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  • Author or Editor: R. Prasanna x
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A comparative examination of the morphological attributes of freshly separated and cultured cyanobionts of six species of Azolla, namely A. microphylla, A. filiculoides, A. rubra, A. caroliniana, A. mexicana and A. pinnata, was carried out. Distinct variation with respect to colour and nature of filaments, size and frequency of heterocysts was observed when counterparts of cultured and freshly separated cyanobionts from each species of Azolla were compared. The cyanobionts from A. pinnata showed distinctly larger cells compared with the cyanobionts from other Azolla species, whereas the cyanobiont of A. mexicana resembled Nostoc in exhibiting coiled filaments. The other cyanobionts exhibited mostly straight filaments similar to Anabaena. This investigation brings out clearly the morphological variations existing among the cyanobionts belonging to the different species of Azolla and the transitional changes under in vitro conditions, need to characterise the cyanobionts at inter- and intraspecific level using molecular tools in the future for a more reliable classification system of the cyanobionts associated with Azolla.

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Twenty cyanobacterial strains of the genus Tolypothrix, including 15 strains of T. tenuis, three strains of T. ceylonica, and one each of T. nodosa and T. bouteillei, that were collected from various agro-ecological regions of India were evaluated for important parameters related to nitrogen fixing potential, such as acetylene reduction activity, total protein and chlorophyll content. Distinct differences were observed in nitrogen fixing potential at both inter- and intraspecific levels. The T. tenuis strains, in general, exhibited superior nitrogen fixing ability as compared to strains belonging to other species. A statistical procedure based on simultaneous consideration of performances of various strains with respect to different parameters under study aided in identification of three highly promising T. tenuis accessions, namely ARM586, ARM75 and ARM460, for potential exploitation as biofertilisers.

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The influence of inorganic carbon compounds (sodium bicarbonate and carbon dioxide) on cell volume of nitrogen fixing cyanobacteria - Nostoc calcicola and its mutant resistant to high concentrations of bicarbonate (HCO3 -R), and Anabaena sp. and its mutant resistant to high concentrations of carbon dioxide (CO2 R) was investigated. Morphologically, HCO3 -R and CO2 R mutants (isolated through mutagenesis with MNNG) exhibited shorter trichomes consisting of 4-20 cells per trichome. Following incorporation of HCO3 - or CO2 in the growth medium, the cell volume increased in the wild type strains and their mutants in a concentration dependent manner. It was concluded that the significant effect on cell volumes of wild type and mutants, may be due to intracellular influx of bicarbonate ions or CO2 molecules.

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The pigment accumulating potential of two strains of Anabaena was evaluated in the presence of various sugars (glucose, sucrose and jaggery), when incubated under light/darkness. Both strains exhibited excellent potential for phycocyanin (PC), phycoerythrin (PE) and total phycobiliproteins (PBS) production in light, in the presence of sugars. In terms of accumulation of % phycobiliproteins / proteins, Anabaena cylindrica (ATCC 29414) was observed to be more responsive to jaggery while sucrose and glucose were more stimulatory for Anabaena sp. (cyanobiont isolated from Azolla mexicana ). Significant enhancement in PC and PE content by supplementation with sugars emphasises the need for in-depth analysis of the interactions between assimilation of sugars and pigment production pathways in cyanobacteria.

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Abstract  

The extraction of nitric acid by tri-n-butyl phosphate (TBP), tri-sec-butyl phosphate (TsBP) and tri-iso-amyl phosphate (TiAP) solutions in n-dodecane are reported. The results indicate that increase in carbon chain length of the alkyl group of the phosphate as well as introduction of branching near the phosphoryl (P=O) group of the phosphate do not affect significantly the extraction of nitric acid.

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The role of blue green algal (BGA) biofertilizers has been limited to its relevance and utilization in rice crops, and scanty information is available on their use in conjunction with organic amendments and their influence on wheat (Triticum aestivum) . An experiment was conducted from November 2003 to April 2004 in the fields of the Indian Agricultural Research Institute (IARI), New Delhi, India to evaluate the effect of vermicompost, farmyard manure and biofertilizers (BGA and Azotobacter ) in different combinations with chemical fertilizers (N 40 P 30 K 30 ) in wheat (var. HD 2687). Selected soil biological parameters (cyanobacterial diversity/abundance, nitrogenase activity and the phototrophic biomass of soil cores) were measured. The application of vermicompost in combination with BGA biofertilizer (B+V+N 40 P 30 K 30 ) brought about a significant increase in nitrogenase activity (from 0.1 in N 80 P 30 K 30 to 2.0 nmoles mg chl −1 h −1 ), while Azotobacter + BGA (+N 40 P 30 K 30 ) treatment gave the highest values of chlorophyll (1.19 μg g −1 soil). The addition of vermicompost and farmyard manure (+N 40 P 30 K 30 ) enhanced cyanobacterial abundance, and cyanobacterial genera such as Nostoc, Anabaena, Calothrix, Oscillatoria and Phormidium were the dominant forms observed under the wheat crop. The synergistic effect of organic amendments, biofertilizers and chemical fertilizers, especially BGA inoculants, advocates their utilization in wheat crops to improve soil fertility.

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A wide variety of pigments, like chlorophyll, carotenoids and phycobiliproteins, which exhibit colours ranging from green, yellow, brown to red are present in algae. Increasing awareness of harmful effects of synthetic dyes and inclination of society towards the usage of natural products, such as plant / microbial based colours in food and cosmetics, has led to the exploitation of microalgae as a source of natural colours. Algal pigments have great commercial value as natural colorants in nutraceutical, cosmetics and pharmaceutical industry, besides their health benefits. Spirulina, Dunaliella capsules are now commonly prescribed health foods for improving vitality and longevity of human beings. This review describes the distribution, structure of these pigments in algae, with emphasis on specific techniques for extraction and purification, along with different methods of biomass production and commercially feasible techniques documented in literature. An overview of the industrial applications of these natural colouring agents in diagnostics, food and cosmetics industry is also provided.

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