Papers by Bjarnheidur Gudmundsdottir
Fish & Shellfish Immunology
The effects of extracellular antigens isolated from Aeromonas salmonicida ssp. achromogenes, were... more The effects of extracellular antigens isolated from Aeromonas salmonicida ssp. achromogenes, were tested on leukocyte cultures from the head-kidney of Atlantic salmon (Salmo salar L.) fingerlings. Samples from vaccinated fingerlings were compared to samples from control fingerlings that were injected with incomplete Freunds adjuvant (IFA) or phosphate buffered saline (PBS). The antigen preparations used for the comparative studies were extracellular products (ECP) and a 20 kDa toxic metallo-caseinase (AsaP1). Lipopolysaccharide (LPS) isolated from the bacterium was tested on unvaccinated fingerlings only. All antigen preparations were mitogenic to cultures from unvaccinated fish. In cultures from vaccinated fish there were difficulties in discerning between mitogenic effects, adjuvant induced cell activation and possible specific responses to the antigens. ([} 1995 Academic Press Limited
Acta Crystallographica Section F-structural Biology and Crystallization Communications, 2009
Infections due to atypical strains of the Gram-negative bacterium Aeromonas salmonicida cause aty... more Infections due to atypical strains of the Gram-negative bacterium Aeromonas salmonicida cause atypical furunculosis and related diseases of both feral and cultivated fish stocks in freshwater and marine environment. More than 20 farmed and 30 wild fish species have been reported to harbor atypical A. salmonicida. The isolated strains are found to be a heterogeneous group as regards many phenotypic and genotypic characteristics. The clinical and pathological features of infection are different as many factors are involved, e.g. various hosts, strains and environment. Infections of fish in the temperate regions of the Northern hemisphere are most frequently reported, although disease problems have also occurred in other parts of the world as Australia, the Mediterranean and Chile. In Iceland atypical furunculosis has been the main bacterial disease in the salmonid farming industry. As diseases caused by atypical strains are of emerging importance worldwide, the prospects of their cont...
ÁGRIP Í þessu riti er gerð grein fyrir sjúkdómum sem gaetir á mismunandi þroskastigum þorsksins, ... more ÁGRIP Í þessu riti er gerð grein fyrir sjúkdómum sem gaetir á mismunandi þroskastigum þorsksins, allt frá frumfóðrun þorsklirfa til seiðaeldis í strandkerum og síðan áframeldis á sláturfiski í sjókvíum. Einnig er fjallað um helstu eiginleika ónaemiskerfis fiska, með áherslu á þorsk, og í hverju það er frábrugðið því sem gerist meðal dýra með heitt blóð. Áhersla er lögð á stöðu mála hér á landi. Í íslensku þorskeldi hefur gaett svipaðra sjúkdómsvalda og í þorskeldi erlendis. Bakteríusýkingar sem helst hafa látið til sín taka, enn sem komið er, eru kýlaveikibróðir (Aeromonas salmonicida undirtegund achromogenes) og vibríuveiki (Listonella anguillarum). Auk þess hefur orðið vart Flexibacter-sýkingar á roði þorsks. Utan á tálknum og roði gaetir helst sýkinga af völdum einfruma sníkjudýra (Ichthyobodo tegund og Trichodina tegundir). Sýkingar af völdum tveggja annarra tegunda frumdýra, annars vegar í tálknum og ýmsum innri líffaerum (Loma tegund) og hins vegar í gervitálknum (X-cell disea...
Acta Crystallographica Section A Foundations of Crystallography, 2010
Page s143 s143 describe the structure of a new class of CBP from the parapoxvirus, Orf virus. The... more Page s143 s143 describe the structure of a new class of CBP from the parapoxvirus, Orf virus. The crystals of this protein were challenging to produce and optimized significantly through the use of somewhat surprising additives. Crystals occupy Space Group P6 5 22 with unit cell parameters of a = b = 75.62, c = 282.49 Å, α = 90, β = 90, γ = 120 o . The structure was phased using MAD methodologies and currently the 2.1Å structure is undergoing refinement. Early analysis indicates that it is a member of the β-sandwich family but it is quite distinct from other family members when superimposed. Additionally the crystal structure is consistent with a physiologic dimer and displays a very broad β sheet on its surface containing contributions from more than 10 β strands. The dimeric nature of this CBP appears to be a unique property of its class and may be key in explaining how it is able to bind different chemokines from at least two distinct chemokine classes.
