No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Extraction and Purification of an Algicidal Metabolite from a Cyanobacterium, Oscillatoria laetevirens
Abstract
An axenic isolate of planktonic filamentous cyanobacterium, Oscillatoria laetevirens produced a photosystem-II inhibiting herbicidal algicide, apparently responsible for allelopathic interaction in nature. The metabolite was extracted in organic solvents and purified by involving the steps of silica gel-column and thin layer chromatography and reverse phase extraction. The resulting compound showed one peak upon reverse phase HPLC. A bioassay was established to determine specific algicidal activity as minimum inhibitory concentration against indicator cyanobacterium and used for monitoring the extent of purification. The specific algicidal activity of crude preparations declined to 2%, whereas the yield of recovered material was 145%.
... Most of the reports indicate that it is released into the medium in the late exponential phase after cell lysis (Ray & Bagchi 2001, Dias et al. 2002). In the current investigation with Nostoc sp., algicidal activity was detected, on the lawn of two unicellular cyanobacteria (Synechococcus and Synechocystis sp.) at all the stages of growth, increasing with time and with a maximum in the stationary phase culture. ...
... In the current investigation with Nostoc sp., algicidal activity was detected, on the lawn of two unicellular cyanobacteria (Synechococcus and Synechocystis sp.) at all the stages of growth, increasing with time and with a maximum in the stationary phase culture. The correlation between culture age and activity is similar to earlier reports (Ray & Bagchi 2001, Dias et al. 2002). Volk (2007) also reported that the content of exo-metabolites of a cyanobacterium Nostoc insulare changes with growth phase; during the linear growth phase, a non-toxic metabolite was prevalent, while in the stationary phase the content of antimicrobial cytotoxic metabolite was enhanced. ...
The antimicrobial efficacy of hexane, dichloromethane and ethyl acetate extracts of a rice-field cyanobacterium, Nostoc sp., were evaluated against cyanobacteria and phytopathogenic fungi. The maximum production of biocidal compounds was observed in cultures grown for 20 days under optimized conditions (phosphate =1.4 mg/l; light intensity ≈ 3000-4000 lux). Fractionation of the extracts showed six spots on silica-gel-coated plates. Hexane extract was the most potent biocide, showing marked (35-42%) reduction in the growth of fungi, but no negative influences on seed germination or seedling growth of wheat, rice and mung bean, emphasizing its suitability for use in agriculture.
... Cyanobacteria represent an untapped bioresource for a diverse range of secondary metabolites, some of which show unique similarities to plant and animal products (Namikoshi and Rinehart 1996; Bagchi and Ray 2001; Agrawal et al. 2005; Singh et al. 2005a; Capper et al. 2006; Dahms et al. 2006; Volk 2006). Toxins produced by bacteria, algae, and (or) cyanobacteria can be considered allelochemicals, since they inhibit one or more groups of organisms and help to provide a competitive advantage to the producer, which may be important factors contributing to formation and (or) maintenance of cyanobacterial blooms (Gross 2003; Legrand et al. 2003; Prasanna and Jaiswal 2006; Leflaive and TenHage 2007). ...
... obacteria (allelochemicals) show a diverse range of biological activities and affect many biochemical processes within the cell, especially the oxygenic photosynthetic processes. Such chemicals are likely to be involved in the regulation of natural populations and are potentially useful as biochemical tools, i.e., as herbicidal and biocidal agents. Bagchi and Ray (2001) reported that a planktonic cyanobacterial extract showed photosystem II-inhibiting (herbicidal) activity, besides allelopathic activity , which might play a role in competitive ability of the strain in nature. Doan et al. (2000) reported alkaloids from Fischerella and Calothrix that inhibited RNA synthesis of other organisms, indicating ...
Allelopathic interactions involving cyanobacteria are being increasingly explored for the pharmaceutical and environmental significance of the bioactive molecules. Among the toxic compounds produced by cyanobacteria, the biosynthetic pathways, regulatory mechanisms, and genes involved are well understood, in relation to biotoxins, whereas the cytotoxins are less investigated. A range of laboratory methods have been developed to detect and identify biotoxins in water as well as the causal organisms; these methods vary greatly in their degree of sophistication and the information they provide. Direct molecular probes are also available to detect and (or) differentiate toxic and nontoxic species from environmental samples. This review collates the information available on the diverse types of toxic bioactive molecules produced by cyanobacteria and provides pointers for effective exploitation of these biologically and industrially significant prokaryotes.
