active agricultural soil denitrifiers. The FTRs were incubated with nitrate and 13 C 6 ‐glucose under anoxic conditions...

Summary Deep‐sea coral reefs do not receive sunlight and depend on plankton. Little is known about the plankton composition at such reefs, even though they constitute habitats for many invertebrates and fish. We investigated plankton communities from three reefs at 260–350 m depth at hydrocarbon fields off the mid‐ N orwegian coast using a combination of cultivation and small subunit ( SSU ) rRNA gene and transcript sequencing...

Summary The first step of nitrification is catalysed by both ammonia‐oxidizing bacteria (AOB) and archaea (AOA), but physicochemical controls on the relative abundance and function of these two groups are not yet fully understood, especially in freshwater environments. This study investigated ammonia‐oxidizing populations in nitrifying rotating biological contactors (RBCs) from a municipal wastewater treatment plant. Individua...

Summary Peatlands represent an enormous carbon reservoir and have a potential impact on the global climate because of the active methanogenesis and methanotrophy in these soils. Uncultivated methanotrophs from seven European peatlands were studied using a combination of molecular methods. Screening for methanotroph diversity using a particulate methane monooxygenase‐based diagnostic gene array revealed that Methylocystis ‐rela...

Summary The concentrations of one‐carbon substrates that fuel methylotrophic microbial communities in the ocean are limited and the specialized guilds of bacteria that use these molecules may exist at low relative abundance. As a result, these organisms are difficult to identify and are often missed with existing cultivation and gene retrieval methods. Here, we demonstrate a novel proof of concept: using environmentally‐releva...

Summary Hexachlorocyclohexane (HCH)‐degrading bacteria are believed to mediate natural attenuation of HCH contamination and have potential for active bioremediation processes. This study addressed the very limited understanding of the distribution, diversity and substrate specificity of such bacteria from 13 soil samples, varying in levels of HCH contamination, from four sites in Spain. Hexachlorocyclohexane removal occurred i...

Summary Microarray technology was used to characterize and compare hexachlorocyclohexane (HCH) contaminated soils from Spain. A library of 2290 hypervariable 16S rRNA gene sequences was prepared with serial analysis of ribosomal sequence tags (SARST) from a composite of contaminated and uncontaminated soils. By designing hybridization probes specific to the 100 most abundant ribosomal sequence tags (RSTs) in the composite libr...

Summary Two decades of culture‐independent studies have confirmed that microbial communities represent the most complex and concentrated pool of phylogenetic diversity on the planet. There remains a need for innovative molecular tools that can further our knowledge of microbial diversity and its functional implications. We present the method and application of serial analysis of ribosomal sequence tags (SARST) as a novel tool...