Prochlorococcus and Synechococcus are the two most abundant and widespread phytoplankton in the global ocean. To better understand the factors controlling their biogeography, a reference database of the high-resolution taxonomic marker petB, encoding cytochrome b6, was used to recruit reads out of 109 metagenomes from the Tara Oceans expedition. An unsuspected novel genetic diversity was unveiled within both genera, even for the most abundant and well-characterized clades, and 136 divergent petB sequences were successfully assembled from metagenomic reads, significantly enriching the reference database. We then defined Ecologically Significant Taxonomic Units (ESTUs) —that is, organisms belonging to the same clade and occupying a common oceanic niche. Three major ESTU assemblages were identified along the cruise transect for Prochlorococcus and eight for Synechococcus. Although Prochlorococcus HLIIIA and HLIVA ESTUs codominated in iron-depleted areas of the Pacific Ocean, CRD1 and the yet-to-be cultured EnvB were the prevalent Synechococcus clades in this area, with three different CRD1 and EnvB ESTUs occupying distinct ecological niches with regard to iron availability and temperature. Sharp community shifts were also observed over short geographic distances — for example, around the Marquesas Islands or between southern Indian and Atlantic Oceans — pointing to a tight correlation between ESTU assemblages and specific physico-chemical parameters. Together, this study demonstrates that there is a previously overlooked, ecologically meaningful, fine-scale diversity within some currently defined picocyanobacterial ecotypes, bringing novel insights into the ecology, diversity, and biology of the two most abundant phototrophs on Earth.
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A total diet study (TDS) is a public health tool for determining population dietary exposure to chemicals across the entire diet. TDSs have been performed in several countries but the comparability of data produced is limited. Harmonization of the TDS methodology is therefore desirable and the development of comparable TDS food lists is considered essential to achieve the consistency between countries. The aim of this study is to develop and test the feasibility of a method for establishing harmonized TDS food and sample lists in five European countries with different consumption patterns (Czech Republic, Finland, Germany, Iceland and Portugal). The food lists were intended to be applicable for exposure assessment of wide range of chemical substances in adults (18–64 years) and the elderly (65–74 years). Food consumption data from recent dietary surveys measured on individuals served as the basis for this work. Since the national data from these five countries were not comparable, all foods were linked to the EFSA FoodEx2 classification and description system. The selection of foods for TDS was based on the weight of food consumed and was carried out separately for each FoodEx2 level 1 food group. Individual food approach was respected as much as possible when the TDS samples were defined. TDS food lists developed with this approach represented 94.7–98.7% of the national total diet weights. The overall number of TDS samples varied from 128 in Finland to 246 in Germany. The suggested method was successfully implemented in all five countries. Mapping of data to the EFSA FoodEx2 coding system was recognized as a crucial step in harmonization of the developed TDS food lists.
Recently, we have shown that glycoside hydrolases enzymes of family GH17 from proteobacteria (genera Pseudomonas, Azotobacter) catalyze elongation transfer reactions with laminari-oligosaccharides generating (β1 → 3) linkages preferably and to a lesser extent (β1 → 6) or (β1 → 4) linkages. In the present study, the cloning and characterization of the gene encoding the structurally very similar GH17 domain of the NdvB enzyme from Bradyrhizobium diazoefficiens, designated Glt20, as well as its catalytic properties are described. The Glt20 enzyme was strikingly different from the previously investigated bacterial GH17 enzymes, both regarding substrate specificity and product formation. The Azotobacter and Pseudomonas enzymes cleaved the donor laminari oligosaccharide substrates three or four moieties from the non-reducing end, generating linear oligosaccharides. In contrast, the Glt20 enzyme cleaved donor laminari-oligosaccharide substrates two glucose moieties from the reducing end, releasing laminaribiose and transferring the remainder to laminari-oligosaccharide acceptor substrates creating only (β1 → 3) (β1 → 6) branching points. This enables Glt20 to transfer larger oligosaccharide chains than the other type of bacterial enzymes previously described, and helps explain the biologically significant formation of cyclic β-glucans in B. diazoefficiency.
In land-based fish farms, water quality can be controlled to support maximum growth and good feed conversion. Oxygen is an important water quality parameter in aquaculture and the objective of this study was to detect the range of oxygen saturations that maximizes juvenile growth Atlantic cod. The fish (initial body mass 21.9 g) were reared at five different levels of oxygen saturation: 65%, 81%, 103%, 121% and 150% of air saturation, for 98 days. At oxygen saturation under 100%, the growth of the fish decreased linearly with progressively lower oxygen saturation with the final body mass of fish reared at 65% saturation being 24% lower than that of fish reared at 103% saturation. The final body mass of fish reared at 150% saturation was significantly higher (7%) than that of fish reared at 103% saturation. Feed intake was also affected by oxygen saturation and was proportional to growth while the feed conversion ratio was not significantly affected by oxygen levels. The results suggest that oxygen saturation of at least 100% is required to obtain maximum growth of juvenile Atlantic cod.
