Lanthanides and Algae

This chapter discusses the ecological and physiological impacts of lanthanides on algae as primary producers in aquatic environments. Although lanthanides are nonessential elements for living organisms, their bioaccumulation is a common phenomenon. Here, we critically review the ecological effects of increasing levels of lanthanides directly reaching water systems through mining, application of fertilizers, and the production of advanced technologies. We describe interactions between lanthanides and algae, with a particular focus on various applications including fertilizers, tracers, bioindicators, bioremediation, and recycling. We examine the stimulatory effects of low levels of lanthanides versus their toxicity at higher levels and discuss mechanisms by which they may affect the algal cell. This chapter highlights the importance of a better understanding of the biological roles of lanthanides

The Red Microalga <em>Galdieria</em> as a Promising Organism for Applications in Biotechnology

The genus Galdieria refers to red algae and includes microscopic inhabitants of highly acidic (pH 1–2), often volcanic habitats. They are thermophilic or thermo-tolerant organisms, some of them surviving temperatures up to 56°C. As other extremophilic microorganisms, they exhibit unique features derived from their modified metabolisms. In this chapter, we will review the special abilities of Galdieria species such as metabolic flexibility to grow photoautotrophically, heterotrophically or mixotrophically, ability to utilize a whole range of unusual carbon sources, capability of surviving extreme environments or their extremely high resistance to metals. We will discuss the potential of Galdieria for applications in biotechnology, for example, phycocyanin production, nutrient removal from urban wastewaters, bio-mining, treatment of acidic mine drainage, selective metal precipitation, bioremediation of acidic metal-contaminated areas or recovery of critical and scarce metals from secondary sources

Bioaccumulation and toxicity of selenium compounds in the green alga Scenedesmus quadricauda

<p>Abstract</p> <p>Background</p> <p>Selenium is a trace element performing important biological functions in many organisms including humans. It usually affects organisms in a strictly dosage-dependent manner being essential at low and toxic at higher concentrations. The impact of selenium on mammalian and land plant cells has been quite extensively studied. Information about algal cells is rare despite of the fact that they could produce selenium enriched biomass for biotechnology purposes.</p> <p>Results</p> <p>We studied the impact of selenium compounds on the green chlorococcal alga <it>Scenedesmus quadricauda</it>. Both the dose and chemical forms of Se were critical factors in the cellular response. Se toxicity increased in cultures grown under sulfur deficient conditions. We selected three strains of <it>Scenedesmus quadricauda </it>specifically resistant to high concentrations of inorganic selenium added as selenite (Na₂SeO₃) – strain SeIV, selenate (Na₂SeO₄) – strain SeVI or both – strain SeIV+VI. The total amount of Se and selenomethionine in biomass increased with increasing concentration of Se in the culturing media. The selenomethionine made up 30–40% of the total Se in biomass. In both the wild type and Se-resistant strains, the activity of thioredoxin reductase, increased rapidly in the presence of the form of selenium for which the given algal strain was not resistant.</p> <p>Conclusion</p> <p>The selenium effect on the green alga <it>Scenedesmus quadricauda </it>was not only dose dependent, but the chemical form of the element was also crucial. With sulfur deficiency, the selenium toxicity increases, indicating interference of Se with sulfur metabolism. The amount of selenium and SeMet in algal biomass was dependent on both the type of compound and its dose. The activity of thioredoxin reductase was affected by selenium treatment in dose-dependent and toxic-dependent manner. The findings implied that the increase in TR activity in algal cells was a stress response to selenium cytotoxicity. Our study provides a new insight into the impact of selenium on green algae, especially with regard to its toxicity and bioaccumulation.</p

Bio-mining of Lanthanides from Red Mud by Green Microalgae

Red mud is a by-product of alumina production containing lanthanides. Growth of green microalgae on red mud and the intracellular accumulation of lanthanides was tested. The best growing species was Desmodesmus quadricauda (2.71 cell number doublings/day), which accumulated lanthanides to the highest level (27.3 mg/kg/day), if compared with Chlamydomonas reinhardtii and Parachlorella kessleri (2.50, 2.37 cell number doublings and 24.5, 12.5 mg/kg per day, respectively). With increasing concentrations of red mud, the growth rate decreased (2.71, 2.62, 2.43 cell number doublings/day) due to increased shadowing of cells by undissolved red mud particles. The accumulated lanthanide content, however, increased in the most efficient alga Desmodesmus quadricauda within 2 days from zero in red-mud free culture to 12.4, 39.0, 54.5 mg/kg of dry mass at red mud concentrations of 0.03, 0.05 and 0.1%, respectively. Red mud alleviated the metal starvation caused by cultivation in incomplete nutrient medium without added microelements. Moreover, the proportion of lanthanides in algae grown in red mud were about 250, 138, 117% higher than in culture grown in complete nutrient medium at red mud concentrations of 0.03, 0.05, 0.1%. Thus, green algae are prospective vehicles for bio-mining or bio-leaching of lanthanides from red mud

Relationship between starch and lipid accumulation induced by nutrient depletion and replenishment in the microalga Parachlorella kessleri

Photosynthetic carbon partitioning into starch and neutral lipids, as well as the influence of nutrient depletion and replenishment on growth, pigments and storage compounds, were studied in the microalga, Parachlorella kessleri. Starch was utilized as a primary carbon and energy storage compound, but nutrient depletion drove the microalgae to channel fixed carbon into lipids as secondary storage compounds. Nutrient depletion inhibited both cellular division and growth and caused degradation of chlorophyll. Starch content decreased from an initial value of 25, to around 10% of dry weight (DW), while storage lipids increased from almost 0 to about 29% of DW. After transfer of cells into replenished mineral medium, growth, reproductive processes and chlorophyll content recovered within 2 days, while the content of both starch and lipids decreased markedly to 3 or less % of DW; this suggested that they were being used as a source of energy and carbon.This study was supported by grant CREST of Japan Science and Technology Agency, by Grant No. LH12145 of Ministry of Education, Youth and Sports of the Czech Republic, by Grant for International Collaboration Academy of Sciences of the Czech Republic No. M200201205 and by the Technology Agency of the Czech Republic, project No. TE01020080

