Plasmid pMOL28-encoded resistance to nickel is due to specific efflux

Summary

Two strains of the strictly respiratory bacterium Alcaligenes eutrophus were used to study the kinetics of ⁶³Ni²⁺ uptake and efflux: the wild type strain N9A and its transconjugant N9A-M243, which harbors plasmid pMOL28.1 encoding constitutive resistance to nickel. When incubated aerobically in 1 µM NiCl₂ N9A accumulates high, M243 negligibly small amounts of nickel. When exposed to 1 µM NiCl₂ anaerobically, after preincubation at anoxic conditions for 24 h, both strains accumulate almost the same amounts. Aeration results in instantaneous, rapid efflux by M243, but renewed uptake of nickel by N9A. The results suggest that in M243 under normal aerobic conditions two constitutive energy-dependent cation transport systems are functioning concomitantly; a chromosomally determined nickel uptake system and a plasmid-mediated nickel efflux system.

Alcaligenes eutrophus, Nickel resistance, Plasmid, Nickel efflux