Bioactive compounds produced by cyanobacteria

Cyanobacteria produce a large number of compounds with varying bioactivities. Prominent among these are toxins: hepatotoxins such as microcystins and nodularins and neurotoxins such as anatoxins and saxitoxins. Cytotoxicity to tumor cells has been demonstrated for other cyanobacterial products, including 9-deazaadenosine, dolastatin 13 and analogs. A number of compounds in cyanobacteria are inhibitors of proteases — micropeptins, cyanopeptolins, oscillapeptin, microviridin, aeruginosins- and other enzymes, while still other compounds have no recognized biological activities. In general cyclic peptides and depsipeptides are the most common structural types, but a wide variety of other types are also found: linear peptides, guanidines, phosphonates, purines and macrolides. The close similarity or identity in structures between cyanobacterial products and compounds isolated from sponges, tunicates and other marine invertebrates suggests the latter compounds may be derived from dietary or symbiotic blue-green algae.     

A simplified protocol for preparing DNA from filamentous cyanobacteria

The preparation of good quality genomic DNA from microalgae and plants is often time-consuming because of the need to remove contaminants that may interfere with the downstream enzymatic manipulation of the DNA. Simpler protocols have been reported but these are applicable only to a few species and in many cases are not effective for removing trace contaminants. In this report, we describe a modification of existing protocols that significantly simplified the preparation of genomic DNA from cyanobacteria and plants. A key step in our protocol is the precipitation of DNA in a high concentration of salt (2–2.5 M NaCl) in the presence of isopropanol, immediately following phenol and chloroform extractions. The preparation and enzymatic digestion of the DNA can be performed in a single day. The DNA was easily digested in 2 h at normal restriction enzyme concentrations, and is highly suitable for PCR and Southern hybridization. We successfully used this simplified protocol to prepare genomic DNA from several filamentous cyanobacteria, such asAnabaena sp. PCC 7120,Anabaena siamensis, andSpirulina strains M2 and Kenya. This protocol may also be useful for preparing genomic DNA from other algae and from higher plants.     

Exopolysaccharide-producing cyanobacteria and their possible exploitation: A review

Since the early 1950s, more than one hundred cyanobacterial strains,belonging to twenty different genera, have been investigated with regard tothe production and the released exocellular polysaccharides (RPS) into theculture medium. The chemical and rheological properties show that suchpolysaccharides are complex anionic heteropolymers, in about 80% casescontaining six to ten different monosaccharides and in about 90% casescontaining one or more uronic acids; almost all have non-saccharidiccomponents, such as peptidic moieties, acetyl, pyruvyl and/or sulphategroups. Based on such ingredients, cyanobacterial RPSs show promise asthickening or suspending agents, emulsifying or cation-chelating compoundsand the residual capsulated cyanobacterial biomass, following RPSextraction, could be an effective cation-chelating material. Indeed, wheneleven unicellular and filamentous RPS-producing cyanobacteria, selectedon the basis of the anion density of their RPSs and on the abundance oftheir outermost investments, were screened for their ability to removeCu²⁺ from aqueous solutions, a quick and most effective heavy metaladsorption was observed for the unicellular Cyanothece CE 4 and thefilamentous Cyanospira capsulata. These results suggest the possibilityto accomplish, through the exploitation of RPS-producing cyanobacteria,a multiproduct strategy to procure a wide range of biopolymers suited tovarious industrial applications, in addition to the residual biomass effectivein the recovery of heavy metals from polluted waters.     

