Electrooptical properties of soil nitrogen-fixing bacterium Azospirillum brasilense: effect of copper ions

The effects of copper ions on the uptake of some essential metals in the biomass and the electrooptical properties of cell suspensions of the nitrogen-fixing soil bacterium Azospirillum brasilense sp. 245 were studied. Copper cations were shown to be effectively taken up by the cell biomass from the culture medium. The addition of copper ions increased the rate of uptake of some other metals present in the culture medium. This was accompanied by changes in the electrooptical characteristics of cell suspension as measured within the orienting electric field frequency range of 10 to 10,000 kHz. The effects observed during short-term incubation of A. brasilense in the presence of copper cations were less significant than during long-term incubation. These results can be used for rapid screening of microbial cultures for enhanced efficiency of sorption and uptake of metals.