Beneficial bacteria promise to promote the health and productivity of farmed fish species. However, the impact on host physiology is largely strain-dependent, and studies on Arctic char (Salvelinus alpinus), a commercially farmed salmonid species, are lacking. In this study, 10 candidate probiotic strains were subjected to in vitro assays, small-scale growth trials, and behavioral analysis with juvenile Arctic char to examine the impact of probiotic supplementation on fish growth, behavior and the gut microbiome. Most strains showed high tolerance to gastric juice and fish bile acid, as well as high auto-aggregation activity, which are important probiotic characteristics. However, they neither markedly altered the core gut microbiome, which was dominated by three bacterial species, nor detectably colonized the gut environment after the 4-week probiotic treatment. Despite a lack of long-term colonization, the presence of the bacterial strains showed either beneficial or detrimental effects on the host through growth rate enhancement or reduction, as well as changes in fish motility under confinement. This study offers insights into the effect of bacterial strains on a salmonid host and highlights three strains, Carnobacterium divergensV41, Pediococcus acidilactici ASG16, anti Lactiplantibacillus plantarum ISCAR-07436, for future research into growth promotion of salmonid fish through probiotic supplementation.
The North Atlantic Ocean surrounds Iceland, influencing its climate and hosting a rich ecosystem that provides the Icelandic nation with economically valuable marine species. The basis of the Icelandic marine ecosystem consists of communities of diverse microorganisms including bacteria, archaea, and unicellular eukaryotes. While the primary production of Icelandic waters has been monitored since the 50s, there is limited knowledge of the taxonomic and metabolic diversity of the marine microorganisms in Icelandic waters based on molecular techniques. In this study, we conducted annual sampling at four hydrographic stations over several years to characterize marine microbial communities and their metabolic potential. Using 16S ribosomal RNA gene amplicon sequencing and metagenomics, we resolved the microbial community composition on the North and South Shelves of Iceland, analyzed its evolution from 2011 to 2018, identified frequently occurring taxa, and predicted their potential metabolism. The results showed correlations between the marine microbial community profiles and the water masses in spring, between the North and South Shelves of Iceland. The differences in marine microbial diversity appear to be linked to the average seawater temperature in the mixed surface layer at each sampling station which also constrains the relative abundance of photosynthetic microorganisms. This study set a baseline for the marine microbial diversity in Icelandic marine waters and identified three photosynthetic microorganisms – the cyanobacteria Synechococcus and two members of the Chlorophyta clade – as valuable indicator species for future monitoring, as well as for application in ecosystem modeling in context with research on climate change.
This study assessed the environmental impacts of a pelagic fishmeal and fish oil production plant in Iceland with the life cycle assessment methodology. The study focused on assessing the effects of different energy sources for utility production due to the high energy intensity of fishmeal and fish oil production, as quality improved with lower cooking temperature. The environmental hotspots of three different processing scenarios were assessed, where the factory was run on hydropower (Scenario 0), heavy fuel (Scenario 1) and a composition of both (Scenario 2), from cradle-to-factory gate. Midpoint results showed that the raw material acquisition contributed the most to the environmental impact when the fishmeal factory was operating on hydropower. However, drying had the highest impact when heavy fuel oil was used for utility production. This study also demonstrated that lowering the cooking temperature from 90 to 85 °C, led to improved quality and simultaneously reduced environmental impacts during processing. This indicated that a small energy adjustment in the production can have an environmental gain, demonstrating the necessity to optimize each processing step in the fishmeal and fish oil production process both for increased product quality and minimizing environmental impacts.
In the Norwegian oceanic fleet, whitefish onboard processing creates a great amount of rest raw materials. Cod heads are nutritious and a good source for the production of high-quality marine peptides. Frozen cod heads, captured by trawl or longline, were evaluated based on the lightness and redness in the neck cut to compare the quality in heads from the different fishing gears. The heads were subjected to enzymatic hydrolysis. The hydrolysates have been chemically and sensory characterized. There was no significant difference in quality or chemical and sensory characteristics based on type of fishing gear. The resulting hydrolysates were of high quality, although moderately bitter. The study demonstrates that frozen cod heads from the oceanic fleet can be an excellent source of high-quality proteins for human consumption.
