Cadmium induced inhibition of ammonium and phosphate uptake in anacystis nidulans: Interaction with other divalent cations

Abstract

The effect of Cd2+and a combination of Cd2+with non-inhibiting levels of metals like Ca2+, Zn2+and Hg2+on the uptake of ammonia and phosphate by Anacystis nidulans IU625 (ATCC 27144) was investigated. Increasing concentrations of Cd2+resulted in the subsequent inhibition of both NH4+and PO43-uptake. The uptake kinetics was studied by monitoring short-term uptake rates at varying substrate levels. The values for Vmax(maximum uptake capacity) and Km(half saturation constant) were obtained using the double reciprocal plot. The NH4+uptake as such, was found to be more sensitive to the heavy metal than the P043-uptake as fairly low levels of Cd2+were sufficient to inhibit the process significantly. However, the uptake kinetics for both NH4+and PO43-was altered if Cd2+was present in combination with other divalent cations such as Ca2+, Zn2+and Hg2+. Zn2+acted antagonistically to Cd2+toxicity. Similarly, the Ca2+-Cd2+combination protected against inhibition by Cd2+ions. Hg2+behaved differently: the Cd2+-Hg2+combination resulted in increased inhibition. © 1984, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.