Red macroalgae (Phylum Rhodophyta) are considered to be an important source of biologically active metabolites; their use as functional feed ingredients in fish diets can increase disease resistance ...and animal growth. Furthermore, red macroalgae can be cultured in a sustainable and environmentally friendly manner. We evaluate the potential antiviral activity against the infectious salmon anemia (ISA) virus of Chilean red macroalgae as a sustainable feed additive in the Atlantic salmon (Salmo salar) diet. Lyophilized Chilean red macroalgae concentrates were elaborated and added to a commercial diet. Diets were prepared with 0.1, 1.0, and 10.0 % of Gracilaria chilensis and Pyropia columbina separately, and 0.1 and 1.0 % of a mix of both species in a 1:1 ratio. The diets were fed to S. salar over a period of 2 months. We collected data on production parameters and blood samples. The serum and its constituents were challenged with the ISA virus in the presence of Atlantic salmon kidney cells and tested ex vivo for antiviral capacity using a plaque reduction neutralization assay. Fish fed a diet containing 10 % G. chilensis showed a significantly higher specific growth rate compared with fish fed the control diet. The feed conversion ratio was not significantly affected by treatments. Sera from fish fed the algae diets showed a significant increase in antiviral activity against the ISA virus compared with sera of fish fed the control diet that did not include red macroalgae. Diets including G. chilensis (1.0 and 10 %) exhibited the largest increase in antiviral activity.
Saccharophagus degradans 2-40 is capable of hydrolyzing agarose, a red macroalgae-derived polymer, into
d-galactose and 3,6-anhydro-
l-galactose (L-AHG). Its agarase system is receiving much ...attention because it can be used to produce fermentable sugar from agarose. L-AHG is commercially unavailable and is considered a rare sugar with a high value. In this study, cells grown on agarose, agar or red macroalgae biomass were found to have a significantly higher agarase activity and AHG-generating activity than those grown on glucose or galactose. From agar-grown cells, both the volumetric activities of agarases and AHG generation in the cell-free lysate were much higher than in the extracellular fraction. Based on the analyses of the enzyme reaction products, from the reaction with the crude enzymes from cell-free lysate, neoagarobiose with a degree of polymerization (DP) 2 appeared to be the only major product in the initial reaction period, but sugars with DPs 2, 4 and 6 were found to be all predominantly produced by the extracellular enzymes in the initial reaction period. Quantitative analysis of AHG using gas chromatography–mass spectrometry with a derivatization step was also found to be highly reproducible and reliable. These results will be useful for producing L-AHG as a rare sugar to investigate its metabolic fate and commercial utilization.
Despite an increasing potential of red algal biomass as a feedstock, biological conversion of red algal biomass has been limited by lack of feasible microorganisms which can convert structured AHG, ...which is a main component of red algal carbohydrate, into a common metabolite. In the AHG uptake pathway, AHG dehydrogenase (AHGD) is known to be a key step, therefore it is important to find an efficient dehydrogenase to break down 3,6- anhydro-L-galactose (AHG) for practical use of red macroalgae biomass in biorefineries requires. In this study, we isolate a novel AHG dehydrogenase (AHGD) with high activity produced by a newly isolated bacteria strain,
Raoultella ornithinolytica
B6–JMP12. The stability and compatibility of the enzyme were evaluated under various conditions to achieve high enzyme production. The AHGD was partially purified using conventional protein purification techniques such as ammonium sulfate precipitation and ion exchange followed by gel filtration chromatography, 37.24 fold with a final specific activity of 5.47 U/mg of protein with 32% yield recovery. SDS-PAGE was used to determine the molecular weight of the partially purified AHGD and its molecular weight was found to be around ~34 kDa. The optimal pH and temperature for the partially purified AHGD were 7.0 and 35°C, respectively. The
K
m
and
V
max
for 3,6-anhydro-L-galactose are 0.63 mg/mL and 0.38 μM/mL/min, respectively.
SUMMARY
The aim of this study was to analyze the photosynthetic performance of gametophytic and sporophytic (‘Chantransia’) stages of Kumanoa ambigua in culture under UV radiation. We hypothesized ...that both life history stages of K. ambigua would exhibit different photosynthetic responses to UVR exposure. Experiments were performed under three conditions: (i) photosynthetically active radiation (PAR) only (400–700 nm), P control; (ii) PAR + UVA (320–700 nm), PA treatment; and (iii) PAR + UVA + UVB (280–700 nm), PAB treatment. The photosynthetic parameters were measured as in vivo chlorophyll a fluorescence. Differences were found between life stages, observing higher values of NPQ and effective quantum yields (ΔF/Fm′) under UVA and PAR in gametophytes compared to sporophytes. One type of mycosporine‐like amino acid (MAA) was detected in the gametophyte in all treatments, but not in the ‘Chantransia’ stage. The increased photosynthetic performance for some parameters and the presence of MAA in gametophyte suggest that it is less sensitive to UV radiation, particularly UVA, in comparison to sporophyte under culture conditions. This approach is relevant for a better understanding of the adaptation and physiological acclimation of freshwater Rhodophyta to varying light climates in terms of global changes.
► We studied 24 red macroalgae on their mechanisms uptake carbon from different habitats. ► 60% of them have the “proton pump” mechanism inhibited by TRIS buffer. ► These algae are surface-living and ...characterized by high-light tolerance. ► One mechanism is induced by TRIS for the case of other algae. ► These algae are deep-living and low light-tolerance.