Comparative characterization of novel ene‐reductases from cyanobacteria

The growing importance of biocatalysis in the syntheses of enantiopure molecules results from the benefits of enzymes regarding selectivity and specificity of the reaction and ecological issues of the process. Ene‐reductases (ERs) from the old yellow enzyme family have received much attention in the last years. These flavo‐enzymes catalyze the trans‐specific reduction of activated C?C bonds, which is an important reaction in asymmetric synthesis, because up to two stereogenic centers can be created in one reaction. However, limitations of ERs described in the literature such as their moderate catalytic activity and their strong preference for NADPH promote the search for novel ERs with improved properties. In this study, we characterized nine novel ERs from cyanobacterial strains belonging to different taxonomic orders and habitats. ERs were identified with activities towards a broad spectrum of alkenes. The reduction of maleimide was catalyzed with activities of up to 35.5 U mg^?1 using NADPH. Ketoisophorone and (R)‐carvone, which were converted to the highly valuable compounds (R)‐levodione and (2R,5R)‐dihydrocarvone, were reduced with reaction rates of up to 2.2 U mg^?1 with NADPH. In contrast to other homologous ERs from the literature, NADH was accepted at moderate to high rates as well: Enzyme activities of up to 16.7 U mg^?1 were obtained for maleimide and up to 1.3 U mg^?1 for ketoisophorone and (R)‐carvone. Additionally, excellent stereoselectivities were achieved in the reduction of (R)‐carvone (97–99% de). In particular, AnabaenaER3 from Anabaena variabilis ATCC 29413 and AcaryoER1 from Acaryochloris marina MBIC 11017 were identified as useful biocatalysts. Therefore, novel ERs from cyanobacteria with high catalytic efficiency were added to the toolbox for the asymmetric reduction of alkenes. Biotechnol. Bioeng. 2013; 110: 1293–1301. © 2012 Wiley Periodicals, Inc.     

Molecular genetic improvements of cyanobacteria to enhance the industrial potential of the microbe: A review

The rapid increase in worldwide population coupled with the increasing demand for fossil fuels has led to an increased urgency to develop sustainable sources of energy and chemicals from renewable resources. Using microorganisms to produce high‐value chemicals and next‐generation biofuels is one sustainable option and is the focus of much current research. Cyanobacteria are ideal platform organisms for chemical and biofuel production because they can be genetically engineered to produce a broad range of products directly from CO₂, H₂O, and sunlight, and require minimal nutrient inputs. The purpose of this review is to provide an overview on advances that have been or could be made to improve strains of cyanobacteria for industrial purposes. First, the benefits of using cyanobacteria as a platform for chemical and biofuel production are discussed. Next, an overview of cyanobacterial strain improvements by genetic engineering is provided. Finally, mutagenesis techniques to improve the industrial potential of cyanobacteria are described. Along with providing an overview on various areas of research that are currently being investigated to improve the industrial potential of cyanobacteria, this review aims to elucidate potential targets for future research involving cyanobacteria as an industrial microorganism. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1357–1371, 2016     

Margaret Constance Helen Blackler (1902–81)

Cyanobacteria are effective producers of bioactive metabolites, including both acute toxins and potential pharmaceuticals. In the current work, the biological activity of 27 strains of Baltic cyanobacteria representing different taxonomic groups and chemotypes were tested in a wide variety of assays. The cyanobacteria showed strain-specific differences in the induced effects. The extracts from Nodularia spumigena CCNP1401 were active in the highest number of tests, including protease and phosphatase inhibition assays. Four strains from Nostocales and four from Oscillatoriales increased proliferation of mitogen-stimulated human T cells. In antimicrobial assays, Phormidium sp. CCNP1317 (Oscillatoriales) strongly inhibited the growth of six fouling Gammaproteobacteria. The growth of monocotyl Sorghum saccharatum was inhibited by both toxin-producing and ‘non-toxic’ strains. The Baltic cyanobacteria were also found to be a rich source of commercially important enzymes. Among the 19 enzymatic activities tested, alkaline phosphatase, acid phosphatase, esterase (C4 and C8), and naphthol-AS-BI-phosphohydrolase were particularly common. In the cyanobacterial extracts, different peptides which may have been responsible for the observed effects were identified using LC-MS/MS. Their structures were classified to microcystins, nodularins, anabaenopeptins, cyanopeptolins, aeruginosins, spumigins and nostocyclopeptides.     

