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Eslamloo K, Kumar S, Xue X, Parrish KS, Purcell SL, Fast MD, Rise ML. Global gene expression responses of Atlantic salmon skin to Moritella viscosa. Sci Rep 2022; 12:4622. [PMID: 35301338 PMCID: PMC8931016 DOI: 10.1038/s41598-022-08341-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Accepted: 03/03/2022] [Indexed: 12/19/2022] Open
Abstract
Moritella viscosa is a Gram-negative pathogen that causes large, chronic ulcers, known as winter-ulcer disease, in the skin of several fish species including Atlantic salmon. We used a bath challenge approach to profile the transcriptome responses of M. viscosa-infected Atlantic salmon skin at the lesion (Mv-At) and away from the lesion (Mv-Aw) sites. M. viscosa infection was confirmed through RNA-based qPCR assays. RNA-Seq identified 5212 and 2911 transcripts differentially expressed in the Mv-At compared to no-infection control and Mv-Aw groups, respectively. Also, there were 563 differentially expressed transcripts when comparing the Mv-Aw to control samples. Our results suggest that M. viscosa caused massive and strong, but largely infection site-focused, transcriptome dysregulations in Atlantic salmon skin, and its effects beyond the skin lesion site were comparably subtle. The M. viscosa-induced transcripts of Atlantic salmon were mainly involved in innate and adaptive immune response-related pathways, whereas the suppressed transcripts by this pathogen were largely connected to developmental and cellular processes. As validated by qPCR, M. viscosa dysregulated transcripts encoding receptors, signal transducers, transcription factors and immune effectors playing roles in TLR- and IFN-dependent pathways as well as immunoregulation, antigen presentation and T-cell development. This study broadened the current understanding of molecular pathways underlying M. viscosa-triggered responses of Atlantic salmon, and identified biomarkers that may assist to diagnose and combat this pathogen.
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Affiliation(s)
- Khalil Eslamloo
- Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada. .,Hoplite Laboratory, Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada.
| | - Surendra Kumar
- Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Xi Xue
- Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Kathleen S Parrish
- Hoplite Laboratory, Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada
| | - Sara L Purcell
- Hoplite Laboratory, Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada
| | - Mark D Fast
- Hoplite Laboratory, Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada
| | - Matthew L Rise
- Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
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2
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Mekasha S, Linke D. Secretion Systems in Gram-Negative Bacterial Fish Pathogens. Front Microbiol 2022; 12:782673. [PMID: 34975803 PMCID: PMC8714846 DOI: 10.3389/fmicb.2021.782673] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/24/2021] [Indexed: 12/17/2022] Open
Abstract
Bacterial fish pathogens are one of the key challenges in the aquaculture industry, one of the fast-growing industries worldwide. These pathogens rely on arsenal of virulence factors such as toxins, adhesins, effectors and enzymes to promote colonization and infection. Translocation of virulence factors across the membrane to either the extracellular environment or directly into the host cells is performed by single or multiple dedicated secretion systems. These secretion systems are often key to the infection process. They can range from simple single-protein systems to complex injection needles made from dozens of subunits. Here, we review the different types of secretion systems in Gram-negative bacterial fish pathogens and describe their putative roles in pathogenicity. We find that the available information is fragmented and often descriptive, and hope that our overview will help researchers to more systematically learn from the similarities and differences between the virulence factors and secretion systems of the fish-pathogenic species described here.
