Genus Gracilaria Research Articles

The Rhodoexplorer Platform for Red Algal Genomics and Whole Genome Assemblies for Several Gracilaria Species.

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales is a highly diverse and widely distributed order including species that can serve as ecosystem engineers in intertidal habitats and several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole genome assemblies for two species (G. chilensis and G. gracilis), a draft genome assembly of G. caudata, and genome annotation of the previously published G. vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.

Evaluation of growth, primary productivity, nutritional composition, redox state, and antimicrobial activity of red seaweeds Gracilaria debilis and Gracilaria foliifera under pCO2-induced seawater acidification

The genus Gracilaria is an economically important group of seaweeds as several species are utilized for various products such as agar, used in medicines, human diets, and poultry feed. Hence, it is imperative to understand their response to predicted ocean acidification conditions. In the present work, we have evaluated the response of Gracilaria foliifera and Gracilaria debilis to carbon dioxide (pCO2) induced seawater acidification (pH 7.7) for two weeks in a controlled laboratory conditions. As a response variable, we have measured growth, productivity, redox state, primary and secondary metabolites, and mineral compositions. We found a general increase in the daily growth rate, primary productivity, and tissue chemical composition (such as pigments, soluble and insoluble sugars, amino acids, and fatty acids), but a decrease in the mineral contents under the acidified condition. Under acidification, there was a decrease in malondialdehyde. However, there were no significant changes in the total antioxidant capacity and a majority of enzymatic and non-enzymatic antioxidants, except for an increase in tocopherols, ascorbate and glutathione-s-transferase in G. foliifera. These results indicate that elevated pCO2 will benefit the growth of the studied species. No sign of oxidative stress markers indicating the acclimatory response of these seaweeds towards lowered pH conditions. Besides, we also found increased antimicrobial activities of acidified samples against several of the tested food pathogens. Based on these observations, we suggest that Gracilaria spp. will be benefitted from the predicted future acidified ocean.

Research progress in the preparation, structural characterization, bioactivities, and potential applications of sulfated agarans from the genus Gracilaria.

The genus Gracilaria produces 80% of the world's industrial agar. Agar of this genus is a promising biologically active polymer, which has been used in the human diet and folk medicine, alternative for weight loss, treatment of diarrhea, etc. With more attention paid to the genus Gracilaria-sulfated agarans (GSAs), they exhibited multitudinous health benefits in antioxidant, antiviral, antibacterial, prebiotics, anti-tumor, anticoagulant, and antidiabetic. Various preparation procedures of GSAs making the diversities of structure and biological activity. Therefore, this review summarized the isolation, identification, bioactivity potentials, and applications of GSAs, providing a reference to the development of GSAs in functional food and pharmaceutical industry. PRACTICAL APPLICATIONS: The genus Gracilaria is known as a raw material for agar extraction. GSAs are food-grade agaran with the properties of thermoreversible gels at low concentrations, which are commonly used as an additive for making candies as well as raw material for making soup and snacks. They are used in folk medicine to treat diarrhea and other diseases. As an important bioactive macromolecule, GSAs have various biological activities (such as antioxidant, antiviral, antibacterial, probiotic, anti-tumor, anticoagulant, and antidiabetic activities), and have the potential to be developed as functional food and medicine. They could also be used to create innovative agar-based products such as antibacterial films and drug carriers.

