2019 Volume 58 Issue 1 Pages 279-284
Metallic copper is known to have bactericidal effects. In reservoirs, the growth of cyanobacteria affecting water quality is controlled by spraying copper sulfate. In either case, the copper ion is believed to affect the bacteria, but the detailed mechanism is not known. In this study we investigate the influence of copper ions in aqueous solution with other metal ions on cyanobacterial cells and the question where reactive oxygen species are generated. Ultrastructural changes were observed with a transmission electron microscope.
The effects of metal ion solutions containing copper on cyanobacterial cell components were visualized using a fluorescence microscope equipped with a multicolor time lapse recording system. The disappearance rate of each fluorescence (indicating DNA, chlorophyll, cell membranes) was remarkably different depending on the metal ion combination added. Copper ion alone showed a particularly clear influence on DNA; copper and nickel ions combined had an increased effect on chlorophyll; copper with zinc ions caused compaction of DNA and DNA damage by copper ion was prevented. After addition of metal ions, reactive oxygen species were fluorescently visualized in cyanobacterial cells. The subcellular localization of reactive oxygen species varied with the composition of metal ions and predicted the subsequent disappearance of fluorescence of the cell components. Ultrastructural changes were confirmed by transmission electron microscopy, implying that damage was caused by reactive oxygen species generated by the presence of metal ions.
