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[The cholesterol-lowering effect of the unicellular green alga Scenedesmus acutus 276-3a. I. Effect of drum-dried algal material].

In three series of experiments hypercholesterolemia was induced in male Sprague-Dawley rats by a 3% cholesterol-enriched diet. The development of hypercholesterolemia was considerably retarded when 20% Scenedesmus powder was incorporated in the diet. In animals fed with standard diet and cholesterol for 6-8 weeks, the average concentration of blood plasma cholesterol increased from 2.0 to 3.6 mmol/l. In contrast, the final concentration reached only 2.4-2.8 mmol/l in animals receiving the cholesterol diet with algae. The plasma cholesterol level in animals receiving only an algal diet did not appear to be influenced. The mean value at the beginning of the test was 2.0 and 2.2 mmol/l at the end. The level of plasma triglyceride in animals fed on algae with and without the addition of cholesterol was lower than that of the controls. The algae-enriched diet prevented an excessive deposition of cholesterol in the liver. The increase in weight of the livers of rats receiving the cholesterol-enriched standard diet and the cholesterol-enriched algal diet were 2.0 and 0.8 g, respectively. The cholesterol content of the livers increased to 600 and 180 mg, respectively.

Animals↗

[Nutritive value of the spirulina algae (Spirulina maxima)].

Nine experiments were conducted, five of them in vivo to determine the limiting amino acids and digestibility of spiruline algae for the rat, and four in vitro to determine the digestibility of the product in pepsin and ruminal liquid. None of the amino acids studied (lysine, methionine, histidine) added alone or in combination to 10% protein (either crude or true) diets provided exclusively by spiruline, seems to be limiting although the results could be masked by the low palatability and acceptability of the product by the rats. The apparent digestibility of the algae was 67.4%. For the in vitro tests, the algae were subjected to several physical or chemical treatments, and the digestibility of the resulting product determined by four different techniques. In no case did the tested treatments have any effect on its digestibility.

Amino Acids, Essential↗

Extracellular release in Chlorella vulgaris culture and the role of bacteria accompanying - algae in this process.

The effect of different concentrations of nitrogen and phosphorus on extracellular release was investigated. Phosphorus induced the enhanced extracellular release of metabolites by Chlorella vulgaris. No influence of nitrogen on extracellular release was observed. In the initial stages of C. vulgaris culture the algae release was observed. In the initial stages of C. vulgaris culture the algae release compounds readily assimilated by the accompanying bacteria, hence the observed drop of percentage of extracellular release (PER) in culture medium caused by the bacteria. Both, the glycolic acid and the products of photoassimilation released to the environment in the first stages of cultivation were assimilated by the bacteria accompanying-algae at a similar rate. The ageing of C. vulgaris culture resulted in the accumulation of extracellularly released metabolites and increase of PER. These products were not assimilated by the bacteria present in the algal culture.

Chlorella↗

[Blue-green algae as a cause of human disease].

Blue-green algae can cause significant public health problems. There is an abundance of scientific literature on their effects, but much of it either reports laboratory studies of toxicological effects or discusses practical problems affecting water supply. There are many reports of poisonings of farm animals and wildlife, and a number of reports of adverse health effects in humans, but the effects of blue-green algae on human health do not seem to have attracted serious attention amongst practising physicians. It is probable that the occurrence of blue-green algae in algal blooms in the aquatic environment, often with production of toxins, will continue to increase as a result of human activity. It thus seems important that clinicians should become more aware of their effects. On this background the author briefly summarizes proven and potential adverse effects on health.

Cyanobacteria↗

Extracellular release of organic products and growth of bacteria in Anabaena cylindrica (blue-green alga) culture.

The studies were made with stationary cultures of Anabaena cylindrica (blue-green alga). The bacterial microflora accompanying blue-green algae is subject to succession and elimination in the course of growth. The bacteria are able to utilize organic products released by the blue-green algae. The products released by A. cylindrica to the environment are peptide-like compounds.

Chlorophyll↗

[Pharmacology and toxicology of Spirulina alga].

Spirulina, a unicellular filamentous blue-green alga has been consumed by man since ancient times in Mexico and central Africa. It is currently grown in many countries by synthetic methods. Initially the interest in Spirulina was on its nutritive value: it was found almost equal to other plant proteins. More recently, some preclinical testing suggests it has several therapeutic properties such as hypocholesterolemic, immunological, antiviral and antimutagenic. This has led to more detailed evaluations such as nucleic acid content and presence of toxic metals, biogenic toxins and organic chemicals: they have shown absence or presence at tolerable levels according to the recommendations of international regulatory agencies. In animal experiments for acute, subchronic and chronic toxicity, reproduction, mutagenicity, and teratogenicity the algae did not cause body or organ toxicity. In all instances, the Spirulina administered to the animals were at much higher amounts than those expected for human consumption. On the other hand there is scant information of the effects of the algae in humans. This area needs more research.