Effects of seawater sulfur starvation and enrichment on Gracilaria gracilis growth and biochemical composition

The genus Gracilaria, largest biomass producer in coastal regions, encompasses a wide range of species including Gracilaria gracilis. Nowadays, there is a spate of interest in its culture in lagoon where the water sulfate concentration is variable. A laboratory culture was carried out to determine the sulfate concentration effect on their growth as well as their biochemical composition, which were 2.5, 27 or 50 mM, referred to as SSS (sulfur starved seawater), SW (seawater) and SES (sulfur enriched seawater).We found that the sulfate content of the surrounding medium is a key parameter influencing both the alga growth and its composition. However, seawater proved to be the most suitable environment to sustain alga growth, proteins, R-phycoerythrin and agar yields, but sulfur enrichment and starvation affects them. The sulfate degree of agar and therefore its quality is related to the medium sulfate concentration. We conclude that sulfur starvation (2.5 mM) for three weeks, led to severe growth retardation, lower agar yield and quality and indicated the limit potential of G. gracilis for mariculture under these conditions. These results demonstrated that the success of G. gracilis culture in the lagoon is feasible if sulfate concentration is closer to that of seawater.

Effects of temperature and light on the growth and reproduction of an endophytic pest alga Ectocarpus siliculosus (Ectocarpales) found in wild Gracilaria textorii (Gracilariales)

The genus Gracilaria is an economically important macroalgae group that has been cultivated worldwide on a commercial scale. Epiphytic algae are commonly found in both natural and cultured Gracilaria and have become one of the major concerns in the Gracilaria aquaculture. In contrast to the wide reports of epiphytic pests, the endophytic algae inGracilaria have rarely been reported. In this study, we isolated the brown filamentous endophytic macroalgae Ectocarpus siliculosus from the host wild Gracilaria textorii to investigate its growth and reproduction capability under environmental changes. We studied the effects of various temperatures and light levels on growth and reproduction for 12 days. The results revealed that the highest growth rate (26.65 ± 1.78 day−1) of the endophytic pest E. siliculosus was at 25 °C and 50 μmol photons m−2 s−1. Furthermore, the gametangium/sporangium formation and gamete/spore release of the pest E. siliculosus preferred 20 °C with medium and high light intensities. In contrast, the worst performances of growth (3.34 ± 0.49 day−1) and reproduction (0.13 ± 0.09 gametangia/sporangia) occurred at the highest temperature (25 °C) and light level (100 μmol photons m−2 s−1). Our study indicate that optimal temperature can stimulate the rapid growth of E. siliculosus, and the strategy of living inside seaweed helps E. siliculosus avoid the excessive sunlight, which is especially critical for the ones inhabiting on the intertidal rocks. The physiological characteristics of endophytic E. siliculosus may help to inform the best pest management strategies for Gracilaria aquaculture.

Optimization of DNA isolation and amplification protocol for Gracilaria and Sargassum species of Tamil Nadu coast

The present study proposes a simple and rapid protocol to isolate DNA from marine algae of the genus Sargassum and Gracilaria. To identify the easy, fast and low cost method, four methods of DNA isolation viz., The Robertson Labs methods, STE Buffer method, PureFast-Plant Genomic DNA purification kit by Helini Biomolecules, Chennai and DNA Isolation by Heat Lysis Method were chosen for the present study. To optimize the DNA isolation methods, the thalli of Sargassum plagiophyllum C. Ag. and Gracilaria salicornia C.Ag. were employed as a source of DNA. The DNA isolated based on three genomic DNA extraction protocols and by heat lysis method varied with reference to method employed for the isolation. By heat lysis method, the DNA of S. plagiophyllum and G. salicornia was isolated and simultaneously amplified (400 bp) using 23S rRNA gene primers. With these results, the DNA of G. salicornia, G. edulis, G. corticata, G. fergusonii, G. verrucosa, S. aquifolium, S. plagiophyllum, S. polycystum, S. tenerrimum and S. swartzii were isolated and amplified using heat lysis method. The heat lysis method is thereby proven to be efficient, rapid, simple, cost effective and requires only a small fraction of the sample. The heat lysis method can be a successful replacement for the conventional DNA isolation methods, when used specifically for DNA barcoding technique targetting organelle DNA.