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Affiliation(s)
- Sophanit Mekasha
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Dirk Linke
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
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3
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Shea D, Bateman A, Li S, Tabata A, Schulze A, Mordecai G, Ogston L, Volpe JP, Neil Frazer L, Connors B, Miller KM, Short S, Krkošek M. Environmental DNA from multiple pathogens is elevated near active Atlantic salmon farms. Proc Biol Sci 2020; 287:20202010. [PMID: 33081614 PMCID: PMC7661312 DOI: 10.1098/rspb.2020.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The spread of infection from reservoir host populations is a key mechanism for disease emergence and extinction risk and is a management concern for salmon aquaculture and fisheries. Using a quantitative environmental DNA methodology, we assessed pathogen environmental DNA in relation to salmon farms in coastal British Columbia, Canada, by testing for 39 species of salmon pathogens (viral, bacterial, and eukaryotic) in 134 marine environmental samples at 58 salmon farm sites (both active and inactive) over 3 years. Environmental DNA from 22 pathogen species was detected 496 times and species varied in their occurrence among years and sites, likely reflecting variation in environmental factors, other native host species, and strength of association with domesticated Atlantic salmon. Overall, we found that the probability of detecting pathogen environmental DNA (eDNA) was 2.72 (95% CI: 1.48, 5.02) times higher at active versus inactive salmon farm sites and 1.76 (95% CI: 1.28, 2.42) times higher per standard deviation increase in domesticated Atlantic salmon eDNA concentration at a site. If the distribution of pathogen eDNA accurately reflects the distribution of viable pathogens, our findings suggest that salmon farms serve as a potential reservoir for a number of infectious agents; thereby elevating the risk of exposure for wild salmon and other fish species that share the marine environment.
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Affiliation(s)
- Dylan Shea
- Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada
| | - Andrew Bateman
- Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada.,Salmon Coast Field Station, Simoom Sound, British Columbia, Canada.,Pacific Salmon Foundation, Vancouver, British Columbia, Canada
| | - Shaorong Li
- Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
| | - Amy Tabata
- Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
| | - Angela Schulze
- Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
| | - Gideon Mordecai
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Lindsey Ogston
- Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada
| | - John P Volpe
- School of Environmental Studies, University of Victoria, Victoria, British Columbia, Canada
| | - L Neil Frazer
- Department of Earth Sciences, University of Hawaii at Mānoa, Honolulu, Hawaii, Canada
| | - Brendan Connors
- Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, British Columbia, Canada
| | - Kristina M Miller
- Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
| | - Steven Short
- Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada.,Department of Biology, University of Toronto Mississauga, Mississauga, British Columbia, Canada
| | - Martin Krkošek
- Department of Ecology and Evolutionary Biology, University of Toronto, Ontario, Canada.,Salmon Coast Field Station, Simoom Sound, British Columbia, Canada
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4
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Carvalho LA, Whyte SK, Braden LM, Purcell SL, Manning AJ, Muckle A, Fast MD. Impact of co-infection with Lepeophtheirus salmonis and Moritella viscosa on inflammatory and immune responses of Atlantic salmon (Salmo salar). JOURNAL OF FISH DISEASES 2020; 43:459-473. [PMID: 32100325 DOI: 10.1111/jfd.13144] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 01/16/2020] [Accepted: 01/17/2020] [Indexed: 06/10/2023]
Abstract
This study was conducted to determine the effects of a co-infection with Moritella viscosa at different exposure levels of sea lice Lepeophtheirus salmonis in Atlantic salmon (Salmo salar). M. viscosa (1.14 × 106 cfu/ml) was introduced to all experimental tanks at 10 days post-lice infection (dpLs). Mean lice counts decreased over time in both the medium lice co-infection (31.5 ± 19.0 at 7 dpLs; 16.9 ± 9.3 at 46 dpLs) and high lice co-infection (62.0 ± 10.8 at 7 dpLs; 37.6 ± 11.3 at 46 dpLs). There were significantly higher mortalities and more severe skin lesions in the high lice co-infected group compared to medium lice co-infected group or M. viscosa-only infection. Quantitative gene expression analysis detected a significant upregulation of genes in skin from the high lice co-infection group consistent with severe inflammation (il-8, mmp-9, hep, saa). Skin lesions retrieved throughout the study were positive for M. viscosa growth, but these were rarely located in regions associated with lice. These results suggest that while M. viscosa infection itself may induce skin lesion development in salmon, co-infection with high numbers of lice can enhance this impact and significantly reduce the ability of these lesions to resolve, resulting in increased mortality.
