M. Svenning - Academia.edu (original) (raw)

Papers by M. Svenning

Biological Nitrogen Fixation for the 21st Century, 1998

Cyanobacteria enter into efficient nitrogen-fixing symbiosis with a wide range of representatives... more Cyanobacteria enter into efficient nitrogen-fixing symbiosis with a wide range of representatives within the plant kingdom. These include plants from the divisions: Bryophyta (mosses, liverworts and hornworts), gymnosperms of the family Cycadaceae, an aquatic ferns within Pteridohyta (Azolla) and an angiosperm Gunnera, as well as diverse lichenized fungi. This host range places cyanobacteria in an exclusive position among symbiotic nitrogen-fixers. With few exceptions the cyanobacteria belongs to the filamentous genus Nostoc. Very little is known about the diversity of symbiotic cyanobacteria both within and between the different host plants.

Science of The Total Environment, 2020

Anaerobic oxidation of CH 4 (AOM) was a major sink in the water of 4 Siberian lakes. • AOM mitiga... more Anaerobic oxidation of CH 4 (AOM) was a major sink in the water of 4 Siberian lakes. • AOM mitigated 60-100% of the produced CH 4. • All four lakes shared the same predominant methanotrophs in AOM hotspots. • AOM was attributed to Methylobacter and other Methylomonadaceae. • Methanotrophs co-occurred with denitrifiers and iron-cycling partners.

Applied and Environmental Microbiology, 1998

The presence of repeated DNA (short tandemly repeated repetitive [STRR] and long tandemly repeate... more The presence of repeated DNA (short tandemly repeated repetitive [STRR] and long tandemly repeated repetitive [LTRR]) sequences in the genome of cyanobacteria was used to generate a fingerprint method for symbiotic and free-living isolates. Primers corresponding to the STRR and LTRR sequences were used in the PCR, resulting in a method which generate specific fingerprints for individual isolates. The method was useful both with purified DNA and with intact cyanobacterial filaments or cells as templates for the PCR. Twenty-three Nostoc isolates from a total of 35 were symbiotic isolates from the angiosperm Gunnera species, including isolates from the same Gunnera species as well as from different species. The results show a genetic similarity among isolates from different Gunnera species as well as a genetic heterogeneity among isolates from the same Gunnera species. Isolates which have been postulated to be closely related or identical revealed similar results by the PCR method, ind...

Annals of Botany, 1996

Nodulated white clover plants {Trifolium repens L.) of a Norwegian ecotype from Pasvik (70° N) we... more Nodulated white clover plants {Trifolium repens L.) of a Norwegian ecotype from Pasvik (70° N) were grown in flowing solution culture. Root temperature was 17 °C until 51 d after sowing, when it was lowered decrementally over 5 d to 7 °C in four of the eight plant culture units. After a further 24 h, mineral N was supplied automatically at 20 //M NH 4 NO 3 in three culture units at each root temperature (7 and 17 °C) over 17 d. The remaining two units provided control plants solely dependent on N 2 fixation at 7 and 17 °C. The supply of NH 4 NO 3 greatly reduced the nodule biomass per plant at 17 °C over 17 d compared with control plants, but had little effect at 7 °C. The nodule decline at 17 °C accompanied an acute and progressive decrease in specific rate of N 2 fixation, from 9 mmol N d" 1 g" 1 nodule d.wt on day 0 to zero by day 10. Whilst initial rates of N 2 fixation were lower at 7 °C, the mineral N-induced decrease in fixation rates was also less severe than at 17 °C and specific fixation rates recovered after reaching a minimum on day 11. N 2 fixation accounted for 36% of the total uptake of N by +min.N plants during the treatment period at 7 °C as opposed to only 13% at 17 °C. The total N 2 fixed at 7 °C was 86% of that fixed at 17 °C, although the specific growth rate (d.wt) at 7 °C was only 55 % of that at 17 °C. Addition of NH 4 NO 3 at 7 °C had little effect on the gross amount of N 2 fixed subsequently. In contrast, total N 2 fixation by +min.N plants at 17 °C was only 24% of that fixed by the corresponding controls. The possible mechanisms by which mineral N affects N 2 fixation are discussed.

Genome announcements, Jan 12, 2015

The genomes of Methylosarcina lacus LW14(T) (=ATCC BAA-1047(T) = JCM 13284(T)), Methylobacter sp.... more The genomes of Methylosarcina lacus LW14(T) (=ATCC BAA-1047(T) = JCM 13284(T)), Methylobacter sp. strain 21/22, Methylobacter sp. strain 31/32, Methylomonas sp. strain LW13, Methylomonas sp. strain MK1, and Methylomonas sp. strain 11b were sequenced and are reported here. All the strains are obligately methanotrophic bacteria isolated from the sediment of Lake Washington.