The effects on photosynthesis of acetazolamide (AZ, an inhibitor of the external carbonic anhydrase) and TRIS buffer at pH 8.7 were assessed in 24 species of red macroalgae. Only
Palmaria palmata was unaffected by both substances. The rest of species were classified into three groups according to their sensitivity to TRIS and AZ. Photosynthesis of fourteen species was significantly inhibited by both TRIS and AZ. Inhibition by TRIS varied from almost 100% to 25% while AZ produced similar effects. Inhibition by TRIS was completely reverted by increasing the dissolved inorganic carbon concentration (DIC). This species group had half-saturation constants for photosynthesis (
K
m(DIC)) ranging from 0.5 to 1.1
mM of DIC. TRIS produced a significant increase of
K
m(DIC). Altogether, these results indicate that the algae sensitive to TRIS are capable of using HCO
3
− efficiently at pH 8.7. Furthermore, the buffering capacity of TRIS was responsible for its inhibitory effect on photosynthesis suggesting that HCO
3
− use was facilitated by excretion of protons outside the plasma membrane, which creates regions of low pH resulting in a higher-than-ambient CO
2 concentration. In contrast, photosynthesis by two
Porphyra species analysed was slightly stimulated by TRIS and completely inhibited by AZ, suggesting that the mechanism was different. In a third group of seaweeds, photosynthesis was insensitive to TRIS but it was significantly inhibited by AZ. These species had relatively high values of
K
m(DIC) indicating that they relied on purely diffusive entry of CO
2 generated by external carbonic anhydrase activity. Consequently, the results demonstrate that external carbonic anhydrase is widespread among red macroalgae since only
P. palmata was insensitive to AZ. The functional significance of this enzyme was quite variable among the tested species.
Three antimalarial meroditerpenes have been isolated from two Fijian red macroalgae. The absolute stereochemistry of callophycolide A (
1), a unique macrolide from
Callophycus serratus, was ...determined using a combination of Mosher’s ester analysis, circular dichroism analysis with a dimolybdenum tetraacetate complex, and conformational analysis using NOEs. In addition, two known tocopherols, β-tocopherylhydroquinone (
4) and δ-tocopherylhydroquinone (
5), were isolated from
Amphiroa crassa. By oxidizing
5 to the corresponding δ-tocopherylquinone (
6), antimalarial activity against the human malaria parasite
Plasmodium falciparum was increased by more than 20-fold.
An agar-hydrolyzing marine bacterium, strain GNUM08120, was isolated from Sargassum fulvellum collected from Yeongil bay of East Sea of Korea. The isolate was Gram-negative, aerobic, motile with ...single polar flagellum, and grew at 1-10% NaCl, pH 5.0-8.0, and 15-37oC. G+C content and the predominant respiratory quinone were 46.13 mol% and Q-8, respectively. The major cellular fatty acids were Summed feature 3 (24.5%), C16:0 (21.7%), and C18:1ω7c (12.5%). Based on 16S rRNA gene sequence similarity and DNA-DNA hybridization analyses, strain GNUM08120 was identified as a novel subspecies of Alteromonas macleodii, designated Alteromonas macleodii subsp. GNUM08120. Production of agarase by strain GNUM08120 was likely repressed by the effect of carbon catabolite repression caused by glucose. The crude agarase prepared from 12 h culture broth of strain GNUM08120 exhibited an optimum pH and temperature for agarase activity at 7.0 and 40oC, respectively. The crude enzyme produced (neo)agarobiose, (neo)agarotetraose, and (neo)agarohexaose as the hydrolyzed product of agarose.
Barcodes based on mitochondrial cytochrome oxidase (mtDNA CO1) sequences are being used for broad taxonomic groups of animals with demonstrated success in species identification and cryptic species ...discovery, but it has become clear that complementation by a nuclear marker system is necessary, in particular for the barcoding of plants. Here, we propose the nuclear internal transcribed spacer (ITS) as a potentially usable and complementary marker for species identification of red macroalgae, as well as present a primary workflow for species barcoding. Data show that for most red macroalgal genera (except members of the family Delesseriaceae), the size of ITS region ranges from 600 to 1200 bp, and contains enough variation to generate unique identifiers at either the species or genus levels. Consistent with previous studies, we found that the ITS sequence can resolve closely related species with the same fidelity as mtDNA CO1. Significantly, we confirmed that length polymorphism in the ITS region (including 5.8S rRNA gene) can be utilized as a character to discriminate red macroalgal species. As a complementary marker, the verifiable nuclear ITS region can speed routine identification and the detection of species, advance ecological and taxonomic inquiry, and permit rapid and accurate analysis of red macroalgae.
Two red macroalgae species,
Gracilaria cornea and
Chondrophycus poiteaui, were evaluated for their intra and extracellular Cd
2+ accumulation capacity, photosynthetic response and thiol peptide ...production. Algae were exposed for 3 and 7 days to 0.1 and 1
μg
CdCl
2
ml
−1 (0.89 and 8.9
μM). Intracellular accumulation of Cd
2+ by
G. cornea was relatively low, only comprising 20% of total metal (intracellular
+
extracellular). In contrast,
C. poiteaui accumulated intracellularly close to 100% of total Cd
2+. In both species, metal uptake was dependent on the external Cd
2+ concentration, metal exposure time and cell wall composition. In response to Cd
2+ exposure, low amounts of thiol peptides were synthesized and the major difference between
G. cornea and
C. poiteaui was in the cell wall composition. The absence of insoluble polysaccharides in the cell wall of
C. poiteaui suggested that this insoluble fraction might be involved in establishing an efficient barrier for the intracellular accumulation of Cd
2+. This is the first study in which the cell wall composition, its influence on Cd
2+ accumulation and intracellular responses in red macroalgae are evaluated.
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