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Phosphorus (P) is an essential macronutrient central to the exchange and storage of energy and information in the cell. Due to its limited bioavailability, P often becomes a limiting nutrient in aquatic and terrestrial ecosystems hence the studies of responses to stress caused by P starvation cyanobacteria, the primary producers, are of considerable interest. Indeed, the availability of P is among main factors limiting diazotrophy in cyanobacteria. To gain a deeper understanding of the effect of P starvation on cyanobacteria in non-diazotrophic conditions, we studied a model system of two near—isogenic strains, Nostoc sp. PCC 7120 and Nostoc sp. PCC 7118 differ in their ability to form heterocysts. Specifically, we investigated the differences in the responses of these strains to P starvation by comparing their growth kinetics, photosynthetic pigment content, ultrastructural rearrangements of vegetative cells, and the expression profile of key genes of phosphorus metabolism. The tolerance of PCC 7120 to P starvation was higher than that of PCC 7118, which manifested itself in a higher growth rate, less profound ultrastructural changes (in particular, phycobilisomes as well as polyphosphate reserves were retained in the cells of PCC 7120). At the same time, the accumulation of cyanophycin, a depot of nitrogen and energy, increased several-fold in the cells of both strains during P starvation, but this increase was larger in PCC 7118 cells. Assumably, the increased resilience of the PCC 7120 to P starvation stems from its higher ability to accumulate intracellular reserves of P in the form of polyphosphates. Our findings suggest that the phenotypic differences between the strains Nostoc sp. PCC 7118 and Nostoc sp. PCC 7120 are not limited to the different ability to form heterocysts. A deeper understanding of the drivers of stress response phenotypic diversity in near-isogenic strains would require a comparative analysis of their whole-genome sequences. [ABSTRACT FROM AUTHOR]

Apart from their functions in the nervous system of animals, neurotransmitters operate as regulatory agents and signals in diverse kingdoms of life. Some neurotransmitters have recently been revealed to exert specific effects on microalgae, predominantly functioning as algal growth stimulators. This article presents new data on the effects of such neurotransmitters as serotonin, norepinephrine, dopamine, histamine, and acetylcholine on the fatty acid and pigment composition of the green microalga Scenedesmus quadricauda (Turp.) Breb. K-1149. It was established that acetylcholine and, to a lesser extent, histamine increased the total fatty acid content of S. quadricauda cells, whereas serotonin and dopamine decreased the fatty acid content. Acetylcholine, histamine, and norepinephrine elevated the percentage of polyunsaturated fatty acids; in contrast, serotonin and dopamine increased the share of saturated fatty acids. Acetylcholine and, to a lesser extent, norepinephrine increased the total chlorophyll content per gram of dry weight in S. quadricauda, while histamine decreased the chlorophyll content. Histamine also increased the chlorophyll a/chlorophyll b and carotenoid/chlorophyll ratios, which were decreased by dopamine. The data obtained are of biotechnological and ecological interest. The stimulation of fatty acid accumulation and the increase in the percentage of polyunsaturated species was caused by the neurotransmitters acetylcholine and histamine at low (1–10 μM) concentrations, which potentially enables facilitating the biotechnological production of health-promoting preparations for therapeutic and cosmetic purposes. However, other neurotransmitters (dopamine and serotonin) tested increased the relative content of saturated fatty acids; therefore, they apparently can be used to stimulate biofuel production, since saturated fatty acid-rich lipids are advantageous raw materials for biodiesel production. The impact of neurotransmitters on microalgal fatty acid composition and photosystem components may be considered in terms of ongoing chemical interaction between microalgae and other aquatic ecosystem components that are known to produce neurotransmitters. [ABSTRACT FROM AUTHOR]

The productivity of microalgal cultures and their resilience to unfavorable conditions is largely determined by the availability of mineral nutrients, particularly nitrogen. Nitrogen starvation is a strong stressor that induces a broad range of responses in microalgae at the cell and cell population (culture) levels. These responses such as lipogenesis and secondary carotenogenesis are widely used in biotechnology to obtain valuable secondary metabolites of microalgae. It was believed that microalgal cells lack specific structures that function as long-term nitrogen depot, but recent studies assigned this role to microcrystalline inclusions constituted by nitrogenous bases (most often guanine). It is also known that purine microcrystals are biophotonic structures widespread in nature. These structures modify the intensity and spectral composition of radiation in illuminated cells and tissues of living organisms. In this regard, we studied (i) the dynamics of the formation of guanine crystals in the cells of green carotenogenic microalgae from the genus Coelastrella (C. thermophila NAMSU CM1/23 and C. rubescens IPPAS C-2066) depending on the availability of nitrogen in the medium and (ii) the effect of the presence of these crystals on cell resilience to high light intensity. Nitrogen-rich crystal inclusions were accumulated in cells when the cultures reached the stationary growth phase in a medium with ample nitrate nitrogen. During rapid growth, these inclusions were hardly detectable in the cells and disappeared during cultivation in the absence of nitrogen. Optical polarization microscopy and Raman microspectroscopy demonstrated that these nitrogen-rich inclusions are birefringent microcrystals composed of guanine. C. thermophila cells harboring abundant guanine crystals showed resistance to short-term (10–15 min) exposure to high-intensity light (600 µmol PAR quanta/m2/s). The results obtained are discussed in the context of the multifaceted role of guanine crystals in the stress tolerance of microalgae. [ABSTRACT FROM AUTHOR]

