Symbiotic associations in the phenotypically-diverse brown alga Saccharina japonica

The brown alga Saccharina japonica (Areschoug) Lane, Mayes, Druehl et Saunders is a highly polymorphic representative of the family Laminariaceae, inhabiting the northwest Pacific region. We have obtained 16S rRNA sequence data in symbiont microorganisms of the typical form (TYP) of S. japonica and its common morphological varieties, known as "longipes" (LON) and "shallow-water" (SHA), which show contrasting bathymetric distribution and sharp morphological, life history traits, and ecological differences. Phylogenetic analysis of the 16S rRNA sequences shows that the microbial communities are significantly different in the three forms studied and consist of mosaic sets of common and form-specific bacterial lineages. The divergence in bacterial composition is substantial between the TYP and LON forms in spite of their high genetic similarity. The symbiont distribution in the S. japonica forms and in three other laminarialean species is not related to the depth or locality of the algae settlements. Combined with our previous results on symbiont associations in sea urchins and taking into account the highly specific character of bacteria-algae associations, we propose that the TYP and LON forms may represent incipient species passing through initial steps of reproductive isolation. We suggest that phenotype differences between genetically similar forms may be caused by host-symbiont interactions that may be a general feature of evolution in algae and other eukaryote organisms. Bacterial symbionts could serve as sensitive markers to distinguish genetically similar algae forms and also as possible growth-promoting inductors to increase algae productivity.     

Seasonal changes in the content of lipids and photosynthetic pigments in a brown alga Saccharina cichorioides

Seasonal changes in the contents of lipids and photosynthetic pigments (PSP) were investigated in a brown alga Saccharina cichorioides Miyabe (Phaeophyceae, the family Laminariaceae). The content of lipids varied from 0.27 to 0.60% of the algal fresh weight. The content of glyceroglycolipids (GL) was much greater in the time of spore formation (June–July and September–October), phospholipids — in the spring and in September–October, and the content of neutral lipids — in the spring and in November. In the period of spore release (August and October), the level of GL and polyunsaturated fatty acids (PUFA) sharply decreased. A high level of PUFA was observed from March to July and in November. In August and October, the same as in the spring, the proportion of saturated fatty acids (FA) was great. The content of chlorophylls from March to November varied from 20.3 to 26.9%, and the level of carotenoids — from 10.7 to 16.1%. Total content of PSP was relatively high in March and in August–September. Free sterols accounted for 3.4–7.3% of total lipids; their proportion was greater in spring than in summer and autumn.     

Characterization of a type III polyketide synthase (sjPKS1) gene and its expression in response to light in the economic brown alga Saccharina japonica

Journal of Applied Phycology - Phlorotannins are among the most important defensive molecules in kelp. They have been majorly identified in brown algae so far. Type III polyketide synthase (PKS) is...     

Thermotropic behaviour of membrane lipids from brown marine alga Laminaria japonica

Microcalorimetry was used to show that transition-temperature ranges of phospho- and glycolipids of the brown marine alga Laminaria japonica were similar (from -62 to -47 degrees C up to 62-65 degrees C), except for monogalactosyldiacylglycerol, the low-temperature limit of which was shifted to -78 degrees C. As was shown by polarizing microscopy, the low-enthalpy peaks at temperatures of approx. 30-45 degrees C corresponded to isotropic melting of galactolipids and coincided with the high-temperature limit for photosynthetic and mitochondrial activity of the algae. As a whole, a classical interrelation was observed between thermotropic behaviour and the fatty acid unsaturation of lipids.     

Seasonal variation in the antifouling defence of the temperate brown alga Fucus vesiculosus

The important role of marine epibiotic biofilms in the interactions of the host with its environment has been acknowledged recently. Previous studies with the temperate brown macroalga Fucus vesiculosus have identified polar and non-polar compounds recovered from the algal surface that have the potential to control such biofilms. Furthermore, both the fouling pressure and the composition of the epibiotic bacterial communities on this macroalga varied seasonally. The extent to which this reflects a seasonal fluctuation of the fouling control mechanisms of the host is, however, unexplored in an ecological context. The present study investigated seasonal variation in the anti-settlement activity of surface extracts of F. vesiculosus against eight biofilm-forming bacteria isolated from rockweed-dominated habitats, including replication of two populations from two geographically distant sites. The anti-settlement activity at both sites was found to vary temporally, reaching a peak in summer/autumn. Anti-settlement activity also showed a consistent and strong difference between sites throughout the year. This study is the first to report temporal variation of antifouling defence originating from ecologically relevant surface-associated compounds.     

