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Cyanobacteria are well-distributed, because of their ability to acclimate to various environments. Recently, cyanobacteria have received more research attention due to increasing pollution problems and global warming. They have many potential applications in the biotechnology sectors such as pharmaceuticals, bioplastics production, and cosmetics. Cyanobacteria produce many biologically active compounds that are utilized as anti-inflammatory, antiviral, antibacterial, and antifungal agents. The bioactive metabolites extracted from cyanobacteria include alkaloids, fatty acids, lipopeptides, and amides. In this minireview, the potential of some biotechnical applications are summarized to provide an account of the recent advancements in cyanobacteria research. [ABSTRACT FROM AUTHOR]

Microcystinase (MlrA) is the most specific catalyst and the most efficient enzyme of known microcystins (MCs) detoxification pathways. Very recently, direct MlrA application has effectively degraded MCs within industrial processes, demonstrating MlrA application for sustainable in situ MCs remediation. Heterologous MlrA expression in cyanobacteria offers a unique opportunity, linking harmful MCs remediation with emerging cyanobacterial biotechnologies. Here, we first generate a novel Synechocystis sp. PCC 6803 (6803) using non-native trc promoter for MlrA expression. Whole-cell MlrA activity was comparable to previously described expression via native 6803 PcpcB 560 promoter, while cellular extracts of the new strain showed significantly higher MlrA yields (2–15 times, depending on the age of the cultures). Furthermore, efficiency of MlrA production under multiple photoautotrophic cultivation conditions varied, but was not improved by Na 2 CO 3 supplementation nor under increased light, indicating the need to explore new photoautotrophic chassis for higher MlrA productivity. Methods for MlrA stabilization are critical for industrial development, thus lyophilization of MlrA-enriched cellular extracts was explored. Recovered MlrA activity was not statistically different from initial MlrA activity following storage of lyophilized extracts at −20 °C for 20 weeks. In contrast, storage at 20 °C and storage of aqueous lysates at 4 °C resulted in progressive MlrA activity loss. Such stabilized lyophilizate may offer a checkpoint for further optimization of upstream processes (production), while expanding potential for downstream investigations (application), contributing simultaneously to novel MlrA-based MCs remediation approaches and to cyanobacterial biotechnology. [Display omitted] • Significantly higher MlrA activity obtained under trc promoter. • First report of lyophilization to stabilize MlrA enzyme from cyanobacteria chassis. • -20 °C storage of lyophilized cell extracts preserved MlrA activity. • Effect of photoautotrophic cultivation conditions on MlrA yield. [ABSTRACT FROM AUTHOR]

Cyanobacteria are promising chassis for synthetic biology applications due to the fact that they are photosynthetic organisms capable of growing in simple, inexpensive media. Given their slower growth rate than other model organisms such as Escherichia coli and Saccharomyces cerevisiae , there are fewer synthetic biology tools and promoters available for use in model cyanobacteria. Here, we compared a small library of promoter–riboswitch constructs for synthetic biology applications in Anabaena sp. PCC 7120, a model filamentous cyanobacterium. These constructs were designed from six cyanobacterial promoters of various strengths, each paired with one of two theophylline-responsive riboswitches. The promoter–riboswitch pairs were cloned upstream of a chloramphenicol acetyltransferase (cat) gene, and CAT activity was quantified using an in vitro assay. Addition of theophylline to cultures increased the CAT activity in almost all cases, allowing inducible protein production with natively constitutive promoters. We found that riboswitch F tended to have a lower induced and uninduced production compared to riboswitch E for the weak and medium promoters, although the difference was larger for the uninduced production, in accord with previous research. The strong promoters yielded a higher baseline CAT activity than medium strength and weak promoters. In addition, we observed no appreciable difference between CAT activity measured from strong promoters cultured in uninduced and induced conditions. The results of this study add to the genetic toolbox for cyanobacteria and allow future natural product and synthetic biology researchers to choose a construct that fits their needs. [ABSTRACT FROM AUTHOR]

Abstract In this study, we use ultrafast time-resolved absorption and fluorescence spectroscopies to examine A. marina phycobilisomes isolated from cells grown under light of different intensities and spectral regimes. Investigations were performed at room temperature and at 77 K. The study demonstrates that if complexes are stabilized by high phosphate (900 mM) buffer, there are no differences between them in temporal and spectral properties of fluorescence. However, when the complexes are allowed to disassemble into trimers in low phosphate (50 mM) buffer, differences are clearly observed. The fluorescence properties of intact or disassembled phycobilisomes from cells grown in low intensity white light are unresponsive to variation in phosphate concentration. This antenna complex was further studied in detail with application of femtosecond time-resolved absorption at room temperature. Combined spectroscopic and kinetic analysis of time-resolved fluorescence and absorption data of this antenna allowed us to identify spectrally different forms of phycocyanobilins and to propose a simplified model of how they could be distributed within the phycobilisome structure. Graphical abstract Unlabelled Image Highlights • A. marina phycobilisomes grown in light of different intensities and spectral ranges studied with time-resolved spectroscopy • Fluorescence properties of phycobilisome from cells grown in low intensity white light unresponsive to low phosphate buffer • Spectroscopic and kinetic analysis of this phycobilisome allows identify spectrally different forms of phycocyanobilins • A minimal model of how they are distributed within the phycobilisome structure proposed [ABSTRACT FROM AUTHOR]

Biological control of cyanobacteria is a well-researched area with a central focus on laboratory-scale studies. Numerous reports have been made on algicidal isolates, with bacteria as a major component of the antagonists. The research in this review draws a brief summary of what is currently known in the area of freshwater cyanobacteria being inhibited by bacterial isolates. Proteobacteria, Bacteroidetes and Firmicutes are among the most commonly reported phyla of bacteria associated with or employed in this research area. However, there are limited reports of upscaling these control measures beyond the laboratory scale. Lytic control agents are the most commonly reported in the literature with subsequent cyanotoxin release. From a water quality perspective, this is not feasible. Based on the available literature, temperature, pH and nutrient changes have been explored in this short review as possible contributors to less optimal bacterial performance. Moreover, the investigation into optimising some of these parameters may lead to increased bacterial performance and, therefore, viability for upscaling this biological control. Through the compilation of current research, this review offers insight to live predator-prey cell interactions between cyanobacteria and algicidal bacteria. [ABSTRACT FROM AUTHOR]

Cyanobacteria are an ideal host for biofuel production. Although efforts have been made to genetically engineer cyanobacteria for efficient production of biofuels and other important chemicals, the tools that can be applied to cyanobacteria are still limited. A new gene regulation tool, riboregulator, has been examined for application in cyanobacteria. A riboregulator is a nature-inspired RNA tool, which is composed of two artificially designed RNA fragments. Owing to its high specificity and efficacy, it is suitable for metabolic engineering in cyanobacteria, and several studies have been done to optimize and improve the function of the riboregulator. In this review, we focus on the recent improvements made to riboregulators and compare them with other RNA-mediated gene regulation tools developed in cyanobacteria to investigate future applications of riboregulators. [ABSTRACT FROM AUTHOR]