Photogeneration of hydrogen in microalgae is thought to be among the mechanisms increasing their resilience to stresses including those caused by nutrient deprivation by re-routing the flow of electrons and reducing power in the cell. Metabolism of phosphorus (P), an essential nutrient, and its reserve forms such as polyphosphate (PolyP), is affected by and plays a role in the responses to diverse stresses, too. However, the potential interplay of the capability of photogeneration of hydrogen and turnover of phosphorus-rich inclusions in stressed microalgae cells so far escaped the attention of researchers. Here, we present a quantitative ultrastructural view of the turnover of P-rich inclusions in the model microalga Chlamydomonas reinhardtii strains, the parent strain CC-425 and its hydEF-1 mutant lacking hydrogenase activity as a function of sulfur and oxygen availability in the medium. In addition to the electron microscopy cell image analysis of the studied strains, we followed the elemental composition of the inclusions in different (sub) compartments of the cells obtained with energy dispersive X-ray spectroscopy. The stress caused by sulfur deprivation and subsequent transition of the microalgae culture to anaerobic conditions declined the size of phosphorus-containing inclusions but increased their number in the parent strain. Overall, the accumulation of the phosphorus-rich inclusions in hydEF-1 mutant was much lower than in the fully functional parent strain regardless of the cultivation conditions. We believe that impaired hydrogenase activity and correspondingly reduced sink of electrons and reducing power in the mutant strain indirectly affects the turnover of P and its reserves in the cell. These effects were manifested by the changes in the abundance, morphology, and elemental composition of the P-containing inclusions. We hypothesized that the sulfur-deprivation stress increased the initiation of the biosynthesis of PolyP chains, but their elongation and hence the formation of large PolyP-containing inclusions was hindered by anaerobiosis. [ABSTRACT FROM AUTHOR]

Green microalgae capable of accumulating secondary carotenoids are the most important objects of biotechnology, and the search for new strains with unique properties, in particular, those adapted to growth at low temperatures and high salinity in the environment, is an urgent task. The NAMSU SBB-20 microalga strain was isolated from an algal-bacterial biofilm found on the coast of the White Sea in the littoral zone of the Solovetsky Archipelago. Identification of the strain showed its belonging to the species Halochlorella rubescens P.J.L.Dangeard. The species H. rubescens was first described for the White Sea. Under conditions of high light intensity, ultrastructural changes in cells are shown, among which destruction of the photosynthetic apparatus and the formation of cytoplasmic and chloroplast lipid inclusions are noted. It was shown that the culture of the NAMSU SBB-20 strain is capable of acquiring an orange color under unfavorable growth conditions. An assessment was made of the effect of the composition of the medium and the intensity of illumination on the pigment composition of the algae. The highest absolute values of the accumulation of carotenoids were noted during cultivation in light with an intensity of 150 μmol PAR quanta/m2/s on BG-11 media containing no source of phosphorus (15.66 ± 0.18 mg/L) or nitrogen (15.95 ± 0.56 mg/L). The described strain has a biotechnological potential due to the initial halotolerance and the accumulation of high values of secondary carotenoids in the biomass. [ABSTRACT FROM AUTHOR]

