Optimization of Iron dependent cyanobacterial (Synechococcus, Cyanophyceae) bioreporters to measure iron bioavailability

Publisher:
Blackwell Publishing Ltd
Publication Type:
Journal Article
Citation:
Journal of Phycology, 2006, 42 (2), pp. 324 - 335
Issue Date:
2006-01
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Complex chemistry and biological uptake pathways render iron bioavailability particularly difficult to assess in natural waters. Bioreporters are genetically modified organisms that are useful tools to directly sense the bioavailable fractions of solutes. In this study, three cyanobacterial bioreporters derived from Synechococcus PCC 7942 were examined for the purpose of optimizing the response to bioavailable Fe. Each bioreporter uses a Fe-regulated promoter ( isiAB, irpA and mapA), modulated by distinct mechanisms under Fe deficiency, fused to a bacterial luciferase ( luxAB). In order to provide a better understanding of the way natural conditions may affect the ability of the bioreporter to sense iron bioavailability, the effect of relevant environmental parameters on the response to iron was assessed. Optimal conditions (and limits of applicability) for the use of these bioreporters on the field were determined to be: a 12 h (1224 h) exposure time, temperature of 15°C (15°C22°C), photon flux density of 100 ?mol photons·m-2·s-1 (37200 lmol photons·m-2·s-1), initial biomass of 0.60.8 lg chlorophyll a (chl a)·L-1 (0.31.5 lg chl a·L-1) or approximately 105 bioreporter cells·mL-1, high phosphate (10 lM), and low micronutrients (absent).
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