Escalating concerns about CO2 emission from fossil fuel utilization and environmental pollution from fossil-derived plastic waste call for the sustainable production and utilization of renewable biodegradable plastic materials. Polyhydroxyalkanoates (PHAs) are biodegradable and biocompatible thermoplastics with thermal and mechanical properties comparable to conventional plastics; thus, they are promising materials to mitigate environmental pollution. (R)-3-Hydroxybutyrate (3HB), which is the most common building-block for PHAs, has the potential to be utilized in various medical applications and can also serve as a precursor to a variety of value-added stereospecific chemicals. In addition, it can be produced by microorganisms, such as engineered cyanobacteria, from inexpensive renewable resources such as waste CO2. However, higher titer and rate of (R)-3HB production by cyanobacteria beyond that found in the current literature are critical for commercial applications. Herein, we employed a facile strategy to identify the rate-limiting step in the photoautotrophic production of (R)-3HB by the cyanobacterium Synechocystis and found that acetoacetyl-CoA reductase activity is the bottleneck in the process. Optimization of the gene's ribosome binding site led to a 2.2-fold increase in enzyme activity. In the culture medium of the engineered organism, the (R)-3HB titer reached 1.84 g L−1 within 10 days, with a peak productivity of 263 mg L−1 day−1, using CO2 and light as the sole carbon and energy sources. Moreover, dramatic changes in carbon partition were discovered in the (R)-3HB-producing cells along the course of cultivation using 13C-metabolic flux analysis; after the rapid growth phase, a majority of carbon flux was redirected from the cell mass formation to the production of (R)-3HB in the engineered Synechocystis under the examined experimental conditions. [ABSTRACT FROM AUTHOR]

In our search for thermophilic and acid-tolerant nucleoside 2′-deoxyribosyltransferases (NDTs), we found a good candidate in an enzyme encoded by Chroococcidiopsis thermalis PCC 7203 (CtNDT). Biophysical and biochemical characterization revealed CtNDT as a homotetramer endowed with good activity and stability at both high temperatures (50-100 °C) and a wide range of pH values (from 3 to 7). CtNDT recognizes purine bases and their corresponding 2′-deoxynucleosides but is also proficient using cytosine and 2′-deoxycytidine as substrates. These unusual features preclude the strict classification of CtNDT as either a type I or a type II NDT and further suggest that this simple subdivision may need to be updated in the future. Our findings also hint at a possible link between oligomeric state and NDT’s substrate specificity. Interestingly from a practical perspective, CtNDT displays high activity (80-100%) in the presence of several water-miscible co-solvents in a proportion of up to 20% and was successfully employed in the enzymatic production of several therapeutic nucleosides such as didanosine, vidarabine, and cytarabine. [ABSTRACT FROM AUTHOR]

Cyanobacteria alkane synthetic pathway has been heterologously constructed in many microbial hosts. It is by far the most studied and reliable alkane generating pathway. Aldehyde deformylating oxygenase (i.e., ADO, key enzyme in this pathway) obtained from different cyanobacteria species showed diverse catalytic abilities. This work indicated that single aldehyde reductase deletions were beneficial to Nostoc punctiforme ADO-depended alkane production in Escherichia coli even better than double deletions. Fatty acid metabolism regulator (FadR) overexpression and low temperature increased C18:1 fatty acid supply, and in turn stimulated C18:1-derived heptadecene production, suggesting that supplying ADO with preferred substrate was important to overall alkane yield improvement. Using combinational methods, 1 g/L alkane was obtained in fed-batch fermentation with heptadecene accounting for nearly 84% of total alkane. [ABSTRACT FROM AUTHOR]

Phytochrome photoreceptors control plant growth, development, and the shade avoidance response that limits crop yield in highdensity agricultural plantings. Cyanobacteriochromes (CBCRs) are distantly related photosensory proteins that control cyanobacterial metabolism and behavior in response to light. Photoreceptors in both families reversibly photoconvert between two photostates via photoisomerization of linear tetrapyrrole (bilin) chromophores. Spectroscopic and biochemical studies have demonstrated heterogeneity in both photostates, but the structural basis for such heterogeneity remains unclear. We report solution NMR structures for both photostates of the red/green CBCR NpR6012g4 from Nostoc punctiforme. In addition to identifying structural changes accompanying photoconversion, these structures reveal structural heterogeneity for residues Trp655 and Asp657 in the red-absorbing NpR6012g4 dark state, yielding two distinct environments for the phycocyanobilin chromophore. We use site-directed mutagenesis and fluorescence and absorbance spectroscopy to assign an orangeabsorbing population in the NpR6012g4 dark state to the minority configuration for Asp657. This population does not undergo full, productive photoconversion, as shown by time-resolved spectroscopy and absorption spectroscopy at cryogenic temperature. Our studies thus elucidate the spectral and photochemical consequences of structural heterogeneity in a member of the phytochrome superfamily, insights that should inform efforts to improve photochemical or fluorescence quantum yields in the phytochrome superfamily. [ABSTRACT FROM AUTHOR]

Cyanobacteria are the only prokaryotes that perform oxygenic photosynthesis. Their evolutionary relation to plastids in eukaryotic phototrophs and their increasing utilization as green cell factories initiated the use of systems biology approaches early on. For select model strains, extensive ‘omics’ data sets have been generated, and genome-wide models have been elucidated. Moreover, the results obtained may be used for the optimization of cyanobacterial metabolism, which can direct the biotechnological production of biofuels or chemical feedstock. Synthetic biology approaches permit the rational construction of novel metabolic pathways that are based on the combination of multiple enzymatic activities of different origins. In addition, the manipulation of whole metabolic networks by CRISPR-based and sRNA-based technologies with multiple parallel targets will further stimulate the use of cyanobacteria for diverse applications in basic research and biotechnology. [ABSTRACT FROM AUTHOR]

The cyanobacterium Synechococcus sp. R42DM, isolated from an industrially polluted site Vatva, Gujarat, India was recognized to produce phycocyanin (PC) as major phycobiliprotein. In present study, the combinatorial approach of chemical and physical methods i.e. Triton-X 100 treatment and ultra-sonication was designed for extraction of PC. From cell extract, the intact and functional-PC was purified up to purity 4.03 by ammonium sulphate fractionation and ion-exchange chromatography. The PC displayed considerable in vitro antioxidant and radical-scavenging activity. This PC was further noticed to scavenge intracellular-ROS and to increase tolerance against thermal and oxidative stress in Caenorhabditis elegans . Moreover, the PC was noticed to improve the physiological behaviour and longevity of C. elegans . In addition, the PC showed remarkable stability under physico-chemical stressors, which is desirable for their use in biomedical applications. In conclusion, present paper added up evidence in support of the prospective use of PC as an antioxidant nutraceutical. [ABSTRACT FROM AUTHOR]

The composition and distribution characteristics of bacterial communities in biofilms attached to hydraulic concrete structure (HCS) surfaces were investigated for the first time in four reservoirs in the middle and lower reaches of the Yangtze River Basin using 16S rRNA Miseq sequencing. High microbial diversity was found in HCS biofilms, and notable differences were observed in different types of HCS. Proteobacteria , Cyanobacteria and Chloroflexi were the predominant phyla, with respective relative abundances of 35.3%, 25.4% and 13.0%. The three most abundant genera were Leptolyngbya , Anaerolineaceae and Polynucleobacter . The phyla Beta-proteobacteria and Firmicutes and genus Lyngbya were predominant in CGP, whereas the phyla Cyanobacteria and Chloroflexi and genera Leptolyngbya , Anaerolinea and Polynucleobacter survived better in land walls and bank slopes. Dissolved oxygen, ammonia nitrogen and temperature were characterized as the main factors driving the bacterial community composition. The most abundant groups of metabolic functions were also identified as ammonia oxidizers, sulphate reducers, and dehalogenators. Additionally, functional groups related to biocorrosion were found to account for the largest proportion (14.0% of total sequences) in gate piers, followed by those in land walls (11.5%) and bank slopes (10.2%). Concrete gate piers were at the greatest risk of biocorrosion with the most abundant negative bacterial groups, especially for sulphate reducers. Thus, it should be paid high attention to the biocorrosion prevention of concrete gate piers. Overall, this study contributed to the optimization of microbial control and the improvement of the safety management for water conservation structures. [ABSTRACT FROM AUTHOR]