The effect of nitrogen starvation and, for the first time, low temperature, as well as their simultaneous effect, on the physiology and ultrastructure of cells of microalgae of the genus Lobosphaera (Chlorophyta, Trebouxiophyceae) was studied. Nitrogen deficiency in both strains led to a decrease in the content of chlorophyll by three times and an increase in the proportion of carotenoids by two times. A decrease in the content of both chlorophyll and carotenoids was observed at +10°C. The simultaneous effect of two factors resulted in a threefold decrease in the chlorophyll content in NAMSU 924/2 and a sixfold decrease in NAMSU (CALU) 1497; the proportion of carotenoids in both strains decreased by 1.5–2 times. Data on ultrastructural changes in cells of microalgae of the genus Lobosphaera under the influence of stress factors have been obtained. A similar nature of the response in both strains to stress conditions was noted. Nitrogen deficiency led to the accumulation of numerous lipid droplets in the cytoplasm of cells along the cell wall. Long-term incubation on a nitrogen-free medium led to the filling of the entire volume of cells with lipid droplets, disassembly of the membrane system of chloroplasts, that reduction in sizeand being located between densely lying lipid droplets. At low temperatures, the number of thylakoids decreased, while the interthylakoid space and the size of chloroplasts increased. With simultaneous exposure to nitrogen starvation and low temperature, numerous lipid droplets accumulated, the number of thylakoids decreased, the interthylakoid space and the size of the chloroplast increased, which was noted under separate exposure to stress factors. The pyrenoid in both strains did not undergo significant changes in all cases. [ABSTRACT FROM AUTHOR]

Green microalgae Lobosphaera sp. IPPAS С-2047 and Micractinium simplicissimum IPPAS С-2056 were examined for the first time for cell tolerance to elevated concentrations of manganese applied in the form of MnCl2. Analyses of cell photosynthetic activity by chlorophyll fluorometry and the dynamic patterns of absorbance changes of cell suspensions at the peak of chlorophyll absorption revealed differential tolerance of two microalgae species to manganese. The acute toxicity assayed in 4-day treatments became apparent at manganese concentrations equal to or higher than 1 g/L for M. simplicissimum cells and at concentrations above 10 g/L for Lobosphaera sp. Transmission electron microscopy and energy-dispersive X-ray spectroscopy were used to study the subcellular distribution of manganese in microalgal cells under elevated nontoxic concentrations of manganese in the medium. The results with Lobosphaera sp. established the lack of individual manganese-containing inclusions on cell surfaces and in the cell interior; the intracellular distribution of manganese was dispersed with elevated accumulation of this element in the region of thylakoids and plastoglobules. The occurrence of manganese and phosphorus in plastoglobules was found for the first time. Apparently, these compartments become accessible for accumulation of Mn and P upon the translocation of thylakoid components during stress-induced disassembling of their structure. The cells of M. simplicissimum were able to oxidize the exoplasmic Mn2+ with the formation of manganese nanoparticles in the intercellular matrix as well as on the cell surface and within the cell walls. In addition, the manganese permeating into the cells was shown to compartmentalize in vacuoles and bind to the polyphosphate granules. [ABSTRACT FROM AUTHOR]

Coelastrella rubescens Kaufnerová & Eliás (Chlorophyceae) is a green, single-celled algae that lives in the terrestrial-air environment. Under stress conditions, its cells go into a state characterized by low photosynthetic activity and high content of reserve lipids and secondary carotenoids. For the first time, a comparative morphological, ultrastructural, and elemental analysis of vacuolar inclusions in the C. rubescens NAMSU R1 strain when cultivated on a mineral medium under conditions of low and high (causing stress) light intensity. Microalgae cells stained with the fluorescent dye DAPI showed signs of the presence of polyphosphates. Polarization microscopy in cells of C. rubescens has identified structures capable of refracting polarized light, which is typical of crystals. Cell analysis of C. rubescens with the transmission electron microscopy (TEM) method revealed the presence of various vacuoles with heterogeneous contents (autophagic bodies, crystalloids, and rounded globules of inhomogeneous electron density). With the exception of autophagic bodies noted in cells only in bright light, these inclusions were characteristic of microalgae cells, regardless of the intensity of illumination. The elemental composition of vacuolar inclusions was characterized by TEM in combination with energy-dispersive X-ray spectroscopy: the predominant content of nitrogen, phosphorus, or both elements simultaneously was established in them. The potential physiological role of C. rubescens vacuolar inclusions is discussed. [ABSTRACT FROM AUTHOR]

The immobilization of cells of a mixed culture of the microalgae (MA) Micractinium sp. NAMSU A-19 and cyanobacteria (CB) Synechococcus sp. 1Dp66E-1 on a chitosan-based polymer was studied. A polycationic sorbent based on a natural chitosan polymer with a molecular weight of 600 kDa was obtained from the crosslinking of chitosan with glutaraldehyde via cryopolymerization. It has a high affinity for the surface structures of oxygenic phototrophic microorganisms (OPMs) and enables strong cellular attachment to the sorbent surface. The study of the kinetics and evaluation of the effectiveness of mixed-culture immobilization showed a high sorption capacity of the chitosan sorbent. During the first hour of cultivation, the immobilization efficiency was on average 40–52%, and, almost all cells were immobilized after 48 h. The highly porous, nontoxic, and biodegradable sorbent provided steady cellular attachment for 7 days of cultivation and did not affect the growth of immobilized mixed culture, either on the surface or in the inner layers of the polymer. The study of mixed-culture immobilization via scanning electron microscopy showed that CB and MA cells are tightly attached to the surface of the chitosan sorbent. This is followed by the formation of strands of the extracellular polymer matrix and a biofilm consisting of cells of the mixed culture of MA and CB and heterotrophic bacteria associated with Micractinium sp. Immobilization on a chitosan sorbent contributes to an increase in the bioremoval of nitrates and phosphates by the tested mixed culture. [ABSTRACT FROM AUTHOR]

