Isolation of a heavy metal-resistant 4-Chloronitrobenzene degrader Cupriavidus sp. D4 and cloning of its cnb genes

Abstract

Strain D4 was isolated from the sludge of the wastewater treating system of a 4-Chloronitrobenzene (4-CNB) manufacturer. It was able to utilize 4-CNB as the sole carbon and nitrogen source for growth. Strain D4 was preliminarily identified as Cupriavidus sp. based on its physiological & biochemical characteristics and 16S rRNA gene sequence analysis. It could completely degrade 300 mg L −1 of 4-CNB within 25 h under the condition of 30 °C and pH 7.0. Strain D4 could also degrade 4-CNB in presence of heavy metals including Co 2+, Cd 2+, Pb 2+, Zn 2+, Mn 2+and so on, therefore it was an excellent candidate for the bio-treatment of 4-CNB and heavy metals co-contaminated environments. The main 4-CNB degrading related genes ( cnb A, B, Cab, D, G, Z) and arsenate resistance gene fragment of strain D4 were cloned, sequenced and analyzed, which showed high similarity with the corresponding genes of a reported 4-CNB-degrader, strain CNB-1. The cnb genes of strain D4 were located on two plasmids. This is the first report on the degradation of 4-CNB by the strain from the genus of Cupriavidus sp.