淡水有害底栖蓝藻研究进展

底栖蓝藻在全球淡水水域内广泛分布,在河流、湖泊、湿地、泉水水域等均有发现。相比于浮游蓝藻,底栖蓝藻因其隐蔽性、采样困难等关注度较低。针对近十几年有害底栖蓝藻不断过量繁殖的情况,本文对有害底栖蓝藻种类、主要的环境影响因子、有害次级代谢物及监测分析方法进行了总结概括。阐述了在有害底栖蓝藻生物量集聚过程中,光照、温度、营养盐、基质、水流等主要环境因子间的交互关联,并指出藻垫小生境内有害底栖蓝藻与微生物群落间作用的重要性。分析了不同属种有害底栖蓝藻的代谢物种类及影响代谢物产出的因素,总结了目前定性和定量分析有害底栖蓝藻的方法并指出其不足,对预测、定位高水平的有害底栖蓝藻提出了建议。本文为进一步研究有害底栖蓝藻异常增殖机制和有效防控方法提供了参考和借鉴。     

Wewakamide A and guineamide G, cyclic depsipeptides from the marine cyanobacteria Lyngbya semiplena and Lyngbya majuscula

Two new cyclic depsipeptides wewakamide A (1) and guineamide G (2) have been isolated from the marine cyanobacterium Lyngbya semiplena and Lyngbya majuscula, respectively, collected from Papua New Guinea. The amino and hydroxy acid partial structures of wewakamide A and guineamide G were elucidated through extensive spectroscopic techniques, including HR-FABMS, 1D (1)H and (13)C NMR, as well as 2D COSY, HSQC, HSQCTOCSY, and HMBC spectra. The sequence of the residues of wewakamide A was determined through a combination of ESI-MS/MS, HMBC, and ROESY. Wewakamide A possesses a β-amino acid, 3-amino-2-methylbutanoic acid (Maba) residue, which has only been previously identified in two natural products, guineamide B (3) and dolastatin D (4). Although both new compounds (1,2) showed potent brine shrimp toxicity, only guineamide G displayed significant cytotoxicity to a mouse neuroblastoma cell line with LC(50) values of 2.7 micrometer.     

Bioactive compound production by thermophilic and thermotolerant cyanobacteria (blue-green algae)

A thermotolerant species of Phormidium produced extracellular anti-microbial material during batch culture. Although this material was inactive when screened against a number of other cyanobacteria, it inhibited the growth of a wide range of Gram-positive and Gram-negative heterotrophic bacteria, Candida albicans and Cladosporium resinae.The authors are with the Department of Biological Sciences, University of Dundee, Dundee DD1 4HN, UK     

蓝细菌固碳合成乳酸技术的发展与展望

乳酸是一种重要的工业化学品,被广泛应用于各个行业。近年来,随着聚乳酸(PLA)市场的兴起,乳酸原料的需求也在不断增加。糖基异养生产乳酸所带来的高昂成本与市场需求的矛盾吸引着研究人员积极寻找其他有利的解决方案。蓝细菌光合固碳生产乳酸是一种潜力巨大的新型原料供应策略,基于光合自养的细胞工厂,可以在单一平台上以太阳能为驱动力,从二氧化碳中直接生产出高光学纯度的乳酸。该方法原料廉价易得、过程简单可控、产物明确且易分离,同时达到节能减排和高附加值产品生产的双重效果,具有重要的研究与应用价值。文中回顾了蓝细菌固碳产乳酸技术的发展历程,从代谢基础、代谢工程策略、代谢动力学分析与技术应用等方面,梳理其研究进展和所遇到的技术难点,并对该技术的未来进行展望。     

Compounds produced from potential tunicate-blue-green algal symbiosis: A review

Tunicates of the family Didemnidae can be host to two genera of blue-green algae:Synechocystis andProchloron. The presence of symbiotic algae raises questions as to the exact origin of the biologically important metabolites which have been isolated from tunicates in recent years. Is the compound produced by the tunicate, the alga, or through a combined effort of both organisms? Although this question cannot be fully addressed at the present time, there is evidence which supports the argument that the metabolic origin of certain ascidian metabolites resides in the alga, or is due to a collaborative effort of both organisms. The purpose of this review is to present compounds isolated from tunicates that possess a likely symbiotic relationship with eitherSynechocystis orProchloron. Attention will also be given to the ecology of the organisms and the biological activities of metabolites isolated.     