It was shown that the studied petroleum products, kerosene and gasoline, contain microfloccules of heterogeneous microbial biofilms, the cells of which are integrated in a polymer matrix containing acidic polysaccharides. Thirteen bacterial strains were microbiologically isolated from petroleum products, and their taxonomy was identified via analysis of the 16S rRNA sequence. Kerosene was characterized by a diverse bacterial composition, including the following genera: Sphingobacterium, Alcaligenes, Rhodococcus, and Deinococcus. The gasoline bacterial community included only two genera: Bacillus and Paenibacillus. Representatives of the Deinococcus genus that are capable of growing on hydrocarbons were isolated from fuels for the first time. Strains isolated from gasoline (Bacillus safensis Bi13 and Bacillus sp. Bi14) proved to be the most effective biodegraders of all n-alkanes, isoalkanes, cycloalkanes, alkenes, and aromatic hydrocarbons, whereas the strain Rhodococcus erythropolis Bi6, which was isolated from kerosene, effectively decomposed only n-alkanes and trimethylbenzene. Both types of the studied petroleum products contained hydrocarbon-oxidizing communities, some members of which were more active in hydrocarbon biodegradation, while others were capable of producing biosurfactants and compounds with emulsifying activity (Deinococcus sp. Bi7) or had increased (well above average) cell-wall hydrophobicity (Sphingobacterium sp. Bi5 from kerosene; Bacillus pumilus Bi12 from gasoline). The indicated properties of the studied strains make them promising for use in bioremediation. [ABSTRACT FROM AUTHOR]

The toxicity of polyethylenimine-based sorbents and their extracts was evaluated, and their effect on the bioluminescence of Photobacterium phosphoreum photobacteria was studied. These test bacteria are commonly used as objects to evaluate the toxicity of various materials. The analyzed materials were synthesized via polyethylenimine (PEI) cross-linking with diethylene glycol diglycidyl ether (DGDE) at mass contents of the latter of 1.9–120.0% with subsequent freezing. It was found that the degree of luminescence inhibition in P. phosphoreum cells depended on the PEI/DGDE ratio in the sorbent. Sorbents with a high DGDE content (60–120%) did not affect the cell luminescence activity, while those with a lower percentage of the cross-linker (0.9–30%) exhibited a pronounced inhibitory effect on luminescence of photobacteria according to the data obtained with the standard biotesting method. It was also established that the inhibitory effect of sorbents with a reduced DGDE percentage (<30%) in a phosphate buffer was significantly lower than that in salt solutions. Water and ethanol extracts of sorbents with a DGDE mass proportion of more than 15% did not significantly inhibit the luminescence of P. phosphoreum in 1 h of incubation. The immobilization of P. phosphoreum cells on the surface and internal parts of the studied sorbents was observed via scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) are dangerous micropollutants that exhibit biotoxicity even in low (ng/L range) concentrations. Apart from direct toxicity to living organisms, NPs can absorb and transfer organic or inorganic toxicants as well as potentiate the toxicity of other micropollutants. Increasing use of NPs in industrial and domestic applications leads to their increased production and discharge into the environment giving rise to diverse risks for ecosystems. These risks are exacerbated by the resilience of NPs to biodegradation in natural ecosystems and traditional wastewater treatment plants. Efficient NP removal technologies are complex and expensive, so they cannot be affordably replicated in common wastewater treatment plants. Despite the risks associated with NPs, humanity will not abandon their use in the nearest future, since NPs are now at the foundation of many modern technologies. The biodestruction and biosorption of NPs using microalgae cultures and algal-bacterial consortia are considered promising approaches regarding environmental safety and the conservation of natural resources. However, the progress of this approach is hindered by the paucity and fragmentary nature of the information about the effects of NPs on microalgae cells and microbial communities. This review attempts to fill this gap, at least partially, by considering common industrial NP types based on metals and their oxides as well as carbon nanomaterials. The pathways of their entry into aquatic ecosystems, toxicity to living organisms, accumulation and biotransformation in cells, synergistic effects of NPs in combination with heavy metals and antibiotics, as well as methods for the bio-removal of NPs and nanomaterials from aquatic ecosystems using microalgae are discussed. [ABSTRACT FROM AUTHOR]

