Chlorella sorokiniana dietary supplementation increases antioxidant capacities and reduces ros release in mitochondria of hyperthyroid rat liver

The ability of aerobic organisms to cope with the attack of radicals and other reactive oxygen species improves by feeding on foods containing antioxidants. Microalgae contain many molecules showing in vitro antioxidant capacity, and their food consumption can protect cells from oxidative insults. We evaluated the capacity of dietary supplementation with 1% dried Chlorella sorokiniana strain 211/8k, an alga rich in glutathione, α-tocopherol, and carotenoids, to counteract an oxidative attack in vivo. We used the hyperthyroid rat as a model of oxidative stress, in which the increase in metabolic capacities is associated with an increase in the release of mitochondrial reactive oxygen species (ROS) and the susceptibility to oxidative insult. Chlorella sorokiniana supplementation prevents the increases in oxidative stress markers and basal oxygen consumption in hyperthyroid rat livers. It also mitigates the thyroid hormone-induced increase in maximal aerobic capacities, the mitochondrial ROS release, and the susceptibility to oxidative stress. Finally, alga influences the thyroid hormone-induced changes in the factors involved in mitochondrial biogenesis peroxisomal proliferator-activated receptor-γ coactivator (PGC1-1) and nuclear respiratory factor 2 (NRF-2). Our results suggest that Chlorella sorokiniana dietary supplementation has beneficial effects in counteracting oxidative stress and that it works primarily by preserving mitochondrial function. Thus, it can be useful in preventing dysfunctions in which mitochondrial oxidative damage and ROS production play a putative role

Sulfur Starvation in Extremophilic Microalga Galdieria sulphuraria: Can Glutathione Contribute to Stress Tolerance?

This study reports the effects of sulfur (S) deprivation in cultures of Galdieria sulphuraria (Cyanidiophyceae). Galdieria is a unicellular red alga that usually grows, forming biomats on rocks, in S-rich environments. These are volcanic areas, where S is widespread since H2S is the prevalent form of gas. The glutathione content in Galdieria sulphuraria is much higher than that found in the green algae and even under conditions of S deprivation for 7 days, it remains high. On the other hand, the S deprivation causes a decrease in the total protein content and a significant increase in soluble protein fraction. This suggests that in the conditions of S starvation, the synthesis of enzy-matic proteins, that metabolically support the cell in the condition of nutritional stress, could be up regulated. Among these enzymatic proteins, those involved in cell detoxification, due to the accumulation of ROS species, have been counted

Simultaneous biochemical and physiological responses of the roots and leaves of pancratium maritimum (Amaryllidaceae) to mild salt stress

Pancratium maritimum (Amaryllidaceae) is a bulbous geophyte growing on coastal sands. In this study, we investigated changes in concentrations of metabolites in the root and leaf tissue of P. maritimum in response to mild salt stress. Changes in concentrations of osmolytes, glutathione, sodium, mineral nutrients, enzymes, and other compounds in the leaves and roots were measured at 0, 3, and 10 days during a 10‐day exposure to two levels of mild salt stress, 50 mM NaCl or 100 mM NaCl in sandy soil from where the plants were collected in dunes near Cuma, Italy. Sodium accumulated in the roots, and relatively little was translocated to the leaves. At both concentrations of NaCl, higher values of the concentrations of oxidized glutathione disulfide (GSSG), compared to reduced glutathione (GSH), in roots and leaves were associated with salt tolerance. The concentration of proline increased more in the leaves than in the roots, and glycine betaine increased in both roots and leaves. Differences in the accumulation of organic osmolytes and electron donors synthesized in both leaves and roots demonstrate that osmoregulatory and electrical responses occur in these organs of P. maritimum under mild salt stress

Impact of sulfur starvation in autotrophic and heterotrophic cultures of the Extremophilic Microalga Galdieria Phlegrea (Cyanidiophyceae)

In plants and algae, sulfate assimilation and cysteine synthesis are regulated by sulfur (S) accessibility from the environment. This study reports the effects of S deprivation in autotrophic and heterotrophic cultures of Galdieria phlegrea (Cyanidiophyceae), a unicellular red alga isolated in the Solfatara crater located in Campi Flegrei (Naples, Italy), where H2S is the prevalent form of gaseous S in the fumarolic fluids and S is widespread in the soils near the fumaroles. This is the first report on the effects of S deprivation on a sulfurous microalga that is also able to grow heterotrophically in the dark. The removal of S from the culture medium of illuminated cells caused a decrease in the soluble protein content and a significant decrease in the intracellular levels of glutathione. Cells from heterotrophic cultures of G. phlegrea exhibited high levels of internal proteins and high glutathione content, which did not diminish during S starvation, but rather glutathione significantly increased. The activity of O-acetylserine(thiol)lyase (OASTL), the enzyme synthesizing cysteine, was enhanced under S deprivation in a time-dependent manner in autotrophic but not in heterotrophic cells. Analysis of the transcript abundance of the OASTL gene supports the OASTL activity increase in autotrophic cultures under S deprivation

Aggiornamenti e novità sulle conoscenze di Pancratium maritimum (Amaryllidaceae)