Xanthogenate nucleic acid isolation from cultured and environmental cyanobacteria

The isolation of high-quality nucleic acids from cyanobacterial strains, in particular environmental isolates, has proven far from trivial. We present novel techniques for the extraction of high molecular weight DNA and RNA from a range of cultured and environmental cyanobacteria, including stains belonging to the genera Microcystis , Lyngbya , Pseudanabaena , Aphanizomenon , Nodularia , Anabaena , and Nostoc , based on the use of the nontoxic polysaccharide solubilizing compound xanthogenate. These methods are rapid, require no enzymatic or mechanical cell disruption, and have been used to isolate both DNA and RNA free of enzyme inhibitors or nucleases. In addition, these procedures have proven critical in the molecular analysis of bloom-forming and other environmental cyanobacterial isolates. Finally, these techniques are of general microbiological utility for a diverse range of noncyanobacterial microorganisms, including Gram-positive and Gram-negative bacteria and the Archea.     

PROTEIN PHOSPHATASE INHIBITORY ACTIVITY IN EXTRACTS OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

A large-scale screening program was initiated to evaluate laboratory-cultured blue-green algae (cyanobacteria) as a source of novel compounds with inhibitory activity against certain serine/threonine protein phosphatases. Over 1600 extracts, representing 816 cyanophyte strains with broad habitat and taxonomic diversity, were screened. Inhibitors were identified in extracts produced from all orders tested except Chamaesiphonales, and the family Stigonemataceae was found to contain proportionally more inhibitors as compared to the total screen.     

Sulfate inhibition of molybdenum-dependent nitrogen fixation by planktonic cyanobacteria under seawater conditions: a non-reversible effect

The trace element molybdenum is a central component of several enzymes essential to bacterial nitrogen metabolism, including nitrogen fixation. Despite reasonably high dissolved concentrations (for a trace metal) of molybdenum in seawater, evidence suggests that its biological reactivity and availability are lower in seawater than in freshwater. We have previously argued that this difference is related to an inhibition in the uptake of molybdate (the thermodynamically stable form of molybdenum in oxic natural waters) by sulfate, a stereochemically similar ion. Low molybdenum availability may slow the growth rate of nitrogen-fixing cyanobacteria, and in combination with an ecological control such as grazing by zooplankton, keep fixation rates very low in even strongly nitrogen-limited coastal marine ecosystems. Here we present results from a seawater mesocosm experiment where the molybdenum concentration was increased 10-fold under highly nitrogen-limited conditions. The observed effects on nitrogen-fixing cyanobacterial abundance and nitrogen-fixation inputs were much smaller than expected. A follow-up experiment with sulfate and molybdenum additions to freshwater microcosms showed that sulfate (at seawater concentrations) greatly reduced nitrogen fixation by cyanobacteria and that additions of molybdenum to the levels present in the seawater mesocosm experiment only slightly reversed this effect. In light of these results, we re-evaluated our previous work on the uptake of radio-labeled molybdenum by lake plankton and by cultures of heterocystic cyanobacteria. Our new interpretation indicates that sulfate at saline estuarine levels (>8–10 mM) up to seawater (28 mM) concentrations does inhibit molybdenum assimilation. However, the maximum molybdenum uptake rate (V _max) was a function of the sulfate concentration, with lower V _max values at higher sulfate levels. This indicates that this inhibition is not fully reversed at some saturating level of molybdenum, as assumed in a simple competitive inhibition model. A multi-enzyme, mixed kinetics model with two or more uptake enzyme systems activated in response to the environmental sulfate and molybdate conditions may better explain the repressive effect of sulfate on Mo-mediated processes such as nitrogen fixation.     

