Hepatosplenomegaly and phytotoxicity of a planktonic cyanobacterium Nostoc sp. BHU001 isolated from agricultural pond

Nostoc sp. BHU001, a planktonic cyanobacterium isolated from an agricultural pond in India, was examined for its toxicity. Mice, administered intraperitoneally with Nostoc sp. BHU001 crude extract (50 mg kg^?1 body weight) died at 4.5 h. Examination of liver and spleen showed microcystin (MC)-like symptoms. Serum enzyme aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities increased by 1.6–1.8 and 2.6–3.0-folds, respectively at 50 and 100 mg crude extract kg^?1 body weight. Thin layer chromatography of the crude extract produced five bands (N-1 to N-5). UV absorption maxima of band N-4 corresponded to that of standard microcystin-LR. Further analysis of the band N-4 by high-performance liquid chromatography gave a retention time (R _t ) of 4.61 min similar to that of standard microcystin–LR (LR stands for lysine and arginine). Total MC content was quantified by enzyme-linked immunosorbent assay, and was 189.9 μg g^?1 of crude extract, 9.8 μg l^?1 of spent medium and 5.5 μg l^?1 of pond water. Exposure of rice (Oryza sativa var. Sonam) seeds to the crude extract did not affect their germination, but inhibited the root and shoot growth of seedlings by 27.3 and 42.89 folds at 3 mg ml^?1 crude extract, respectively.