Changes in the abundance of a taxon can have large effects on communities, particularly if that taxon is a strong interactor. These changes may arise as a consequence of environmental change, recruitment from dormant stages, or quirks of population dynamics, and have effects that ripple through a community interaction network. We hypothesized that cyanobacteria, which are increasing in many freshwater lakes globally, may be strong interactors because they can exert large and persistent effects on the biomass and composition of other phytoplankton. To test this hypothesis, we evaluated how the phytoplankton community responded to different densities of Gloeotrichia echinulata, a large colonial cyanobacterium increasingly observed in low-nutrient lakes in northeastern North America, in an in situ mesocosm experiment. We observed that many phytoplankton taxa, especially diatoms and green algae, responded primarily to increased nutrient availability (a result of Gloeotrichia's nitrogen fixation and translocation of phosphorus from the sediments), while a few taxa (two euglenophytes, one dinoflagellate, and one cyanobacterium) responded to both the direct and indirect effects of Gloeotrichia. Surprisingly, Gloeotrichia reduced the compositional variability of the phytoplankton community relative to the non-Gloeotrichia control treatment; there was no effect on the aggregate temporal variability of total non-Gloeotrichia biovolume. Moreover, experimentally increased densities of Gloeotrichia coincided with increasing complexity of the phytoplankton community in network analyses of taxon co-occurrences, as indicated by significantly greater network density and transitivity and shorter path lengths. Taken together, these findings suggest that Gloeotrichia may be a strongly interacting species in low-nutrient lakes, with the potential to increase the resilience of phytoplankton communities to future disturbance by increasing compositional stability and network complexity. [ABSTRACT FROM AUTHOR]

Water safety is one of the most pervasive problems afflicting people throughout the world. Microcystin-LR (MC-LR), a representative toxin released by cyanobacteria, poses an increasing and serious threat to water safety. In order to develop facile, specific and sensitive detection methods for MC-LR, we fabricated an ultrasensitive fluorescence aptasensor using the enhanced fluorescence of UCNP and the effective quenching ability, high affinity toward single strand DNA (ssDNA) of MoS 2 (termed as FAUM). This assay specifically determined MC-LR in the linear range of 0.01–50 ng/ml with a limit of detection (LOD) of 0.002 ng/ml. The real water sample results indicated that this FAUM assay owns well enough reliability and feasibility to allow the determination of MC-LR. This aptamer-based method might be a promising strategy for a variety of sensing applications. [ABSTRACT FROM AUTHOR]

Cyanobacterial and algal mass development, or blooms, have severe effects on freshwater and marine systems around the world. Many of these phototrophs produce a variety of potent toxins, contribute to oxygen depletion, and affect water quality in several ways. Coexisting antagonists, such as cyanolytic bacteria, hold the potential to suppress, or even terminate, such blooms, yet the nature of this interaction is not well studied. We isolated 31 cyanolytic bacteria affiliated with the genera Pseudomonas, Stenotrophomonas, Acinetobacter, and Delftia from three eutrophic freshwater lakes in Sweden and selected four phylogenetically diverse bacterial strains with strong-to-moderate lytic activity. To characterize their functional responses to the presence of cyanobacteria, we performed RNA sequencing (RNA-Seq) experiments on coculture incubations, with an initial predator-prey ratio of 1:1. Genes involved in central cellular pathways, stress-related heat or cold shock proteins, and antitoxin genes were highly expressed in both heterotrophs and cyanobacteria. Heterotrophs in coculture expressed genes involved in cell motility, signal transduction, and putative lytic activity. L,D-Transpeptidase was the only significantly upregulated lytic gene in Stenotrophomonas rhizophila EK20. Heterotrophs also shifted their central metabolism from the tricarboxylic acid cycle to the glyoxylate shunt. Concurrently, cyanobacteria clearly show contrasting antagonistic interactions with the four tested heterotrophic strains, which is also reflected in the physical attachment to their cells. In conclusion, antagonistic interactions with cyanobacteria were initiated within 24 h, and expression profiles suggest varied responses for the different cyanobacteria and studied cyanolytes. IMPORTANCE Here, we present how gene expression profiles can be used to reveal interactions between bloom-forming freshwater cyanobacteria and antagonistic heterotrophic bacteria. Species-specific responses in both heterotrophs and cyanobacteria were identified. The study contributes to a better understanding of the interspecies cellular interactions underpinning the persistence and collapse of cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

Calcium being a signaling molecule and mediator of cell response, we examined the modulation in fatty acid and hydrocarbon profiles of wild type cyanobacterium Anabaena sp. PCC 7120 and its ntcA mutant under the influence of different calcium chloride concentrations (0-10 mM). Dynamic modifications in fatty acid and hydrocarbon profile were evident through GC-FID analysis of extracted lipids. In the wild type, increase in CaCl2 (10 mM) resulted in unsaturation of fatty acids (observed in terms of high MUFA/PUFA ratio) while hydrocarbon production was distinctly high in the mutant strain compared to wild type at all tested concentrations. The synthesis of short chain hydrocarbons (C5-C8) were dominated at inhibitory concentration (10 mM CaCl2) in mutant strain. Results suggest that the increase in MUFA/PUFA ratio at inhibitory concentration in wild type, and higher percentage of hydrocarbons in mutant strain, may be attributed to the survival and acclimation strategies under altered calcium environment. Our results also suggest the involvement of the ntcA gene (master regulator of N2 metabolism) in regulation of carbon metabolism; specifically fatty acid, hydrocarbon, and other metabolic compounds essential for maintenance and sustenance of growth under stress condition. Thus, our study outlines basic acclimation response along with possibilities of production of fatty acid and hydrocarbon derived biofuel and other bioactive compounds in Anabaena sp. PCC 7120 under altered calcium levels which could be of biotechnological interest. [ABSTRACT FROM AUTHOR]

Prochlorothrix hollandica is filamentous non-heterocystous cyanobacterium which possesses the chlorophyll a/b light-harvesting complexes. Despite the growing interest in unusual green-pigmented cyanobacteria (prochlorophytes) to date only a few sequenced genome from prochlorophytes genera have been reported. This study sequenced the genome of Prochlorothrix hollandica CCAP 1490/1T (CALU1027). The produced draft genome assembly (5.5 Mb) contains 3737 protein-coding genes and 114 RNA genes. [ABSTRACT FROM AUTHOR]

Using a phylogenomic approach, we have identified and subclassified a new family of carotenoid-binding proteins. These proteins have sequence homology to the N-terminal domain (NTD) of the Orange Carotenoid Protein (OCP), and are referred to as Helical Carotenoid Proteins (HCPs). These proteins comprise at least nine distinct clades and are found in diverse organisms, frequently as multiple paralogs representing the distinct clades. These seem to be out-paralogs maintained from ancient duplications associated with subfunctionalization. All of the HCPs share conservation of the residues for carotenoid binding, and we confirm that carotenoid binding is a fundamental property of HCPs. We solved two crystal structures of the Nostoc sp. PCC 7120 HCP1 protein, each binding a different carotenoid, suggesting that the proteins flexibly bind a range of carotenoids. Based on a comprehensive phylogenetic analysis, we propose that one of the HCP subtypes is likely the evolutionary ancestor of the NTD of the OCP, which arose following a domain fusion event. However, we predict that the majority of HCPs have functions distinct from the NTD of the OCP. Our results demonstrate that the HCPs are a new family of functionally diverse carotenoid-binding proteins found among ecophysiologically diverse cyanobacteria. [ABSTRACT FROM AUTHOR]

