2022 年 61 巻 1 号 p. 206-212
Exposure to pure copper (Cu), Cu containing alloy surfaces, or cupric (Cu2+) ion containing solutions is toxic to microorganisms including bacteria and cyanobacteria. The present study describes the effect of Zn2+ ions on Cu2+ ion induced toxicity and structural changes in cyanobacterium Synechococcus elongatus PCC7942 (S. elongatus). Cyanobacteria were treated with aqueous Cu2+, Zn2+ and Ni2+ ion containing solutions mimicking the metal ratios in pure Cu (C1020), brass (C2600, C2680, C2200, C2300, C2801), and nickel silver (C7521, C7701). Cells were observed by fluorescent and electron microscope. Chemically fixed and high–pressure frozen cells were used for ultra–structural observations by TEM. Co–localization of elements including Cu, Zn, and P was observed by EDX elemental mapping. Zn2+ ions at more than 0.13% were found to have a protective effect against DNA damage caused by Cu2+. When cells come in contact with a specific range of Zn2+ concentrations (0.13 to 0.2%) in the solution, cyanobacterial cells go through a transient DNA compaction. Zn2+ ions colocalized with DNA; however, ROS formation was not significantly changed with Zn2+ ion percentage increase.