Animals↗

The blue-green algae in nuclear power plant cooling water.

A study was undertaken to determine the effects of passage through the cooling system of the Zion Nuclear Plant, Illinois, U.S.A., on the blue-green algae present in lake water. The blue-green algae were isolated by means of membrane filtration, enumerated and identified to genera. As a result of cooling system passage there was a definite reduction in the numbers of blue-green algae. This reduction appeared to be due to mechanical, as well as elevated temperature, damage. A few genera showed only a slight change in number.

Cyanobacteria↗

Blue-green algae toxicosis in cattle.

Twenty-four of 175 heifers died after ingesting water from a stock pond containing blue-green algae (genus Microcystis) in southern Colorado. Affected cattle were found dead or had signs of nervousness, and were recumbent, weak, anorectic, and hypersensitive to noise when first examined. All cattle died within 3 days after the onset of signs. At necropsy, the rumen contained blue-green algae, and the liver was larger than normal, friable, and dark red. The most important histologic lesion was hepatocyte degeneration and necrosis. Intraperitoneal administration of lyophilized cell material from the bloom caused hepatic necrosis and death in mice, and water from the pond had clumps of cells surrounded by a clear calyx, consistent with the appearance of organisms of the genus Microcystis. Samples of pond water were examined by means of high-pressure liquid chromatography; microcystin-LR, one of the hepatotoxins produced by Microcystis spp, was found. Chromatography may be useful in the diagnosis of blue-green algae toxicosis.

Animals↗

[Contents of various nutrients, minerals and seasonal fluctuations in Porphyra columbina, an edible marine algae from the Argentine Patagonian++ coast].

Porphyra columbina (Rodophyta Bangiales), one of the most important edible seaweeds, grows abundantly in the southern Argentine coast. Their mineral content and seasonal fluctuations were determined because there is no national data about their nutritional value. Samples were collected from April 1993 to February 1994 from Golfo San Jorge (30 Km South of Comodoro Rivadavia). Algae were washed with sea water and dried at room temperature (20-2 degrees C) for 24 hs, following the local processing procedure. Moisture and ashes were determined according to A.O.A.C. After mineralization with nitric acid sodium and potassium were determined by flame photometry; calcium, magnesium and iron by atomic absorption spectrophotometry (AAS); and phosphorus by Gomori's method. The results, expressed per 100 g dry algae showed the following values: moisture content: 7.03 to 11.00 g/100 g; ashes: 16.18 to 22.70 g/100 g; sodium: 3.18 to 6.41 g/100 g; potassium 1.24 to 1.96 g/100 g; magnesium: 600 to 836 mg/100 g; phosphorus: 78 to 276 mg/100 g; calcium: 63 to 108 mg/100 g and iron: 3.9 to 26.4 mg/100 g. The results of composition of algae as manufactured in the region showed important seasonal differences, with the highest values of ashes, sodium, potassium and magnesium in winter season (June and July).

Argentina↗

Algae-to-host horizontal gene transfer in Paramecium bursaria is associated with host adaptation during endosymbiosis.

Paramecium bursaria maintains a stable endosymbiosis with green algae, yet the evolutionary consequences of this association remain unclear. Here, we screened the host genome for algal-derived horizontally transferred genes (HTGs) using a lineage-aware workflow designed to detect horizontal gene transfer (HGT) between two defined lineages. We identified 16 candidate HTGs, including four putative newly transferred genes and 12 homologous transferred genes, most of which were functionally associated with redox homeostasis and metabolism. Five HTGs showed symbiosis-dependent expression. RNAi knockdown of GH32s and SATs reduced host proliferation, total cell area, and motility, while GH32s knockdown also reduced endosymbiont load. Duplication patterns suggest that most transfers may have occurred after the P. bursaria lineage diverged from the sampled Paramecium species but before its lineage-specific whole-genome duplication (WGD). The HTGs also showed host-associated shifts in GC content and gene length, while representative HTGs retained conserved domains and functional motifs. Together, our results support algae-to-host HGT in P. bursaria and suggest that some transferred genes may contribute to metabolic integration during endosymbiosis.

Gene Transfer, Horizontal↗

Genome analysis of the glycosphingolipid-producing green alga tetraselmis sp. NKG400013.