Effect of subcritical water hydrolysate in the brown seaweed Saccharina japonica as a potential antibacterial agent on food-borne pathogens

Seaweeds are rich in bioactive compounds which have well-documented antioxidant properties. They also have antimicrobial activities against food pathogenic microorganisms. This study uses an extract of the brown seaweed, Saccharina (Laminaria) japonica, produced by subcritical water hydrolysis (SWH) for investigating its potential to inhibit bacteria. De-oiled S. japonica was obtained by supercritical carbon dioxide extraction. The reaction temperatures for hydrolysis of raw and de-oiled S. japonica were maintained from 200 to 280 °C. The experiment was done with condition 1.3–6.0 MPa for the reaction pressure and 1:10 (w/v) for the ratio of material to water. The antibacterial activities of raw and de-oiled S. japonica produced by SWH were determined by using the agar diffusion method. Antibacterial activity was tested against two Gram-negative (Escherichia coli and Salmonella typhimurium) and two Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus). The antibacterial activities of hydrolysate water with catalyst at 240 °C showed better bacterial inhibition than the others. Strong antibacterial activity was found using de-oiled material with acetic acid added, with a zone of inhibition of S. typhimurium (14.33?±?0.06 mm) and E. coli (13.00?±?0.09 mm). On the other hand, the weakest antibacterial inhibition was found for S. aureus (12.83?±?0.10 mm) and B. cereus (12.50?±?0.09 mm).     

Antioxidant activity of brown alga Saccharina bongardiana from Kamchatka (Pacific coast of Russia). A methodological approach

The present study aims to investigate the levels of polyphenols and antioxidant activity in one of the most important commercial species of seaweeds in Kamchatka, an edible brown seaweed Saccharina bongardiana. Six extracts of S. bongardiana, acetone, methanol, ethanol, and the respective 70 % aqueous solutions, were assessed for total phenol content in order to determine the most efficient extracting solvent. The total phenol content was measured by the Folin–Ciocalteu method and expressed as phloroglucinol equivalents (PGE). The antioxidant tests used were 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, linoleic acid-β carotene oxidation inhibiting assay, and Fe²⁺ ion chelating method. Higher phenolic contents were obtained using aqueous organic solvents, as compared to the respective absolute solvents; 70 % acetone was found to be the most efficient solvent (1.039 mg PGE 100 mg^?1 dry algal powder). High significant correlations were noted between total phenol content and the tested antioxidant activities; so the aqueous organic extracts exhibited the highest antioxidant activities versus DPPH radicals (EC₅₀ values of 0.6–1.1 mg dry weight (DW) mL^?1), linoleic acid-β carotene oxidation (74–78 % at 0.8 mg DW mL^?1), as well as ferrous ions (EC₅₀ values of 5.0–7.9 mg DW mL^?1). Some methodological recommendations regarding the assays used and the expression of results are proposed.     

Effect of temperature on the development of Saccharina japonica gametophytes

Spores (collected at 10?±?1 °C, 2 h after releasing) and young gametophytes (newly generated from spores cultured at 10?±?1 °C for 8 days) of Saccharina japonica were first cultured at 15?±?1, 19?±?1, and 23?±?1 °C for various times (2, 5, and 8 days) and then at 10?±?1 °C (culturing patterns S and G, respectively). Spores were also cultured at a constant of 10?±?1 °C (pattern C) and used as the control. The length and percentage of young gametophytes, size and percentage of gametophytes, and ratio of female to male gametophytes were measured in order to determine the effect of temperature on the development of gametophytes. Temperature and exposure time of spores and young gametophytes at the first culturing temperature significantly affected the development of gametophytes as were indicated by all biological parameters except the ratio of female to male gametophytes. The spores were more sensitive to temperature than young gametophytes. Gametophytes developed from the spores that survived temperature stress can recover their growth. High temperature selection at the early developmental stages of gametophytes was effective for screening gametophytes applicable for breeding high temperature-resistant varieties and hybrids.     