The chemical composition of Calanus finmarchicus was analyzed at 21 stations from three regions where 12 transects were sampled from 0 to 50 m depth, including stage composition analysis at the Siglunes and Selvogsbanki transects in relation to the effects of different water masses, during a survey in Icelandic waters during 11–29 May 2018. The stage composition of C. finmarchicus at the northern transect of Siglunes was mostly made up of copepodites CI–CIII, around 76%, whereas older copepods CV–CVI dominated, around 64%, at the southern transect of Selvogsbanki. The dry weight (dw) and lipid content of C. finmarchicus were overall highest in the southwest (160 ± 60 μg dw ind−1 and 60 ± 20 μg lipids ind−1) and lowest in the east (120 ± 20 μg dw ind−1 and 30 ± 10 μg lipids ind−1). Total astaxanthin content ranges from 0.14 to 0.27 μg mg−1 dw. Chitin made up 2–4% of the dw. The diatom marker C20:5n3 was prolific in the copepods southwest of Iceland, while the dinoflagellate markers C18:4n3 and C22:6n3 dominated in the copepods east of Iceland. The results indicate that C. finmarchicus found in the south of Iceland developed faster than those in the north, with the variation in chemical composition and developmental time highly influenced by hydrographic regions.
Alginate (alginic acid) is a linear polysaccharide, wherein (1→4)-linked β-D-mannuronic acid and its C5 epimer, α-L-guluronic acid, are arranged in varying sequences. Alginate lyases catalyze the depolymerization of alginate, thereby cleaving the (1→4) glycosidic linkages between the monomers by a β-elimination mechanism, to yield unsaturated 4-deoxy-L–erythro-hex-4-enopyranosyluronic acid (Δ) at the non-reducing end of resulting oligosaccharides (α-L–erythro configuration) or, depending on the enzyme, the unsaturated monosaccharide itself. In solution, the released free unsaturated monomer product is further hydrated in a spontaneous (keto-enol tautomerization) process to form two cyclic stereoisomers. In this study, two alginate lyase genes, designated alyRm3 and alyRm4, from the marine thermophilic bacterium Rhodothermus marinus (strain MAT378), were cloned and expressed in Escherichia coli. The recombinant enzymes were characterized, and their substrate specificity and product structures determined. AlyRm3 (PL39) and AlyRm4 (PL17) are among the most thermophilic and thermostable alginate lyases described to date with temperature optimum of activity at ∼75 and 81°C, respectively. The pH optimum of activity of AlyRm3 is ∼5.5 and AlyRm4 at pH 6.5. Detailed NMR analysis of the incubation products demonstrated that AlyRm3 is an endolytic lyase, while AlyRm4 is an exolytic lyase, cleaving monomers from the non-reducing end of oligo/poly-alginates.
We present a structural and functional analysis of the thermophilic DNA polymerase Thermus thermophilus MAT72 phage vB_Tt72. The enzyme shows low sequence identity (<30%) to the members of the type-A family of DNA polymerases, except for two yet uncharacterized DNA polymerases of T. thermophilus phages: φYS40 (91%) and φTMA (90%). The Tt72 polA gene does not complement the Escherichia coli polA- mutant in replicating polA-dependent plasmid replicons. It encodes a 703-aa protein with a predicted molecular weight of 80,490 and an isoelectric point of 5.49. The enzyme contains a nucleotidyltransferase domain and a 3′-5′ exonuclease domain that is engaged in proofreading. Recombinant enzyme with His-tag at the N-terminus was overproduced in E. coli, subsequently purified by immobilized metal affinity chromatography, and biochemically characterized. The enzyme exists in solution in monomeric form and shows optimum activity at pH 8.5, 25 mM KCl, and 0.5 mM Mg2+. Site-directed analysis proved that highly conserved residues D15, E17, D78, D180, and D184 in 3′-5′ exonuclease and D384 and D615 in the nucleotidyltransferase domain are critical for the enzyme's activity. Despite the source of origin, the Tt72 DNA polymerase has not proven to be highly thermoresistant, with a temperature optimum at 55 °C. Above 60 °C, the rapid loss of function follows with no activity > 75 °C. However, during heat treatment (10 min at 75 °C), trehalose, trimethylamine N-oxide, and betaine protected the enzyme against thermal inactivation. A midpoint of thermal denaturation at Tm = 74.6 °C (ΔHcal = 2.05 × 104 cal mol−1) and circular dichroism spectra > 60 °C indicate the enzyme's moderate thermal stability.
