Environmental toxicity: Exposure and impact of chromium on cyanobacterial species

The effect of chromium and its mixed salts on nitrogenase activity of various indigenously isolated cyanobacterial strains using Acetylene Reduction Assay (ARA) has been studied. The studies have been performed at varying level of metal, chromium VI and chromium III (0-20 mg/L) and salts (0-2000 mg/L) concentrations in long term and short term duration. It has been observed that the nitrogenase activity of all the strains varied. Based on nitrogenase activity, a few strains have been identified showing positive behavior. Furthermore, depending on their response, the strains have been categorized into sensitive, tolerant and adapted ones. In monocomponent system, Nostoc puncitforme HH-19 has been found to adapt itself to both forms of chromium under long as well as short term stress conditions with increased nitrogenase activity possible due to defensive mechanism.