Mungbean is an important leguminous crop providing protein for the rural and urban poor in South and Southeast Asia. An experiment was conducted in free air carbon dioxide enrichment facility (FACE) ring to study the impact of increased CO2 level on growth and biomass partitioning in mungbean crop. The crop was grown under ambient (400 µmol mol-1) and elevated CO2 concentration (550 µmol mol-1) with 5 doses of P with and without cyanobacterial inoculation. Elevated CO2 significantly increased biomass accumulation in mungbean crop which was further increased by P and cyanobacteria application. Leaf biomass increased by 34.4% at increased CO2 level. Maximum biomass allocation to seeds was observed with P dose of 16 mg kg-1 soil in both ambient and elevated CO2 conditions. Allocation was more in high CO2 treatment. The study concludes that mungbean crop grown under elevated CO2 condition accumulates more biomass which gets further improved by application of P nutrient and cyanobacteria inoculation. [ABSTRACT FROM AUTHOR]

The traditional genus Aphanizomenon comprises a group of filamentous nitrogen-fixing cyanobacteria of which several memebers are able to develop blooms and to produce toxic metabolites (cyanotoxins), including hepatotoxins (microcystins), neurotoxins (anatoxins and saxitoxins) and cytotoxins (cylindrospermopsin). This genus, representing geographically widespread and extensively studied cyanobacteria, is in fact heterogeneous and composed of at least five phylogenetically distant groups ( Aphanizomenon , Anabaena / Aphanizomenon like cluster A, Cuspidothrix , Sphaerospermopsis and Chrysosporum ) whose taxonomy is still under revision. This review provides a thorough insight into the phylogeny, ecology, biogeography and toxicogenomics (cyr, sxt, and ana genes) of the five best documented “ Aphanizomenon ” species with special relevance for water risk assessment: Aphanizomenon flos-aquae , Aphanizomenon gracile , Cuspidothrix issatschenkoi , Sphaerospermopsis aphanizomenoides and Chrysosporum ovalisporum . Aph. flos-aquae , Aph. gracile and C. issatschenkoi have been reported from temperate areas only whereas S. aphanizomenoides shows the widest distribution from the tropics to temperate areas. Ch. ovalisporum is found in tropical, subtropical and Mediterranean areas. While all five species show moderate growth rates (0.1–0.4 day −1 ) within a wide range of temperatures (15–30 °C), Aph. gracile and A. flos-aquae can grow from around (or below) 10 °C, whereas Ch. ovalisporum and S. aphanizomenoides are much better competitors at high temperatures over 30 °C or even close to 35 °C. A. gracile has been confirmed as the producer of saxitoxins and cylindrospermopsin, C. issatschenkoi of anatoxins and saxitoxins and Ch. ovalisporum of cylindrospermopsin. The suspected cylindrospermopsin or anatoxin-a production of A. flos-aquae or microcystin production of S. aphanizomenoides is still uncertain. This review includes a critical discussion on the the reliability of toxicity reports and on the invasive potential of “ Aphanizomenon ” species in a climate change scenario, together with derived knowledge gaps and research needs. As a whole, this work is intended to represent a key reference for scientists and water managers involved in the major challenges of identifying, preventing and mitigating toxic Aphanizomenon blooms. [ABSTRACT FROM AUTHOR]

Using satellite imagery to quantify the spatial patterns of cyanobacterial toxins has several challenges. These challenges include the need for surrogate pigments – since cyanotoxins cannot be directly detected by remote sensing, the variability in the relationship between the pigments and cyanotoxins – especially microcystins (MC), and the lack of standardization of the various measurement methods. A dual-model strategy can provide an approach to address these challenges. One model uses either chlorophyll -a (Chl -a ) or phycocyanin (PC) collected in situ as a surrogate to estimate the MC concentration. The other uses a remote sensing algorithm to estimate the concentration of the surrogate pigment. Where blooms are mixtures of cyanobacteria and eukaryotic algae, PC should be the preferred surrogate to Chl -a . Where cyanobacteria dominate, Chl -a is a better surrogate than PC for remote sensing. Phycocyanin is less sensitive to detection by optical remote sensing, it is less frequently measured, PC laboratory methods are still not standardized, and PC has greater intracellular variability. Either pigment should not be presumed to have a fixed relationship with MC for any water body. The MC-pigment relationship can be valid over weeks, but have considerable intra- and inter-annual variability due to changes in the amount of MC produced relative to cyanobacterial biomass. To detect pigments by satellite, three classes of algorithms (analytic, semi-analytic, and derivative) have been used. Analytical and semi-analytical algorithms are more sensitive but less robust than derivatives because they depend on accurate atmospheric correction; as a result derivatives are more commonly used. Derivatives can estimate Chl -a concentration, and research suggests they can detect and possibly quantify PC. Derivative algorithms, however, need to be standardized in order to evaluate the reproducibility of parameterizations between lakes. A strategy for producing useful estimates of microcystins from cyanobacterial biomass is described, provided cyanotoxin variability is addressed. [ABSTRACT FROM AUTHOR]

The cyanobacterium Cylindrospermopsis raciborskii is a widespread species increasingly being recorded in freshwater systems around the world. It is of particular concern because strains in some geographic areas are capable of producing toxins with implications for human and animal health. Studies of this species have increased rapidly in the last two decades, especially in the southern hemisphere where toxic strains are prevalent. A clearer picture is emerging of the strategies adopted by this species to bloom and out-compete other species. This species has a high level of flexibility with respect to light and nutrients, with higher temperatures and carbon dioxide also promoting growth. There are two types of toxins produced by C. raciborskii: cylindrospermopsins (CYNs) and saxitoxins (STXs). The toxins CYNs are constitutively produced irrespective of environmental conditions and the ecological or physiological role is unclear, while STXs appear to serve as protection against high salinity and/or water hardness. It is also apparent that strains of this species can vary substantially in their physiological responses to environmental conditions, including CYNs production, and this may explain discrepancies in findings from studies in different geographical areas. The combination of a flexible strategy with respect to environmental conditions, and variability in strain response makes it a challenging species to manage. Our ability to improve bloom prediction will rely on a more detailed understanding of the complex physiology of this species. [ABSTRACT FROM AUTHOR]

La Polledrara di Cecanibbio is a Pleistocene fossiliferous deposit near Rome (Italy) where large quantities of bones, belonging mainly to elephants, have been discovered and ‘musealized’ under an enclosing structure. The prevailing environmental conditions inside the museum and the exposition in situ of the fossilized remains have resulted in the development of phototrophic biofilms on the bones and the nearby sediments. Samples of bones and sediment were investigated with different microscopy techniques (light, confocal laser scanning, scanning electron and petrographic microscopes) that allowed the identification of the cyanobacterium Leptolyngbya sp. as the almost entirely dominant organism of the biofilms. The present study identifies for the first time endolithic activity of this cyanobacterium on exposed fossilized bones. There was some indication that this species was euendolithic but this remains to be elucidated. The development of these phototrophic biofilms greatly reduces the aesthetic value of the site and evidence suggests that they may cause extensive structural damage to the bones, threatening the scientific and cultural assets of one of the richest fossiliferous deposits in Italy. This study on the biodeterioration of fossil remains gives useful insights for the conservation of this spectacular site. [ABSTRACT FROM AUTHOR]