Effects of Ascophyllum marine plant extract powder (AMPEP) on tissue growth, proximate, phenolic contents, and free radical scavenging activities in endemic red seaweed Gracilaria corticata var. cylindrica from India

The red algal genus Gracilaria has considerable economic importance due to its agar content and rapid growth. This study was conducted on endemic Gracilaria corticata var. cylindrica to optimize different concentrations of AMPEP (0.01, 0.1, and 1.0 g L−1) and exposure time (15, 30, and 60 min) as a plant growth stimulant. Effect of 0.1 g L−1 and 30 min was found to be maximum in enhancing the daily growth rate and branch induction. The highest daily growth rate and number of branches were 7.62 ± 0.4% day−1 and 40.33 ± 8.6%, respectively. After 7 weeks, the plants were harvested and tested for carbohydrate, protein, lipid, and total phenolic content and free radical scavenging activity. Treatment with concentration of 0.1 g L−1 and exposure time 30 min showed the highest total carbohydrate (7.78 ± 0.08%), lipid (0.83 ± 0.11%), and total phenolic content (0.38 ± 0.01%) while treatment with 1 g L−1 and 60 min exposure time showed highest protein content (0.53 ± 0.01%). The antioxidant activity response was also observed and it showed less scavenging activity compare with the control. Application of AMPEP can have capacity for producing large numbers of plantlets within 4–5 weeks, making it highly attractive for implementation in sustainable seaweed farming. The present study also confirmed the commercial utility of indigenous resource G. corticata var. cylindrica for farming and catering domestic agar demand.

Antioxidant Sulfated Polysaccharide from Edible Red Seaweed Gracilaria birdiae is an Inhibitor of Calcium Oxalate Crystal Formation.

The genus Gracilaria synthesizes sulfated polysaccharides (SPs). Many of these SPs, including those synthesized by the edible seaweed Gracilaria birdiae, have not yet been adequately investigated for their use as potential pharmaceutical compounds. Previous studies have demonstrated the immunomodulatory effects of sulfated galactans from G. birdiae. In this study, a galactan (GB) was extracted from G. birdiae and evaluated by cell proliferation and antioxidant tests. GB showed no radical hydroxyl (OH) and superoxide (O2−) scavenging ability. However, GB was able to donate electrons in two further different assays and presented iron- and copper-chelating activity. Urolithiasis affects approximately 10% of the world’s population and is strongly associated with calcium oxalate (CaOx) crystals. No efficient compound is currently available for the treatment of this disease. GB appeared to interact with and stabilize calcium oxalate dihydrate crystals, leading to the modification of their morphology, size, and surface charge. These crystals then acquired the same characteristics as those found in healthy individuals. In addition, GB showed no cytotoxic effect against human kidney cells (HEK-293). Taken together, our current findings highlight the potential application of GB as an antiurolithic agent.

Analysis of functional traits in female gametophytic and tetrasporophytic life phases of industrially important red alga Gracilaria dura (Rhodophyta: Gracilariacae)

The rhodophyte seaweed genus Gracilaria is fast replacing Gelidium in global agar trade. Recently, Gracilaria dura from Indian waters has emerged as species of choice due to its quality agarose. The triphasic life cycle provides an opportunity for selecting an elite cultivar. Here we report diversity pertaining to functional traits over 3 months (January, February and March) among two distinct life phases, the tetrasporophyte and the female gametophyte. It was evident that functional trait related to growth was distinct in tetrasporophytes than in female gametophytes; while those of survival (antioxidant, proximate composition and pigments) were prominent in female gametophytes. Both the lowest 3.42 ± 0.38% day−1 (female gametophytes) and highest 5.17 ± 0. 21% day−1 (terasporophytes) growth rates were in January with 33% higher growth in the latter. Of the survival traits, antioxidant potential ranged from 0.51 ± 0.08 to 1.1 ± 0.03 mg g−1 FW ascorbic acid equivalent. Furthermore, female gametophytes collected in March reported 53.60%, 28.40% and 50.40% higher activity than the tetrasporophytes of January, February and March, respectively. The female gametophyte in March showed 23% and 19.40% higher protein content than the tetrasporophytes of January and February, respectively. Sixty-one metabolites were identified of which 29 were common, with sugars as the major portion (77.69% in February to 89.38% in January) and amine derivatives the least (0.30% in January to 0.51% in February). Studies of bio-ecophysiology of this alga are currently being undertaken by our group.