Microalgae are gaining attention as sustainable resources for the production of valuable compounds, including biofuels, pigments, and bioactive metabolites. To support metabolic engineering and genome editing approaches aimed at enhancing these traits, high-quality genome assemblies are essential; however, genomic information remains limited for many microalgal lineages. Tetraselmis sp. NKG400013 is a green alga known for high glycosphingolipid accumulation with distinctive structural features. Here, we report a draft genome assembly of this strain generated using PacBio HiFi sequencing and transcriptome-supported annotation. The assembled genome spans 423.7 Mbp, with 74.5% repetitive sequences and 15,322 predicted protein-coding genes. Comparative analyses across 11 green algal species revealed a positive correlation between genome sizes and repeat contents, indicating that transposable element expansion, particularly long terminal repeat retrotransposons, has substantially contributed to genome enlargement in Tetraselmis. Genome-wide functional annotation and ortholog inference identified core enzymes required for glycosylceramide biosynthesis. Both sphingolipid Δ4 and Δ8 desaturases were identified in Tetraselmis and their coexistence suggests an expanded capacity for long-chain base modification that may underlie its distinctive glycosphingolipid profile. These results establish a genomic framework for understanding the high glycosphingolipid-producing capacity of NKG400013 and provide insights into the evolutionary diversification of sphingolipid metabolism in green algae.

Chlorophyta↗

STRONTIUM AND CALCIUM UPTAKE BY THE GREEN ALGA, OOCYSTIS EREMOSPHAERIA.

The uptake of calcium and strontium by a green unicellular alga cultured in media containing these elements in concentrations found in nature is directly proportional to the concentration in the media. Variation in the concentration of either element has a slight inverse influence on the uptake of the other. The increase of strontium uptake when the calcium concentration is very low indicates that strontium is substituted for calcium when calcium is limited and suggests that the alga requires either element.

Calcium↗

Harvesting of algae by froth flotation.

A highly efficient froth flotation procedure has been developed for harvesting algae from dilute suspensions. The method does not depend upon the addition of flotants. Harvesting is carried out in a long column containing the feed solution which is aerated from below. A stable column of foam is produced and harvested from a side arm near the top of the column. The cell concentration of the harvest is a function of pH, aeration rate, aerator porosity, feed concentration, and height of foam in the harvesting column. The economic aspects of this process seem favorable for mass harvesting of algae for food or other purposes.

Eukaryota↗

Unicellular green alga Chlamydomonas reinhardtii as an activation system for 2-aminofluorene.

Despite the promutagenic/procarcinogenic potential, polycyclic aromatic amines are widely spread in the environment. Biotransformation of the polycyclic aromatic amine 2-aminofluorene (2-AF) was proved in mammals and higher plants. The algal cell/microbe coincubation assay is an additional system that complemented those proved in mammals and higher plants, useful for detection and conversion of environmental promutagens, mainly in aquatic environments. The unicellular green algae may be a good activating system in coincubation assays in that the algal cells exist as a natural system. To increase the effectiveness of this metabolizing system, different modifications of the standard experimental procedure were conducted. Algae can accumulate and metabolize promutagenic pollutants, some of which may differ from those activated by the animal microsome metabolizing system (S9 mix) and by the plant cell/microbe coincubation assay. 2-AF was activated in the algal cell/ microbe coincubation assay in which wild-type Chlamydomonas reinhardtii cells were used as an activating system and the bacteria Salmonella typhimurium TA98, YG1024, and yeast Saccharomyces cerevisiae D7 as the genetic indicator organisms. It was converted to the mutagenic product(s) for the strain YG1024, but the strain TA98 did not exhibit any increase in the mutant yield of His+ revertants. Consequently, metabolites from 2-AF are substrates for O-acetyltransferase. A direct comparison of algal 2-AF activation with mammalian activation system (S9 mix) proved the higher activity of mammalian microsome system (S9 mix). After the combination of both activation systems, a slight synergetic effect was found. Although the genetic endpoints induced by 2-AF using both modifications of the algal cell/S. cerevisiae coincubation assay and those obtained in intact yeast cells were similar at the equitoxic concentrations, 2-AF activation by the algal supernatant slightly increased the genetic endpoints studied.

Animals↗

Biologically active steroid from the green alga Ulva lactuca.

The marine green alga, Ulva lactuca, was shown to contain 3-O-beta-D glucopyranosyl-stigmasta-5,25-dien. The structure of the compound was established on the basis of its spectroscopic data and it was extracted for the first time from this alga. The topical antiinflammatory activity of this compound was examined using the mouse ear oedema assay as an experimental model of topical inflammation. Also, the antimicrobial activity of the isolated compound was tested against 10 various microorganisms (G+, G-, fungi and yeast strains).

Administration, Topical↗

High-cell-density fed-batch cultivation of the docosahexaenoic acid producing marine alga Crypthecodinium cohnii.

