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The efficiency of cyanobacterial strains as biodiesel feedstock varies with the dwelling habitat. Fourteen indigenous heterocystous cyanobacterial strains from rice field ecosystem were screened based on growth kinetic and fuel parameters. The highest biomass productivity was obtained in Nostoc punctiforme MBDU 621 (19.22 mg/L/day) followed by Calothrix sp. MBDU 701 (13.43 mg/L/day). While lipid productivity and lipid content was highest in Nostoc spongiaeforme MBDU 704 (4.45 mg/L/day and 22.5% dwt) followed by Calothrix sp. MBDU 701 (1.54 mg/L/day and 10.75% dwt). Among the tested strains, Nostoc spongiaeforme MBDU 704 and Nostoc punctiforme MBDU 621 were selected as promising strains for good quality biodiesel production by Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE) and Graphical Analysis for Interactive Assistance (GAIA) analysis. [ABSTRACT FROM AUTHOR]

Trichodesmium is an enigmatic bloom forming, non-heterocystous cyanobacterium reported most frequently in the coastal waters of India. However, the toxigenic potential of this globally significant N 2 fixing cyanobacterium has not been characterized. In this study, we report for the first time the presence of potent multi-class neurotoxins such as Anatoxin-a, Saxitoxins, Gonyautoxin and hepatotoxins like MC-LR, MC-YA from a bloom material of Trichodesmium sp. MBDU 524 collected at the Gulf of Mannar region. Toxins were determined using liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) analysis of HPLC purified aqueous and solvent fractions. Molecular phylogenetic analysis through 16S rRNA gene sequencing showed the close relationship with Trichodesmium erythraeum clade. The toxigenic potential was validated through brine shrimp toxicity assay and showed 100% mortality after 48 h of incubation. The results suggest the potential toxigenic and environmental impacts of Trichodesmium bloom sample from the Gulf of Mannar region. [ABSTRACT FROM AUTHOR]

The present study highlights the importance of cyanobacteria in plant growth promotion and screened the effect of biomass wet extract (BWE 1% and BWE 10%) of twenty cyanobacterial strains on the morphometric parameters of Pisum sativum L. seedlings after germination. Cyanobacterial BWE treatment significantly increased the radicle, plumule and total seedling length along with percentage of response than the control treatment with water. At BWE 1% treatment, Scytonema bohneri MBDU 104 showed 73.3% of the total seedling response, whereas Dolichospermum spiroides MBDU 903 showed increased total seedling length of 5.69 cm among other strains tested. All the tested strains varied among themselves at different parameters. To identify the most potent isolate, all the tested morphometric parameters were evaluated using a multi – criteria decision analysis (MCDA) of PROMETHEE-GAIA software. The isolate Scytonema bohneri MBDU 104 was selected as the potent plant growth promoting cyanobacteria and its BWE was purified using preparative – HPLC and analysed by LC-MS/MS for identifying possible plant growth elicitors. Phytohormones like indole-3 acetic acid (IAA), indole-3 butyric acid (IBA) and cinnamic acid along with free volatile fatty acids were identified and implicated for plant growth promotion by cucumber seed germination bioassay. [ABSTRACT FROM AUTHOR]

Abstract: The genetic background and activities of the enzymes involved in H2 production were investigated from ten distinct H2 producing cyanobacteria, revealed by a recent screening. All strains are N2-fixing, filamentous and heterocystous. Southern hybridization revealed that the tested strains possess the genes encoding the conventional nitrogenase (nifHDK1), and lack the alternative nitrogenases. The high H2 production rate of these strains was shown not to be dependent on the presence of highly active nitrogenase or bidirectional hydrogenase enzymes. Moreover, most of the strains possessed a highly active uptake hydrogenase enzyme. We also examined the structure of the nif and hup operons encoding nitrogenase and uptake hydrogenase enzymes in the Calothrix 336/3 strain, the best H2 producer in the screening. We concluded that the ability of the cyanobacteria to produce high levels of H2 is not directly linked to the maximum capacities of the enzymes involved in H2 production. [Copyright &y& Elsevier]

Screening of 55 different cyanobacterial strains revealed that an extract from Nostoc XPORK14A drastically modifies the amplitude and kinetics of chlorophyll a fluorescence induction of Synechocystis PCC 6803 cells. After 2 d exposure to the Nostoc XPORK14A extract, Synechocystis PCC 6803 cells displayed reduced net photosynthetic activity and significantly modified electron transport properties of photosystem II under both light and dark conditions. However, the maximum oxidizable amount of P700 was not strongly affected. The extract also induced strong oxidative stress in Synechocystis PCC 6803 cells in both light and darkness. We identified the secondary metabolite of Nostoc XPORK14A causing these pronounced effects on Synechocystis cells. Mass spectrometry and nuclear magnetic resonance analyses revealed that this compound, designated as M22, has a non-peptide structure. We propose that M22 possesses a dual-action mechanism: firstly, by photogeneration of reactive oxygen species in the presence of light, which in turn affects the photosynthetic machinery of Synechocystis PCC 6803; and secondly, by altering the in vivo redox status of cells, possibly through inhibition of protein kinases. [ABSTRACT FROM AUTHOR]

Abstract: Cyanobacteria are the only bacteria capable of performing oxygenic photosynthesis in which they harness solar energy and convert it into chemical energy stored in carbohydrates. Under specific conditions, cyanobacteria can use solar energy to produce also molecular hydrogen. Biodiversity among cyanobacteria for H2 production has not been efficiently studied. Here we report the screening of 400 cyanobacterial strains isolated from the Baltic Sea and Finnish lakes for efficient H2 producers. Approximately 50% of these strains produced detectable amounts of H2. Ten strains produced similar or up to 4 times as much of H2 as the hydrogenase mutants of Anabaena PCC 7120 and Nostoc punctiforme ATCC 29133 specifically engineered in different laboratories to produce higher amounts of H2. All ten H2 producers are N2-fixing filamentous, heterocystous strains, seven of them are benthic and three are planktonic strains. Different culturing parameters, such as light intensity, cell density, pH and temperature had a pronounced effect on the H2 production rates of the two good H2 producers, Calothrix 336/3 and XPORK 5E strains. Notably, the culture conditions for optimal H2 production varied between different cyanobacterial strains. [Copyright &y& Elsevier]