DNA Damage during G2 Phase Does Not Affect Cell Cycle Progression of the Green Alga Scenedesmus quadricauda

DNA damage is a threat to genomic integrity in all living organisms. Plants and green algae are particularly susceptible to DNA damage especially that caused by UV light, due to their light dependency for photosynthesis. For survival of a plant, and other eukaryotic cells, it is essential for an organism to continuously check the integrity of its genetic material and, when damaged, to repair it immediately. Cells therefore utilize a DNA damage response pathway that is responsible for sensing, reacting to and repairing damaged DNA. We have studied the effect of 5-fluorodeoxyuridine, zeocin, caffeine and combinations of these on the cell cycle of the green alga Scenedesmus quadricauda. The cells delayed S phase and underwent a permanent G2 phase block if DNA metabolism was affected prior to S phase; the G2 phase block imposed by zeocin was partially abolished by caffeine. No cell cycle block was observed if the treatment with zeocin occurred in G2 phase and the cells divided normally. CDKA and CDKB kinases regulate mitosis in S. quadricauda; their kinase activities were inhibited by Wee1. CDKA, CDKB protein levels were stabilized in the presence of zeocin. In contrast, the protein level of Wee1 was unaffected by DNA perturbing treatments. Wee1 therefore does not appear to be involved in the DNA damage response in S. quadricauda. Our results imply a specific reaction to DNA damage in S. quadricauda, with no cell cycle arrest, after experiencing DNA damage during G2 phase

Plastoskeletální protein FtsZ a dělení chloroplastů v zelených řasách

FtsZ protein, an ancestral homologue of eukaryotic tubulin, is the key effector in regulation of bacterial division. In plants, the FtsZ protein participates in chloroplast division. We have studied the chloroplast division in the green unicellular alga Scenedesmus quadricauda. To uncouple chloroplast and nucleocytoplasmic division cycles, we used 5-fluorodeooxyuridine (FdUrd). The amount and localization of FtsZ during the cell cycle was followed using immunoblotting and immunofluorescence staining on semi-thin sections. Antibody against FtsZ reacts with 49kD protein in Scenedesmus quadricauda and this protein is localized in chloroplast.The level of FtsZ protein increases during growth phase with maximum in time of chloroplast division. Localization of FtsZ protein is changing during the cell cycle, but we have not observed Z-ring, described in higher plant

Aktivita thioredoxin reduktázy v divokém a selen rezistentích kmenech řasy Scenedesmus quadricauda rostoucích v přítomnosti anorganických sloučenin selenu

We have selected resistant strains of Scenedesmus quadricauda able to tolerate high selenium concentration up to 400 mg/L added either as selenate Na2SeO4 (strain SeVI) or selenite Na2SeO3 (strain SeIV). We have investigated activity of selenoprotein thioredoxin reductase (TR) in both wild type and Se-resistant strains. Concomitantly, a total amount of organically bound selenium was evaluated in biomass dry weight. We have found that activity of TR rapidly increases in the SeVI resistant strain in the presence of selenate, while no effect on TR activity was found in SeIV resistant strain and only slight increase in wild type in the presence of selenit

Cirkadiální hodiny se neúčastní načasování buněčného dělení v řase Chlamydomonas reinhardtii

To determine whether the circadian clock functions in control the entry of algal cells into the cell cycle, we have tested the green alga Chlamydomonas reinhardtii in a wide range of growth conditions both light intensity and temperature. We monitored the course of the cell cycles in asynchronous as well as in synchronized cultures. The cultures were grown either at the continuous light or at alternating light/dark periods. The length of the cell cycle was monitored also at different temperatures and in “circadian” mutant. We have evidenced that the length of the cell cycle corresponding to circadian times can be attained only under relatively narrow range of growth conditions and even in this case the “circadian time” is a result of given growth conditions and not of any circadian gating. These results suggest that the intrinsic circadian clock does not play any role in timing of the cell cycle division in the green alga Chlamydomona

Exploring Mycosporine-Like Amino Acids (MAAs) as Safe and Natural Protective Agents against UV-Induced Skin Damage

Prolonged exposure to harmful ultraviolet radiation (UVR) can induce many chronic or acute skin disorders in humans. To protect themselves, many people have started to apply cosmetic products containing UV-screening chemicals alone or together with physical sunblocks, mainly based on titanium–dioxide (TiO2) or zinc-oxide (ZnO2). However, it has now been shown that the use of chemical and physical sunblocks is not safe for long-term application, so searches for the novel, natural UV-screening compounds derived from plants or bacteria are gaining attention. Certain photosynthetic organisms such as algae and cyanobacteria have evolved to cope with exposure to UVR by producing mycosporine-like amino acids (MAAs). These are promising substitutes for chemical sunscreens containing commercially available sunblock filters. The use of biopolymers such as chitosan for joining MAAs together or with MAA-Np (nanoparticles) conjugates will provide stability to MAAs similar to the mixing of chemical and physical sunscreens. This review critically describes UV-induced skin damage, problems associated with the use of chemical and physical sunscreens, cyanobacteria as a source of MAAs, the abundance of MAAs and their biotechnological applications. We also narrate the effectiveness and application of MAAs and MAA conjugates on skin cell lines