Vigdis Torsvik

• Professor Emeritus at University of Bergen

During the last decades, our knowledge about the activity of sponge-associated microorganisms and their contribution to biogeochemical cycling has gradually increased. Functional groups involved in carbon and nitrogen metabolism are well documented, whereas knowledge about microorganisms involved in the sulfur cycle is still limited. Both sulfate r...

Terrestrial tropical methane seep habitats are important ecosystems in the methane cycle. Methane oxidizing bacteria play a key role in these ecosystems as they reduce methane emissions to the atmosphere. Here, we describe the isolation and initial characterization of two novel moderately thermophilic and acid-tolerant obligate methanotrophs, assig...

Arctic ecosystems are warming rapidly, which is expected to promote soil organic matter (SOM) decomposition. In addition to the direct warming effect, decomposition can also be indirectly stimulated via increased plant productivity and plant-soil C allocation, and this so called “priming effect” might significantly alter the ecosystem C balance. In...

Arctic ecosystems are warming rapidly, which is expected to promote soil organic matter (SOM) decomposition. In addition to the direct warming effect, decomposition can also be indirectly stimulated via increased plant productivity and plant-soil C allocation, and this so called "priming effect" might significantly alter the ecosystem C balance. In...

Terrestrial methane seeps and rice paddy fields are important ecosystems in the methane cycle. Methanotrophic bacteria in these ecosystems play a key role in reducing methane emission into the atmosphere. Here, we describe three novel methanotrophs, designated BRS-K6, GFS-K6 and AK-K6, which were recovered from three different habitats in contrasti...

Terrestrial methane seeps and rice paddy fields are important ecosystems in the methane cycle. Methanotrophic bacteria in these ecosystems play a key role in reducing methane emission into the atmosphere. Here, we describe three novel methanotrophs, designated BRS-K6, GFS-K6 and AK-K6, which were recovered from three different habitats in contrasti...

Permafrost-affected soils in the Northern latitudes store huge amounts of organic carbon (OC) that is prone to microbial degradation and subsequent release of greenhouse gases to the atmosphere. In Greenland, the consequences of permafrost thaw have only recently been addressed, and predictions on its impact on the carbon budget are thus still high...

Cryoturbation, the burial of topsoil material into deeper soil horizons by repeated freeze-thaw events, is an important storage mechanism for soil organic matter (SOM) in permafrost-affected soils. Besides abiotic conditions, microbial community structure and the accessibility of SOM to the decomposer community are hypothesized to control SOM decom...

Introduction Basic Methods Estimating Genetic Diversity: Model Experiment with Cultured Isolates Examples of Application of the DNA Reassociation Method Conclusions References

Antibiotic-resistant bacteria were isolated from sediment samples collected beneath two fish farms west of Bergen (Norway). The samples were collected just after the fish had been treated with oxytetracycline. Eighty-four bacterial isolates were tested for susceptibility to antibacterial agents. Most of the isolates were resistant to oxytetracyclin...

A novel thermophilic member of the family Thermaceae, designated strain 2M70-1(T), was isolated from the wall of an active white smoker chimney collected in the Soria Moria vent field at 71 °N in the Norwegian-Greenland Sea. Cells of the strain were Gram-negative, non-motile rods. Growth was observed at 37-75 °C (optimum 65 °C), at pH 6-8 (optimum...

INTRODUCTION The successful construction of large-insert community DNA (i.e., metagenomic) libraries from natural environments is dependent on several parameters, including effective cell lysis, DNA purity, and a high transformation efficiency. One problem associated with constructing metagenomic libraries from soil microbes is the co-isolation of...

16S rRNA molecules in a microbial strain can differ due to nucleotide variation between their genes. This is a typical trait of fast-growing bacteria to cope with different niches. We investigated characteristics of 16S rRNA genes in Vibrio splendidus strain PB1-10, from the normal flora of Atlantic halibut. Sequencing of 16S rRNA gene clones detec...

We describe here an improved method for isolating, purifying, and cloning DNA from diverse soil microbiota. Soil microorganisms were extracted from soils and embedded and lysed within an agarose plug. Nucleases that copurified with the metagenomic DNA were removed by incubating plugs with a high-salt and -formamide solution. This method was used to...

Archaeal populations are abundant in cold and temperate environments, but little is known about their potential response to climate change-induced temperature changes. The effects of temperature on archaeal communities in unamended slurries of weakly acidic peat from Spitsbergen were studied using a combination of fluorescent in situ hybridization...

There is no general consensus on how to define an extreme environment. From an anthropocentric point of view, physicochemical conditions supporting mammalian life appear as normal, and conditions deviating from these are considered as extreme. However, what is extreme and what is normal for microbes remains debatable, and the concept “extreme” as w...