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Affiliation(s)
- Laura A Carvalho
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
| | - Shona K Whyte
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
| | | | - Sara L Purcell
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
| | - Anthony J Manning
- Food Fisheries and Aquaculture Department, The New Brunswick Research and Productivity Council (RPC), Fredericton, NB, Canada
| | - Anne Muckle
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
| | - Mark D Fast
- Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada
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Frisch K, Småge SB, Johansen R, Duesund H, Brevik ØJ, Nylund A. Pathology of experimentally induced mouthrot caused by Tenacibaculum maritimum in Atlantic salmon smolts. PLoS One 2018; 13:e0206951. [PMID: 30383870 PMCID: PMC6211739 DOI: 10.1371/journal.pone.0206951] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 10/22/2018] [Indexed: 11/18/2022] Open
Abstract
Mouthrot, caused by Tenacibaculum maritimum is a significant disease of farmed Atlantic salmon, Salmo salar on the West Coast of North America. Smolts recently transferred into saltwater are the most susceptible and affected fish die with little internal or external clinical signs other than the characteristic small (usually < 5 mm) yellow plaques that are present inside the mouth. The mechanism by which these smolts die is unknown. This study investigated the microscopic pathology (histology and scanning electron microscopy) of bath infected smolts with Western Canadian T. maritimum isolates TmarCan15-1, TmarCan16-1 and TmarCan16-5 and compared the findings to what is seen in a natural outbreak of mouthrot. A real-time RT-PCR assay based on the outer membrane protein A specific for T. maritimum was designed and used to investigate the tissue tropism of the bacteria. The results from this showed that T. maritimum is detectable internally by real-time RT-PCR. This combined with the fact that the bacteria can be isolated from the kidney suggests that T. maritimum becomes systemic. The pathology in the infected smolts is primarily mouth lesions, including damaged tissues surrounding the teeth; the disease is similar to periodontal disease in mammals. The pathological changes are focal, severe, and occur very rapidly with little associated inflammation. Skin lesions are more common in experimentally infected smolts than in natural outbreaks, but this could be an artefact of the challenge dose, handling and tank used during the experiments.
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Affiliation(s)
- Kathleen Frisch
- Cermaq Group AS, Oslo, Norway
- Fish Disease Research Group, Department of Biology, University of Bergen, Bergen, Norway
- * E-mail:
| | - Sverre Bang Småge
- Cermaq Group AS, Oslo, Norway
- Fish Disease Research Group, Department of Biology, University of Bergen, Bergen, Norway
| | | | | | | | - Are Nylund
- Fish Disease Research Group, Department of Biology, University of Bergen, Bergen, Norway
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Karlsen C, Ottem KF, Brevik ØJ, Davey M, Sørum H, Winther-Larsen HC. The environmental and host-associated bacterial microbiota of Arctic seawater-farmed Atlantic salmon with ulcerative disorders. JOURNAL OF FISH DISEASES 2017; 40:1645-1663. [PMID: 28449237 DOI: 10.1111/jfd.12632] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 02/10/2017] [Accepted: 02/12/2017] [Indexed: 06/07/2023]
Abstract
The Norwegian aquaculture of Atlantic salmon (Salmo salar L.) is hampered by ulcerative disorders associated with bacterial infections. Chronic ulceration may provide microenvironments that disturb the normal microbial biodiversity of external surfaces. Studying the composition of microbial communities in skin ulcers will enhance our understanding of ulcer aetiology. To achieve this, we tested marine farmed Atlantic salmon and sampled the base and edge of ulcers at the end of winter (April) and end of summer (September), in addition to skin mucus of healthy individuals. In order to assess microbiota associated with the host and obtain insight into the environmental ecology, we also sampled sea water, the sediment layer underneath the farm facility and the distal intestine of Atlantic salmon. The skin microbiota of Atlantic salmon was different from that of the surrounding water. Residential Tenacibaculum and Arcobacter species persistently dominated the cutaneous skin and ulcer mucus surfaces of Atlantic salmon during both winter and summer periods. The intestinal microbiota was dominated by Mycoplasma with an increase in Aliivibrio and Alcaligenes abundance in the intestine of fish with ulcerative disorder at the end of winter. These findings suggest the presence of resilient microbes in the mucus surfaces of Atlantic salmon.
