Effects of nitrobenzene contamination and of bioaugmentation on nitrification and ammonia-oxidizing bacteria in soil.

Bioaugmentation of nitrobenzene-contaminated soil was performed by inoculation with Pseudomonas putida ZWL73, which can grow on nitrobenzene as carbon and nitrogen sources and release free ammonium from the aromatic ring via a partial-reductive pathway. Removal of nitrobenzene was effectively enhanced with concurrent accumulation of ammonium in the bioaugmented soil. Moreover, the negative impact of nitrobenzene contamination on culturable bacterial types and soil nitrification was reduced by strain ZWL73. Changes in the community structure of ammonia-oxidizing bacteria, determined by denaturing gradient gel electrophoresis, were associated with changes in environmental factors in nitrobenzene-contaminated soil, including concentrations of nitrobenzene, ammonium, nitrite and nitrate, but their influence was attenuated in the bioaugmented soil. Overall, P. putida ZWL73 shows promising abilities for effective removal of nitrobenzene and for attenuating the negative effects of nitrobenzene contamination on soil functioning.