Chromium (VI) induced oxidative stress in halotolerant alga Dunaliella salina and D. tertiolecta isolated from sambhar salt lake of Rajasthan (India)
- Cellular and molecular biology (Noisy-le-Grand, France)
- Published over 4 years ago
Chromium (Cr) is one of the most serious pollutants in aquatic systems. This study was performed to understand the effect of Cr (VI) on halophilic algal strains of D. salina and D. tertiolecta. The results revealed good tolerance of D. salina towards chromium (VI) up to 8 ppm concentration, whereas tolerance level in D. tertiolecta was up to 2 ppm concentration. Cr (VI) not only inhibited the growth of D. tertiolecta, but also showed increased inhibition in the level of photosynthetic pigments, protein and carbohydrate. Results have revealed that chromium (VI) induced higher increase in lipid peroxidation and H2O2 production in D. tertiolecta than the D. salina, particularly at higher concentration of chromium (VI). Chromium (VI) induced increase in the rate of RNO bleaching, loss of pigments and thiol (—SH) group was relatively higher in D. tertiolecta than the D. salina, which is indicating that D. tertiolecta was prone to Cr (VI) induced oxidative stress. Results on RNO bleaching in the presence of radical quenchers suggested that OHdeg radical played an important role in the chromium (VI)—induced general oxidative stress in D. tertiolecta.
For many years, increasing demands for fossil fuels have met with limited supply. As a potential substitute and renewable source of biofuel feedstock, microalgae have received significant attention. However, few of the current algal species produce high lipid yields to be commercially viable. To discover more high yielding strains, next-generation sequencing technology is used to elucidate lipid synthetic pathways and energy metabolism involved in lipid yield. When subjected to manipulation by genetic and metabolic engineering, enhancement of such pathways may further enhance lipid yield.
Assessment of atrazine toxicity to the estuarine phytoplankter, Dunaliella tertiolecta (Chlorophyta), under varying nutrient conditions
- Environmental science and pollution research international
- Published over 1 year ago
Anthropogenic inputs of chemical environmental contaminants are frequently associated with developing harmful algal blooms, but little is known about how estuarine phytoplankton assemblages respond to multiple, co-occurring chemical stressors in chronically disturbed habitats. The goals of this research were to establish a robust protocol for testing the effects of atrazine on estuarine phytoplankton, and then to use that protocol to compare the effects of atrazine exposure with and without nutrient enrichment on a cosmopolitan estuarine/marine alga, Dunaliella tertiolecta (Chlorophyta). Atrazine sensitivity in nutrient-replete media (96-h growth inhibition [Formula: see text]) was 159.16 μg l-1, but sensitivity was influenced by exposure duration, and inhibitory effects of herbicide on algal growth decreased under imbalanced nutrient regimes and low nitrogen and phosphorus supplies. These findings advance knowledge about how nutrient regimes and herbicides interact to control estuarine phytoplankton population dynamics.
Microalgae are rich source of various bioactive molecules such as carotenoids, lipids, fatty acids, hydrocarbons, proteins, carbohydrates, amino acids, etc. and in recent year’s carotenoids from algae gained commercial recognition in the global market for food and cosmeceutical applications. However, the production of carotenoids from algae is not yet fully cost effective to compete with synthetic ones. In this context the present review examines the technologies/methods in relation to mass production of algae, cell harvesting for extraction of carotenoids, optimizing extraction methods etc. Research studies from different microalgal species such as Spirulina platensis, Haematococcus pluvialis, Dunaliella salina, Chlorella sps., Nannochloropsis sps., Scenedesmus sps., Chlorococcum sps., Botryococcus braunii and Diatoms in relation to carotenoid content, chemical structure, extraction and processing of carotenoids are discussed. Further these carotenoid pigments, are useful in various health applications and their use in food, feed, nutraceutical, pharmaceutical and cosmeceutical industries was briefly tocuhced upon. The commercial value of algal carotenoids has also been discussed in this review. Possible recommendations for future research studies are proposed.
The influence of arsenate and phosphate levels in water on the formation of arsenic-containing lipids (arsenolipids) and water-soluble arsenicals by a unicellular marine alga was investigated by exposing Dunaliella tertiolecta to five regimes of arsenic and phosphate, and determining the biosynthesized organoarsenicals with HPLC/mass spectrometry. Under all conditions, the major arsenolipid produced by D. tertiolecta was the novel phytyl 5-dimethylarsinoyl-2-O-methyl-ribofuranoside (AsSugPhytol546) representing ca. 35-65% of total arsenolipids. The new compound contains a phytol aglycone and a methoxy group replacing a sugar hydroxyl - two structural features not previously observed for arsenolipids. Minor arsenolipids were several previously reported arsenosugar phospholipids (AsSugPLs, in particular AsSugPL958 and the previously unknown AsSugPL978), the relative quantities of which increased with increasing phosphate exposure, and an arsenic-containing hydrocarbon (AsHC360), which remained unaffected by the different treatments. The relative amount of total arsenolipids produced by D. tertiolecta remained remarkably constant (ca. 45% of total As) and independent of the culture conditions. In contrast, with rising As-concentrations we observed an increase of hydrophilic arsenicals, which were dominated by arsenate and arsenosugars. The results highlight a possible major difference in arsenic biochemistry between macroalgae and unicellular algae with potential implications for how various algae handle their natural arsenic exposure in the world’s oceans.