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Affiliation(s)
- C Karlsen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences (NMBU), Oslo, Norway
- Laboratory for Microbial Dynamics (LaMDa), Department of Pharmaceutical Biosciences, Center of Integrative Microbial Evolution (CIME), School of Pharmacy, University of Oslo, Oslo, Norway
| | | | | | - M Davey
- Department of Biological Sciences, University of Oslo, Oslo, Norway
| | - H Sørum
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences (NMBU), Oslo, Norway
| | - H C Winther-Larsen
- Laboratory for Microbial Dynamics (LaMDa), Department of Pharmaceutical Biosciences, Center of Integrative Microbial Evolution (CIME), School of Pharmacy, University of Oslo, Oslo, Norway
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7
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Host specificity and clade dependent distribution of putative virulence genes in Moritella viscosa. Microb Pathog 2014; 77:53-65. [PMID: 25277600 DOI: 10.1016/j.micpath.2014.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 08/25/2014] [Accepted: 09/11/2014] [Indexed: 12/13/2022]
Abstract
Moritella viscosa is the aetiological agent of winter-ulcer disease in farmed salmonids in the North Atlantic. Previously, two major (typical and variant) genetic clades have been demonstrated within this bacterial species, one of which is almost solely related to disease in Atlantic salmon (Salmo salar). In the present study infection trials demonstrated that 'typical' M. viscosa isolated from Norwegian Atlantic salmon was highly virulent in this fish species but resulted in lower levels of mortality in rainbow trout. 'Variant' M. viscosa isolated from rainbow trout resulted in modest mortality levels in both Atlantic salmon and rainbow trout. To investigate the possible genetic background for inter-strain virulence differences, 38 M. viscosa isolates of diverse geographical origin and host species and a number of other Moritella spp. were investigated for the presence/absence of putative virulence related homologs. All isolates were positive for DNA sequences coding for; the Type VI secretion ATPase (clpV), hemolysin co-regulated protein (hcp), bacterioferritins (bfrA and bfrB), lectin (hemG), phospholipase D (pld), multifunctional autoprocessing repeats-in-toxin (martxA), aerolysin (aer), invasin (inv), and cytotoxic necrotizing factor (cnf), with the exception of one isolate in which cnf could not be confirmed. The product of an ABC transporter metal-binding lipoprotein (mat) was consistently detected although 11 isolates, all phylogenetically related, appear to produce a truncated version. A putative insecticidal toxin complex (mitABC) was detected almost exclusively in 'typical' Atlantic salmon isolates, and our data indicate that this complex of genes is expressed and co-transcribed. Transmission electron microscopy investigation revealed pili and flagella surface structures on nine M. viscosa representing both typical and variant isolates. Our results provide strong support for the existence of host specificity/high virulence in 'typical' M. viscosa related to Atlantic salmon. The gene distribution also provides further support for the genetic division within M. viscosa, and constitutes a basis for further study of the importance of the mitABC complex in winter-ulcer pathogenesis.
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Karlsen C, Vanberg C, Mikkelsen H, Sørum H. Co-infection of Atlantic salmon (Salmo salar), by Moritella viscosa and Aliivibrio wodanis, development of disease and host colonization. Vet Microbiol 2014; 171:112-21. [PMID: 24745624 DOI: 10.1016/j.vetmic.2014.03.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/27/2014] [Accepted: 03/08/2014] [Indexed: 11/19/2022]
Abstract
Two species of bacteria are repeatedly isolated from farmed fish with winter-ulcer disease. Moritella viscosa is the aetiological agent of the disease; the significance of Aliivibrio wodanis is uncertain but has not been related to the primary pathogenesis. A cell culture infection model showed that A. wodanis adhered to, but did not invade the fish cells. Exposure to culture supernatant of A. wodanis caused the fish cells to vacoulate, retract, round up and detach from the surface, and rearrange the actin filaments of the cytoskeleton. These observations suggest that the bacterium secretes toxins into the extracellular environment. Any pathologic effect of A. wodanis and the effect of co-culturing with M. viscosa was studied in Atlantic salmon (Salmo salar) bath challenged with; only M. viscosa or only A. wodanis or both bacteria together. Both M. viscosa and A. wodanis were re-isolated from external surfaces and internal organs from live and deceased co-infected fish. It is further hypothesized that A. wodanis colonization might influence the progression of a M. viscosa infection. This is to our knowledge the first study that reproduces field observations where both bacteria infect Atlantic salmon.