The best known polymers (alginate, carrageenan, and acrylamide) were examined for their potential use as carriers of mycelium cells of Aspergillus ochraceus VKM-F4104D, a producer of fibrinolytic protease activator of protein C in human blood plasma during its deep cultivation. The morpho-cytological features of the development of A. ochraceus VKM-F4104D mycelium in granules of carrageenan and calcium alginate are shown. The conditions for the cultivation of micromycete immobilized in granules of 3.5% calcium alginate were optimized. The immobilized cells of the producer mycelium demonstrated increased stability and were able to synthesize protein-C protease-activator in blood plasma at the maximum level for 10 or more days. In addition, immobilized mycelial cells during cultivation can be used repeatedly (up to five cycles). [ABSTRACT FROM AUTHOR]

The immobilization of the microalgae (MA) of cells on biosorbents based on polyethyleneimine and cellulose-containing plant components is studied. Polyethyleneimine-based polycationic polymers have a high level of affinity for the surface structures of the MA and ensure that the cells are strongly attached to the surface of the sorbent. The introduction of plant fillers in the composition of such polymers allows us to increase their biodegradation rate and reduce costs. In the present study, six insoluble porous polymeric materials obtained by the cryopolymerization of a mixture of polyethyleneimine and various plant components using diethylene glycol diglycidyl ether were synthesized. The lyophilized biomass of plant cell cultures of Ajuga turkestanica and Polyscias fruticosa, as well as the cell-structured material (CSM) obtained from their biomass, is used as a bio-filler. Studying the kinetics and evaluating the efficiency of the immobilization of cells of the model MA culture showed the high sorption ability of the obtained materials: after 24 h of cultivation, the efficiency of immobilization was 72–77%. Assessment of the level of the photosynthetic activity of the MA cells using the method of pulse-simulated fluorimetry demonstrated that the studied biosorbents did not have any toxic effect on the cells and did not affect their functional activity. Novel biosorbents can be effectively used to collect the biomass of microorganisms from natural aquatic environments and industrial cultivators. [ABSTRACT FROM AUTHOR]

The current problem with phosphorus fertilizers are shortage of rock phosphate from which it is produced and adverse impact of their production and use on the environment. A promising solution is use of phosphorus-rich biomass of microalgae as biofertilizer, but possible impact of such fertilizers on the biological activity and microbiome of soils remain unknown in many aspects. We investigated the effect of Chlorella vulgaris IPPAS C-1 (Chlorophyceae) biomass application on yield, biological activity, efficacy of the rhizobia- and cyanobacteria-based growth promoting formulations, as well as the microbiome of the soil during cultivation of beans (Phaseolus vulgaris L.) cvr. "Strela." Total and specific yield, actual nitrification and denitrification, carbon dioxide and methane emission were determined for soil samples from the rhizosphere. The taxonomic structure of the prokaryotic community of the bean rhizosphere was determined by NGS of 16s rRNA gene amplicons on the Illumina platform. The metagenomic data were analyzed using software tools QIIME and VAMPS. It was found that the application of biomass of C. vulgaris IPPAS C-1 as a phosphorus biofertilizer increased the bulk yield of beans. It also allowed to achieve the specific yield (per plant) level provided by traditional fertilizers. The biomass application did not (i) impact the biological activity of the soil, (ii) did not increase the level of denitrification, and (iii) did not increase significantly the soil emission of the "greenhouse gases." The Chlorella biomass application hamper the growth-promoting effect of the bacterial preparations made from rhizobia and cyanobacteria. Also, no significant changes in the taxonomic composition of the soil of the rhizosphere microbiome upon the application of the Chlorella biomass were revealed. Collectively, the results indicate the possibility of at least partial replacement of chemical fertilizers with phosphorus biofertilizers from microalgae biomass in the field growing of beans. [ABSTRACT FROM AUTHOR]

Abstract—A biocomposite material has been created on the basis of a polymer matrix (a copolymer of acrylonitrile and methyl methacrylate) with incorporated biogenic elements in the form of beet pulp and immobilized strains of bacteria or an association of bacteria isolated from contaminated petroleum products. The high activity of the created material in the processes of purification of model seawater from hydrocarbons has been shown. [ABSTRACT FROM AUTHOR]

