Differential Sensitivity of Nitrogen-Fixing, Filamentous Cyanobacterial Species to an Organochlorine Insecticide - 6, 7, 8, 9, 10, 10- Hexachloro-1, 5, 5a, 6, 9, 9a-Hexahydro-6, 9- Methano-2, 4, 3-Benzodioxathiepine-3-Oxide

Application of pesticides in the paddy fields has deleterious effects on non-target organisms including cyanobacteria which are photosynthesizing and nitrogen fixing micro-organisms contributing significantly towards soil fertility and crop yield. Pesticide contamination in the paddy fields has manifested into a serious global environmental concern. To study the effect of one such pesticide, three cyanobacterial strains; Anabaena fertilissima, Aulosira fertilissima and Westiellopsis prolifica were selected for their stress responses to an Organochlorine insecticide 6, 7, 8, 9, 10, 10-hexachloro-1, 5, 5a, 6, 9, 9a-hexahydro-6, 9-methano-2, 4, 3benzodioxathiepine-3-oxide, with reference to their photosynthesic pigments-chlorophyll-a and carotenoids as well as accessory pigments-phycobiliproteins (phycocyanin, allophycocyanin and phycoerythrin), stress induced biochemical metabolites like carbohydrates, proteins, amino acids, phenols and enzymes-nitrate reductase, glutamine synthetase and succinate dehydrogenase. All the three cyanobacterial strains were adversely affected by the insecticide doses and inhibition was dose dependent. Reduction in photosynthetic and accessory pigments, metabolites, nitrogen fixing and respiratory enzymes of the test organisms were accompanied with an initial increase in their total protein at lower Organochlorine doses. On the other hand, increased amount of phenols in all the insecticide treated concentrations was indicative of stressed activities of the organisms. Keywords—biochemical metabolites, endosulfan, enzymes, pigments N.K. J.I. is with the Institute of Science and Technology for Advanced Studies and Research (ISTAR), VALLABH VIDYANAGAR 388120, GUJARAT, INDIA (phone: 02692-234955; fax: 02692-234955; e-mail: [email protected]). A.A. Bora is with the Institute of Science and Technology for Advanced Studies and Research (ISTAR), VALLABH VIDYANAGAR 388120, GUJARAT, INDIA (phone: 02692-234955; fax: 02692-234955). R.N. Kumar is with the Natubhai V.Patel College of Pure And Applied Sciences (NVPAS), VALLABH VIDYANAGAR 388120, GUJARAT, INDIA. M.K. Amb is with the Institute of Science and Technology for Advanced Studies and Research (ISTAR), VALLABH VIDYANAGAR 388120, GUJARAT, INDIA (phone: 02692-234955; fax: 02692-234955).