Genome announcements, Jan 27, 2013

Robust growth of the gammaproteobacterium Methylomicrobium buryatense strain 5G on methane makes ... more Robust growth of the gammaproteobacterium Methylomicrobium buryatense strain 5G on methane makes it an attractive system for CH4-based biocatalysis. Here we present a draft genome sequence of the strain that will provide a valuable framework for metabolic engineering of the core pathways for the production of valuable chemicals from methane.

Current Plant Science and Biotechnology in Agriculture

... Entero-bacterial Repetitive Intergenic Consensus (ERIC)-PCR fingerprinting of chromosomal DNA... more ... Entero-bacterial Repetitive Intergenic Consensus (ERIC)-PCR fingerprinting of chromosomal DNA revealed 114 different ERIC types, with only one found at both sites. ... trifolii nodulating red clover are thus common and genetically diverse in the sampled soils (Duodu et al., 2007 ...

The ISME Journal, 2013

The functioning of Arctic soil ecosystems is crucially important for global climate, and basic kn... more The functioning of Arctic soil ecosystems is crucially important for global climate, and basic knowledge regarding their biogeochemical processes is lacking. Nitrogen (N) is the major limiting nutrient in these environments, and its availability is strongly dependent on nitrification. However, microbial communities driving this process remain largely uncharacterized in Arctic soils, namely those catalyzing the rate-limiting step of ammonia (NH 3) oxidation. Eleven Arctic soils were analyzed through a polyphasic approach, integrating determination of gross nitrification rates, qualitative and quantitative marker gene analyses of ammonia-oxidizing archaea (AOA) and bacteria (AOB) and enrichment of AOA in laboratory cultures. AOA were the only NH 3 oxidizers detected in five out of 11 soils and outnumbered AOB in four of the remaining six soils. The AOA identified showed great phylogenetic diversity and a multifactorial association with the soil properties, reflecting an overall distribution associated with tundra type and with several physico-chemical parameters combined. Remarkably, the different gross nitrification rates between soils were associated with five distinct AOA clades, representing the great majority of known AOA diversity in soils, which suggests differences in their nitrifying potential. This was supported by selective enrichment of two of these clades in cultures with different NH 3 oxidation rates. In addition, the enrichments provided the first direct evidence for NH 3 oxidation by an AOA from an uncharacterized Thaumarchaeota-AOA lineage. Our results indicate that AOA are functionally heterogeneous and that the selection of distinct AOA populations by the environment can be a determinant for nitrification activity and N availability in soils.

Soil Biology and Biochemistry, 2006

We compared trapping of Rhizobium leguminosarum biovar trifolii isolates under field soil and non... more We compared trapping of Rhizobium leguminosarum biovar trifolii isolates under field soil and non-soil environmental conditions. Isolates were obtained from white clover (Trifolium repens L.) and red clover (T. pratense L.) grown directly in the field and from plants inoculated with soil from the same site using a plant infection technique. Isolates were identified by genomic polymerase chain reaction (PCR) fingerprinting using primers derived from the enterobacterial repetitive intergenic consensus (ERIC) sequences. The isolates trapped from soil dilutions in the laboratory included a number of major ERIC types that were not found in the field trapped nodules, suggesting that sampling of clover Rhizobium strains from soil dilutions may not be representative of the field nodulating population.

Soil Biology and Biochemistry, 2005

... soil. 2.5.4. Phospholipid fatty acid and ergosterol analysis. The procedure for extraction of... more ... soil. 2.5.4. Phospholipid fatty acid and ergosterol analysis. The procedure for extraction of phospholipid fatty acids (PLFA) was as described by Frostegård et al. (1993) and modified by Johansen and Olsson (2005). Purification ...

Physiologia Plantarum, 1998

Journal of Bacteriology, 2011

Methylobacter tundripaludum SV96 T (ATCC BAA-1195) is a psychrotolerant aerobic methane-oxidizing... more Methylobacter tundripaludum SV96 T (ATCC BAA-1195) is a psychrotolerant aerobic methane-oxidizing gammaproteobacterium ( Methylococcales , Methylococcaceae ) living in High Arctic wetland soil. The strain was isolated from soil harvested in July 1996 close to the settlement Ny-Ålesund, Svalbard, Norway (78°56′N, 11°53′E), and described as a novel species in 2006. The genome includes pmo and pxm operons encoding copper membrane monooxygenases (Cu-MMOs), genes required for nitrogen fixation, and the nirS gene implicated in dissimilatory nitrite reduction to NO but no identifiable inventory for further processing of nitrogen oxides. These genome data provide the basis to investigate M. tundripaludum SV96, identified as a major player in the biogeochemistry of Arctic environments.