We investigated seasonal variations in cyanobacterial biomass and the forms of its dominant population ( M. aeruginosa) and their correlation with environmental factors in the water source area of Chaohu City, China from December 2011 to October 2012. The results show that species belonging to the phylum Cyanophyta occupied the maximum proportion of phytoplankton biomass, and that the dominant population in the water source area of Chaohu City was M. aeruginosa. The variation in cyanobacterial biomass from March to August 2012 was well fitted to the logistic growth model. The growth rate of cyanobacteria was the highest in June, and the biomass of cyanobacteria reached a maximum in August. From February to March 2012, the main form of M. aeruginosa was the single-cell form; M. aeruginosa colonies began to appear from April, and blooms appeared on the water surface in May. The maximum diameter of the colonies was recorded in July, and then gradually decreased from August. The diameter range of M. aeruginosa colonies was 18.37-237.77 μm, and most of the colonies were distributed in the range 20-200 μm, comprising 95.5% of the total number of samples. Temperature and photosynthetically active radiation may be the most important factors that influenced the annual variation in M. aeruginosa biomass and forms. The suitable temperature for cyanobacterial growth was in the range of 15-30°C. In natural water bodies, photosynthetically active radiation had a significant positive influence on the colonial diameter of M. aeruginosa ( P <0.01). [ABSTRACT FROM AUTHOR]

Eruption of blue-green algal blooms occurs frequently in eutrophic lakes and fish ponds, with associated unpleasant odor and horrid scums. In the present study, we conducted a pre-test experiment in 3 m outdoor concrete ponds to determine the optimum concentration of aluminum sulfate (alum) required for reduction of the cyanobacterial blooms without negative effect on fish growth. As a consequence, 10 mg L alum was named as the optimum concentration that was applied in 1000 m earthen fish ponds. Obtained results showed that Secchi disc values significantly increased from 10 to 24 cm after 14 days of alum application. Alum-treated ponds showed a reduction in total phytoplankton counts by 94 and 96 % compared to the corresponding controls after 10 and 14 days, respectively. Abundance of blue-green algae in the treated ponds was decreased by 98 % compared to the corresponding control after 14 days of alum application. Consequently, dissolved oxygen, pH, total phosphorus, orthophosphate, and chlorophyll ' a' content declined significantly. Our study revealed that using 10 mg L of alum is an effective way to control cyanobacterial blooms in eutrophic waters, especially in fish ponds, without negative effect in water quality. [ABSTRACT FROM AUTHOR]

Three contrasting land use systems: reserve forests, rice fields and coal fields located at Upper Assam region of North East India were explored for documenting diversity and species composition of N2-fixing cyanobacteria. Altogether 24 taxa (16 heterocystous and 8 non-heterocystous) belonging to nine different genera were isolated. The Shannon's diversity index was highest in rice fields (1.946), followed by reserve forest (1.485) and coal fields (0.975). Results of relative abundance revealed the dominance of Nostoc and Anabaena in the reserve forests and rice fields, whereas both were missing in the coal contaminated sites. Oscillatoria was the dominant genus and the species belonging to this genus were abundant in coal field areas. Canonical Correspondence Analysis revealed that environmental factors and physico-chemical properties cumulatively decided the composition and distribution of cyanobacteria in different land use systems of the region. [ABSTRACT FROM AUTHOR]

Cyanobacterial lipid droplets (LDs) are packed with hydrophobic energy-dense compounds and have great potential for biotechnological expression and the compartmentalization of high value compounds. Nostoc punctiforme normally accumulates LDs containing neutral lipids, and small amounts of heptadecane, during the stationary phase of growth. In this study, we further enhanced heptadecane production in N. punctiforme by introducing extrachromosomal copies of aar/adc genes, and report the discovery of a putative novel lipase encoded by Npun_F5141, which further enhanced alkane production. Extra copies of all three genes in high light conditions resulted in a 16-fold higher accumulation of heptadecane compared to the wild type strain in the exponential phase. LD accumulation during exponential phase also increased massively to accommodate the heptadecane production. A large number of small, less fluorescent LDs were observed at the cell periphery in exponential growth phase, whereas fewer number of highly fluorescent, much larger LDs were localized towards the center of the cell in the stationary phase. These advances demonstrate that cyanobacterial LDs are an ideal model platform to make industrially relevant compounds, such as alkanes, during exponential growth, and provide insight into LD formation in cyanobacteria. [ABSTRACT FROM AUTHOR]

The potential of cyanobacteria-based compost formulations was evaluated in cotton crop at two agro-ecological locations (Nagpur and Sirsa) as plant growth promoting (PGP) and biocontrol agents. Compost-based formulations fortified with Calothrix sp. or Anabaena sp. enhanced germination and fresh weight of plants, and microbiological activity by 10–15%, besides increased available nitrogen (by 20–50%) in soil at Nagpur. In the fungi-infected fields at Sirsa, Anabaena–T. viride biofilmed formulation performed the best, recording 11.1% lower plant mortality than commercial Trichoderma formulation. Scanning electron microscopy confirmed the colonisation of inoculated cyanobacteria/biofilms on roots. Significant correlation between mortality, increased activity of hydrolytic enzymes and fresh weight of plant roots were recorded. Calothrix sp. and Anabaena sp. proved promising as both PGP and biocontrol agents, while biofilmed formulations substantially reduced mortality of cotton plants in sick plots. This study illustrates the promise of cyanobacteria as viable inoculation option for integrated nutrient and pest management strategies of cotton. [ABSTRACT FROM PUBLISHER]

Despite their pivotal role as primary producers, there is little information as to the diversity and physiology of cyanobacteria in the meltwater ecosystems of polar regions. Thirty cyanobacterial mats from Adelaide Island, Antarctica were investigated using 16S rRNA gene pyrosequencing and automated ribosomal intergenic spacer analysis, and screened for cyanobacterial toxins using molecular and chemical approaches. A total of 274 operational taxonomic units (OTUs) were detected. The richness ranged between 8 and 33 cyanobacterial OTUs per sample, reflecting a high mat diversity. Leptolyngbya and Phormidium (c. 55% and 37% of the OTUs per mat) were dominant. Cyanobacterial community composition was similar between mats, particularly those obtained from closely adjacent locations. The cyanotoxin microcystin was detected in 26 of 27 mats (10–300 ng g-1 organic mass), while cylindrospermopsin, detected for the first time in Antarctica, was present in 21 of 30 mats (2–156 ng g-1 organic mass). The latter was confirmed via liquid chromatography-mass spectrometry and by the presence of the cyrAB and cyrJ genes. This study demonstrates the usefulness of pyrosequencing for characterizing diverse cyanobacterial communities, and confirms that cyanobacteria from extreme environments produce a similar range of cyanotoxins as their temperate counterparts. [ABSTRACT FROM AUTHOR]

