Production of hepatotoxin by the cyanobacterium Scytonema sp strain BT 23

The preliminary screening of several cyanobacteria, using mice bioassay, revealed the production of a hepatotoxin by the cyanobacterium Scytonema sp. strain BT 23 isolated from soil. An intraperitoneal injection of the crude toxin (LD50 56 mg/kg body wt) from this strain caused the death of the mice within 40 min, and the animals showed clinical signs of hepatotoxicity. The toxin was purified and partially characterized. The active fraction appears to be nonpolar in nature and shows absorption peaks at 240 and 285 nm. The purified toxin had an LD50 of 100 mu g/kg body wt and the test mice died within 40 min of toxin administration. The toxin-treated mice showed a 1.65-fold increase in Liver weight at 40 min and the liver color changed to dark red due to intrahepatic hemorrhage and pooling of blood. Furthermore, the administration of the toxin to test mice induced a 2.58, 2.63, and 2.30-fold increase in the activity of the serum enzymes alanine aminotransferase, lactate dehydrogenase, and alkaline phosphatase, respectively. Further experiments with the C-14-labeled toxin revealed a maximum accumulation of the toxin in the liver. The clinical symptoms in the mice were similar to those produced by microcystin-LR. These results suggest that hepatotoxins may also be produced in non bloom-forming planktonic cyanobacteria.