The life cycle of cyanobacteria Dolichospermum flos-aquae causing the blooming of waters of the boreal zone is studied. The mass propagation of the D. flos-aquae in the plankton stage occurs due to their ability to realize high biotic potential, defined by the combination of features developed during evolution, which the other partners of the plankton community lack. These include: adaptation to a certain growth temperature; low demand for nutrients; nitrogen fixation and intracellular accumulation of phosphates; and the ability of trichomes to migrate, allowing them to occupy the optimal parts of the euphotic zone for photosynthesis. It is established that the trichomes of D. flos-aquae consist of heterocysts and vegetative cells of different maturity, generosity, and activity during the planktonic stage, and their ratio changes throughout the life cycle of microorganisms. It is believed that the primary and secondary metabolites released by D. flos-aquae into the medium take part in the regulation of their own population growth, including cell destruction at the final stage of blooming, akinetes formation, and the simultaneous suppression in propagation of community partners. With the dominance of one species, the released toxic metabolites increase in years with an anticyclone type of weather, resulting in the reduction of species diversity and the simplification of the biotic community structure. [ABSTRACT FROM AUTHOR]

Abstract: The molecular genetic, morphometric, and physiological-biochemical characteristics of three isolates of the carotenogenic microalga Haematococcus sp. obtained in different regions of the Caucasus and Crimea were studied. According to the results of light microscopy and PCR analysis of 18s rDNA gene fragments, all isolates were identified as Haematococcus pluvialis (clade Chlorogonia, order Volvocales, class Chlorophyceae). It is shown that the strains isolated in the mountainous and valley areas of the Black Sea region differ in important characteristics relevant for mass cultivation: cell size, growth rate, stress tolerance, mass fraction of total carotenoids and astaxanthin in dry matter, and their yield per liter of the start culture. The H. pluvialis isolates most promising for further research and the development of a cultivation technology for the Black Sea regions of the Caucasus and Crimea were strains IMBR-3 (Sevastopol) and IMBR-1 (Adler), which were characterized by the highest astaxanthin production (16.77 ± 1.32 and 17.12 ± 0.72 mg/(L day), respectively). [ABSTRACT FROM AUTHOR]

A new rapid method for analytical control of sulfur compounds in hydrocarbon media using test agents has been developed. The method is based on the interaction of an indicator (solid-phase reagent) with sulfur-containing compounds and the subsequent detection of the product by linear-colorimetric and spectrophotometric means. A new rapid method with spectrophotometric and colorimetric detection has also been developed for quantitative determination of sulfur- and nitrogen-containing substances simultaneously present in hydrocarbon media. [ABSTRACT FROM AUTHOR]

The purpose of this work was to investigate the sorbents on the basis of polyethylenimine (PEI) intended for collecting biomass of microalgae (MA). For this purpose, a series of porous and insoluble polymeric materials were synthesized by cross-linking of PEI with epichlorohydrine. The analysis of kinetics and efficiency of immobilization assessed for the model culture Chlorella vulgaris, revealed that already within 3 h of incubation, 39-75% of MA cells attached to the surface of tested sorbents. It was shown that on the initial stage of immobilization the sorption activity of polymeric materials depended on the “PEI:crosslinker” ratio. One of the tested sorbents was additionally quartenized by alkylation with dimethyl sulphate resulting in sharp increase of its sorption activity. The estimation of the MA desorption from polymeric surface showed that most Ch. vulgaris cells were practically irreversibly immobilized on all tested sorbents based on the PEI cross-linked with epichlorohydrine. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1021443722330020 [ABSTRACT FROM AUTHOR]

Three new cyanobacterial strains, that have been previously purified from the hydroid Dynamena pumila (L., 1758), isolated from the White Sea, were studied using scanning and transmission electron microscopy methods and were characterized by using almost complete sequence of the 16S rRNA gene, internal transcribed spacer 16S-23S rRNA, and part of the gene for 23S rRNA. The full nucleotide sequences of the rRNA gene clusters were deposited to GenBank (HM064496.1, GU265558.1, JQ259187.1). Comparison of rRNA gene cluster sequences of Synechococcus cyanobacterium 1Dp66E-1, Oscillatoriales cyanobacterium 2Dp86E, and Nostoc sp. 10Dp66E with all sequences present at the GenBank shows that these cyanobacterial strains do not have 100% identity with any organisms investigated previously. Furthermore, for the first time heterotrophic bacterium, associated with Nostoc sp. 10Dp66E, was identified as a member of the new phylum Gemmatimonadetes, genus of Gemmatimonas (GenBank accession number is JX437625.1). Phylogenetic analysis showed that cyanobacterium Synechococcus sp. 1Dp66E-1 forms the unique branch and belongs to a cluster of Synechococcus, including freshwater and sea strains. Oscillatoriales cyanobacterium 2Dp86E belongs to a cluster of Leptolyngbya strains. Isolate Nostoc sp. 10Dp66E forms unique branch and belongs to a cluster of the genus Nostoc, with the closest relative of Nostoc commune isolates [ABSTRACT FROM AUTHOR]