... The ability of Cyanobacteria to synthesize peptides, depsipeptides, polyketides and alkaloids etc. (Rastogi andSinha 2009, Nunnery et al. 2010) fascinates the researchers for their pharmaceutical and biotechnological exploitations (Thajuddin and Subramanian 2005, Sielaff et al. 2006, Spolaore et al. 2006. Cyanobacteria produce a wide range of secondary metabolites, including antialgal substances (Bagchi andRay 2001, Volk andFurkert 2006). Compounds from Cynobacteria were isolated which display inhibitory effects on bacterial growth (Mian et al. 2003, Rao et al. 2007, Kaushik et al. 2009, Das and Pradhan 2010, Vijaya and Ashok 2010, fungal growth (Noaman et al. 2004, Kasinathan et al. 2009), cancer cells (Kinghorn et al. 2009). ...
Antimicrobial activities and minimum inhibitory concentration (MIC) values of various solvent extracts of Microcystis aeruginosa were studied. When tested against 17 Gram negative fish pathogenic bacteria belonging to 4 strains of Aeromonas hydrophila, 2 strains of Pseudomonas putida, 2 strains of P. aeruginosa, 2 strains of P. fluorescens, 6 Vibrio species Edwardsiella tarda and 6 animal serotypes of Escherichia coli, all the solvent extracts showed positive response except aqueous extract. Hot ethanolic extract showed maximum zone size (19 mm) against A. hydrophila (AH1) and E. coli (O111). The crude ethanolic extract was partially purified employing thin layer chromatography (TLC) and silica gel column chromatography techniques. Both crude as well as polar fractions showed positive results against selected pathogens. The antibacterial activities support that freshwater Cyanobacteria are still a promising source of new bioactive natural products. It is possible to develop specific microalgal based biologically active compound for aquaculture and to avoid resistance development against antibiotics used in human medicine.
... For inhibition tests, methanolic extracts corresponding to 0.2 mg dry wt of original cell mass or equivalent methanol were added to 1 ml of elastase (Type IV porcine pancreas; Sigma E0258) assay mixture [6]. Elastase-inhibitory metabolite from Microcystis Ku2 was purified by modification of Bagchi and Ray [7]. Methanolic extract (250 ml) corresponding to 5 g dry wt was refluxed for 6–8 h at 85°C with 2.5% of KOH and the condensed fraction was hydrolyzed with 15 ml of 0.1 M HCl at 45°C. ...
A unicyanobacterial isolate of cyanobacterium, identified as Microcystis Ku2, produced a mammalian elastase-inhibitory lipid derivative. Protease inhibitors in cyanobacteria are unequivocally peptides. Since this metabolite appeared in lipid phase, we worked on a hypothesis that whether metabolite other than peptides could be responsible for the characteristic inhibition. It was purified by saponification and reverse phase column chromatography. The resulting compound was tentatively characterized as a glycolipid with structure of sulfated di-pentose derivative of ceramide (MW = 956 Da). The apparent IC(50) for elastase was 1.3 μM.
... A number of nucleosides -tubercidin, toyocamycin and their corresponding derivatives isolated from Scytonemataceae members were observed to be toxic towards Aspergillus oryzae, Candida albicans, Penicillium notatum and Saccharomyces cerevisiae [13]. A diverse range of compounds are also known to exhibit a bioregulatory role as a result of their cytotoxic, immunosuppressive and enzyme-inhibiting activities which are of tremendous pharmaceutical significance [14,15]. However, the role of hydrolytic enzymes, which are implicated in fungicidal activity of several biocontrol strains, has not been explored in these photosynthetic prokaryotes. ...
A set of seventy axenised and unicyanobacterial isolates belonging to the genus Anabaena were evaluated for biocidal activity against a set of phytopathogenic fungi. Among them, 35 Anabaena strains showed zone of inhibition against one or more fungi. The extracellular filtrates from 4 and 8 weeks old cultures of these Anabaena strains were further evaluated in terms of hydrolytic enzymes, proteins and IAA employing standard methods. Significant differences were also observed among the strains in terms of their FPase, chitosanase and xylanase activity, while low and relatively similar values of CMCase, cellobiase and protease activity were recorded in the strains analyzed. IAA production was also observed in all the strains. Comparative evaluation of activity of hydrolytic enzymes and antifungal activity revealed that such enzymes may contribute to the fungicidal activity of the cyanobacterial strains, besides other bioactive compounds, including IAA, which are established promising traits for biocontrol agents. This study is a first time report on the production of hydrolytic enzymes by these oxygenic photosynthetic prokaryotes, which can be potential candidates for the development of biocontrol agent(s) against selected phytopathogenic fungi.
