IMPACT OF SOME HEAVY METALS ON ACCESSORY PIGMENTS OF ANABAENA ORYZAE (FRITSCH)

摘要

Cyanobacteria exhibit an extraordinary resistance to many environmental factors including metal pollution. Anabaena oryzae trichomes collected from some rice fields were used to study the basic mechanisms underlying the toxicity of heavy metal(s) tolerance. The heavy metals namely manganese (Ⅱ), cobalt (Ⅲ), copper (Ⅱ), zinc (Ⅱ) and mercury (Ⅱ) were used to study the chlorophyll, carotenoid and phycobiloprotein contents of the cyanobacterium. Observations were made on every 4th day for the short-term duration of 28 days. The species growth response under different concentrations (0.001, 0.01, 0.1,1.0%) was determined and heavy metal tolerance was reported by using different parameters. The accessory pigments content decreased drastically, revealing the toxic effects that intracellular heavy metals impose on cellular metabolism and extracellularly. The metal ions may bind to mucilaginous material found outside the gram negative cell wall. The mercury, zinc and copper treated trichomes at higher concentrations showed lethality to the cells and manganese and cobalt showed less impact on the cells under investigation. The toxicity of the studied metals was analyzed and found to be in the order of Hg > Cu > Zn > Co > Mn.