Feasibility of farming the agarose-yielding red alga Gracilaria dura using tube-net cultivation in the open sea along the Gujarat coast of NW India

ABSTRACT Despite some perceptions of economic risk, the global aquaculture industry continues to attract new entrepreneurs and investors. However, to sustain this trend, innovative and cost-effective strategies are needed. In recent years, algal farming has been shown to be a sustainable activity in the global Blue Economy. In 2015, harvests of the red algal agarophyte genus Gracilaria surged to over 114,100 tons dry weight which constituted ca. 91% of the total raw material for industrial agar production. We carried out a trial of experimental farming of the agar-yielding alga known as Gracilaria dura using a tube-net method along the Gujarat coast, India. The mean daily growth rate (DGR) of this agarophyte ranged from 1.88 ± 0.23% day−1 to 3.30 ± 0.25% day−1. Similarly, the mean yield varied between 0.62 ± 0.03 kg and 1.05 ± 0.02 kg fresh wt m−1 of tube-net. A Pearson correlation showed that both DGR and biomass yield were positively correlated with temperature. In addition, the DGR was significantly positively correlated with air temperature (r = 0.916; p < 0.01) whereas biomass yield was also positively correlated with surface seawater temperature (r = 0.986; p < 0.001). The economic projections for four harvests per year revealed that the value of the product was US$5577, while the investment required for the necessary tube-net infrastructure was US$1797 thereby providing US$1890 as profit to single farmers, a significant amount in the coastal communities of Gujarat. Thus, undertaking commercial farming of G. dura in Indian waters could diversify the livelihood of artisanal, coastal fishermen and further encourage the indigenous production of agarose.

Marine Algae of the Genus Gracilaria as Multi Products Source for Different Biotechnological and Medical Applications.

Gracilaria has been shown to be an important source of marine bioactive natural biomaterials and compounds. Although there are no enough patents used Gracilaria worldwide, the current study tries to put the Gracilaria on the spot for further important patents in the future. The current study investigates the pharmaceuticals and biochemical activity of Gracilaria because no previous studies have been carried out to examine the biochemical and pharmaceutical activates of Gracilaria from the Suez Canal of Egypt as an excellent source for bioactive compounds. Different advanced experimental models and analytical techniques, such as cytotoxicity, total antioxidant capacity, anticancer, and anti-inflammatory profiling were applied. The phytochemical analysis of different constituents was also carried out. The mineral analysis revealed the presence of copper (188.3 ppm) and iron (10.07 ppm) in addition to a remarkable wealth of selenium and sulfur contents giving up to 36% of its dry mass. The elemental analysis showed high contents of sulfur and nitrogen compounds. The GCMS profiling showed varieties of different bioactive compounds, such as fatty acids, different types of carotenoids in addition to pigments, alkaloids, steroids. Many other compounds, such as carbohydrates and amino acids having antioxidant, anti-inflammatory, and antiviral activities, etc. were identified. The cytotoxicity activity of Gracilaria marine extract was very effective against cancerous cell lines and showed high ability as a potent antitumor due to their bioactive constituents. Specialized screening assays using two anticancer experimental models, i.e., PTK and SKH1 revealed 77.88% and 84.50% inhibition anticancer activity; respectively. The anti-inflammatory activities investigated using four different experimental models, i.e., COX1, COX2, IL6, and TNF resulted in 68%, 81.76%, 56.02% and 78.43% inhibition; respectively. Moreover, Gracilaria extracts showed potent anti-Alzheimer with all concentrations. Gracilaria proved to be a multi-product source of marine natural products for different biotechnological applications. Our recommendation is to investigate the Gracilaria bioactive secondary metabolites in order to create and innovate in more patents from current important seaweeds (Gracilaria).

