Blar i forfatter "Willassen, Nils Peder"

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    • The alternative sigma factor RpoQ regulates colony morphology, biofilm formation and motility in the fish pathogen Aliivibrio salmonicida 

      Khider, Miriam; Willassen, Nils Peder; Hansen, Hilde (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-12)
      <i>Background</i>: Quorum sensing (QS) is a cell-to cell communication system that bacteria use to synchronize activities as a group. LitR, the master regulator of QS in <i>Aliivibrio salmonicida</i>, was recently shown to regulate activities such as motility, rugosity and biofilm formation in a temperature dependent manner. LitR was also found to be a positive regulator of <i>rpoQ</i>. RpoQ ...

    • The autoinducer synthases LuxI and AinS are responsible for temperature-dependent AHL production in the fish pathogen Aliivibrio salmonicida 

      Hansen, Hilde; Purohit, Amit Anand; Leiros, Hanna-Kirsti S.; Johansen, Jostein; Kellermann, Stefanie J.; Bjelland, Ane Mohn; Willassen, Nils Peder (Journal article; Tidsskriftartikkel, 2015-03-24)
      Background: Quorum sensing (QS) is a cell-to-cell communication system used by bacteria to regulate activities such as virulence, bioluminescence and biofilm formation. The most common QS signals in Gram-negative bacteria are N-acyl-homoserine lactones (AHLs). Aliivibrio salmonicida is the etiological agent of cold water vibriosis in Atlantic salmon, a disease which occurs mainly during seasons ...

    • Biochemical characterization of a family 15 carbohydrate esterase from a bacterial marine Arctic metagenome 

      De Santi, Concetta; Willassen, Nils Peder; Williamson, Adele Kim (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Background The glucuronoyl esterase enzymes of wood-degrading fungi (Carbohydrate Esterase family 15; CE15) form part of the hemicellulolytic and cellulolytic enzyme systems that break down plant biomass, and have possible applications in biotechnology. Homologous enzymes are predicted in the genomes of several bacteria, however these have been much less studied than their fungal counterparts. ...

    • Bioprospecting around Arctic islands: Marine bacteria as rich source of biocatalysts 

      De Santi, Concetta; Altermark, Bjørn; de Pascale, Donatella; Willassen, Nils Peder (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-11)
      We have investigated the biotechnological potential of Arctic marine bacteria for their ability to produce a broad spectrum of cold-active enzymes. Marine bacteria exhibiting these features are of great interest for both fundamental research and industrial applications. Macrobiota water and sediment samples have been collected during 2010 and 2011expeditions around the Lofoten and Svalbard islands. ...

    • Characterization of a cold-active and salt tolerant esterase identified by functional screening of Arctic metagenomic libraries 

      De Santi, Concetta; Altermark, Bjørn; Pierechod, Marcin Miroslaw; Ambrosino, Luca; de Pascale, Donatella; Willassen, Nils Peder (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-19)
      Background: The use of metagenomics in enzyme discovery constitutes a powerful approach to access to genomes of unculturable community of microorganisms and isolate novel valuable biocatalysts for use in a wide range of biotechnological and pharmaceutical fields. Results: Here we present a novel esterase gene (lip3) identified by functional screening of three fosmid metagenomic libraries, ...

    • Closely-related Photobacterium strains comprise the majority of bacteria in the gut of migrating Atlantic cod (Gadus morhua) 

      Le Doujet, Typhaine; De Santi, Concetta; Klemetsen, Terje; Hjerde, Erik; Willassen, Nils Peder; Haugen, Peik (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-17)
      <p><i>Background - </i>The population of Atlantic cod (<i>Gadus morhua</i>), also known as Northeast Arctic cod, migrating Atlantic cod, or simply “skrei,” lives mainly in the Barents Sea and Svalbard waters and migrates in annual cycles to the Norwegian coast in order to spawn eggs during late winter. It is the world’s largest population of Atlantic cod, and the population is distinct from the ...