The study describes the identification of type VI secretion systems (T6SSs) in Moritella viscosa,... more The study describes the identification of type VI secretion systems (T6SSs) in Moritella viscosa, the aetiological agent of winter ulcer disease. Despite the availability of commercial vaccines, M. viscosa causes significant financial losses in salmonid farming. The T6SS transports bacterial proteins from the cell into the environment or directly into host cells, and has been implicated with bacterial virulence. Therefore, information on the presence of a T6SS in M. viscosa is of interest and could give further insight into the biology of the bacterium. The aim of the study was to identify potential T6SSs in M. viscosa and to determine whether it possesses active T6S, providing further insight into the biology of the bacterium.The genome of M. viscosa 06/09/139 was screened for homology with known T6SS encodinggenes. Two genetically distinct loci, termed Moritella Type Six Secretion 1 and 2 (mts1 and mts2), as encoding putative T6SSs. Each locus contained known T6S core genes. The m...
High mortality rates commonly observed during the early life stages of intensively reared Atlanti... more High mortality rates commonly observed during the early life stages of intensively reared Atlantic halibut have among other things been related to high bacterial numbers and an unfavourable bacterial community The study describes the effects of two different methods for environmental shading on larval survival and numbers of cultivable bacteria in the culture water and the gastrointestinal
High mortality rates commonly observed during the early life stages of intensively reared Atlanti... more High mortality rates commonly observed during the early life stages of intensively reared Atlantic halibut have among other things been related to high bacterial numbers and an unfavourable bacterial community. The study describes the effects of two different methods for environmental shading on larval survival and numbers of cultivable bacteria in the culture water and the gastrointestinal tract of first feeding larvae at Fiskey Ltd. Larval survival was not affected by the method used for environmental shading. Lower bacterial numbers were observed in the tank water with environmental shading provided by inorganic clay as compared with marine algae, primarily during the first days of exogenous feeding. Gram negative, fermentative bacteria dominated the cultivable community in the gastrointestinal tract of larvae during the first weeks in feeding. The use of inorganic clay has clear economic advantages as compared to the use of marine microalgae, and the commercial producer has used...
Journal of fish diseases, 2014
The metalloendopeptidase AsaP1 is one of the major extracellular virulence factors of A. salmonic... more The metalloendopeptidase AsaP1 is one of the major extracellular virulence factors of A. salmonicida subsp. achromogenes, expressed as a 37-kDa pre-pro-peptide and processed to a 19-kDa active peptide. The aim of this study was to construct mutant strains secreting an AsaP1-toxoid instead of AsaP1-wt, to study virulence of these strains and to test the potency of the AsaP1-toxoid bacterin and the recombinant AsaP1-toxoids to induce protective immunity in Arctic char. Two A. salmonicida mutants were constructed that secrete either AsaP1E294A or AsaP1Y309F . The secreted AsaP1Y309F -toxoid had weak caseinolytic activity and was processed to the 19-kDa peptide, whereas the AsaP1E294A -toxoid was found as a 37-kDa pre-pro-peptide suggesting that AsaP1 is auto-catalytically processed. The LD50 of the AsaP1Y309F -toxoid mutant in Arctic char was significantly higher than that of the corresponding wt strain, and LD50 of the AsaP1E294A -toxoid mutant was comparable with that of an AsaP1-def...
Laeknabladid
The main bacterial diseases in Icelandic aquaculture are furunculosis, bacterial kidney disease (... more The main bacterial diseases in Icelandic aquaculture are furunculosis, bacterial kidney disease (BKD) and vibriosis. Atypical furunculosis caused by A. salmonicida ssp. achromogenes is an endemic disease causing high mortality in salmonids yearly. Classical furunculosis caused by A. salmonicida ssp. salmonicida was first diagnosed in Iceland in 1995. At Keldur the research focus has been on studying the virulence mechanism of A. salmonicida ssp. achromogenes, the immune response evoked in the fish, and vaccine development. Farmed salmonids have been vaccinated with good results against atypical furunculosis with an autogenous bacterin since 1992. Recent results indicate some crossprotection of the autogenous bacterin of A. salmonicida ssp. achromogenes against classical furunculosis. BKD caused by Renibacterium salmoninarum is another endemic disease in Iceland. An intensive program for brood fish screening has been developed. Fertilized eggs from all infected parents are destroyed ...