Morphological and genetic analysis of Gracilaria sp. cultured in ponds and coastal waters

Seaweeds of the genus Gracilaria are an important aquaculture commodity, commonly cultured in brackish water ponds as well as in coastal waters. In South Sulawesi, Indonesia, the Gracilaria acultured in ponds has been named G. verrucosa, while Gracilaria cultured in coastal waters has been named G. gigas. Morphologically, these two types of Gracilaria do look different. Detailed examination shows that they appear to have similarities. This study aimed to examine whether these two types of Gracilaria are different species or not. The study used morphological characters and COI mitochondrial gene barcoding to assess the Gracilaria types cultured in ponds and coastal waters. Samples were collected from Ujung Baji Village in Takalar Regency, the main seaweed producing region in South Sulawesi Province, Indonesia. The results indicate that both Gracilaria types have similar genetic characteristics as well as shared morphological characters. Based on these analyses, it is considered that both Gracilaria types cultivated may be strains of the same species.

Sulfated polysaccharides from the marine algae Gracilaria caudata prevent tissue damage caused by ligature-induced periodontitis.

Sulfated polysaccharides (PLS) extracted from the marine algae of the genus Gracilaria showed biological activity in different inflammatory models, except for periodontitis. Thus, this study aimed to evaluate the effectiveness of the treatment with PLS from Gracilaria caudata in ligature-induced periodontitis. 40 animals distributed into 5 groups were used (the control group (unligated), the ligated untreated group, and the ligated groups treated with 2.5, 5.0 and 10.0 mg/kg of PLS with intraperitoneal injection, respectively). After 20 days of treatment, the animals were killed and the following parameters were evaluated: Gingival Bleeding Index (GBI), Probing Pocket Depth (PPD), Myeloperoxidase (MPO) activity, Alveolar Bone Loss (ABL) for periodontal tissues; histopathological examination of gingival and liver tissues (Steatosis score); glutathione and malondialdehyde concentrations in the liver, serum levels of alanine aminotransferase and aspartate aminotransferase. The data revealed that treatment with 2.5 mg/kg of PLS showed the best anti-inflammatory effects with reduction of GBI, PPD and MPO activity, as well as oxidative stress and steatosis in liver. Our results indicated that the adjunct treatment with PLS from Gracilaria caudata could prevent the periodontal and hepatic tissue alteration caused by periodontitis.

Technoeconomic Sensibility Analysis of Industrial Agar Production from Red Algae

Red algae are one of the three main groups of macroalgae, these are found mainly in marine ecosystems and are used for the elaboration of foods, cosmetics, among others. Macroalgae of the genus Gracilaria sp. They are one of the sources of agar production, a polysaccharide formed by different units of galactose, which are associated forming two different polysaccharides, agarose and agaropectin. Because the agar has several purposes, it is appropriate to evaluate the economic response of the production. In this work was developed the economic evaluation and the technoeconomic sensibility analysis of the industrial production of agar from red algae, using the evaporation route, which employs seven units of operation, in order to analyze the behavior of the process when changer occur in the technoeconomic environment of the process as break-even point, on-stream efficiency, raw material cost, among others. Results show that for a processing capacity of 8,640 t/y of macroalgae with a plant life of 15 y, the total capital investment (TCI) was $11,937,000 and fixed capital investment (FCI) was $7,022,000 for a plant located in North Colombia. In addition, annualized total operating costs (AOC) were calculated in $24,514,000. Critical technoeconomic variables were raw material costs, product selling price and normalized variable operating costs (NVOC).

Environmental Evaluation of Agar Production from Macroalgae Gracilaria sp.