    • Co-cultivation and transcriptome sequencing of two co-existing fish pathogens Moritella viscosa and Aliivibrio wodanis 

      Hjerde, Erik; Karlsen, Christian; Sørum, Henning; Parkhill, Julian; Willassen, Nils Peder; Thomson, Nicholas R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-10)
      Background: Aliivibrio wodanis and Moritella viscosa have often been isolated concurrently from fish with winterulcer disease. Little is known about the interaction between the two bacterial species and how the presence of one bacterial species affects the behaviour of the other. Results: The impact on bacterial growth in co-culture was investigated in vitro, and the presence of A. wodanis has an ...

    • Comparative analysis of HiSeq3000 and BGISEQ-500 sequencing platform with shotgun metagenomic sequencing data 

      Kumar, Animesh; Robertsen, Espen Mikal; Willassen, Nils Peder; Fu, Juan; Hjerde, Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-29)
      Recent advances in sequencing technologies and platforms have enabled to generate metagenomics sequences using different sequencing platforms. In this study, we analyzed and compared shotgun metagenomic sequences generated by HiSeq3000 and BGISEQ-500 platforms from 12 sediment samples collected across the Norwegian coast. Metagenomics DNA sequences were normalized to an equal number of bases for ...

    • Complete genome sequence of Vibrio anguillarum strain NB10, a virulent isolate from the Gulf of Bothnia 

      Holm, Kåre Olav; Nilsson, Kristina; Hjerde, Erik; Willassen, Nils Peder; Milton, Debra L (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-09-02)
      Vibrio anguillarum causes a fatal hemorrhagic septicemia in marine fish that leads to great economical losses in aquaculture world-wide. Vibrio anguillarum strain NB10 serotype O1 is a Gram-negative, motile, curved rod-shaped bacterium, isolated from a diseased fish on the Swedish coast of the Gulf of Bothnia, and is slightly halophilic. Strain NB10 is a virulent isolate that readily colonizes ...

    • Critical Assessment of Metagenome Interpretation: the second round of challenges 

      Meyer, Fernando; Fritz, Adrian; Deng, Zhi-Luo; Koslicki, David; Lesker, Till Robin; Gurevich, Alexey; Robertson, Gary; Alser, Mohammed; Antipov, Dmitry; Beghini, Francesco; Bertrand, Denis; Brito, Jaqueline J.; Brown, C. Titus; Buchmann, Jan; Buluç, Aydin; Chen, Bo; Chikhi, Rayan; Clausen, Philip T. L. C.; Cristian, Alexandru; Dabrowski, Piotr Wojciech; Darling, Aaron E.; Egan, Rob; Eskin, Eleazar; Georganas, Evangelos; Goltsman, Eugene; Gray, Melissa A.; Hansen, Lars Hestbjerg; Hofmeyr, Steven; Huang, Pingqin; Irber, Luiz; Jia, Huijue; Jørgensen, Tue Sparholt; Kieser, Silas D.; Klemetsen, Terje; Kola, Axel; Kolmogorov, Mikhail; Korobeynikov, Anton; Kwan, Jason; LaPierre, Nathan; Lemaitre, Claire; Li, Chenhao; Limasset, Antoine; Malcher-Miranda, Fabio; Mangul, Serghei; Marcelino, Vanessa R.; Marchet, Camille; Marijon, Pierre; Meleshko, Dmitry; Mende, Daniel R.; Milanese, Alessio; Nagarajan, Niranjan; Nissen, Jakob; Nurk, Sergey; Oliker, Leonid; Paoli, Lucas; Peterlongo, Pierre; Piro, Vitor C.; Porter, Jacob S.; Rasmussen, Simon; Rees, Evan R.; Reinert, Knut; Renard, Bernhard; Robertsen, Espen Mikal; Rosen, Gail L.; Ruscheweyh, Hans-Joachim; Sarwal, Varuni; Segata, Nicola; Seiler, Enrico; Shi, Lizhen; Sun, Fengzhu; Sunagawa, Shinichi; Sørensen, Søren Johannes; Thomas, Ashleigh; Tong, Chengxuan; Trajkovski, Mirko; Tremblay, Julien; Uritskiy, Gherman; Vicedomini, Riccardo; Wang, Zhengyang; Wang, Ziye; Wang, Zhong; Warren, Andrew; Willassen, Nils Peder; Yelick, Katherine; You, Ronghui; Zeller, Georg; Zhao, Zhengqiao; Zhu, Shanfeng; Zhu, Jie; Garrido-Oter, Ruben; Gastmeier, Petra; Hacquard, Stephane; Häußler, Susanne; Khaledi, Ariane; Maechler, Friederike; Mesny, Fantin; Radutoiu, Simona; Schulze-Lefert, Paul; Smit, Nathiana; Strowig, Till; Bremges, Andreas; Sczyrba, Alexander; McHardy, Alice Carolyn (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-04-08)
      Evaluating metagenomic software is key for optimizing metagenome interpretation and focus of the Initiative for the Critical Assessment of Metagenome Interpretation (CAMI). The CAMI II challenge engaged the community to assess methods on realistic and complex datasets with long- and short-read sequences, created computationally from around 1,700 new and known genomes, as well as 600 new plasmids ...