Associations of cyanobacteria and actinomycetes were formed experimentally from the cyanobacterium Anabaena variabilis ATCC 29413 and the streptomycetes isolated from apogeotropic roots of sago plants. Based on their phenotypic properties and the 16S rRNA gene sequencing, the streptomycetes were identified as representatives of Streptomyces pluricolorescens (strains 1 and 2). Cyanobacteria developing in monoculture and in association with an actinomycete were essentially different in their morphological and physiological-biochemical characteristics. In associations, cyanobacteria showed a higher (by tens of times) nitrogen-fixing activity compared to the monoculture and the morphological modifications of which were not observed in the monoculture (increase in cell size, increase in the portion of heterocysts among vegetative cells, appearance of the forms of unbalanced growth of cyanobacteria as giant, disc-shaped, curved, and rhomboid cells). At extremely low humidity (aw 0.50), associated cyanobacterial cells remained viable, whereas in the monoculture, chlorophyll decomposition and cells death occurred. The methods of high-resolution (H1 600 MHz) nuclear magnetic resonance (NMR) and pulsed-gradient spin echo NMR revealed a fraction of mobile protons in lyophilized samples of the cyanobacterium-actinomycete association, which was evidence of the presence of free water. This fraction was not found in the lyophilized samples of cyanobacterial and streptomycete monocultures. The revealed differences can explain the survival of cyanobacterial cells in associations. [ABSTRACT FROM AUTHOR]

Formation and location of phenolic compounds in apogeotropic roots (coralloid roots) were studied in six cycad species, which belong to the genera Cycas, Encephalartos, and Ceratozatnia. Total contents of soluble phenolic compounds in coralloid roots in all species studied varied insignificantly, with except for Ceratozainia mexicana that accumulated three times higher amounts of phenolic compounds. Phenolic compounds were accumulated in cell walls of cortical parenchyma of coralloid roots, in intercellular spaces, and in specialized storage cells, found in all zones of apogeotropic roots. The greatest number of phenol-storing cells was situated in the cortical parenchyma of the central part of coralloid roots, adjacent to a zone where active symbiotic cyanobacteria were localized, and in the coralloid root basal region lacking viable forms of cyanobionts. It was suggested that phenolic compounds affect the formation of symbiosis between cyanobacteria and apogeotropic roots of cycad plants, as well as their metabolism. [ABSTRACT FROM AUTHOR]

The ultrastructure of the cyanobionts of the greenhouse-grown cycads Cycas circinalis, Ceratozamia mexicana, and Encephalartos villosus was studied. The cyanobiont microcolonies grown in the intercellular space of the cyanobacterial zone of cortical parenchyma in the cycad coralloid roots contained two specific forms of vegetative cells with a reduced cell wall, namely, protoplasts and spheroplasts. The protoplasts and spheroplasts exhibited ultrastructural properties indicating the overproduction of two extracellular substances, one of which resembled the mucilage polysaccharides and the other was protein-like. The substances were likely to be synthesized intracellularly and then be excreted with the aid of surface vesicles or by ruptures in the cytoplasmic membrane to form, respectively, a mucilagious extracellular matrix and an additional electron-opaque envelope around the cell. At the late developmental stages, the excretion of these substances was accompanied by degradative changes in the cells, leading eventually to cell death. The physiological role of these specific cell forms and the factors that induce their development and death in the cell populations of cyanobionts are discussed. [ABSTRACT FROM AUTHOR]

The ultrastructure of the cyanobionts of the greenhouse-grown cycads Cycas circinalis, Ceratozamia mexicana, and Encephalartos villosus was studied. In addition to heterocysts with the typical ultrastructure, the cyanobiont microcolonies also contained altered heterocysts with reduced cell walls, which might dominate in all regions of the coralloid roots. The altered heterocysts represented a protoplast enclosed in a heterocyst-specific envelope with additional layers. Some heterocysts contained an additional reticular protoplast-enclosing sheath below the heterocyst-specific envelope, whereas the other heterocysts contained an additional electron-opaque outer layer. The substance of the inner sheath of the former heterocysts resembled the polysaccharides of mucilage, which fills the intercellular space, whereas the electron-opaque outer layer of the latter heterocysts probably had a protein nature. The substances that constitute the sheath and the outer layer are likely to be synthesized intracellularly and then released with the aid of membrane-bounded vesicles or by ruptures in the cytoplasmic membrane. [ABSTRACT FROM AUTHOR]