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Affiliation(s)
- Christian Karlsen
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway.
| | - Christin Vanberg
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway
| | | | - Henning Sørum
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway
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Bjornsdottir B, Hjerde E, Bragason BT, Gudmundsdottir T, Willassen NP, Gudmundsdottir BK. Identification of type VI secretion systems in Moritella viscosa. Vet Microbiol 2012; 158:436-42. [PMID: 22425489 DOI: 10.1016/j.vetmic.2012.02.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 02/18/2012] [Accepted: 02/20/2012] [Indexed: 10/28/2022]
Abstract
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.
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Affiliation(s)
- Bryndis Bjornsdottir
- Institute for Experimental Pathology, University of Iceland, Keldur v/Vesturlandsveg, 112 Reykjavik, Iceland
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10
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LitR of Vibrio salmonicida is a salinity-sensitive quorum-sensing regulator of phenotypes involved in host interactions and virulence. Infect Immun 2012; 80:1681-9. [PMID: 22371373 DOI: 10.1128/iai.06038-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio (Aliivibrio) salmonicida is the causal agent of cold-water vibriosis, a fatal bacterial septicemia primarily of farmed salmonid fish. The molecular mechanisms of invasion, colonization, and growth of V. salmonicida in the host are still largely unknown, and few virulence factors have been identified. Quorum sensing (QS) is a cell-to-cell communication system known to regulate virulence and other activities in several bacterial species. The genome of V. salmonicida LFI1238 encodes products presumably involved in several QS systems. In this study, the gene encoding LitR, a homolog of the master regulator of QS in V. fischeri, was deleted. Compared to the parental strain, the litR mutant showed increased motility, adhesion, cell-to-cell aggregation, and biofilm formation. Furthermore, the litR mutant produced less cryptic bioluminescence, whereas production of acylhomoserine lactones was unaffected. Our results also indicate a salinity-sensitive regulation of LitR. Finally, reduced mortality was observed in Atlantic salmon infected with the litR mutant, implying that the fish were more susceptible to infection with the wild type than with the mutant strain. We hypothesize that LitR inhibits biofilm formation and favors planktonic growth, with the latter being more adapted for pathogenesis in the fish host.
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Bjornsdottir B, Gudmundsdottir T, Gudmundsdottir BK. Virulence properties of Moritella viscosa extracellular products. JOURNAL OF FISH DISEASES 2011; 34:333-343. [PMID: 21401642 DOI: 10.1111/j.1365-2761.2011.01246.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Moritella viscosa is the causative agent of winter ulcer disease of marine fish. Knowledge of its pathogenicity is limited and there are no reports comparing the virulence properties of a collection of bacterial isolates. The in vivo and in vitro virulence of the extracellular products (ECP) of 22 M. viscosa isolates was screened. Two non-virulent Canadian isolates and a Norwegian isolate with reduced virulence produced non-lethal ECP. Correlation was obtained between cytotoxin and haemolysin production of M. viscosa. Isolates from salmon produced ECP with lower cytotoxic and haemolytic activities than ECP of isolates originating from other hosts. Correlation was not found between lethality of ECPs in salmon and cytotoxic or haemolytic activities. All isolates secreted esterases and a metallopeptidase (MvP1), degraded starch and produced siderophores. Variable levels of ECP protein concentration, different enzymatic activities and siderophore production could not explain differences in virulence. The results show that virulent M. viscosa isolates secrete a lethal toxic factor of unknown nature and that cytotoxin production may reflect host adaptation. Cell-culture models may not be optimal for determining the virulence of M. viscosa, as no association between cytotoxicity and bacterial virulence was obtained. Non-virulent strains may be useful in future research on M. viscosa virulence, as construction of mutants has not been successful.
