To observe the impact of N and P concentrations on utilization of iron by bioreporter Palr0397-luxAB, a series of and concentrations in Fraquil medium with three
Fe3+ concentrations were set to determine the response of luciferase activities to the concentrations of N and P. In Fraquil medium with 10 or 100 nM Fe3+, luciferase activity of bioreporter Palr0397-luxAB was enhanced with the increase in concentration and decreased slightly (remaining at a high level) with ranging from 100 to 900 μM (Fig. 3a); similarly, its luciferase activity increased significantly when increased from 0.1 to 1 μM and varied a little with further increase in concentration (Fig. 3b). In Fraquil medium with 1000 nM Fe3+, its luciferase activity increased slightly with the increased N and P concentrations. When the concentrations of N and check details P were high enough (e.g. 100 μM and 10 μM in this study), further increases in N and P concentrations had little influence on the luciferase activity, showing that iron utilization might not be affected by the uptake of N and P in cells. The variation of N and P concentrations had no effect on luciferase activity of bioreporter in 1000 nM Fe3+ concentration condition, which also indicated that iron utilization was not directly related with the uptake of N and P in cells. Fur acts as a http://www.selleckchem.com/products/bay-57-1293.html transcriptional repressor of iron-regulated promoters by virtue
of its iron-dependent DNA-binding activity to regulate expression of several genes involved in iron homeostasis (Escolar P450 inhibitor et al., 1999). At high concentrations, Co2+ and Mn2+ presumably
mimic Fe2+ (Bagg & Neilands, 1987; Hantke, 1987), and Zn2+ can also activate Fur in vitro (Bagg & Neilands, 1987). So these metals could possibly interfere with iron detection. In addition, other metals such as Cu2+ can compete with iron to chelate dissolved organic siderophores secreted by cells, thus decreasing iron availability (Nicolaisen et al., 2008). The concentrations of metals in lakes greatly varied and are easily affected by surrounding environments. Take the concentration ranges of Co2+, Zn2+, and Cu2+ in Wuhan City (China) for instance; they were 3.7–4.9, 13.1–181.2, and 18.4–83.8 nM in Donghu Lake located in a scenic area, were 7.8–17.6, 1.2–285.1, and 43.1–916.7 nM in Moshui Lake situated in an industrial area, and were 4.9–6.8, 0–0.9, and 58.4–67.7 nM in Houguan Lake in the suburbs (Yu et al., 2007). In an attempt to determine the influence of Co2+, Mn2+, Zn2+, and Cu2+ concentrations on iron bioavailability, luciferase activity of bioreporter Palr0397-luxAB at six concentrations of Co2+, Mn2+, Zn2+, and Cu2+ was, respectively, measured in Fraquil medium with three Fe3+ concentrations. The increase in Mn2+ concentration had no effect on luciferase activity of the bioreporter (Fig. 3d).