In this study, the interrelation between nitrogen availability and prokaryotic diversity are studied using a well-characterised system from a long-term field experiment on a loamy sandy soil. The prokaryotic potential functional diversity and community composition were assessed using community-level physiological profiling (CLPP), and their phyloge...

Effects of water regime on archaeal communities in Arctic soils from Spitsbergen were studied using denaturing gradient gel electrophoresis (DGGE) of amplified 16S rRNA genes, with subsequent sequencing of amplicons and ordination analysis of binary DGGE data. Samples with major differences in soil water regime showed significant differences in the...

Whole-community DNA was extracted from two pasture soils, the cultivable and directly extractable bacterial subsets of one of the soils, and two aquatic bacterioplankton communities. The percent guanine+cytosine (%G+C) base distribution, derived using thermal denaturation profiles, and parameterised using a generalised logistic equation, varied mar...

The assessment of diversity within microbial communities is one of the most challenging and fascinating aspects of microbiology, especially in light of the fact that we know so little about it. This is refiected by estimates of the number of bacterial species that exist on Earth today, which vary between 10 and 10. There is a substantial amount of...

Due to the fact that the Bacteria and Archaea are dif?cult to distinguish on the basis of their morphology by microscopy, they have traditionally been grouped together under the heading prokaryotes. However, after the advent of molecular phylogenetics, we now know that the Bacteria and Archaea are as different from each other as they are from the E...

Emissions of the greenhouse gas methane from Arctic wetlands have been studied extensively, though little is known about the ecology and community structure of methanogenic archaea that catalyze the methane production. As part of a project addressing microbial transformations of methane in Arctic wetlands, we studied archaeal communities in two wet...

This review mainly discusses three related topics: the application of ecological theories to soil, the measurement of microbial diversity by molecular techniques and the impact of transgenic plants and microorganisms on genetic diversity of soil. These topics were debated at the Meeting on Soil Emergency held in Erice (Trapani, Italy) in 2001 for t...

Halibut, the largest of all flatfishes is a valuable species with a great potential for aquaculture. Bacteria play an important role in regulating the health of the early life stages. The present article is the first broad-range molecular analysis of bacterial communities in larvae of the Atlantic halibut (Hippoglossus hippoglossus). DNA was extrac...

On Jul 21, 2004 this sequence version replaced gi:50262010.

The diversity of prokaryotes inhabiting solar saltern ponds was determined by thermal melting and reassociation of community DNA. These measurements were compared with fingerprinting techniques such as terminal restriction fragment length polymorphisms (T-RFLP) analysis, denaturant gradient gel electrophoresis (DGGE), and cloning and sequencing app...

Soils sustain an immense diversity of microbes, which, to a large extent, remains unexplored. A range of novel methods, most of which are based on rRNA and rDNA analyses, have uncovered part of the soil microbial diversity. The next step in the era of microbial ecology is to extract genomic, evolutionary and functional information from bacterial ar...

There are probably millions of species in the microorganismal domains Bacteria and Archaea (the prokaryotes), and we are only just beginning to work out the basic principles governing their distribution and abundance in natural environments. One characteristic that has become clear is that prokaryote diversity in aquatic environments is orders of m...

The aim of this study was to explore the potential of a combined chemical and microbiological approach as part of a study of organic carbon oxidation processes in sediments. An assessment of microbiological diversity using molecular techniques was carried out in combination with high resolution chemical measurements at the sediment-water interface...

Electron microscopy and biomolecular methods have been used to describe and identify microbial communities inhabiting the glassy margins of ocean floor basalts. The investigated samples were collected from a neovolcanic ridge and from older, sediment-covered lava flows in the rift valley of the Knipovich Ridge at a water depth around 3500 m and an...

The study examined the effects of the fungicide fenpropimorph (in the formulation Corbel) on primary decomposer organisms in soil. Bacterial and fungal succession was followed on dead young barley roots buried in fungicide-treated or untreated soil. Fenpropimorph was added to the soil in a concentration realistically achieved in field topsoil when...

Molecular methods were used to characterize the diversity of a methanotrophic population in an agricultural soil. For this purpose we have used DGGE analysis of functional and phylogenetic markers. Functional markers utilised comprised the pmoA-gene coding for the alpha-subunit of the particulate methane monooxygenase (pMMO) present in all known me...

According to guidelines for the approval of pesticides, side-effects on soil microorganisms should be determined by studying functional parameters such as carbon or nitrogen mineralisation. However, the microbial diversity may have been markedly changed following pesticide use despite unaltered metabolism, and such changes may affect soil fertility...