Accuracy in reporting captures is a key element to achieve fisheries sustainability. However, identification of the catches might be a challenge when two or more species are morphologically similar and caught jointly, like the mixed fisheries of black hakes in East Atlantic African waters. Black hakes (Merluccius senegalensis and M. puddle) are tough to differentiate without previous training due to their high morphological resemblance. The two species are managed as a single stock, although the biological differences between them suggest the need for a separate management. In this study, a total of 806 black hakes were visually identified by fishermen on deck of fishing vessels operating in Mauritania and Senegal waters, then assigned to a species by sequencing 450bp of the Mitochondrial Control Region. Comparing the results with visual identification we found 31.4% of the total catch were incorrectly labeled on board by the fishermen. The accuracy of the fishermen's identification depended on the depth of capture and on fish size, larger individuals caught from deeper waters being more correctly assigned to M. puddle. Mislabelling biased to M. puddle suggests that M. senegalensis, already cataloged as endangered, is being underreported, which could endanger the conservation of this species and threaten the sustainability of black hake fisheries. Our results highlight the need for separate evaluation of the stocks in mixed fisheries for morphologically similar fish. Thus, monitoring through DNA barcoding in the very first step of the seafood chain surveys would improve accurate species delimitation and reduce its impact on the correct assessment of the stocks.
Background/objectives: Malnutrition is common among older adults. Dietary intervention studies in older adults aiming to improve anthropometric measures and physical function have been inconsistent. We aimed to investigate the effects of nutrition therapy in combination with home delivered meals and oral nutritional supplements (ONS) in community-dwelling older adults discharged from hospital.
Methods: A total of 106 participants (>65 years) were randomized into the intervention group (n = 53) and into the control group (n = 53). The intervention group received individual nutrition therapy (five in person visits and three phone calls) and freely delivered energy- and protein-rich foods, while the control group received standard care. Dietary intake, anthropometrics, and short physical performance battery (SPPB) were assessed at baseline and at endpoint.
Results: Energy intake at baseline was similar in both groups (~1500 kcal at the hospital) but there was a significant increase in energy intake and body weight in the intervention group (+919 kcal/day and 1.7 kg, P < 0.001 in both cases) during the study period, compared to a significant decrease in both measures among controls (-815 kcal/day and -3.5 kg, P < 0.001 in both cases). SPPB score increased significantly in the intervention group while no changes were observed among controls.
Conclusions: Most Icelandic older adults experience substantial weight loss after hospital discharge when receiving current standard care. However, a 6-month multi-component nutrition therapy, provided by a clinical nutritionist in combination with freely delivered supplemental energy- and protein-dense foods has beneficial effects on body weight, physical function, and nutritional status.
Study registration: This study was registered at ClinicalTrials.gov ( NCT03995303 ).
The island of Surtsey was formed in 1963–1967 on the offshore Icelandic volcanic rift zone. It offers a unique opportunity to study the subsurface biosphere in newly formed oceanic crust and an associated hydrothermal-seawater system, whose maximum temperature is currently above 120 ° C at about 100m below surface. Here, we present new insights into the diversity, distribution, and abundance of microorganisms in the subsurface of the island, 50years after its creation. Samples, including basaltic tuff drill cores and associated fluids acquired at successive depths as well as surface fumes from fumaroles, were collected during expedition 5059 of the International Continental Scientific Drilling Program specifically designed to collect microbiological samples. Results of this microbial survey are investigated with 16S rRNA gene amplicon sequencing and scanning electron microscopy. To distinguish endemic microbial taxa of subsurface rocks from potential contaminants present in the drilling fluid, we use both methodological and computational strategies. Our 16S rRNA gene analysis results expose diverse and distinct microbial communities in the drill cores and the borehole fluid samples, which harbor thermophiles in high abundance. Whereas some taxonomic lineages detected across these habitats remain uncharacterized (eg, Acetothermiia, Ammonifexales), our results highlight potential residents of the subsurface that could be identified at lower taxonomic rank such as Thermaerobacter, BRH-c8a (Desulfallas-Sporotomaculum), Thioalkalimicrobium, and Sulfurospirillum. Microscopy images reveal possible biotic structures attached to the basaltic substrate. Finally, microbial colonization of the newly formed basaltic crust and the metabolic potential are discussed on the basis of the data.