Structural characteristics and biological activity of Fucoidans from the brown algae Alaria sp. and Saccharina japonica of different reproductive status

Structural characteristics and the antitumor activity of fucoidans isolated from vegetative and reproductive tissue of the brown algae Alaria sp. and Saccharina japonica were studied. The reproductive status of the brown algae affected the yield of fucoidans and their structural characteristics. The fucoidan yield was 5.7% (w/w on the basis of the dried algae weight) for fertile and 3.8% for sterile Alaria sp. and 1.42 and 0.71% for fertile and sterile S. japonica, respectively. The fucoidans from fertile Alaria sp. and S. japonica had a slightly higher degree of sulfation and a somewhat more homogeneous monosaccharide composition, with predominate amounts of fucose and galactose, than those isolated from sterile algae tissue. The fucoidans from both the sterile and fertile brown algae tissue tested possessed selective cytotoxicity towards human breast cancer (T-47D) and melanoma (RPMI-7951) cell lines, but not to normal mouse epidermal cells (JB6 Cl41), and effectively inhibited the proliferation and colony formation of the breast cancer and melanoma cell lines. The fucoidans from reproductive tissue of brown algae possessed higher antitumor activity than those from vegetative plants.     

Sulfated polysaccharides from brown seaweeds Saccharina japonica and Undaria pinnatifida: isolation, structural characteristics, and antitumor activity

During the last decade brown seaweeds attracted much attention as a source of polysaccharides, namely laminarans, alginic acids, and sulfated polysaccharides—fucoidans, with various structures and biological activities.In this study, sulfated polysaccharides were isolated from brown seaweeds Saccharina japonica (formerly named Laminaria) and Undaria pinnatifida and their antitumor activity was tested against human breast cancer T-47D and melanoma SK-MEL-28 cell lines.The sulfated polysaccharide form S. japonica was highly branched partially acetylated sulfated galactofucan, built up of (1→3)-α-l-fucose residues. The sulfated polysaccharide from U. pinnatifida was partially acetylated highly sulfated galactofucan consisting of (1→3)- or (1→3);(1→4)-α-l-fucose residues.Fucoidans from S. japonica and U. pinnatifida distinctly inhibited proliferation and colony formation in both breast cancer and melanoma cell lines in a dose-dependent manner. These results indicated that the use of sulfated polysaccharides from brown seaweeds S. japonica and U. pinnatifida might be a potential approach for cancer treatment.     

Structural variation in the brown alga Sargassum cymosum and its effects on associated amphipod assemblages.

The presence of diverse biological substrates adds complexity to coastal landscapes and increases the number of ecological niches that can be used by the mobile epifauna. Studies on the influence of structural complexity have focused mainly on algal host species, but there is little information about the influence of intraspecific structural variation on the associated mobile epifauna. In this work, we examined whether intraspecific variation in the brown alga Sargassum cymosum influenced the structure of amphipod assemblages on two shores with different wave exposure. At least 15 fronds were randomly sampled at Fortaleza and Perequê-Mirim beaches, on the Atlantic coast of S?o Paulo state, southeastern Brazil, and 12 variables were measured for each alga. The amphipods were identified and counted. The greatest structural variation in S. cymosum occurred within shores, whereas the differences between shores were mainly related to algal size. These characteristics influenced amphipod assemblages differently on each shore, with the greatest effects being associated with variables related to morphological complexity, such as holdfast size, the number and size of branches, and the extent of cover by sessile colonial animals. These findings show that monospecific algal banks are not homogeneous, and that morphological differences and interactions with other biological substrates can influence the mobile epifaunal assemblages.     