    • Differential expression profiling of ΔlitR and ΔrpoQ mutants reveals insight into QS regulation of motility, adhesion and biofilm formation in Aliivibrio salmonicida 

      Khider, Miriam; Hjerde, Erik; Hansen, Hilde; Willassen, Nils Peder (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-15)
      <i>Background</i>: The coordination of group behaviors in bacteria is achieved by a cell-cell signaling process called quorum sensing (QS). QS is an intercellular communication system, which synchronously controls expression of a vast range of genes in response to changes in cell density and is mediated by autoinducers that act as extracellular signals. <i>Aliivibrio salmonicida</i>, the causative ...

    • Effects of Probiotic Supplementation on the Gut Microbiota and Antibiotic Resistome Development in Preterm Infants 

      Esaiassen, Eirin; Hjerde, Erik; Cavanagh, Jorunn Pauline; Pedersen, Tanja; Andresen, Jannicke Hanne; Rettedal, Siren; Støen, Ragnhild; Nakstad, Britt; Willassen, Nils Peder; Klingenberg, Claus (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-16)
      <i>Objectives</i>: In 2014 probiotic supplementation (<i>Lactobacillus acidophilus and Bifidobacterium longum subspecies infantis;</i> Infloran®) was introduced as standard of care to prevent necrotizing enterocolitis (NEC) in extremely preterm infants in Norway. We aimed to evaluate the influence of probiotics and antibiotic therapy on the developing gut microbiota and antibiotic resistome in ...

    • Exploring the transcriptome of luxI- and ΔainS mutants and the impact of N-3-oxo-hexanoyl-L- and N-3-hydroxy- decanoyl-L-homoserine lactones on biofilm formation in Aliivibrio salmonicida 

      Khider, Miriam; Hansen, Hilde; Hjerde, Erik; Johansen, Jostein A; Willassen, Nils Peder (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-30)
      <i>Background</i>: Bacterial communication through quorum sensing (QS) systems has been reported to be important in coordinating several traits such as biofilm formation. In <i>Aliivibrio salmonicida</i> two QS systems the LuxI/R and AinS/R, have been shown to be responsible for the production of eight acyl-homoserine lactones (AHLs) in a cell density dependent manner. We have previously ...

    • Expression profiling reveals Spot 42 small RNA as a key regulator in the central metabolism of Aliivibrio salmonicida 

      Hansen, Geir Åsmund; Ahmad, Rafi; Hjerde, erik; Fenton, Christopher Graham; Willassen, Nils Peder; Haugen, Peik (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      Spot 42 was discovered in Escherichia coli nearly 40 years ago as an abundant, small and unstable RNA. Its biological role has remained obscure until recently, and is today implicated in having broader roles in the central and secondary metabolism. Spot 42 is encoded by the spf gene. The gene is ubiquitous in the Vibrionaceae family of gamma-proteobacteria. One member of this family, Aliivibrio ...

