Browsing by Author "Megharaj, M."
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Item Heavy metal toxicity to bacteria – Are the existing growth media accurate enough to determine heavy metal toxicity?(Chemosphere, 2021, 2021) Rathnayake, I.; Megharaj, M.; Krishnamurti, G; Bolan, N. S.; Naidu, R.A new minimal medium was formulated considering the limitations of the existing media for testing heavy metal sensitivity to bacteria. Toxicity of cadmium and copper to three bacteria was investigated in the new medium and ...Item Medium composition affects the heavy metal tolerance of microalgae: a comparison(Journal of Applied Phycology, 2021, 2021) Rathnayake, I.V.N.; Megharaj, M.; Beer, M.; Naidu, RaviTolerance of the three metals cadmium (Cd), copper (Cu), and zinc (Zn) by four microalgal species was investigated in three different culture media available in the literature together with a modified version in order to ...Item Sensitivity of Four Cyanobacterial Isolates from Tropical Freshwaters to Environmentally Realistic Concentrations of Cr6+(Springer US., 2016) Munagamage, T.; Rathnayake, I.V.N.; Pathiratne, A.; Megharaj, M.Sensitivity of four tropical cyanobacteria viz. Coelosphaerium sp., Synechococcus sp., Oscillatoria sp. and Chroococcus sp. to environmentally relevant concentrations of Cr6+, Cd2+ and Zn2+was assessed based on fluorescence change as a proxy for growth reduction. At 24 h exposure, the growth reduction inthe cyanobacteria followed the order: Zn2+ < Cr6+ ≤ Cd2+. Of the four cyanobacteria, Synechococcus was the most sensitive for Cr6+, where as Chroococcus was the most sensitive for Cd2+and Zn2+. Sensitivity was gradually decreased by 96 h implying the acquisition of tolerance by cyanobacteria to heavy metal ions with prolonged exposure.Item Whole cell microalgal-cyanobacterial array biosensor for monitoring Cd, Cr and Zn in aquatic systems(Water Science and Technology, 2021, 2021) Rathnayake, I. V. N.; Munagamage, T; Pathirathne, A.; Megharaj, M.Bioavailable content of metals in aquatic systems has become critical in assessing the toxic effect of metals accumulating in the environment. Considering the need for rapid measurements, an optical microalgal-cyanobacterial array biosensor was developed using two strains of microalgae, Mesotaenium sp. and a strain of cyanobacteria Synechococcus sp. to detect Cd2+, Cr6+ and Zn2+ in aquatic systems. Microalgal and cyanobacterial cells were immobilized in a 96-well microplate using sol-gel method using silica. Optimum operational conditions for the biosensor array such as exposure time, storage stability, pH, and multiple metal effect were tested. A 10 min exposure time yielded optimum fluorescence values. Metal toxicity increased with decreasing pH, resulting in low relative fluorescence (%) and decreased with increasing pH, resulting in higher relative fluorescence (%). The optimum storage time for biosensor strains were 4 weeks for microalgal cultures and 8 weeks for cyanobacterial culture, at 4 °C storage temperature. The metal mixtures showed less effect on the inhibition of relative fluorescence (%) of microalgal/cyanobacterial cultures, displaying an antagonistic behavior among the metals tested. As a single unit, this photosynthetic array biosensor will be a valuable tool in detecting multi-metals in aquatic systems.