Agar is a polysaccharide that is extracted from algae of the Rhodophyta class, better known as red algae. Since the discovery of agar extraction, an attempt has been made to optimize this process in order to obtain a high-quality product that produces less negative environmental impacts and is economically profitable. In the present study, the environmental analysis of the agar production process was carried out from red macroalgae of the genus Gracilaria sp. For which, the WAR algorithm or Waste Reduction algorithm was used by the implementation of the WARGUI software and Microsoft Excel. Initially, the environmental impact assessment was carried out in which different categories were evaluated to determine the total environmental impact potential generated by the process. Subsequently, we analyzed both the flow of toxicological and atmospheric environmental impacts generated by the limits of the system, as well as those generated by the total process chemistry. Finally, we compared the variation of the total environmental impacts generated after the change of the energy source. Results shows that the highest environmental impacts are generated when the energy consumed by the process is included in the evaluation. The highest atmospheric impacts value obtained was 107 PEI/hr, as well as the toxicological impacts, the highest value of PEI generated was 118 PEI/hr, which is low compared to other processes. In addition, in the analysis of the effect of energy source, the highest impact was 17.7 PEI/hr and when the gas is used as an energy source, the total environmental impacts were reduced by 16%.

Gracilaria suzannae sp. nov. (Gracilariales, Rhodophyta), a new flattened species from northeast Brazil based on morphological and molecular evidence

:A new species of Gracilaria, G. suzannae sp. nov., is described on the basis of detailed morphological, anatomical and molecular evidence from recent collections from intertidal reefs of northeastern Brazil. Diagnostic features of the new species include: tufted and tough thalli with subdichotomous, alternate to irregular branches; some branches incurved, with discrete marginal teeth, giving thalli a dentate to lacerate appearance in the upper parts; an abrupt transition of cell size between cortical and medullary regions; spermatangial conceptacles of the textorii type; and mature cystocarps with inconspicuous inner pericarp and few tubular nutritive filaments, particularly in basal portions. Universal plastid amplicon sequences of G. suzannae formed a distinct group within the genus Gracilaria, with intraspecific divergence of 0.24%. In the rbcL analysis, G. suzannae was recovered as sister to a well-supported clade containing G. occidentalis from the United States, with interspecific divergence of 1.3%. Unlike our specimens, the thallus habit of G. occidentalis is repeatedly forked, with smooth margins and rounded apices. Furthermore, G. suzannae was phylogenetically positioned close to a major clade composed of Indo-Pacific flat species with lobed, spiny or denticulate margins, all of which diverged 1.1 to 4.8% from G. suzannae. Gracilaria suzannae becomes the 16th flat species of Gracilaria reported for Brazil.

Depth-Dependent Pigment Fluctuations in the Agarophyte Gracilaria corticata at Intertidal Waters

Red macroalgae from the genus Gracilaria (agarophytes) are of ecological and pharmaceutical importance particularly for agar production. In this study, the red, agarophyte alga Gracilaria corticata was investigated for fluctuations of main and accessory pigments and total carotenoids at two depths during its growing season. The alga was sampled from coastal waters in Brice coast, Chabahar, southern Iran, from December to March in shallow (2–3 m) and higher (5–6 m) depths. The accessory pigments (phycoerythrin, phycocyanin and alophycocyanin), chlorophyll a, and total carotenoids were extracted three times using appropriate solvents and estimated through spectroscopy (mg g−1 dry weight). All pigments of G. corticata increased with depth showing significant differences between the two depths (p < 0.05). Phycoerythrin and phycocyanin were utmost at a depth of 5–6 m in December and January. The highest allophycocyanin and chlorophyll a contents were found at a depth of 5–6 m in February, and total carotenoids were of greatest values at depths of 2–3 m and 5–6 m in March and February, respectively (p < 0.05). The pigment ratios (phycobilin/chlorophyll and total carotenoids/chlorophyll a) at the two depths displayed marked monthly variations (p < 0.05). The greatest phycobilin/chlorophyll a (0.4 ± 0.2418) was found in December (5–6 m) and the ratio of carotenoids/chlorophyll a (0.31 ± 0.0058) was highest in March (2–3 m). The remarkable increases in major and accessory pigments with depth could indicate maximum biomass and production of G. corticata, especially in the months of February and March, which is important for field harvesting operations.