The heterotrophic marine alga Crypthecodinium cohnii is known to produce docosahexaenoic acid (DHA), a polyunsaturated fatty acid with food and pharmaceutical applications, during batch cultivation on complex media containing sea salt, yeast extract, and glucose. In the present study, fed-batch cultivation was studied as an alternative fermentation strategy for DHA production. Glucose and acetic acid were compared as carbon sources. For both substrates, the feed rate was adapted to the maximum specific consumption rate of C. cohnii. In glucose-grown cultures, this was done by maintaining a significant glucose concentration (between 5 and 20 g/L) throughout fermentation. In acetic acid-grown cultures, the medium feed was automatically controlled via the culture pH. A feed consisting of acetic acid (50% w/w) resulted in a higher overall volumetric productivity of DHA (r(DHA)) than a feed consisting of 50% (w/v) glucose (38 and 14 mg/L/h, respectively). The r(DHA) was further increased to 48 mg/L/h using a feed consisting of pure acetic acid. The latter fermentation strategy resulted in final concentrations of 109 g/L dry biomass, 61 g/L lipid, and 19 g/L DHA. These are the highest biomass, lipid, and DHA concentrations reported to date for a heterotrophic alga. Vigorous mixing was required to sustain aerobic conditions during high-cell-density cultivation. This was complicated by culture viscosity, which resulted from the production of viscous extracellular polysaccharides. These may present a problem for large-scale industrial production of DHA. Addition of a commercial polysaccharide-hydrolase preparation could decrease the viscosity of the culture and the required stirring.

Acetic Acid↗

Halogenated monoterpene production by microplantlets of the marine red alga Ochtodes secundiramea within an airlift photobioreactor under nutrient medium perfusion.

Macrophytic marine red algae are a unique source of novel and bioactive terpenoids, including halogenated monoterpenes. Biomass and halogenated monoterpene production by regenerated microplantlet suspension cultures derived from the red alga Ochtodes secundiramea were studied within a perfusion airlift photobioreactor. Photobioreactor cultivations were carried out at 26 degrees C, 140 microE m(-2)s(-1) light intensity, 0.3 air L(-1) culture min(-1) aeration (3500 ppm CO(2)), and ESS/seawater medium perfusion rate of 0.2 L medium L(-1) culture d(-1). Macronutrient concentrations in the perfusion medium were adjusted to provide nitrate delivery rates of 0.0063, 0.077, and 0.74 mmol L(-1) d(-1) at a fixed N:P ratio of 19:1. Growth was maximized at the highest nutrient delivery rate, where 10 g dry biomass L(-1) culture was achieved after 30 days of cultivation. GC-MS analysis of dichloromethane extracts from cell biomass revealed that O. secundiramea microplantlets produced myrcene, three acyclic halogenated monoterpenes (10-bromomyrcene, 10-bromo-7-chloromyrcene, 3,10-dibromomyrcene), and one cyclic halogenated monoterpene (6-bromo-1,2,8-trichloro-3,4-ochtodene). 10E-bromomyrcene levels were much higher than those of its isomer 10Z-bromomyrcene, demonstrating stereoselective halogenation. Maximum yields of 10E-bromomyrcene and 6-bromo-1,2,8-trichloro-3,4-ochtodene were 15 and 13 micromol/g dry cell mass, respectively. Increasing the rate of nutrient delivery increased the accumulation of myrcene and 10-bromomyrcene during the first 14 days in culture. Furthermore, the yield selectivity toward higher halogenated monoterpenes increased as the rate of nutrient delivery decreased. From this data, a biogenic scheme was proposed where cyclic and acyclic halogenated monoterpenes are derived from sequential halogenation of myrcene, their common precursor.

Bioreactors↗

Diatom/copepod interactions in plankton: the indirect chemical defense of unicellular algae.

Numerous coexisting species can be observed in the open oceans. This includes the complex community of the plankton, which comprises all free floating organisms in the sea. Traditionally, nutrient limitation, competition, predation, and abiotic factors have been assumed to shape the community structure in this environment. Only in recent years has the idea arisen that chemical signals and chemical defense can influence species interactions in the plankton as well. Key players at the base of the marine food web are diatoms (unicellular algae with silicified cell walls) and their main predators, the herbivorous copepods. It was assumed that diatoms represent a generally good food source for the grazers but recent work indicates that some species use chemical defenses. Secondary metabolites, released by these algae immediately after wounding, are targeted not against the predators themselves but rather at interfering with their reproductive success. This strategy allows diatoms to reduce the grazer population, thereby influencing the marine food web. This review addresses the chemical ecology of the defensive oxylipins formed by diatoms and the question of how these metabolites can act in such a dilute environment. Aspects of biosynthesis, bioassays, and the possible implications of such a chemical defense for the plankton community structure are also discussed.

Aldehydes↗