Considering the limited number of studies on the biological effects on human health of cyanobacterial compounds that cause taste and odor, the present study assessed the cytotoxic and genotoxic potentials of 2-methylisoborneol (2-MIB) and geosmin (GEO) using the MTT assay and the in vitro comet and cytokinesis-block micronucleus (CBMN-Cyt) assays in human HepG2 cells. The toxicogenomics of genes responsive to DNA damage and metabolization by the exposure of cells to 2-MIB and GEO were also investigated. The results showed that concentrations of 2-MIB and GEO above 100 and 75 μg/mL, respectively, were cytotoxic to HepG2 cells. Doses of 2-MIB (12.5, 25, 50, 75 and 100 μg/mL) and GEO (12.5, 25, 50, and 75 μg/mL) were unable to induce neither DNA damage nor events associated with chromosomal instability. Similarly, no concentration of each compound induced increments in the expression of CDKN1A , GADD45α , MDM2 and TP53 DNA damage responsive genes as well as in CYP1A1 and CYP1A2 metabolizing genes. Although cytotoxicity was observed, concentrations that caused it are much higher than those expected to occur in aquatic environments. Thus, environmentally relevant concentrations of both compounds are not expected to exhibit cytotoxicity or genotoxicity to humans. [ABSTRACT FROM AUTHOR]

Management strategies that prevent the onset of nuisance and noxious cyanobacteria blooms are needed to preserve the integrity and safety of freshwater resource uses. Scientifically defensible data are needed regarding efficacy of proactive approaches in order to assist water resource managers in making informed decisions. As phosphorus availability has been indicated as a crucial aspect of cyanobacteria presence/dominance in freshwater systems, the integration of novel technologies to inactivate phosphorus is a critical component to achieve improved water quality. Phoslock (Phoslock Water Solutions, Ltd.) phosphorus locking technology is composed of the element lanthanum in a bentonite clay matrix that has a high specificity to bind and inactivate soluble reactive phosphorus. This research evaluated the phosphorus binding efficiency of Phoslock in aqueous and sediment matrices and the consequent impact on algae assemblage composition and water quality parameters. Laguna Niguel Lake in California afforded an opportunity to evaluate the operational effectiveness of Phoslock in a system historically plagued by high phosphorus concentrations, potentially toxic cyanobacteria ( Aphanizomenonflos- aquae dominant), and lake closures. Phoslock was able to rapidly (<2 weeks) and significantly ( p < 0.0005) decrease total (>80 %) and free reactive (>95 %) phosphorus in the water column and shift potentially releasable sediment phosphorus fractions to residual forms after treatment. Despite documented cyanobacteria blooms and high pretreatment cell densities, cyanobacteria levels remained below or near detection limits and only comprised a small fraction of the algae assemblage following Phoslock application. This study provides water resource managers an information on operational implementation and efficacy of a phosphorus binding technology. [ABSTRACT FROM AUTHOR]

In this study, cDNA microarrays were developed from 3569 mRNA reads to analyze the expression profiles of the transcriptomes of Synechocystis sp. PCC6803 under low temperature (LT) stress. Among the genes on the cDNA microarrays, 899 LT-affected genes exhibited a 1.5-fold (or greater) difference in expression compared with the genes from normal unstressed Synechocystis sp. PCC6803. Of the differentially expressed genes, 353 were up-regulated and 246 were down-regulated. The results showed that genes involved in photosynthesis were activated at LT (10°C), including genes for photosystem I, photosystem II, photosynthetic electron transport, and cytochrome b6/f complex. Moreover, desB, one of four genes that encode the fatty acid desaturases, was also induced by LT. However, the LT conditions to some degree enhanced the transcription of some genes. In addition, LT (10°C) may reduce cellular motility by regulating the transcription of spkA ( sll1575), a serine/threonine protein kinase. The results reported in this study may contribute to a better understanding of the responses of the Synechocystis cell to LT, including pathways involved in photosynthesis and repair. [ABSTRACT FROM AUTHOR]

Background The world faces the challenge to develop sustainable technologies to replace thousands of products that have been generated from fossil fuels. Microbial cell factories serve as promising alternatives for the production of diverse commodity chemicals and biofuels from renewable resources. For example, polylactic acid (PLA) with its biodegradable properties is a sustainable, environmentally friendly alternative to polyethylene. At present, PLA microbial production is mainly dependent on food crops such as corn and sugarcane. Moreover, optically pure isomers of lactic acid are required for the production of PLA, where D-lactic acid controls the thermochemical and physical properties of PLA. Henceforth, production of D-lactic acid through a more sustainable source (CO2) is desirable. Results We have performed metabolic engineering on Synechocystis sp. PCC 6803 for the phototrophic synthesis of optically pure D-lactic acid from CO2. Synthesis of optically pure D-lactic acid was achieved by utilizing a recently discovered enzyme (i.e., a mutated glycerol dehydrogenase, GlyDH"). Significant improvements in D-lactic acid synthesis were achieved through codon optimization and by balancing the cofactor (NADH) availability through the heterologous expression of a soluble transhydrogenase. We have also discovered that addition of acetate to the cultures improved lactic acid production. More interestingly, 13C-pathway analysis revealed that acetate was not used for the synthesis of lactic acid, but was mainly used for synthesis of certain biomass building blocks (such as leucine and glutamate). Finally, the optimal strain was able to accumulate 1.14 g/L (photoautotrophic condition) and 2.17 g/L (phototrophic condition with acetate) of D-lactate in 24 days. Conclusions We have demonstrated the photoautotrophic production of D-lactic acid by engineering a cyanobacterium Synechocystis 6803. The engineered strain shows an excellent D-lactic acid productivity from CO2. In the late growth phase, the lactate production rate by the engineered strain reached a maximum of ~0.19 g D-lactate/L/day (in the presence of acetate). This study serves as a good complement to the recent metabolic engineering work done on Synechocystis 6803 for L-lactate production. Thereby, our study may facilitate future developments in the use of cyanobacterial cell factories for the commercial production of high quality PLA. [ABSTRACT FROM AUTHOR]

Cyanobacteria are important players in the global carbon cycle, accounting for approximately 25% of global CO2 fixation. Their CO2-concentrating mechanisms (CCMs) are thought to play a key role in cyanobacterial calcification, but the mechanisms are not completely understood. In Synechocystis sp. strain PCC 6803, a single Ca2+/H+ exchanger (Slr1336) controls the Ca2+/H+ exchange reaction. We knocked out the exchanger and investigated the effects on cyanobacterial calcification and CCMs. Inactivation of slr1336 significantly increased the calcification rate and decreased the zeta potential, indicating a relatively stronger Ca2+-binding ability. Some genes encoding CCM-related components showed increased expression levels, including the cmpA gene, which encodes the Ca2+-dependent HCO3- transporter BCT1. The transcript level of cmpA in the mutant was 30 times that in wild type. A Western blot analysis further confirmed that protein levels of CmpA were higher in the mutant than the wild type. Measurements of inorganic carbon fluxes and O2 evolution proved that both the net HCO3- uptake rate and the BCT1 transporter supported photosynthetic rate in the slr1336 mutant were significantly higher than in the wild type. This would cause the mutant cells to liberate more OH- ions out of the cell and stimulate CaCO3 precipitation in the microenvironment. We conclude that the mutation of the Ca2+/H+ exchanger in Synechocystis promoted the cyanobacterial calcification process by upregulating CCMs, especially the BCT1 HCO3- transporter. These results shed new light on the mechanism by which CCM-facilitated photosynthesis promotes cyanobacterial calcification. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cyanobacteria and microalgae are promising for sustainable production of commodities. [•] Cyanobacteria promising for small molecules (e.g. ethanol) that can be secreted. [•] Microalgae promising for the accumulation of storage products (e.g. lipids). [ABSTRACT FROM AUTHOR]