In this study, a changepoint model, which can detect either a mean shift or a trend change when accounting for autocorrelation in short time-series, was investigated with simulations and a new method is proposed. The changepoint hypotheses were tested using a likelihood ratio test. The test statistic does not follow a known distribution and depends on the length of the time-series and the autocorrelation. The results imply that it is not possible to detect autocorrelation and that the estimate of the autocorrelation parameter is biased. It is therefore recommended to use critical values from the empirical distribution for a fixed autocorrelation.
Atlantic sea cucumber (Cucumaria frondosa) is a marine invertebrate that occurs naturally in the North Atlantic. Its collagen rich body walls make the sea cucumber an appreciated food source in many countries. The heteroglycans derived from the cartilage of Atlantic sea cucumbers have shown potential as a source of bioactive compounds, but further investigation is needed to confirm this hypothesis. The objectives of this work were to test the immunomodulating properties of heteroglycan fractions (FCFs) derived from Atlantic sea cucumbers toward phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 macrophages. Oxygen Radical Absorbance Capacity (ORAC) was determined and cell culture media was collected and analyzed for the presence of pro-inflammatory and anti-inflammatory cytokines (TNF-α, IL-6, and IL-10). FCFs toxicity toward macrophages was evaluated by light microscopy and confirmed by XTT proliferation assay. Heteroglycans derived from cartilage of Atlantic sea cucumber showed immunomodulatory activity in THP-1 macrophages. FCF-1, −2, and - 3) at concentrations 0.1–100 µg / mL induced levels of TNF-α, IL-6, and IL-10 proofing their bioactivity towards THP-1 macrophages. However, fractions of FCF-1 and FCF-2 may have induced oxidative stress in the macrophages, which possibly could lead to decreased cellular viability.
This study utilized Life Cycle Assessment (LCA) to quantify the environmental impacts of 1 kg of live-weight Arctic char, cultivated in an Icelandic land-based aquaculture farm. The functional unit included assessments of three different feed types; standard feed with high inclusion levels of marine ingredients (Conv.), experimental feed with high inclusion levels of agricultural ingredients (ECO) and a hypothetical Black soldier fly larvae based feed (BSF). Results of the study indicated that the feed production causes the greatest environmental impacts from all feed types considered. The Black soldier fly based feed demonstrated the best environmental performance of the three feed types. Furthermore, it can be concluded that by increasing agriculture based ingredients at the cost of marine based ingredients, a better environmental performance can be reached. This study demonstrated the importance of feed production for aquaculture in terms of environmental impacts and showed that byoptimizing feed consumption, reducing the amount of fishmeal and fish oil and even creating new types of feed from novel ingredients, the overall impacts of aquaculture can be greatly reduced .
The thermophile Rhodothermus marinus produces extracellular polysaccharides (EPSs) that forms a distinct cellular capsule. Here, the first data on EPS production in strains DSM4252T and MAT493 are reported and compared. Cultures of both strains, supplemented with either glucose, sucrose, lactose or maltose showed that the EPS were produced both in the exponential and stationary growth phase and that production in the exponential phase was boosted by maltose supplementation, while stationary phase production was boosted by lactose . The latter was higher, resulting in 8.8 (DSM4252T) and 13.7 mg EPS / g cell dry weight (MAT493) in cultures in marine broth supplemented with 10 g / L lactose. The EPSs were heteropolymeric with an average molecular weight of 8 × 104 Da and different monosaccharides, including arabinose and xylose. FT-IR spectroscopy revealed presence of hydroxyl, carboxyl, N-acetyl, amine, and sulfate ester groups, showing that R. marinus produces unusual sulfated EPS with high arabinose and xylose content.
Interruption of a temperature-controlled cold-chain, is a common problem during transportation and storage of food. The objective of the study was to investigate stability of Atlantic mackerel as subjected to temperature abuse (−12 ° C for 1 month) followed by storage at a constant temperature (−25 ° C) for 9 months, and compared to stable storage (- 25 ° C). Diversity in composition of the raw material as affected by feeding state was investigated. Evaluation of quality attributes (gaping, peritoneum) was performed, as well as lipid hydroperoxide, thiobarbituric reactive substances, and free fatty acids. The temperature abuse resulted in increased gap and peritoneum deterioration, lipid degradation compared to fish stored at a constant temperature. Results indicated that fish caught in July has a higher amount of polyunsaturated and saturated fatty acids, but less monounsaturated fatty acids than fish caught in September. Therefore, fish from September was more prone to degradation during storage than fish caught in July.
The aim of this study was to investigate the effects of ambient temperatures (9, 16, 21 ° C) and holding time (0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 h) on rate and quantity of temperature changes and drip losses for whitefish fillets. Different types of fillets were used for the experiment, fresh deepwater redfish (Sebastes mentella) fillets (105 g) and two sizes of saithe (Pollachius virens) fillets (289 g and 634 g). The fillet temperature increased with time, and more rapidly at higher ambient temperatures, particularly with smaller sized fillets. Similarly, the rate and quantity of drip formation were affected by all experimental factors. The effects decreased (p <0.05) in the following order: holding time> type of fillets> ambient temperature. The rate of changes in both temperature and drip loss were greater during the first hour of holding but leveled off with longer holding time. Results indicated that time-temperature abuse, even during relatively short (<1 h) exposure of fillets, may lead to significant economic losses due to weight reduction of the products.