Degradation of copper-NTA by Mesorhizobium sp. NCIMB 13524

In a series of enrichment isolations, a mixed culture was obtained from soil which was able to degrade copper nitrilotriacetate. In phosphate buffered (metal-complexing) medium this mixed culture grew on and completely degraded Mn-, Fe-, Co-, Cu- and Zn-NTA after 14 d incubation at 30°C. In PIPES-buffered (non-complexing) medium, the mixed culture completely degraded free NTA and Mn-, Fe- and Zn-NTA; Cu-NTA was partially degraded (54%) and Co-NTA was not degraded. A pure culture of Mesorhizobium sp. (NCIMB 13524) isolated from the mixed culture completely degraded free NTA and Mn-, Fe-, Co-, Ni- Cu-, and Zn-NTA in phosphate buffer after 2–24 d incubation at 30°C. In PIPES buffer, growth and NTA degradation by Mesorhizobium sp. was inhibited stoichiometrically by copper, suggesting that only the free NTA was degraded. In addition, fully complexed Ni-NTA was not degraded in PIPES buffer, and Co-NTA was only partially degraded (18.1%). The importance of speciation, and the effect of the buffer on NTA degradation is discussed.