Rannsóknir og þróun eru undirstaða allra atvinnugreina. Atvinnugrein sem heldur ekki í við framfa... more Rannsóknir og þróun eru undirstaða allra atvinnugreina. Atvinnugrein sem heldur ekki í við framfarir og þróun þrífst ekki eða dafnar til lengdar. Á Tilraunastöð Háskóla Íslands í meinafraeði að Keldum eru stundaðar rannsóknir sem tengjast dýraheilbrigði og sjúkdómum í dýrum og mönnum. Þar er veitt ráðgjöf og þjónusta í þágu heilbrigðiseftirlits, sjúkdómagreininga og sjúkdóma varna fyrir búfé, eldisfiska og önnur dýr. Nemar í líffraeði, lífefnafraeði, lífeindafraeði og dýralaekningum vinna rannsóknarverkefni á fraeða sviðum stofnunarinnar sem hluta af grunn eða framhaldsnámi sínu. Með vaxandi innflutningi, hnatt vaeðingu og hlýnandi loftslagi má gera ráð fyrir að nýir smitsjúkdómar berist til landsins í auknum maeli. Fyrir utan haettulega smitsjúkdóma sem herja á búpening og geta valdið fjárhagslegu tjóni eru margir af varasömustu smit sjúkdómum í mönnum svokallaðar súnur (zoonosis), en það eru sýklar sem smitast úr dýrum í fólk (s.s. fuglaflensa, svínaflensa, ebólaveira og flei...
Veterinary Microbiology, 2012
The study describes the identification of type VI secretion systems (T6SSs) in Moritella viscosa,... more The study describes the identification of type VI secretion systems (T6SSs) in Moritella viscosa, the aetiological agent of winter ulcer disease. Despite the availability of commercial vaccines, M. viscosa causes significant financial losses in salmonid farming. The T6SS transports bacterial proteins from the cell into the environment or directly into host cells, and has been implicated with bacterial virulence. The aim of the study was to identify potential T6SSs in M. viscosa and to determine whether it possesses active T6S, providing further insight into the biology of the bacterium. The genome of M. viscosa 06/09/139 was screened for homology with known T6SS encoding genes. Two genetically distinct loci, termed Moritella Type Six Secretion 1 and 2 (mts1 and mts2), were identified as encoding putative T6SSs. Each locus contained known T6S core genes. The mts2 locus contained species specific genes, some of which have not previously been connected with T6S. The mts1 locus showed sequence homology and synteny to T6SSs of the fish pathogen Aliivibrio salmonicida and a non-pathogenic Moritella sp. PE36. The mts2 locus was more similar to a Vibrio parahaemolyticus T6SS. A functional T6SS was confirmed through identification of secreted Mts1-M, a hemolysin coregulated protein (Hcp) which is a part of the secretion system. Both virulent and avirulent M. viscosa isolates expressed two genes encoding Hcp, mts1-M and mts2-M. The results show that M. viscosa has a functional T6S, but the role of the secretion system and possible connections with virulence need further examination.
Veterinary Microbiology, 2008
Survival problems are encountered at early stages of intensive fish rearing and antibiotics are w... more Survival problems are encountered at early stages of intensive fish rearing and antibiotics are widely used to remedy the situation. Probiotics may provide a potential alternative method to protect larvae from opportunistic and pathogenic bacteria and promote a balanced environment. This study was designed to search for new probiotics to target this critical period in cod rearing. Potential probionts were selected from the natural microbiota of cod aquacultural environment. The selection was based on several criteria: pathogen inhibition potential, growth characteristics, strain identification, metabolite production and adhesion to fish cell lines. Our study demonstrated that 14% of screened bacteria (n=188) had antagonistic properties towards fish pathogens. The majority of these isolates were Gram-positive (81%), belonging to Firmicutes (69.2%) and Actinobacteria (11.5%) phyla based on 16S rRNA gene sequencing. Only 6 (3.2%) of 188 isolates could inhibit all three pathogens tested: Vibrio anguillarum, Aeromonas salmonicida subsp. achromogenes and Vibrio salmonicida. Differences observed in activity intensity and spectrum among inhibitory isolates emphasise the need to develop probiotic mixtures for efficient prophylactic methods. Comparison of growth behaviour of inhibitory isolates and pathogens at cod rearing temperatures, metabolite production and adhesion capacity were considered for final probiont selection. Four promising isolates that could be used as a mixed supplement to rearing water were identified as putative probiotic bacteria. This study emphasises the importance and potential of lactic acid bacteria in aquaculture.
Veterinary Microbiology, 2009
Moritella viscosa causes winter ulcer disease in salmonids. The aim of the present work was to is... more Moritella viscosa causes winter ulcer disease in salmonids. The aim of the present work was to isolate and partially characterise an extracellular peptidase from M. viscosa, and to study its role in virulence. The peptidase, termed MvP1, was a 38-kDa metallopeptidase produced in late exponential growth. The optimum temperature for MvP1 was 40 degrees C, but the enzyme was active over a broad range of temperatures. MvP1 was non-lethal to salmon at concentrations up to 0.22microg/g fish, but extracellular products were lethal to salmon. MvP1 degraded casein, gelatin and collagen from lumpfish skin. It caused considerable tissue necrosis and hemorrhages at the site of injection, and affected cell-cell adhesions in EPC and BF-2 cell lines, but was not highly cytotoxic. The peptidase partially degraded fish IgM heavy chain but was non-hemolytic. The mvp1 gene was sequenced and encoded a 734-aa polypeptide containing a signal sequence, an N-terminal propeptide, a mature peptidase domain and a C-terminal propeptide. The MvP1 propeptide undergoes both N-terminal and C-terminal processing and different C-terminal processing results in the formation of several active isoforms of the mature peptidase. The catalytic domain showed highest sequence similarity with several vibriolysins (EC 3.4.24.25) originating from Pseudoalteromonas strains, showing up to 80% aa identity. The results indicate that MvP1 is a previously unknown vibriolysin that might affect M. viscosa virulence by aiding in the invasion and dissemination of the bacterium in its host, by causing tissue destruction.