Pancratium maritimum L., bulbosa perenne degli ambienti dunali costieri, è un taxon relativamente recente se comparato con le specie del genere a gravitazione mediterranea. Gli studi noti su questa specie hanno analizzato vari aspetti della biologia (riproduttivi, biochimici, filogenetici, genetici, ecc.). Tuttavia, esistono ancora lacune scientifiche, tra cui l’assenza di studi su ampio areale di genetica di conservazione e sugli adattamenti eco-morfofisiologici alle condizioni di stress. Per ampliare le conoscenze su P. maritimum, la Fondazione Nando Peretti nel novembre 2012 ha finanziato un progetto triennale sulla conoscenza e la salvaguardia di questa specie (Progetto 2012-83). In questo contributo si presentano i risultati ottenuti per le diverse linee di ricerca finora affrontate, che vanno dalle analisi ad ampio areale dei popolamenti, usando un approccio sia genetico che GIS, alla caratterizzazione morfologica e eco-fisiologica di varie popolazioni

Different behaviour between autotrophic and heterotrophic Galdieria sulphuraria (Rhodophyta) cells to nitrogen starvation and restoration. Impact on pigment and free amino acid contents

The unicellular red alga Galdieria sulphuraria is a polyextremophilic organism with a metabolic flexibility to grow autotrophically or heterotrophically. Galdieria can also produce and accumulate biotechnologically attractive products such as pigments (phycocyanin) and proteins. In this research we studied the effects of nitrogen starvation and its subsequent restoration on pigment and free amino acid contents both in photoautotrophic and heterotrophic cells. Following the nitrogen starvation, the levels of the primary photosynthetic pigments decreased both in autotrophic and heterotrophic cells, except for the chlorophyll a marginally diminished in heterotrophic cells. Ammonium supply to G. sulphuraria N starved cells caused a significant increase of total chlorophylls both in autotrophic and heterotrophic cells. It was observed how such increase was more rapid and marked in heterotrophic cells than in the autotrophic ones. Under N starvation, phycocyanin contents decreased in both autotrophic and in heterotrophic cells; however, after a time-lapse of 24 hours, they resulted significantly higher in heterotrophic cells. In Galdieria sulphuraria, like in other microalgae, free amino acid contents were profoundly dependent on nitrogen status of the cells but heterotrophic cells maintained much higher levels, especially of glutamate, respect to autotrophic ones. In general, cells grown in the presence and absence of light showed different responses toward N availability; in particular heterotrophic cells seemed to respond quicker to the ammonium restoration compared to autotrophic ones

Tissue localization and the physiological effects induced by an environmentally relevant mix of heavy metals in the liverwort Conocephalum conicum L. Dum

Tissue accumulation, ultrastructural alterations, oxidative stress, and effects on photosynthesis were assessed in the liverwort Conocephalum conicom exposed in vitro to heavy metals (HM) concentrations in three sites of the Savone River, representative of different anthropic impacts. The uptake and accumulation of HM in the thallus of the liverwort was first studied, and the biological effects in relation to the different accumulation sites of HM along thallus, ribs and wings, were then investigated, considering: bioaccumulation (by atomic absorption spectrometry), localization (by X-ray scanning electron microscopy microanalysis), ultrastructural damage of photosynthetic parenchyma (by transmission electron microscopy), oxidative stress (by ROS contents and antioxidant enzymes activities determination), photosynthesis (by chlorophyll fluorescence). The results showed the HM bioaccumulation in C. conicom was dependent by their concentrations in the contaminated water. As for spatial localization, HM preferentially accumulated in the nerve of gametophytes respect to the wings. With respect to tissue localization, HM were mainly found in the hyaline and in the photosynthetic parenchyma. Essential metals (Cu and Zn) were accumulated at higher concentrations with respect to non-essential metals (Pb and Cd). At the ultrastructural level, HM caused alterations of the fine structure of the cells, most evident along the nerve, inducing marked alterations of the chloroplast structure and therefore of the photosynthetic capacity. Based on the results of the presented study, C.conicum can be used as a marker to indicate heavy metal pollution in water natural resources

Enhancement of Pigments Production by Nannochloropsis oculata Cells in Response to Bicarbonate Supply

In this study, the effects of bicarbonate addition on growth and pigment contents of the unicellular microalga Nannochloropsis oculata, were evaluated. N. oculata represents an interesting source of biomolecules widely used for food supplements and nutraceuticals. The bicarbonate was supplemented to microalgae cultures at concentrations of 0, 6, 18, 30, 42 and 60 mM. The cultures supplemented with salt at highest concentrations (42 and 60 mM) showed a significant increase in algal growth, demonstrated by the optical density spread. The intracellular content of pigments such as chlorophyll a and total carotenoids reached the highest values in cells from cultures supplied with bicarbonate. In fact, concentrations of bicarbonate from 30 to 60 mM strongly improved, for a short period of only 72 h, the cellular levels of chlorophylls and carotenoids. These are interesting pigments with commercial applications. The utilization of bicarbonate could represent an interesting sustainable opportunity to improve microalgae cultivation for cellular growth and pigment contents

Enhancement of pigments production by nannochloropsis oculata cells in response to bicarbonate supply

In this study, the effects of bicarbonate addition on growth and pigment contents of the unicellular microalga Nannochloropsis oculata, were evaluated. N. oculata represents an interesting source of biomolecules widely used for food supplements and nutraceuticals. The bicarbonate was supplemented to microalgae cultures at concentrations of 0, 6, 18, 30, 42 and 60 mM. The cultures supplemented with salt at highest concentrations (42 and 60 mM) showed a significant increase in algal growth, demonstrated by the optical density spread. The intracellular content of pigments such as chlorophyll a and total carotenoids reached the highest values in cells from cultures supplied with bicarbonate. In fact, concentrations of bicarbonate from 30 to 60 mM strongly improved, for a short period of only 72 h, the cellular levels of chlorophylls and carotenoids. These are interesting pigments with commercial applications. The utilization of bicarbonate could represent an interesting sustainable opportunity to improve microalgae cultivation for cellular growth and pigment contents