Comparison of bioethanol production from cultivated versus wild Gracilaria verrucosa and Gracilaria gigas

The seaweed genus Gracilaria is a potential candidate for the production of bioethanol due to its high carbohydrate content. Gracilaria is abundant throughout the world and can be found in both wild and cultivated forms. Differences in the ecological factors such as temperature, salinity, and light intensity affecting wild and cultivated specimens may influence the biochemical content of seaweeds, including the carbohydrate content. This study aimed to investigate the proximate composition and potential bioethanol production of wild and cultivated G. gigas and G. verrucosa. Bioethanol was produced using separate hydrolysis fermentation (SHF), employing a combination of enzymatic and acid hydrolysis, followed by fermentation with Saccharomyces cerevisiae ATCC 200062. The highest carbohydrate content was found in wild G. gigas. The highest galactose and glucose contents (20.21 ± 0.32 and 9.70 ± 0.49 g L−1, respectively), as well as the highest production of bioethanol (3.56 ± 0.02 g L−1), were also found in wild G. gigas. Thus, we conclude that wild G. gigas is the most promising candidate for bioethanol production. Further research is needed to optimize bioethanol production from wild G. gigas. Domestication of wild G. gigas is a promising challenge for aquaculture to avoid overexploitation of this wild seaweed resource.

The complete mitochondrial genome of the economic red alga, Gracilaria chilensis

Gracilaria chilensis is an economically important marine alga. In this study, we obtained complete mitogenome of G. chilensis by high-throughput sequencing, which was mapped as a circular molecule of 26,897 bp with 27.56% GC content and was identified 53 genes, including 25 protein-coding genes, 2 rRNA genes, 26 tRNA genes, and 1 group II intron inserted into the trnI gene. In addition, a 162-bp stable stem loop was found in intergenic regions, which was most likely associated with DNA transcription and replication. The Bayesian phylogenetic tree of Gracilariaceae revealed that G. chilensis and G. salicornia and G. changii shared a closer relationship than G. vermiculophylla in the genus Gracilaria.

Cultivation of three color strains of Gracilaria domingensis in an integrated organic system

Species of the genus Gracilaria are widely distributed around the world, and many are wild harvested and cultivated for phycocolloid production (agar) and human food. This study investigated the growth performance of three color strains of Gracilaria domingensis in an integrated organic system. The three chromatic variants (red, green, and brown) were cultured in a shrimp farm at two depths (surface and 20 cm). The highest relative growth rates were obtained in the first week of cultivation for all three strains studied. Although the growth rates and biomass were slightly higher at a depth of 20 cm, significant differences were not observed at different depths (p < 0.05). The growth of the three strains varied significantly over time (p < 0.001). The maximal growth values obtained were 11.25 ± 1.50% day−1 (red), 12.76 ± 3.96% day−1 (green), and 7.86 ± 1.75% day−1 (brown). The mean growth rates for the whole period were 4.63 ± 6.97, 3.38 ± 9.09, and 2.16 ± 6.61% day−1 for the red, green, and brown strains, respectively. The pigment content (chlorophyll a, phycocyanin, and phycoerythrin) of the three strains studied was higher at a depth of 20 cm, while the maximum electron transport rate (ETRmax) and photosynthetic efficiency were higher at the surface. The high growth rates obtained in this study demonstrate the great potential of this species for integrated organic farming. Moreover, the ecological success shown by the red strain suggests that this strain is the most suitable for integrated cultivation.