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The effect of copper at concentrations of 10, 20, and 50 μg/L on population growth, chlorophyll a fluorescence, and content of photosynthetic pigments (chlorophyll a and carotenoids) of the diatom Thalassiosira nordenskioeldii was studied. It was shown that at metal concentrations of 10 and 20 μg/L, the cell number started to increase from the first days of the experiment and, by the end of the experiment, exceeded that in the control group by 5.8- and 5.6 times, respectively. The intensity of chlorophyll a fluorescence and the content of photosynthetic pigments under these conditions were higher than in the control throughout the experiment. At a metal concentration of 50 μg/L, the growth of the cell population was inhibited at the beginning of the experiment; by the end of the experiment, the cell number exceeded that in control. The same pattern was recorded for the other parameters too. Based on the obtained data, it is hypothesized that copper at the studied concentrations may contribute to the proliferation of T. nordenskioeldii in the natural environment. [ABSTRACT FROM AUTHOR]

The effect of heavy metals cadmium, lead, and nickel on the growth and physiological state of raphidophyte algae Heterosigma akashiwo MBRU_HAK-SR11 (Y. Hada) Y. Hada ex Y. Hara, M. Chihara during 7 days of experiments has been assessed. It was found that cadmium and nickel at concentrations of 10 and 20 µg/L stimulated H. akashiwo growth, while lead inhibited it at these concentrations. Chlorophyll a and carotenoids content increased with the addition of 10 μg/L of cadmium and 20 μg/L of nickel, and the content of carotenoids was higher than that in the control with the addition of 20 μg/L of cadmium. With the introduction of lead, an increase in the level of chlorophyll a and a decrease in the content of carotenoids were observed. The content of ROS increased with the introduction of cadmium and lead and decreased with the introduction of nickel. Cadmium had an effect on the production of neutral lipids: their content increased and decreased by the end of the experiment. Nickel stimulated the accumulation of neutral lipids H. akashiwo, while lead had no effect on their content. Metals had the least effect on forward and side light scattering and fluorescence of chlorophyll a. The absence of pronounced changes in direct and lateral light scattering indirectly indicates that the algae cells did not change morphologically under toxic exposure. Thus, cadmium, lead, and nickel at concentrations of 10–20 µg/L changed physiological processes in algae. [ABSTRACT FROM AUTHOR]

The influence of zinc and iron at concentrations of 50 and 100 μg/L on cell number, chlorophyll a fluorescence, the level of photosynthetic pigments, and reactive oxygen species, as well as neutral lipids, was studied in the raphidophyte alga Heterosigma akashiwo. Zinc has been found to affect on physiological and biochemical processes without affecting the population dynamics of the microalgae. It was revealed that iron has a negative effect on the fluorescence of chlorophyll a and the levels of photosynthetic pigments, reactive oxygen species, and neutral lipids. The most toxic metal for H. akashiwo was iron. It was shown that the used concentrations of the studied metals do not contribute to the development of H. akashiwo blooms. [ABSTRACT FROM AUTHOR]

In our study we investigated the growth, biochemical composition, and ultrastructure of Tisochrysis lutea microalgae in enrichment culture during 30 days experiment. The number of T. lutea cells increased throughout the experiment. We noted an increase in the size and number of lipid droplets containing fatty acids and carotenoids, including fucoxanthin, in the exponential and stationary phases of their growth. It has been established that the total content of carotenoids reaches a maximum in the stationary phase and decreases in the dying phase. During the stationary phase, exocytosis was observed in cells with the release of lipid droplets. This study demonstrates the potential of the T. lutea clone MBRU_Tiso-08 from the Marine Biobank Bioresource Collection of the National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, as a raw material for domestic biotechnology aimed at the combined extraction of carotenoids (including fucoxanthin) and lipids (including docosahexaenoic and eicosapentaenoic fatty acids). [ABSTRACT FROM AUTHOR]

The spectrophotometric method is used to count the number of microalgal cells. Regression equations were obtained for four species of the genus Tetraselmis (Chlorophyta), that are widely used in biotechnology. The correlation coefficients between cell number and absorbance were 0.856, 0.941, 0.787, and 0.916 for Tetraselmis viridis, T. striata, T. maculata, and Tetraselmis sp. respectively, which demonstrates the precision of this method for cell counting. [ABSTRACT FROM AUTHOR]