Journal of Applied Microbiology, 2007

Aims: To analyse the symbiotic variations within indigenous populations of rhizobia nodulating re... more Aims: To analyse the symbiotic variations within indigenous populations of rhizobia nodulating red clover (Trifolium pratense L.) in soils of northern Norway and Sweden at different times of the growing season. Methods and Results: A total of 431 nodule isolates sampled under field conditions in summer and autumn, were characterized genetically by targeting both chromosomal and symbiotic genes. The Enterobacterial Repetitive Intergenic Consensus polymerase chain reaction (PCR) fingerprinting of chromosomal DNA revealed considerable variation within the isolated populations that was more influenced by geographical origin than sampling time. Analysis of PCR amplified nodEF gene on the symbiotic plasmid by restriction fragment length polymorphism revealed a high proportion of nod types common to the two studied sites. The symbiotic efficiency of the isolates, representing both dominating and rare nodEF genotypes, showed high N 2 fixation rates in symbiosis with the host plant in a greenhouse experiment using the 15 N isotope dilution method. Conclusions: Effective N 2-fixing strains of Rhizobium leguminosarum bv. trifolii nodulating red clover are common and genetically diverse in these northern Scandinavia soils. Significance and Impact of the Study: This study provides information on the variability, stability and dynamics of resident populations of rhizobia nodulating red clover in Scandinavian soils which has practical implications for applying biological nitrogen fixation in subarctic plant production.

Journal of Agricultural, Biological, and Environmental Statistics, 2011

In this paper we describe novel methodology for evaluating competition among strains of Rhizobium... more In this paper we describe novel methodology for evaluating competition among strains of Rhizobium bacteria which can be found naturally occurring in or can be introduced into soil. Rhizobia can occupy nodules on the roots of legume plants allowing the plant to 'fix' atmospheric nitrogen. Our model defines competitive outcomes for a community (the multinomial count of nodules occupied by each strain at the end of a time period) relative to the past state of the community (the proportion of each strain present at the beginning of the time period) and incorporates this prior information in the analysis. Our approach for assessing competition provides an analogy to multivariate methods for continuous responses in competition studies and an alternative to univariate methods for discrete responses that respects the multivariate nature of the data. It can also handle zero values in the multinomial response providing an alternative to compositional data analysis methods, which traditionally have not been able to facilitate zero values. The proposed experimental design is based on the simplex design and the model is an extension of multinomial baseline category logit models that includes multiple offsets and random terms to allow for correlation among clustered responses. Supplemental materials for this article are available from the journal website.

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2006

FEMS Microbiology Ecology, 2003

A new method for isolation of methane oxidising bacteria (methanotrophs) is presented. Soil sampl... more A new method for isolation of methane oxidising bacteria (methanotrophs) is presented. Soil samples from a wetland area and a landfill were plated on polycarbonate membranes, which were incubated in a methane^air atmosphere using a non-sterile soil suspension as the medium. The membrane acted as a permeable growth support. The membrane method resulted in selective growth conditions, which allowed isolation of methane oxidising bacteria. The method resulted in isolation of both type I and type II methanotrophs from natural wetland and landfill soils. The isolates obtained from the landfill were dominated by type II methanotrophs and included several isolates carrying the gene for soluble methane monooxygenase (sMMO). Repetitive element sequence-based PCR fingerprinting documented genotypic diversity at the strain level. The presented method is a promising tool for easy and rapid isolation of different indigenous methanotrophs from an environment of interest.

Environmental Microbiology, 2005

The symbiotic and saprophytic persistence of three unmarked Rhizobium leguminosarum biovar trifol... more The symbiotic and saprophytic persistence of three unmarked Rhizobium leguminosarum biovar trifolii (Rlt) strains introduced into a field site in Iceland were followed. This site was free of clover cultivation and initially devoid of clover-nodulating rhizobia as tested by nodulation studies. Nodule occupancy by strains was identified based on their distinct ERIC-polymerase chain reaction (PCR) DNA fingerprint patterns. The survival and persistence of the individual strains in soil were monitored by the quantitative real-time PCR (qRT-PCR) assay, targeting the host-specific nodE gene. The most dominant strain in the nodule population, Rlt 20-15, showed relatively less saprophytic survival ability and maintained high numbers only in the presence of the appropriate host plant. Conversely, the minor nodule occupant, Rlt 32-28, persisted in soil at a relatively higher abundance both in the presence of its host legumes and in the presence of a non-host grass. The qRT-PCR assay was successfully applied to quantify rhizobial strains directly in soil without culturing or nodulation. However, the assay demonstrated less sensitivity compared with the plant infection most-probable-number (MPN) method for estimating the population size of rhizobia in soil. The quantitative detection limit of our qRT-PCR assays was 1 x 10(3) cells per gram of soil, as opposed to the MPN test which has a detection limit of 10 cells per gram of soil.