Abstract: The use of reflector film in a cyanobacteria culture rack provides a good light intensity. The effect of light intensity on Spirulina platensis biomass, phycobiliprotein and amino acid content using KNO3 and urea as a nitrogen sources were studied. Maximum biomass productivity 6.9 mg ml−1and 6.1 mg ml−1 with light reflector (LR) + urea and LR + KNO3 respectively, were noticed. The C-phycocyanin (148.1 ± 2.2 mg g−1) and allophycocyanin (45.2 ± 0.94 mg g−1) contents were reached maximum at 4 klx. The rack system with reflector gave good effect of light intensity (4.8–6.0 klx) than the normal system (2–3 klx). Results showed that reflector used cultivation improved biomass, proteinic pigments and protein biosynthesis in S. platensis. This method of cultivation is simple, inexpensive and requires low energy. [Copyright &y& Elsevier]

Abstract: The use of microalgae and cyanobacteria for the production of biofuels and other raw materials is considered a very promising sustainable technology due to the high areal productivity, potential for CO2 fixation and use of non-arable land. The production of oil by microalgae in a large scale plant was studied using emergy analysis. The joint transformity calculated for the base scenario was 1.32E + 5 sej/J, the oil transformity was 3.51E + 5 sej/J, the emergy yield ratio (EYR) was 1.09 and environmental loading ratio was 11.10 and the emergy sustainability index (ESI) was 0.10, highlighting some of the key challenges for the technology such as high energy consumption during harvesting, raw material consumption and high capital and operation costs. Alternatives scenarios and the sensitivity to process improvements were also assessed, helping prioritize further research based on sustainability impact. [Copyright &y& Elsevier]

Genetically engineered (CE) microalgae are nearing commercial release for biofuels production without sufficient public information or ecological studies to investigate their possible risks. Blue-green algae (cyanobacteria) and eukaryotic green algae are likely to disperse widely from open ponds and, on a smaller scale with lower probability, from enclosed photobioreactors. With powerful molecular techniques, thousands of algal strains have been screened, hybridized, and redesigned to grow quickly and tolerate extreme conditions. Some biologists do not expect GE microalgae to survive in the wild. However, thorough ecological and evolutionary assessments are needed to test this assumption and, if the algae do survive, to confirm that their persistence is highly unlikely to cause environmental harm. Cyanobacteria are especially difficult to evaluate because of the chance of horizontal gene transfer with unrelated microbes. Before novel CE algae enter the environment, key biosafety and environmental risk issues should be formally addressed by teams of experts that include ecologists. [ABSTRACT FROM AUTHOR]

We describe within this paper the development of an affinity sensor for the detection of the cyanobacterial toxin microcystin-LR. The first stage of the work included acquiring and testing of the antibodies to this target. Following the investigation, a heterogeneous direct competitive enzyme-linked immunosorbent assay (ELISA) format for microcystin-LR detection was developed, achieving a detection limit, LLD80 = 0.022 μg L-1. The system was then transferred to an affinity membrane sorbent-based ELISA. This was an amenable format for immunoassay incorporation into a disposable amperometric immunosensor device. This membrane-based ELISA achieved a detection limit, LLD80 = 0.06 μg L-1. A three-electrode immunosensor system was fabricated using thick-film screen-printing technology. Amperometric horseradish peroxidase transduction of hydrogen peroxide catalysis, at low reducing potentials, versus Ag/AgCl reference and carbon counter electrodes, was facilitated by hydroquinone-mediated electron transfer. A detection limit of 0.5 μg L-1 for microcystin-LR was achieved. Similar levels of detection could be obtained using direct electrochemical sensing of the dye produced using the membrane-based ELISA. These techniques proved to be simple, cost-effective, and suitable for the detection of microcystin-LR in buffer and spiked tap and river water samples. [ABSTRACT FROM AUTHOR]

Abstract: This study aimed to provide a cost effective medium to large scale production of Spirulina platensis. This intention was implemented by substituting all the nutrients present in Zarrouk’s medium (SM) with cheaper and locally available commercial fertilizers and chemicals. The Reduced Cost medium contained single super phosphate (SSP), commercial sodium bicarbonate, Muriate of potash (MOP) and crude sea-salt, (Syahat salt). Four grades of nitrogen concentrations representing 10%, 20%, 30% and 40% of SM nitrogen concentration (29.42mM-N) were taken from ammonium nitrate (Treatments 1–4) or urea (Treatments 5–8) respectively, for testing. The alga was grown for 33days at 30±2°C, pH 9, 30μEm2 s−1 irradiance. The growth characteristics (maximum biomass X m, cell productivity P x, specific growth rate μ m and chlorophyll concentration), and biochemical composition (proteins, carbohydrates and lipids) of the alga grown in these media were compared with that cultivated in SM. Significant differences in the growth parameters and biochemical composition were observed for the different nitrogen sources and concentrations. The results revealed that S. platensis could utilize ammonium nitrate most efficiently and that growth was enhanced with increasing the concentrations of ammonium nitrate giving maximum biomass at 0.353g/L (Treatment 3). Further increasing the concentration limited growth. The growth parameters in urea showed a significant decrease associated with increasing urea concentrations. The maximum biomass, chlorophyll and protein yield (0.813±0.018mg/L, 0.0685±0.0024μg/L and 52.62%, respectively) were recorded using Treatment 3 which was comparable with that of SM (0.840±0.008mg/L, 0.0701±0.0089μg/L and 52.95%, respectively). The results indicated that the newly prepared medium can be used profitably for large-scale mass production of protein-rich Spirulina and yields similar performance with cost effective to Zarrouk’s medium. [Copyright &y& Elsevier]

Biotechnological applications of algal polysaccharide as emulsifiers, thickeners and laxatives have led to the screening and selection of certain diazotrophic filamentous cyanobacteria from saline/alkaline soil of Madhya Pradesh, India. Strain specific variation in cell bound, extracellular and total polysaccharide content was quantified under laboratory conditions. Among the cyanobacterial isolates examined Nostoc calcicola RDU-3 was found to produce highest amount (105 mg l) of extracellular polysaccharide on 44th day of growth under diazotrophic growth conditions. Extracellular polysaccharide production of cyanobacterium Nostoc calcicola RDU-3 was optimal at pH-10, temperature 35°C, photoperiod of 24 h and in white light. The Gas Chromatographic analysis of polysaccharide from Nostoc calcicola RDU-3 revealed the presence of ribose (36.03%), xylose (34.13%), rhamnose (29.67%) and glucose (4.0%). The polysaccharide is novel in that it possesses ribose as the predominant monosaccharide with very low levels of glucose. Predominance of ribose monosaccharide is the unique feature which is reported to be used as metabolic supplement to the heart. IR spectrum of extracellular polysaccharide revealed the presence of sulphate group. Such sulphated polysaccharide is reported to have antiviral properties. [ABSTRACT FROM AUTHOR]

