SCREENING OF CYANOBACTERIAL STRAINS FOR SELECTION OF MODERATELY SENSITIVE STRAIN: A TOOL FOR TOXICITY ASSAY

The aim of the present study was to screen five cyanobacterial strains namely Nostoc muscorum, Phormidium, Plectonema. boryanum, Chroococcus sp. and Scytonemasp. against five metals mercury (Hg), nickel (Ni), cadmium (Cd), copper (Cu) and aluminum(Al). The order of toxicity based on survival results for all the strains was found to be Hg> Ni> Cd> Cu> Al. The survival of different cyanobacterial strains towards metal stress led to the finding that response to stress is subjected to interspecific variations and therefore different organisms respond differently and specifically to the environmental stress conditions. N. muscorum was found to be the most sensitive of all the strains so it was used for further growth pattern standardization. Amongst the selected metals Hg was found to be the most toxic at all the selected concentrations. Cu gave contrasting results at different treatment doses. Cd and Ni showed a certain degree of adaptation at low doses whereas Al adapted well at all the chosen concentrations. The present results suggest the unequivocally differential response exhibited by the five environmentally prevalent metals in various cyanobacterial strains establishing Cyanobacteria as an efficient toxicity tool.