Characterization of Effects of Copper, Cadmium and Nickel on the Growth of Nitrosomonas-Europaea

The effects of copper, cadmium and nickel on Nitrosomonas europaea were characterized by growth response. Copper inhibition caused a decrease in the growth rate of N. europaea that occurred immediately after inoculation. Cadmium inhibition caused a sharp decrease in the growth rate that occurred after a certain time period, yielding two distinctive growth rates. Nickel inhibition was characterized by an extended lag phase. The combined effects of copper and nickel affected both growth rate and lag. Combined effects of cadmium and nickel were also observed. The combined effect of nickel and copper was antagonistic with respect to both the growth rate and the lag period. Nickel and cadmium acted synergistically to depress the specific growth rate, but the combined effect was either antagonistic or additive (depending upon substrate concentration) with respect to duration of the lag.