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PH08 Metals in the Environment: Aquatic Biological Perspectives
(PH073) Development of in situ use of cyanobacterial iron-dependent bioreporter in the Laurentian Great Lakes.
Hassler, C1, Twiss, M1, McKay, RML2, Bullerjahn, G2, 1 Clarkson University - Department of Biology, Potsdam, NY, US2 Bowling Green State University - Department of Biological Sciences, Bowling Green, OH, US
ABSTRACT- Quantifying the biologically relevant fraction of trace metal in natural waters is very difficult. For this purpose, bioreporters are being developed in order to directly assess the bioavailable fraction. Iron undergoes complex speciation cycling and is known to limit the primary productivity in parts of oceans and of the Great lakes. Synechococcus PCC 7942 was modified by fusing a Fe responsive promoter (isiAB, implied in the replacement of ferredoxin by flavodoxin) to the genes encoding bacterial luciferase, (luxAB). Under cellular Fe limitation bioluminescence is easily assessed by decanal substrate addition and is linearly related to various pFe from 18.9 to 21.9. The bioreporter was calibrated in FRAQUIL growth media where only pFe was varied following a 12h exposure. The use of various biomass concentrations (30-0.05 g chl-a/L) resulted in pronounced effects on bioluminescence, as the bioreporter response is greater at low biomass concentrations that are representative of the Great Lakes. In order to increase the environmental significance of these assays, a trap was designed to retain the bioreporter without decreasing iron diffusion from natural waters. These traps are to be used to determine iron bioavailability in 20 L of natural whole and 0.45 m-filtered waters from the St. Lawrence River and Lake Superior at their respective temperature and light regime. These experiments allow the assessment of the particulate iron contribution to the bioavailable Fe pool under field conditions. Furthermore, the bioreporter response will be related to voltammetric measurements (CLE-CSV) of iron speciation.
Key words: bioreporter, bioavailability, Great Lakes, iron
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