The halotolerant alga Dunaliella salina is a model for stress tolerance and is used commercially for production of beta-carotene (=pro-vitamin A). The presented draft genome of the genuine strain CCAP19/18 will allow investigations into metabolic processes involved in regulation of stress responses, including carotenogenesis and adaptations to life in high-salinity environments.
The recent increase in nanoparticle (P25 TiO2 NPs) usage has led to concerns regarding their potential implications on environment and human health. The food chain is the central pathway for nanoparticle transfer from lower to high trophic level organisms. The current study relies on the investigation of toxicity and trophic transfer potential of TiO2 NPs from marine algae Dunaliella salina to marine crustacean Artemia salina. Toxicity was measured in two different modes of exposure such as waterborne (exposure of TiO2 NPs to Artemia) and dietary exposure (NP-accumulated algal cells are used to feed the Artemia). The toxicity and accumulation of TiO2 NPs in marine algae D. salina were also studied. Artemia was found to be more sensitive to TiO2 NPs (48h LC50 of 4.21mgL(-1)) as compared to marine algae, D. salina (48h LC50 of 11.35mgL(-1)). The toxicity, uptake, and accumulation of TiO2 NPs were observed to be more in waterborne exposure as compared to dietary exposure. Waterborne exposure seemed to cause higher ROS production and antioxidant enzyme (SOD and CAT) activity as compared to dietary exposure of TiO2 NPs in Artemia. There were no observed biomagnification (BMF) and trophic transfer from algae to Artemia through dietary exposure. Histopathological studies confirmed the morphological and internal damages in Artemia. This study reiterates the possible effects of the different modes of exposure on trophic transfer potential of TiO2 NPs and eventually the consequences on aquatic environment.
Lipid-soluble arsenic compounds, also called arsenolipids, are ubiquitous marine natural products of currently unknown origin and function. In our search for clues about the possible biological roles of these compounds, we investigated arsenic metabolism in the unicellular green alga Dunaliella tertiolecta, and discovered an arsenolipid fundamentally different from all those previously identified; namely, a phytyl 5-dimethylarsinoyl-2-O-methyl-ribofuranoside. The discovery is of particular interest because 2-O-methylribosides have, until now, only been found in RNA. We briefly discuss the significance of the new lipid in biosynthesis and arsenic biogeochemical cycling.
Zeaxanthin is a xanthophyll pigment that is regarded as one of the best carotenoids for the prevention and treatment of degenerative diseases. In the worldwide natural products market, consumers prefer pigments that have been produced from biological sources. In this study, a Dunaliella tertiolecta strain that has 10-15% higher cellular zeaxanthin content than the parent strain (zea1), was obtained by random mutagenesis using ethyl methanesulfonate (EMS) as a mutagen. This mutant, mp3, was grown under various salinities and light intensities to optimize culture conditions for zeaxanthin production. The highest cellular zeaxanthin content was observed at 1.5 M NaCl and 65-85 μmol photons·m(-2)·s(-1), and the highest daily zeaxanthin productivity was observed at 0.6 M NaCl and 140-160 μmol photons·m(-2)·s(-1). The maximal yield of zeaxanthin from mp3 in fed-batch culture was 8 mg·L(-1), which was obtained at 0.6 M NaCl and 140-160 μmol photons·m(-2)·s(-1). These results suggest that random mutagenesis with EMS is useful for generating D. tertiolecta strains with increased zeaxanthin content, and also suggest optimal culture conditions for the enhancement of biomass and zeaxanthin production by the zeaxanthin accumulating mutant strains.
Dunaliella tertiolecta, a halotolerant alga, can accumulate large amounts of neutral lipid, which makes it a potential biodiesel feedstock. In this study, neutral lipids of D. tertiolecta induced by different salinities, N or P starvation were analyzed by TLC, FCM and CLSM. High salinities, N or P starvation resulted in a decrease in cell growth and chlorophyll contents of D. tertiolecta. Neutral lipid contents increased markedly after 3~7 days of N starvation or at low NaCl concentrations (0.5~2.0 M). N starvation had a more dramatic effect on the neutral lipid contents of D. tertiolecta than P starvation. Four putative ME isozymes in different conditions can be detected by using isozyme electrophoresis. Two alternative acetyl-CoA producers, ACL and ACS genes were up-regulated under low salinities and N starvation. It was suggested that low salinities and N starvation are considered as the efficient ways to stimulate lipid accumulation in D. tertiolecta.