Extensive selection of cyanobacterial strains (82 isolates) belonging to the genus Nostoc, isolated from different climatic regions and habitats, were screened for both their secondary metabolite content and their cytotoxic effects to mammalian cell lines. The overall occurrence of cytotoxicity was found to be 33%, which corresponds with previously published data. However, the frequency differs significantly among strains, which originate from different climatic regions and microsites (particular localities). A large fraction of intensely cytotoxic strains were found among symbiotic strains (60%) and temperate and continental climatic isolates (45%); compared with the less significant incidences in strains originating from cold regions (36%), deserts (14%), and tropical habitats (9%). The cytotoxic strains were not randomly distributed; microsites that clearly had a higher occurrence of cytotoxicity were observed. Apparently, certain natural conditions lead to the selection of cytotoxic strains, resulting in a high cytotoxicity occurrence, and vice versa. Moreover, in strains isolated from a particular microsite, the cytotoxic effects were caused by different compounds. This result supports our hypothesis for the environmental dependence of cytotoxicity. It also contradicts the hypothesis that clonality and lateral gene transfer could be the reason for this phenomenon. Enormous variability in the secondary metabolites was detected within the studied Nostoc extracts. According to their molecular masses, only 26% of these corresponded to any known structures; thus, pointing to the high potential for the use of many terrestrial cyanobacteria in both pharmacology and biotechnology. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that microorganisms well-adapted to survival in extreme ecosystems could be considered as new sources of biomolecules that have biotechnological importance. On French Polynesian atolls, microbial mats are developing in water ponds exposed to fluctuations in physical and chemical parameters. In these microbial mats, which are called “kopara” by the inhabitants, bacteria coexist with cyanobacteria, and a synergistic relationship may exist between these two types of living microorganisms. A large number of cyanobacteria and bacteria have been isolated from different mats. Under laboratory conditions, these microorganisms were shown to produce various exopolymers, including exopolysaccharides and poly-β-hydroxyalkanoates, along with pigments for further commercial developments. This manuscript gives an overview of substances isolated and characterized from these bacteria and cyanobacteria and discusses their potential applications in biotechnology. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this research was to evaluate the nutritional characteristics of Aphanothece microscopica Nägeli microalgae developed in the effluent of parboiled rice. The biomass was biologically evaluated by rat growth, during 10days for nitrogen balance studies and 28days for blood analysis. The feeding of Aphanothece biomass diets resulted in a nitrogen balance of 1.42g/rat/day, an apparent biological value of 73.33%, an apparent digestibility of 82.12%, an apparent net protein utilization of 60.21% and a net protein retention of 2.40. Significant differences between the glycemic indices of rats fed with the Aphanothece and those fed with the control diet were not observed. However, the total cholesterol levels in the plasma of rats fed the test diet proved to be significantly lower. These results suggest the use of A. microscopica Nägeli developed in parboiled rice effluent as a potential source of single-cell protein. [Copyright &y& Elsevier]

Abstract: The concept of “photosynthetic biofuels” envisions application of a single organism, acting both as photo-catalyst and producer of ready-made fuel. This concept was applied upon genetic engineering of the cyanobacterium Synechocystis, conferring the ability to generate volatile isoprene hydrocarbons from CO2 and H2O. Heterologous expression of the Pueraria montana (kudzu) isoprene synthase (IspS) gene in Synechocystis enabled photosynthetic isoprene generation in these cyanobacteria. Codon-use optimization of the kudzu IspS gene improved expression of the isoprene synthase in Synechocystis. Use of the photosynthesis psbA2 promoter, to drive the expression of the IspS gene, resulted in a light-intensity-dependent isoprene synthase expression. Results showed that oxygenic photosynthesis can be re-directed to generate useful small volatile hydrocarbons, while consuming CO2, without a prior requirement for the harvesting, dewatering and processing of the respective biomass. [Copyright &y& Elsevier]

Chloroplasts have evolved from a cyanobacterial endosymbiont and been retained for more than 1 billion years by coordinated chloroplast division in multiplying eukaryotic cells. Chioroplast division is performed by ring structures at the division site, encompassing both the inside and the outside of the two envelopes. A part of the division machinery is derived from the cyanobacterial cytokinetic activity based on the FtsZ protein. In contrast, other parts of the division machinery involve proteins specific to eukaryotes, including a member of the dynamin family. Each member of the dynamin family is involved in the division or fusion of a distinct eukaryotic membrane system. To gain insight into the kind of ancestral dynamin protein and eukaryotic membrane activity that evolved to regulate chloroplast division, we investigated the functions of the dynamin proteins that are most closely related to chloroplast division proteins. These proteins in the amoeba Dictyostelium discoideum and Arabidopsis thaliana localize at the sites of cell division, where they are involved in cytokinesis. Our results suggest that the dynamin for chloroplast division is derived from that involved in eukaryotic cytokinesis. Therefore, the chloroplast division machinery is a mixture of bacterial and eukaryotic cytokinesis components, with the latter a key factor in the synchronization of endosymbiotic cell division with host cell division, thus helping to establish the permanent endosymbiotic relationship. [ABSTRACT FROM AUTHOR]

The use of microbial biomass in biosorption is already being studied as a potential alternative to (or combined with) conventional processes, where several algae and microorganisms have already shown promising ability to uptake metals. Cyanobacteria (blue-green algae) are widespread organisms, with specific properties, such as high nutrient removal capacity and tolerance to highly variable conditions which make them well-suited for wastewater and remediation purposes. The main aim of this work was to evaluate the use of a marine cyanobacterium LEANCYA 21 (Synechocystis sp.), collected from the Portuguese southern border, for the removal of selected trace metals when in natural seawater culture medium. It was observed, for the first time, that this particular strain is capable of uptaking Pb, Ni and Zn (at nM levels) from seawater solutions using small amounts of biomass. Uptake values for Pb were up to 90% (0.75 mg g-1 biomass) in 6 h. The specific biosorption curves of Ni and Zn showed that these metals follow a first order kinetics biosorption in batch conditions. Solutions containing multimetals have revealed that Ni uptake is affected by the presence of Pb and Zn. The calculated specific absorption values were high enough to predict a possible application in aquaculture where such low levels of metals may inhibit microalgae growth. [ABSTRACT FROM AUTHOR]

Allophycocyanin (APC) is a phycobiliprotein with various biological and pharmacological properties. An expression vector containing five essential genes in charge of biosynthesis of cyanobacterial APC holo-α subunit (holo-ApcA) was constructed, resulting in over-expression of a fluorescent holo-ApcA in E. coli. After being cultured for 16 h, the dry cell density reached 22.5 g l−1, and the expression of holo-HT-ApcA was up to 1 g l−1 broth. The recombinant protein showed similar spectral features to native APC. [ABSTRACT FROM AUTHOR]

The cyanobacterium Synechococcus sp. PCC 7002 carries two genes, petJ1 and petJ2, for proteins related to soluble, cytochrome c6 electron transfer proteins. PetJ1 was purified from the cyanobacterium, and both cytochromes were expressed with heme incorporation in Escherichia coli. The expressed PetJ1 displayed spectral and biochemical properties virtually identical to those of PetJ1 from Synechococcus. PetJ1 is a typical cytochrome c6 but contains an unusual KDGSKSL insertion. PetJ2 isolated from E. coli exhibited absorbance spectra characteristic of cytochromes, although the α, β, and γ bands were red-shifted relative to those of PetJ1. Moreover, the surface electrostatic properties and redox midpoint potential of PetJ2 (pI 9.7; Em,7 148 ± 1.7 mV) differed substantially from those of PetJ1 (pI 3.8; Em,7 = 319 ± 1.6 mV). These data indicate that the PetJ2 cytochrome could not effectively replace PetJ1 as an electron acceptor for the cytochrome bfcomplex in photosynthesis. Phylogenetic comparisons against plant, algal, bacterial, and cyanobacterial genomes revealed two novel and widely distributed clusters of previously uncharacterized, cyanobacterial c6-like cytochromes. PetJ2 belongs to a group that is distinct from both c6 cytochromes and the enigmatic chloroplast c6A cytochromes. We tentatively designate the PetJ2 group as c6C cytochromes and the other new group as c6B cytochromes. Possible functions of these cytochromes are discussed. [ABSTRACT FROM AUTHOR]