Abstract
Studies on various nitrogen fixing microalgal strains found in the rice paddy field soils are carried out in different parts of the world. In the present study two cyanobacterial strains belonging to the order nostocales, Calothrix sp. and Microchaete sp. were isolated from the rice fields of Karimganj district, South Assam, India and characterized based on their morphological, biochemical and molecular analysis. For the phenotypic characterization - growth, pigments (chlorophyll a, total carotenoid content, phycobiliproteins) and biochemical properties (total carbohydrate and soluble proteins) were studied. The study showed that both strains contain lower phycoerythrin content as compared to the other pigments. The Microchaete strain contain a higher total carotenoid content while chlorophyll a accumulation was higher in the Calothrix strain. Phylogenetic compairision was made using 16S rRNA gene sequences including other sequences of Calothrix, Microchaete and Tolypothrix species from GenBank. The results showed that polyphasic approach provides necessary information for the identification of cyanobacterial species using morphological analysis in combination with molecular techniques.
Highlights
Cyanobacteria are oxygen evolving photoautotropic prokaryotes known to cohabitate with rice and exploited in agriculture for their specific inoculation as nitrogen supplementing biofertilizers in paddy fields[1]
A polyphasic approach involving traditional morphology, biochemical and molecular data has become necessary in recent years
Morphological characterization of strains The morphology of the isolated cyanobacterial strains were studied under light microscope
Summary
Cyanobacteria are oxygen evolving photoautotropic prokaryotes known to cohabitate with rice and exploited in agriculture for their specific inoculation as nitrogen supplementing biofertilizers in paddy fields[1]. They have received much attention in soil due to their nitrogen fixing ability and significant contribution in primary production. Agardh (1824) belong to the order Nostocales and family Rivulariaceae[4,5] It is a polymorphic genus with the general features including hormogonia giving rise to young filaments with terminal heterocyst at only one end of the trichome, mature trichome tapers from base, which bears a terminal heterocyst to apex, vegetative cells disc-shaped, isodiametric or cylindrical[5].
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