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 30degreesC. 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 30degreesC. 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. (C) 2003 Elsevier Ltd. All rights reserved.