The mutual influence of the rafidophyte microalgae Heterosigma akashiwo, which causes algal blooms, and the diatom Thalassiosira pseudonana, which is regularly present in sea waters, was studied under experimental conditions. Experiments were carried out with monocultures, monocultural filtrates, and mixed cultures of different initial concentrations. The growth and physiological state of the microalgae were assessed by flow cytometry. Both algae displayed inhibited growth in co-culture and on filtrates, but growth was suppressed to a greater extent in T. pseudonana. The fluorescence of chlorophyll a and the contents of reactive oxygen species and neutral lipids decreased in H. akashiwo cultures grown on T. pseudonana filtrate. Similar changes were noted in a T. pseudonana culture grown on H. akashiwo filtrate. It is concluded that these algae exhibit allelopathic activity in relation to each other. [ABSTRACT FROM AUTHOR]

Marine microalgae from the divisions Chlorophyta, Bacillariophyta, Dinoflagellata, Haptophyta, Rhodophyta, and cyanobacteria (Cyanophyta) are increasingly used for designing novel antibacterial agents. The present review summarizes information on the antimicrobial activities of these organisms. Particular attention is paid to abiotic factors (light, temperature, salinity, pH of the environment, and nutrients) that enhance their bactericidal properties. The mechanisms of action and the methods for extraction of bioactive substances are analyzed. Species that have a potential to inhibit bacterial growth are noted. A number of microalgae preparations that have undergone clinical trials, those already used to treat bacterial infections, and the species that can serve a basis for designing novel antibiotics are discussed. [ABSTRACT FROM AUTHOR]

The effect of copper (10, 25 and 50 μg/L) on the population growth, physiological state, and ultrastructure of the microalga Heterosigma akashiwo (Raphidophyceae) were studied. Copper had a greater effect on the mitochondrial membrane potential than on chlorophyll a fluorescence. The neutral lipid content was lower in the exposed cell than in control cells throughout the experiment. The morphology of organelles was not altered at any copper concentration; however, the number of vacuoles in the algal cells increased at 25 and 50 μg Cu/L. [ABSTRACT FROM AUTHOR]

This study examines the effect of copper (100 and 200 μg/L) on the cell number dynamics, cell size and ultrastructure, chlorophyll a fluorescence, mitochondrial membrane potential, and neutral lipid content in the microalga Picochlorum maculatum (Chlorophyta) during a 7-day exposure. The addition of copper led to the inhibition of population growth; the cell size and ultrastructure remained unchanged. The fluorescence of chlorophyll a was lower than in the control throughout the experiment; the mitochondrial membrane potential decreased on the third day and recovered on the seventh day. The neutral lipid content decreased and did not reach the control level at the end of the experiment. [ABSTRACT FROM AUTHOR]

For more than the past three decades, flow cytometry has been successfully applied in various, including phytoplankton, studies that require rapid qualitative assessment of the physiological condition, chemical composition, and number of microalgal cells. The potential of this method for solving applied and fundamental problems in microalgae research, the parameters of main fluorescent dyes used for this method, the features of microalgae as study objects, as well as the challenges associated with the use of the method, are discussed in the present review. [ABSTRACT FROM AUTHOR]

A comparative ultrastructural study was performed on microalgae from different taxonomic groups (Dinoflagellata, Haptophyta, Rhodophyta, and Ochrophyta) in batch culture. Intra- and interspecific differences in the cell structure in exponential (7 days), stationary (30 days) and decline phases (60 days) are described. General and specific changes in the microalgal cell morphology (the structure of the photosynthetic apparatus, cell wall, and lipid bodies) were found under stress conditions during long-term cultivation. [ABSTRACT FROM AUTHOR]

The biocompatible silica precursor tetrakis(2-hydroxyethyl)orthosilicate with ethylene glycol residues was used instead of the common alcohol-containing tetraethoxysilane for the first time to prepare a biorecognition element by entrapping the marine microalga Porphyridium purpureum into a silica matrix by a one-stage sol-gel procedure at conditions (pH, ionic strength, and temperature) appropriate for living cells. We show that the microalga immobilized in this way fully maintains its viability and functionality. We furthermore show that the silica matrix had a stabilizing effect, providing microalgal survival and functionality at increased temperature. The high optical transparency of the silica matrix allowed us to study the optical properties of Porphyridium purpureum thoroughly. When irradiated by a laser, intense fluorescence of chlorophyll- a and phycoerythrin of the photosynthetic system was observed. The characteristics of this fluorescence differed notably from that observed with P. purpureum in suspension before immobilization; possible reasons for this and an underlying mechanism are discussed. [ABSTRACT FROM AUTHOR]

Effects of copper at concentrations of 0.13 and 0.25 mg/l on content of photosynthetic pigments, growth, size characteristics, and cell shape of Phaeodactylum tricornutum (Bacillariophyta) microalga were studied. The inhibitory effect of copper on growth parameters was shown to become stronger with increasing concentration of copper in the growth medium. In spite of considerable retardation of cell growth, the concentrations examined had no effect on the content of photosynthetic pigments though affected some morphometric parameters. [ABSTRACT FROM AUTHOR]