Dot blot hybridization with group specific probes and restriction fragment length polymorphism (RFLP) were used for assessing the effect of long-term sewage sludge application on the culturable bacterial flora and total bacterial community in soil. Results obtained using dot blot hybridization with phylogenetic probes on bacterial isolates showed n...

Separation of polymerase chain reaction (PCR)-amplified 16S rDNA products using denaturing gradient gel electrophoresis (DGGE) was tested as a means to study microbial community composition in bulk soil samples. DNA was extracted from six soils from agroecosystems in Norway and the USA under different agronomic treatments (crop, rotation, and tilla...

Microbial diversity and biodiversity are used synonymously to describe the variability among all microorganisms in an assemblage or a community. In the present review the term microorganisms encompasses prokaryotic organisms belonging to the domain Bacteria and Archaea.

The impact of heavy metal contamination on soil bacterial communities was studied in soils amended for many years with sewage sludge contaminated with heavy metals to varying extents. At the broad level of resolution, DNA reassociation analysis indicated a dramatic decrease in bacterial diversity from 16{ omitted}000 bacterial genomes (g soil [wet...

The impact of heavy-metal contamination on archaean communities was studied in soils amended with sewage sludge contaminated with heavy metals to varying extents. Fluorescent in situ hybridization showed a decrease in the percentage of Archaea from 1.3% +/- 0.3% of 4', 6-diamidino-2-phenylindole-stained cells in untreated soil to below the detectio...

The effect of the recipient strain in exogenous plasmid isolations on the captured plasmid types was investigated by comparing HgR plasmids obtained from eight soils using Escherichia coli HB101RIF (γ-Proteobacteria) and Agrobacterium tumefaciens UBAPF2 (α-Proteobacteria). Plasmids isolated from 121 transconjugants were divided into 16 distinct typ...

We used a quantitative PCR method targeting 16S ribosomal DNA using competitive PCR for specific detection of indigenous Pseudomonas DNA in soil hot spots. The amount of Pseudomonas DNA corresponded to the number of culturable Pseudomonas bacteria on Gould's S1 agar. This represents the first use of PCR for quantification of indigenous bacteria in...

Abstract In this study, two different agricultural soils were investigated: one organic soil and one sandy soil, from Stend (south of Bergen), Norway. The sandy soil was a field frequently tilled and subjected to crop rotations. The organic soil was permanent grazing land, infrequently tilled. Our objective was to compare the diversity of the culti...

Two methods of exogenous plasmid isolation were used to evaluate and compare the plasmid incidence and gene mobilizing capacity of eight soils before and after the addition of mercury. Biparental matings (BM) were performed using Pseudomonas putida UWC1 as recipient to obtain conjugative mercury resistance (HgR) plasmids. To obtain mobilizing plasm...

Broad-scale differences in soil microbial community composition were analyzed in two contrasting soils using DNA reassociation and % G+C profiles for analysis on the community-level, and filter- and whole cell hybridization techniques for a coarse-level characterization of larger phylogenetic groups of bacteria. Reassociation analysis of DNA from b...

Molecular techniques were applied for analysing the entire bacterial community, including both the cultivated and non-cultivated part of the community. DNA was extracted from samples of soils and sediments, and a combination of different molecular methods were used to investigate community structure and diversity in these environments. Reassociatio...

Changes in soil microbial activity and diversity after incubation either with nitrogen or with a mixture of methane and air were examined. The perturbation by methane and air were characterized in detail and led to reduced diversity and enrichment of methanotrophs which were identified by denaturing gradient gel electrophoresis and 16S rRNA sequenc...

Denaturing gradient gel electrophoresis (DGGE) profiles of PCR amplified V3 regions of 16S rRNA genes were used to assess the diversity in enrichment cultures with methane as the only carbon and energy source. The enrichments originated from two agricultural soils. One was a sandy soil with low (10%) organic content, the other an organic soil with...

We present a new method for the quantification of DNA in soil. This method is based on a fluorescent dye, PicoGreen (Molecular Probes), that binds specifically to double-stranded DNA. The DNA–PicoGreen complex is quantified in a fluorometer. Using this approach DNA concentrations from 25 pg ml−1 to 1 μg ml−1 may be quantified. The high sensitivity...

Mercury resistance plasmids were exogenously isolated, i.e., recovered after transfer to a model recipient bacterium, from marine air-water interface, bulk water, and biofilm communities during incubation in artificial seawater without added nutrients. Ninety-five plasmids from different environments were classified by restriction endonuclease dige...

The community structure of bacterioplankton in meromictic Lake Saelenvannet was examined by PCR amplification of the V3 region of 16S rRNA from microbial communities recovered from various depths in the water column. Two different primer sets were used, one for amplification of DNA from the domain Bacteria and another specific for DNA from the doma...