Using a unicellular cyanobacterium, Synechococcouselongatus PCC7942, we have shown that cytosolic acidification, O2−; H2O2 production and photosystem II-inactivation are the causes of cell death from bentazone/bromoxynil incubations. Butyric acid evoked solely pH lowering response and yet inhibited PS II activity indicating that herbicide-caused acidification is sufficient to kill the cyanobacterial cells, but other factors like excess H2O2 production due to an imbalance in the peroxide sequestration machinery might be contributory. While the activities of superoxide dismutase and pyrogallol peroxidase increased consequent to herbicide incubations and displayed oligomeric states with mobility shift, catalase and glutathione peroxidase though present remained insensitive.
Mutants of Synechococcus sp. PCC 7942 resistant to a natural photosystem II-inhibitory herbicide, oscillatorin, were isolated from a random mutagenesis with N-methyl-N′-nitro-N-nitrosoguanidine. These mutants had elevated growth rates and photosynthetic activity relative to the wild type, and exhibited a high degree of resistance to phenolic-type but not to the atrazine-class of herbicides. Examination of dichlorophenol indophenol photo-reductions in the wild type with water and diphenyl carbazide electron donors revealed that oscillatorin preferentially affects the water oxidizing complex. A comparative analysis of the content of photosynthesis associated proteins revealed that in one such mutant designated Oscr1, PsbO, the manganese stabilizing protein, was highly expressed even under manganese and calcium deficient growth conditions. The amount of PsbA was also higher in the mutant. Solubilizing Mn from the water oxidizing complex was less inhibitory to photosystem II activity in mutant Oscr1. While wild type showed significant photoinhibition in the presence of lincomycin, mutant Oscr1 was much more resistant. Our results suggest that over-expression of PsbO in the mutant Oscr1 and related stability and integrity of water oxidizing complex confers resistance to the oxidative stress caused by oscillatorin.
The nature of the toxicity of a bloom of blue-green alga, M. aeruginosa (= Anacystis cyanea), that occurred in a man-made lake was investigated. Crude algal bloom extracts were toxic to laboratory mice when injected intraperitoneally. The lethal dose (LD100) of these extracts was 15-30 mg of lyophilized algal bloom per kilogram body weight. The toxin was purified by a procedure that included ammonium sulphate fractionation, solvent extraction, acid precipitation, Sephadex G25 and DEAE-Sephadex chromatography, and high-voltage electrophoresis at pH 6.5. The preparation gave a single spot on high-voltage electrophoresis at pH 9.0, had no free amino group, and was characterized by a simple amino acid composition of equimolar quantities of L-methionine, L-tyrosine, D-alanine, D-glutamic acid, erythro beta-methyl aspartic acid and methylamine. The LD50 for the purified toxin was estimated to be 0.056 mg/kg of mice, and the approximate LD100 is 0.070 mg/kg, based on the total material found from amino acid analysis. Parenteral administration of the purified toxin to mice produced extensive liver lobular haemorrhage and death within 1-3 h. Repeated inoculation of sublethal doses daily over some weeks produced progressive hepatocyte degeneration and necrosis and the development of fine hepatic fibrosis.
An algicidal (herbicidal) metabolite from cyanobacterium Oscillatoria late-virens was purified and the mechanism of action determined. The algicide had a molecular weight of 444 Da, an emperical formula of C29H48O3, and contained phenol, C20 alkane and an α, β-unsaturated carbonyl residue. With K3Fe(CN)6 and benzoquinones, 50% inhibition of photosynthetic electron flow (I50) was attained by 1.25-2.35 μM of algicide. Chlorophyll fluorescence data indicate that the algicide interacted at the acceptor site of photosystem (PS)II, although the mechanism may be different from that of another herbicide, 3-(3,4-dichlorophenyl)-1, 1-dimethyl urea (DCMU). Structural resemblance with phenolic herbicides indicates their common mode of interaction.