Poly-3-hydroxyalkanoates from marine and freshwater cyanobacteria

Polyesters of (R)-3-hydroxybutanoic and (R)-3-hydroxypentanoic acids have been isolated from Aphanothece species, a freshwater cyanobacteri     

Tasiamide F,a potent inhibitor of cathepsins D and E from a marine cyanobacterium

In search of novel protease inhibitors with therapeutic potential, our efforts exploring the marine cyanobacterium Lyngbya sp. have led to the discovery of tasiamide F (1), which is an analogue of tasiamide B (2). The structure was elucidated using a combination of NMR spectroscopy and mass spectrometry. The key structural feature in 1 is the presence of the Phe-derived statine core, which contributes to its aspartic protease inhibitory activity. The antiproteolytic activity of 1 and 2 was evaluated in vitro against cathepsins D and E, and BACE1. Tasiamide F (1) displayed IC₅₀ values of 57 nM, 23 nM, and 0.69 μM, respectively, indicating greater selectivity for cathepsins over BACE1 compared with tasiamide B (2). Molecular docking experiments were carried out for compounds 1 and 2 against cathepsins D and E to rationalize their activity towards these proteases. The dysregulated activities of cathepsins D and E have been implicated in cancer and modulation of immune responses, respectively, and these proteases represent potential therapeutic targets.     

Identification and study of growth and nitrogenase activity of nitrogen fixing cyanobacteria from tropical soil

Identification of cyanobacteria species has been performed on samples coming from two different harvest areas. The most important fixing belongs to Scytonema genus. The other genus identified are Nostoc and Lyngbia. Moreover, these cells are living closely with non-fixing cyanobacteria as well as with bacteria. The growth of cells as well as nitrogenase activity has been studied on a semi-axenic strain of Scytonema, a nitrogen fixing cyanobacterium, isolated from soil crusts. The cell growth is relatively show in liquid medium depleted in combined nitrogen. The growth rate increases when nitrates are supplied to cells. A release of ammonium is observed in medium during cell culture. This release exhibits several maxima and minima during cell growth. The heterocyst cells disappear within four days when filaments are growing in nitrates supplied medium. On the contrary, the heterocyst frequency increases up to more 5% in a nitrogen depleted medium. The heterocyst frequency reaches a maxima after 4 days of culture, then decreases later on. Nitrogenase activity changes during cells growth too. The maximum activity is observed after 5 to 6 days of culture to decrease after even though the cells are still in their exponential phase of growth. Nitrogenase activity increases with light intensity, what indicate a possible relation between photosynthetic and nitrogenase activities.     

The Discovery and Anti-Colorectal Cancer Activities of Cembranolides from the South China Sea Soft Coral Sinularia pendunculata

A new cembranolide, namely, sinupendunculide A ( 1 ), along with eight known related compounds ( 2–9 ), was isolated from the South China Sea Soft coral Sinularia pendunculata. The structure of sinupendunculide A ( 1 ) was established by extensive spectroscopic analysis and X-ray diffraction experiments. In a bioassay, anti-colorectal cancer (CRC) activity was performed, and the results showed that several compounds exhibited cytotoxicity against RKO cells, and a preliminary structure-activity relationship was analysed. Meanwhile, the most effective compound 7 was proven to increase reactive oxygen species levels, which promoted cell apoptosis and inhibited cell proliferation.     

A proteomic approach to iron and copper homeostasis in cyanobacteria.

Cyanobacteria, which are considered to be the chloroplast precursors, are significant contributors to global photosynthetic productivity. The ample variety of membrane and soluble proteins containing different metals (mainly, iron and copper) has made these organisms develop a complex homeostasis with different mechanisms and tight regulation processes to fulfil their metal requirements in a changing environment. Cell metabolism is so adapted as to synthesize alternative proteins depending on the relative metal availabilities. In particular, plastocyanin, a copper protein, and cytochrome c(6), a haem protein, can replace each other to play the same physiological role as electron carriers in photosynthesis and respiration, with the synthesis of one protein or another being regulated by copper concentration in the medium. The unicellular cyanobacterium Synechocystis sp. PCC 6803 has been widely used as a model system because of completion of its genome sequence and the ease of its genetic manipulation, with a lot of proteomic work being done. In this review article, we focus on the functional characterization of knockout Synechocystis mutants for plastocyanin and cytochrome c(6), and discuss the ongoing proteomic analyses performed at varying copper concentrations to investigate the cyanobacterial metal homeostasis and cell response to changing environmental conditions.