Veterinary Immunology and Immunopathology, 2001
Balb/c mice, injected i.p. with extracellular products (ECP) of Aeromonas salmonicida subsp. achr... more Balb/c mice, injected i.p. with extracellular products (ECP) of Aeromonas salmonicida subsp. achromogenes (Asa), displayed symptoms similar to toxic shock syndrome. The LD 50 observed was between 1.5 and 2.0 mg g À1 and the mice died within 19 h. Four in¯ammatory cytokines were measured in mice receiving sublethal ECP doses. TNF-a and IL-6 showed a sharp peak in the serum while IL-1b and IL-2 were not detected. When peritoneal macrophages were cultivated in the presence of ECP, AsaP1 (a toxic caseinolytic metallo-protease puri®ed from ECP) or LPS, all cultures produced TNF-a, IL-6 and IL-1b. The same antigens were mitogenic in spleen cell cultures. Furthermore, IL-2 production, which is a normal T-cell response to ConA stimulation, was downregulated in spleen cell cultures from mice injected with ECP. #
Veterinary Immunology and Immunopathology, 1995
The humoral antibody response of healthy Atlantic salmon and of 'two groups of salmon, naturally ... more The humoral antibody response of healthy Atlantic salmon and of 'two groups of salmon, naturally infected with Aeromonas salmonicida ssp. achromogenes, was examined in some detail.
Peptides, 2011
Cathelicidins are among the best characterized antimicrobial peptides and have been shown to have... more Cathelicidins are among the best characterized antimicrobial peptides and have been shown to have an important role in mammalian innate immunity. We recently isolated a novel mature cathelicidin peptide (codCath) from Atlantic cod and in the present study we functionally characterized codCath. The peptide demonstrated salt sensitivity with abrogation of activity at physiological salt concentrations. In low ionic strength medium we found activity against marine and non-marine Gram-negative bacteria with an average MIC of 10 μM, weak activity against a Gram-positive bacterium (MIC 80 μM), and pronounced antifungal activity (MIC 2.5 μM). The results suggest the kinetics and mode of action of codCath to be fast killing accompanied by pronounced cell lysis. Extracellular products (ECPs) of three marine bacteria caused breakdown of the peptide into smaller fragments and the cleaved peptide lost its antibacterial activity. Proteolysis of the peptide on the other hand was abolished by prior heat-treatment of the ECPs, suggesting a protease involvement. We observed no cytotoxicity of the peptide in fish cells up to a concentration of 40 μM and the selectivity of activity was confirmed with bacterial and mammalian membrane mimetics. We conclude that the potent broad-spectrum activity of codCath hints at a role of the peptide in cod immune defense.
Journal of Fish Diseases, 2003
Atlantic halibut, Hippoglossus hippoglossus (L.), was shown to be sensitive to infection by three... more Atlantic halibut, Hippoglossus hippoglossus (L.), was shown to be sensitive to infection by three different isolates of Aeromonas salmonicida ssp. achromogenes in pre-challenge tests using intraperitoneal (i.p.) and intramuscular (i.m.) injections as well as bath challenges. A commercial furunculosis vaccine, Alphaject 1200, and an autogenous vaccine, AAS, based on the challenge strain, induced immune protection as shown in challenge tests 8 weeks postimmunization. The survival rate of vaccinated fish after i.p. challenge was 100%, whereas mortality of control fish was 61%. Employing i.m. challenge, relative percentage survival induced by the furunculosis vaccine and the AAS vaccine was 47 and 44, respectively. Mortality of i.m. injected controls was 68%. Vaccinated fish behaved normally following vaccination but the weight gain was significantly reduced in vaccinated fish 8 weeks post-vaccination compared with control fish receiving phosphatebuffered saline. At the same time, intra-abdominal adhesions were observed in fish injected with either of the two vaccines or adjuvant alone. Antibody response against A. salmonicida ssp. achromogenes was detected in sera from fish receiving either vaccine.
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Papers by Bjarnheidur Gudmundsdottir