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Congratulations to Lee Hudek who took the prize for the best student poster at the recent meeting of the Australasian Society of Phycology and Aquatic Botany, hosted by Deakin University, Warrnambool Campus. Lee presented the results of his recently completed honours project for which the abstract is listed below. Lee has been recently awarded a Deakin University PhD scholarship to continue on to a PhD in Prof Leigh Ackland’s lab (LES at Burwood) in 2008 and we wish him well.
Molecular basis for zinc uptake and efflux by Nostoc punctiforme: Towards the development of a potential phytoremediation tool.
Lee Hudek, Agnes Michalczyk, David Freestone, Maria Gibson and M. Leigh Ackland
School of Life & Environmental Sciences, Deakin University, 221 Burwood Highway, Burwood Victoria 3125
Heavy metals have been established as having significant detrimental impacts on the environment. While zinc has been identified as a problem in the environment, there is a lack of economical and effective treatment methods for zinc-contaminated waters. One method that could be applied for treating zinc-contaminated waters is phytoremediation. Cyanobacteria are established as suitable for bioremediation use and indicate a potential for use in phytoremediation. In vivo determination of the potential of Nostoc punctiforme in phytoremediation applications was predicted by analysing the viability and genomic response to ZnCl2. Nostoc punctiforme was found to tolerate ZnCl2 concentrations as high as 3.5 mg/L before toxicosis occurs. Three identified zinc-uptake genes and one identified zinc-efflux gene, showed significant up-regulation in response to 3 mg/L ZnCl2, for 3 hours of exposure. At 24 hours of exposure both zinc uptake and efflux genes demonstrated significant down regulation, and by 72 hours further down regulation of zinc uptake and efflux genes occurred. Fluorescent localisation experiments illustrated that intracellular zinc concentrations were low in live cells and that zinc has a higher affinity for binding to dead cells. Quantification of intracellular and extracellular zinc confirmed that intracellular zinc concentrations were low, and that significant levels of zinc bound to the cell wall. These results suggest that N. punctiforme would not be suited for all phytoremediation applications as the live cells do not have a large capacity to remove zinc from contaminated waters. These findings indicate that N. punctiforme would be best suited for phytoextraction applications as zinc has a high affinity for adsorbing to N. punctiforme cells, particularly dead cells.