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Affiliation(s)
- B Bjornsdottir
- Institute for Experimental Pathology, University of Iceland, Reykjavik, Iceland
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12
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Björnsson H, Marteinsson V, Friðjónsson Ó, Linke D, Benediktsdóttir E. Isolation and characterization of an antigen from the fish pathogen Moritella viscosa. J Appl Microbiol 2011; 111:17-25. [DOI: 10.1111/j.1365-2672.2011.05023.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Tunsjø HS, Wiik-Nielsen CR, Grove S, Skjerve E, Sørum H, L'abée-Lund TM. Putative virulence genes in Moritella viscosa: activity during in vitro inoculation and in vivo infection. Microb Pathog 2011; 50:286-92. [PMID: 21334427 DOI: 10.1016/j.micpath.2011.02.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/27/2011] [Accepted: 02/04/2011] [Indexed: 11/30/2022]
Abstract
Moritella viscosa is considered to be the main aetiological agent of winter ulcer disease, primarily affecting farmed salmonid fish in cold marine waters. Transcription profiles of twelve M. viscosa genes, potentially involved in the pathogenesis, were studied during the course of an in vitro cell culture infection assay. Transcription of the same genes was compared in vivo, in head kidney and ulcer tissues of Atlantic salmon challenged with M. viscosa. During the in vitro infection, three putative toxins: a putative repeats in toxin gene (rtxA), a putative cytotoxic necrotizing factor (cnf) and a putative hemolysin increased their transcription significantly with time and coincident with cell rounding. Furthermore, the majority of the genes were stimulated by presence of fish cells and showed higher activity when adhered to fish cells compared to their planktonic counterpart. In vivo gene transcription studies revealed an up-regulation of a putative lateral flagellin in ulcer compared to head kidney tissues in the same individual. A similar trend was seen for cnf and a gene encoding a putative protease, indicating a role for these factors in colonization and tissue damage.
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Affiliation(s)
- Hege Smith Tunsjø
- Norwegian School of Veterinary Science, Department of Food Safety and Infection Biology, Pb 8146 Dep., 0033 Oslo, Norway
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Duodu S, Colquhoun D. Monitoring the survival of fish-pathogenic Francisella in water microcosms. FEMS Microbiol Ecol 2010; 74:534-41. [PMID: 20977492 DOI: 10.1111/j.1574-6941.2010.00973.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
In this report, the survival behaviour of fish pathogenic Francisella in water microcosms was investigated under laboratory conditions. Two isolates of Francisella noatunensis (NCIMB14265(T) and PQ 1106), from fish held in seawater and freshwater, were inoculated into natural (nonsterile) and sterile sea- and freshwater microcosms, respectively, and monitored under different temperature conditions (4, 8 and 12 °C) over a period of 60 days. The culturability of the strains was inversely related to the water temperature. Strain NCIMB14265(T) was found to survive longer in seawater than PQ 1106 held in freshwater at equivalent temperatures. The survival of both strains was higher in sterile than in nonsterile microcosms. These results were confirmed by quantitative PCR analysis targeting the succinate dehydrogenase (sdhA) gene. A cell viability assay coupled with FISH analyses showed that F. noatunensis cells enter a viable but not culturable (VBNC) state after a period in water. However, although metabolically active, the VBNC cells were not pathogenic to cod (Gadhus morhua) following an intraperitoneal challenge, under the conditions tested. The data presented contribute to a better understanding of the behaviour of F. noatunensis in natural seawater and freshwater environments, and show the need for further investigation of the role of VBNC cells in the environmental transmission of this pathogen.
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Affiliation(s)
- Samuel Duodu
- Section for Fish Health, National Veterinary Institute, Oslo, Norway.
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Abstract
Extremophiles can be defined as organisms that can survive in extreme environments that cannot support mammalian life. They include microorganisms that can tolerate temperature extremes, extremes of pH, salinity, hydrostatic pressure and ionizing radiation, as well as low oxygen tension, desiccation and the presence of heavy metals. Psychrophilic organisms also include fish in polar waters and animals that withstand freezing. Rare examples of thermophilic pathogens exist, and the main category of extremophilic animal pathogens comprises psychrophilic and psychrotrophic microorganisms that cause fish diseases, e.g. Flavobacterium psychrophilum, Moritella viscosa, Aliivibrio wodanis and Aliivibrio salmonicida. The most widely known application of an extremophile product in veterinary medicine is DNA polymerase from thermophiles, which is a mainstay of PCR-based diagnostics for an extensive range of animal pathogens. DNA polymerases and other extremophile enzymes are also used in many molecular biology applications and animal genomics. Other extremophile products may find application in veterinary medicine in the future. These include enzymes in biosensors, compatible solutes in skin care products, drug excipients, treatments for respiratory disease, radioprotectants, peptide antibiotics, archaeal lipids for drug delivery and anti-cancer therapeutics.
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Affiliation(s)
- Jane Ann Irwin
- Veterinary Sciences Centre, UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
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