    • Full‐length 16S rRNA gene classification of Atlantic salmon bacteria and effects of using different 16S variable regions on community structure analysis 

      Klemetsen, Terje; Willassen, Nils Peder; Karlsen, Christian René (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-04)
      Understanding fish‐microbial relationships may be of great value for fish producers as fish growth, development and welfare are influenced by the microbial community associated with the rearing systems and fish surfaces. Accurate methods to generate and analyze these microbial communities would be an important tool to help improve understanding of microbial effects in the industry. In this study, ...

    • The genome sequence of the fish pathogen Aliivibrio salmonicida strain LFI1238 shows extensive evidence of gene decay 

      Hjerde, Erik; Holden, Matthew TG; Seeger, Kathy; Lorentzen, Marit Sjo; Bason, Nathalie; Paulsen, Steinar; Willassen, Nils Peder; Churcher, Carol; Harris, David; Norbertczak, Halina; Quail, Michael A; Sanders, Suzanne; Thurston, Scott; Parkhill, Julian; Thomson, Nicholas R (Journal article; Tidsskriftartikkel; Peer reviewed, 2008-12-19)
      <b>Background:</b> The fish pathogen Aliivibrio salmonicida is the causative agent of cold-water vibriosis in marine aquaculture. The Gram-negative bacterium causes tissue degradation, hemolysis and sepsis in vivo.<BR><BR> <b>Results:</b> In total, 4 286 protein coding sequences were identified, and the 4.6 Mb genome of A. salmonicida has a six partite architecture with two chromosomes and four ...

    • High quality draft genome sequence of Streptomyces sp. strain AW19M42 isolated from a sea squirt in Northern Norway 

      Bjerga, Gro Elin Kjæreng; Hjerde, Erik; De Santi, Concetta; Williamson, Adele Kim; Smalås, Arne O.; Willassen, Nils Peder; Altermark, Bjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)

    • Isolation and Characterization of Anti-Adenoviral Secondary Metabolites from Marine Actinobacteria 

      Strand, Mårten; Carlsson, Marcus; Uvell, Hanna; Islam, Koushikul; Edlund, Karin; Cullman, Inger; Altermark, Bjørn; Mei, Ya-Fang; Elofsson, Mikael; Willassen, Nils Peder; Wadell, Göran; Almqvist, Fredrik (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)

    • Lipopolysaccharide O-Antigen Prevents Phagocytosis of Vibrio anguillarum by Rainbow Trout (Oncorhynchus mykiss) Skin Epithelial Cells 

      Lindell, Kristoffer; Fahlgren, Anna; Hjerde, Erik; Willassen, Nils Peder; Fällman, Maria; Milton, Debra L (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      Colonization of host tissues is a first step taken by many pathogens during the initial stages of infection. Despite the impact of bacterial disease on wild and farmed fish, only a few direct studies have characterized bacterial factors required for colonization of fish tissues. In this study, using live-cell and confocal microscopy, rainbow trout skin epithelial cells, the main structural component ...

    • The MAR databases: development and implementation of databases specific for marine metagenomics 

      Klemetsen, Terje; Raknes, Inge A.; Fu, Juan; Agafonov, Alexander; Balasundaram, Sudhagar V.; Tartari, Giacomo; Robertsen, Espen; Willassen, Nils Peder (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-02)
      We introduce the marine databases; <i>MarRef, MarDB</i> and <i>MarCat</i> (https://mmp.sfb.uit.no/databases/), which are publicly available resources that promote marine research and innovation. These data resources, which have been implemented in the Marine Metagenomics Portal (MMP) (https://mmp.sfb.uit.no/), are collections of richly annotated and manually curated contextual (metadata) and sequence ...