The microbial complexes of soil, the rhizosphere, and the rhizoplane of the apogeotropic (coralloid) roots of cycad plants were comparatively studied. The aseptically prepared homogenates of the surface-sterilized coralloid roots did not contain bacterial microsymbiont, indicating that in the root tissues the symbiosis is a two-component one (plant–cyanobacteria). At the same time, associated bacteria belonging to different taxonomic groups were detected in increasing amounts in the cycad rhizoplane, rhizosphere, and the surrounding soil. The bacterial communities found in the cycad rhizoplane and the surrounding soil were dominated by bacteria from the genus Bacillus. The saprotrophic bacteria and fungi colonizing the cycad rhizosphere and rhizoplane were dominated by microorganisms capable of degrading the plant cell walls. The local degradation of the cell wall was actually observed on the micrographs of the thin sections of cycad roots in the form of channels through which symbiotic cyanobacterial filaments can penetrate into the cortical parenchyma. [ABSTRACT FROM AUTHOR]

Examines the structure of cyanobacterial communities formed during the degradation of apogeotropic roots of cycads. Features that characterized the symbiosis of cycads and cyanobacteria; Composition of different species of cyanobacteria in the branches of a single coralloid; Description of the symbiosis of cycads with nitrogen-fixing cyanobacteria as facultative.

The treatment of rape plants grown in nonsterile soil with 2,4-dichlorophenoxyacetic acid (auxin-like growth-promoting substance) or their inoculation with the bacterial association Micrococcussp. + Rhodococcus sp. and/or with the mixed nitrogen-fixing culture Azotobacter nigricans+ Bacillussp. led to the formation of paranodules on the rape roots. The introduced bacteria were detected both in the intercellular space and inside the cells of the paranodules and the rape roots. The nitrogen-fixing activity of the paranodulated plants was two times higher than that of the inoculated plants lacking paranodules and five times higher than that of the control (i.e., not inoculated) plants. The paranodulation led to a 40% increase in the crop yield of rape plants and provided for a statistically significant increase in the total nitrogen as well as protein nitrogen contents of the plants. [ABSTRACT FROM AUTHOR]

Six bacterial strains isolated from the underground roots of the terrestrial orchid Calanthe vestitavar. rubro-oculatawere found to belong to the genera Arthrobacter, Bacillus, Mycobacterium, and Pseudomonas.Strains isolated from the aerial roots of the epiphytic orchid Dendrobium moschatumwere classified into the genera Bacillus, Curtobacterium, Flavobacterium, Nocardia, Pseudomonas, Rhodococcus, and Xanthomonas.The rhizoplane of the terrestrial orchid was also populated by cyanobacteria of the genera Nostocand Oscillatoria, whereas that of the epiphytic orchid was populated by one genus, Nostoc.In orchids occupying different econiches, the spectra of the bacterial genera revealed differed. The microbial complex of the terrestrial orchid rhizoplane differed from that of the surrounding soil. [ABSTRACT FROM AUTHOR]

Three new cyanobacterial strains, that have been previously purified from the hydroid Dynamena pumila (L., 1758), isolated from the White Sea, were studied using scanning and transmission electron microscopy methods and were characterized by using almost complete sequence of the 16S rRNA gene, internal transcribed spacer 16S-23S rRNA, and part of the gene for 23S rRNA. The full nucleotide sequences of the rRNA gene clusters were deposited to GenBank (HM064496.1, GU265558.1, JQ259187.1). Comparison of rRNA gene cluster sequences of Synechococcus cyanobacterium 1Dp66E-1, Oscillatoriales cyanobacterium 2Dp86E, and Nostoc sp. 10Dp66E with all sequences present at the GenBank shows that these cyanobacterial strains do not have 100% identity with any organisms investigated previously. Furthermore, for the first time heterotrophic bacterium, associated with Nostoc sp. 10Dp66E, was identified as a member of the new phylum Gemmatimonadetes, genus of Gemmatimonas (GenBank accession number is JX437625.1). Phylogenetic analysis showed that cyanobacterium Synechococcus sp. 1Dp66E-1 forms the unique branch and belongs to a cluster of Synechococcus, including freshwater and sea strains. Oscillatoriales cyanobacterium 2Dp86E belongs to a cluster of Leptolyngbya strains. Isolate Nostoc sp. 10Dp66E forms unique branch and belongs to a cluster of the genus Nostoc, with the closest relative of Nostoc commune isolates. [ABSTRACT FROM AUTHOR]