Depth-related variation in epiphytic communities growing on the brown alga Lobophora variegata in a Caribbean coral reef

Lobophora variegata is a dominant macroalga on coral reefs across the Caribbean. Over the last two decades, it has expanded its vertical distribution to both shallow and deep reefs along the leeward coast of the island of Cura?ao, Southern Caribbean. However, the ecological implications of this expansion and the role of L. variegata as a living substratum are poorly known. This study compared epiphytic algal communities on L. variegata blades along two depth transects (6?C40?m). The epiphytic community was diverse with a total of 70 species of which 49 were found directly attached to L. variegata. The epiphytic community varied significantly between blade surface, depth and site. The greatest number of genera per blade was found growing on the underside of the blades regardless of site and depth. Filamentous red algae (e.g. Neosiphonia howei) were commonly found on the upperside of the blades over the whole depth gradient, whereas the underside was mainly colonized by calcifying (e.g. Hydrolithon spp., Jania spp., Amphiroa fragillissima), fleshy red algae (e.g. Champia spp., Gelidiopsis spp., Hypnea spinella) and foliose brown alga (e.g. Dictyota spp.). Anotrichum tenue, a red alga capable of overgrowing corals, was a common epiphyte of both blade surfaces. L. variegata plays an important role as a newly available substratum. Thus, its spread may influence other algal species and studies of benthic macroalgae such as L. variegata should also take into consideration their associated epiphytic algal communities.     

Lipids from the brown alga Cystoseira barbata

Two new diunsaturated lipids, related to palmitic acid, were isolated from the brown alga Cystoseira barbata, one of which is toxic to mice during P388 lymphocytic leukemia tests.     

Trihydroxyphlorethols from the brown alga Carpophyllum angustifolium

The structural elucidation of four phloroglucinol derivatives isolated from the ethanolic extract of the brown alga Carpophyllum angustifolium after peracetylation is described. Three of them, trihydroxyheptaphlorethol-A octadecaacetate, trihydroxyoctaphlorethol-A eicosaacetate and trihydroxyoctaphlorethol-B eicosaacetate, are described for the first time. Characterized by three additional hydroxyl groups and two 1,2-diphenoxylated 3,4,5-triacetoxybenzene rings directly linked by an ether bond they are called trihydroxyphlorethols as a novel group of phlorotannins. The structural elucidation was carried out on the basis of spectral data.     

Tetraprenyltoluquinols from the brown alga Cystoseira stricta

Four novel metabolites of mixed biogenesis have been isolated from the brown alga Cystoseira stricta and their structures determined by chemical and spectral methods.     

Diterpenes from the brown alga Dictyota mertensii

Here we report the variation of diterpenes from three populations of the brown alga Dictyota mertensii. The populations were analyzed by ¹H NMR and GC-MS techniques. Both chemical GC-MS and ¹H NMR profiles of D. mertensii presented diterpenes as major constituents. In all populations, we detected the prenylated guaiane diterpenes, dictyoxide, pachydictyol A, isopachydictyol A, dictyol B and its acetate, and dictyol C. Although dictyol H has been described as a taxonomic marker, this diterpene was found in only two of the three studied populations. This result reinforces the need for studies of temporal and geographic variation for the establishment of the taxonomic limits of the species chemical patterns. It was also possible to observe mass spectra fragmentation and proton chemical shift in the NMR spectra characteristic from xeniane diterpenes, for the first time in this species, which led to the detection of dictyodial, suggesting that D. mertensii belongs to the chemotaxonomic group of species D. ciliolata, D. jamaicensis, and D. menstrualis, all of which are producers of diterpene from chemical groups I and III.     

Tetraprenyltoluquinols from the brown alga Cystophora fibrosa

Six cyclised tetraprenyltoluquinols and five stereoisomers with the previously reported amentol skeleton have been isolated from the lipophilic extract of the South African brown alga Cystophora fibrosa. Structures and relative stereochemistry were determined using spectrometric techniques, particularly 1D and 2D NMR, and molecular modelling experiments. The compounds isolated appear to be enantiomeric to compounds with the same skeleton isolated from brown algae of the genus Cystoseira collected in northern Africa and the Mediterranean Sea. The isolation of tetraprenyltoluquinols with the amentol skeleton from this alga suggests that C. fibrosa should be moved from the genus Cystophora into the Cystoseira.